Key Operations Lycoming
description
Transcript of Key Operations Lycoming
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Lycoming Flyer
O P E R A T I O N S
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Mostâpeopleâseemâtoâoperateâonâtheâphilosophyâthatâtheyâcanâbestâgetâtheirâmoneyâsâworthâfromâanyâmechanicalâdeviceâbyâtreatingâitâwithâgreatâcare.âThisâisâprobablyâtrue,âbutâinâmanyâcases,âitâisânecessaryâtoâinterpretâwhatâgreatâcareâreallyâmeans.âThisâisâpar-ticularlyâapplicableâwhenâconsideringâtheâbreak-inâofâaâmodern,âreciprocatingâaircraftâengine.âAircraftâownersâfrequentlyâaskâaboutâtheâproperâproceduresâforârun-inâofâaânewâorârebuiltâengineâsoâtheyâcanâcarefullyâcompleteâtheârequiredâsteps.âManyâofâtheseârecommendedâbreak-inâproceduresâalsoâapplyâtoâenginesâwhichâhaveâbeenâoverhauledâorâhadâaâcylinderâreplaced.
Theâfirstâcarefulâconsiderationâforâengineârun-inâisâtheâoilâtoâbeâused.âTheâlatestârevisionâofâLycomingâServiceâInstructionâ1014âshouldâbeâconsultedâforâthisâinformation.âTheâbasicâruleâwhichâappliesâtoâmostânormallyâaspiratedâLycomingâpistonâenginesâisâsimple:âuseâstraightâmineralâoilâofâtheâproperâviscosityâforâtheâfirstâfiftyâhoursâorâuntilâoilâconsumptionâstabilizes.âThenâswitchâtoâashlessâdispersantâ(AD)âoil.
Theâexceptionsâ toâ theâbasicâ ruleâaboveâareâ theâO-320-HâandâtheâO/LO-360-Eâseries.âTheseâenginesâmayâbeâoperatedâusingââeitherâstraightâmineralâoilâorâashlessâdispersantâoil;âhowever,âifâ theâengineâisâdeliveredâwithâashlessâdispersantâoilâ installed,âitâmustâ remainâonâashlessâdispersantâoil.âTheâLycomingâoilâadditiveâP/NâLW-16702âmustâbeâaddedâ toâ theâO-320-HâandââO/LO-360-Eâenginesâatâairframeâinstallation,âandâeveryâ50âhoursâthereafterâorâatâeveryâoilâchange.âAnâFAA-approvedâlubricatingâoilâthatâcontains,âinâtheâproperâamount,âanâoilâadditiveâequivalentâtoâLW-16702âwillâmeetâtheârequirementsâforâtheâadditiveâasâstatedâinâLycomingâServiceâInstructionâNo.â1014M.
AllâLycomingâturbochargedâenginesâmustâbeâbrokenâinâwithâash-lessâdispersantâoilâonly.
Whenâtakingâdeliveryâofâaânewâaircraft,â thereâisâanotherâpointâwhichâmustâbeâemphasized.âSomeâaircraftâmanufacturersâaddâapprovedâpreservativeâlubricatingâoilâtoâprotectânewâenginesâfromârustâandâcorrosionâatâtheâtimeâtheâaircraftâleavesâtheâfactory.âThisâpreservativeâoilâmustâbeâremovedâbyâtheâendâofâtheâfirstâ25âhoursâofâoperation.
Eachânewâorârebuiltâengineâisâgivenâaâproductionâtestârunâatâtheâfactoryâbeforeâtheâengineâisâdeliveredâtoâanâaircraftâmanufacturerâorâcustomer.âAfterâinstallationâinâtheâaircraft,âtheâengineâisârunâagainâduringâtheâtestâflights.âTheseâtestârunsâwillâensureâthatâtheâengineâisâoperatingânormallyâandâwillâprovideâanâopportunityâtoâlocateâsmallâoilâleaksâorâotherâminorâdiscrepancies.âInâaddition,âtheseâtestârunsâdoâtheâinitialâseatingâofâtheâpistonârings.âTheârestâofâtheâbreak-inâisâtheâresponsibilityâofâtheâpilotâwhoâfliesâtheâaircraftâduringâtheânextâ50âhours.
Aânew,ârebuiltâorâoverhauledâengineâshouldâreceiveâ theâsameâstart,âwarm-upâandâpreflightâchecksâasâanyâotherâengine.âThereâareâsomeâaircraftâownersâandâpilotsâwhoâwouldâpreferâtoâuseâlowâpowerâsettingsâforâcruiseâduringâtheâbreak-inâperiod.âThisâisânotârecommended.âAâgoodâbreak-inârequiresâ thatâ theâpistonâringsâexpandâsufficientlyâtoâseatâwithâtheâcylinderâwalls.âThisâseatingâofâtheâringâwithâtheâcylinderâwallâwillâonlyâoccurâwhenâpressuresâ
insideâtheâcylinderâareâgreatâenoughâtoâcauseâexpansionâofâtheâpistonârings.âPressuresâinâtheâcylinderâonlyâbecomeâgreatâenoughâforâaâgoodâbreak-inâwhenâpowerâsettingsâaboveâ65%âareâused.
Fullâpowerâforâtakeoffâandâclimbâduringâtheâbreak-inâperiodâisânotâharmful;âitâisâbeneficial,âalthoughâengineâtemperaturesâshouldâbeâmonitoredâcloselyâtoâensureâthatâoverheatingâdoesânotâoccur.âCruiseâpowerâsettingsâaboveâ65%,âandâpreferablyâ inâ theâ70%âtoâ75%âofâratedâpowerârange,âshouldâbeâusedâtoâachieveâaâgoodâengineâbreak-in.
Rememberâthatâ ifâ theânewâorârebuiltâengineâisânormallyâaspi-ratedâ(non-turbocharged),âitâwillâbeânecessaryâtoâcruiseâatâlowerâaltitudesâ toâobtainâ theâ requiredâcruiseâpowerâ levels.âDensityââaltitudesâinâexcessâofâ8000âfeetâ(5000âfeetâisârecommended)âwillânotâallowâtheâengineâtoâdevelopâsufficientâcruiseâpowerâforâaâgoodâbreak-in.
Forâthoseâwhoâstillâ thinkâthatârunningâtheâengineâhardâduringâbreak-inâfallsâintoâtheâcategoryâofâcruelâandâunusualâpunishment,âthereâisâoneâmoreâargumentâforâhighâpowerâsettingsâduringâengineâbreak-in.âTheâuseâofâlowâpowerâsettingsâdoesânotâexpandâtheâpistonâringsâenough,âandâaâfilmâofâoilâisâleftâonâtheâcylinderâwalls.âTheâhighâtemperaturesâinâtheâcombustionâchamberâwillâoxidizeâthisâoilâfilmâsoâthatâitâcreatesâaâconditionâcommonlyâknownâasâglazingâofâtheâcylinderâwalls.âWhenâthisâhappens,âtheâringâbreak-inâprocessâstops,âandâexcessiveâoilâconsumptionâfrequentlyâoccurs.âTheâbadânewsâisâthatâextensiveâglazingâcanâonlyâbeâcorrectedâbyâremovingâtheâcylindersâandârehoningâtheâwalls.âThisâisâexpensive,âandâitâisâanâexpenseâthatâcanâbeâavoidedâbyâproperâbreak-inâprocedures.
Toâsummarize,â thereâareâ justâaâfewâitemsâtoârememberâaboutâengineâbreak-in:â
1.âIfâaâpreservativeâoilâhasâbeenâaddedâbyâtheâaircraftâmanufac-turer,âdrainâitânoâlaterâthanâtheâfirstâ25âhoursâofâoperation;
â2.âFollowâtheâengineâmanufacturerâsârecommendationâregardingâtheâoilâtoâbeâusedâforâbreak-inâandâtheâperiodâbetweenâchanges;
3.âRunâtheâengineâatâhighâcruiseâpowerâ levelsâforâbestâpistonâring/cylinderâwallâmating;
4.âContinueâbreak-inâoperationâforâ50âhoursâorâuntilâoilâconsump-tionâstabilizes.âTheseâsimpleâproceduresâshouldâeliminateâ theâpossibilityâofâcylinderâwallâglazingâandâshouldâprepareâtheâengineâforâaâlongâandâsatisfactoryâserviceâlife.
A direct reprint of Service Instruction 1094D
RevisionââDââtoâServiceâInstructionâNo.â1094âsupersedesâallâpreviousâ recommendationsâ andâ shouldâ beâ usedâ forâ engineââleaningâduringânormalâflightâoperations.âAll leaning recommen-dations are based on calibrated instrumentation.
Lycomingâstronglyârecommendsâthatâallâengineâinstrumentationâbeâcalibratedâannually.âAllâinstrumentationâforâmanifoldâpressure,âengineâRPM,âoilâtemperature,âcylinderâheadâtemperature,âexhaustâ
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gasâ temperatureâandâ turbineâ inletâ temperatureâ inâ theâaircraftâshouldâbeâincludedâinâthisâannualâcalibration.
Regardlessâofâ theâ fuelâmeteringâdevice,â fuelâmanagementâofânormallyâaspiratedâenginesâisâprimarilyâdependantâonâtheâinstru-mentationâavailable.âTheâmethodâisâtheâsameâforâbothâfixed-âandâcontrollable-âpitchâpropellers.
LycomingârecommendationsâforâleaningâturbochargedâenginesâinâthisâServiceâInstructionâreferâtoâLycoming-suppliedâturbochargedâengines.âForâaftermarketâturbochargerâinstallations,âcontactâtheâSTCâholderâforâproperâleaningâinstructions.
CHTâ(cylinderâheadâtemperature)âandâTITâ(turbineâinletâtempera-ture)âprobesâareârequiredâforâleaningâturbochargedâengines.âReferâtoâtheâlatestâeditionâofâServiceâInstructionâNo.â1422âforâproperâTITâprobeâlocationsâandâdepth.
A. GENERAL RULES
1.â Withoutâ exception,â observeâ theâ red-lineâ temperatureâlimitsâ duringâ takeoff,â climbâ andâ high-performanceâ cruiseâpowerâoperation.
a.âCylinderâheadâtemperatureâââmaximumâlimitâlistedâinâtheâLycomingâOperatorâsâManual.
b.âOilâ temperatureâ limitâââmaximumâlimitâ listedâ inâ theââLycomingâOperatorâsâManual.
c.âTITâ-âmaximumâallowableâlimitâspecifiedâinâtheâLycomingâOperatorâsâManual.
2.âWheneverâmixtureâ isâ adjusted,â richâorâ lean,â itâ shouldâbeââdoneâslowly.
3. Always return mixture slowly to full before increasing power setting.4.âAtâallâ times,âcautionâmustâbeâ takenânotâ toâshock-coolâ theââcylinders.âTheâmaximumârecommendedâ temperatureâchangeâshouldânotâexceedâ50ËâFâperâminute.
B. LEANING THE NORMALLY ASPIRATED ENGINES
1.âUseâfull-richâmixtureâduringâtakeoffâorâclimb.âCarefulâobser-vationâofâengineâtemperatureâinstrumentsâshouldâbeâpracticedâtoâensureâtheâlimitsâspecifiedâinâLycomingâOperatorâsâManualâareâneverâexceeded.âReferâ toâ theâaircraftâPOHâ(PilotâsâOperatingâHandbook)âorâAFMâ(AircraftâFlightâManual)âforâmoreâspecificâinstructions.
2.âForâ5,000âfeetâdensityâaltitudeâandâabove,âorâhighâambientâtemperatures,â roughnessâorâ reductionâofâpowerâmayâoccurâatâfullârichâmixture.âTheâmixtureâmayâbeâadjustedâtoâobtainâsmoothâengineâoperation.âForâfixed-pitchâpropellers,â leanâtoâmaximumâRPMâ atâ fullâ throttleâ priorâ toâ takeoffâ whereâ airportsâ areâ atââ5,000-feetâdensityâaltitudeâorâhigher.âLimitâoperationâatâfullâthrottleâonâtheâgroundâtoâaâminimum.âForâdirect-driveâandâforânormallyâaspiratedâenginesâwithâaâpropâgovernor,âbutâwithoutâfuelâflowâorâEGT,âsetâthrottleâatâfullâpowerâandâleanâmixtureâatâmaximumâRPMâwithâsmoothâoperationâofâtheâengineâasâaâdecidingâfactor.
3.âForâcruiseâpowersâwhereâbestâpowerâmixtureâ isâ allowed,âslowlyâ leanâ theâmixtureâ fromâfullâ richâ toâmaximumâpower.âBestâpowerâmixtureâoperationâprovidesâtheâmostâmilesâperâhourâforâaâgivenâpowerâsetting.âForâenginesâequippedâwithâfixed-pitchâ
âpropellers,âgraduallyâleanâtheâmixtureâuntilâeitherâtheâtachometerâorâtheâairspeedâindicatorâreadingâpeaks.âForâenginesâequippedâwithâcontrollableâpitchâpropellers,âleanâuntilâaâslightâincreaseâofâairspeedâisânoted.
4.âForâaâgivenâpowerâsetting,âbestâeconomyâmixtureâprovidesâtheâmostâmilesâperâgallon.âSlowlyâleanâtheâmixtureâuntilâengineâopera-tionâbecomesâroughâorâuntilâengineâpowerârapidlyâdiminishesâasânotedâbyâanâundesirableâdecreaseâinâairspeed.âWhenâeitherâcondi-tionâoccurs,âenrichâtheâmixtureâsufficientlyâtoâobtainâanâevenlyâfiringâengineâorâtoâregainâmostâofâtheâlostâairspeedâorâengineâRPM.âSomeâengineâpowerâandâairspeedâmustâbeâsacrificedâtoâgainâaâbestâeconomyâmixtureâsetting.
NOTE â When leaned, engine roughness is caused by mis-firing due to a lean fuel/air mixture which will not support combustion. Roughness is eliminated by enriching slightly until the engine is smooth.
5.âTheâexhaustâgasâtemperatureâ(EGT)âoffersâlittleâimprovementâinâleaningâtheâfloat-typeâcarburetorâoverâtheâproceduresâoutlinedâaboveâbecauseâofâimperfectâmixtureâdistribution.âHowever,âifâtheâEGTâprobeâisâinstalled,âleanâtheâmixtureâtoâ100ËâFâonâtheârichâsideâofâpeakâEGTâforâbestâpowerâoperation.âForâbestâeconomyâcruise,âoperateâatâpeakâEGT.âIfâroughnessâisâencountered,âenrichâtheâmixtureâslightlyâforâsmoothâengineâoperation.
6.âWhenâinstallingâanâEGTâprobe,âtheâprobeâmustâbeâinstalledâinâtheâleanestâcylinder.âContactâtheâairframeâorâkitâmanufacturerâforâtheâcorrectâlocation.âInâexperimentalâorâcustomâapplications,âmultipleâprobeâinstrumentationâisârequired,âandâseveralâpowerâsettingsâshouldâbeâcheckedâ inâorderâ toâdetermineâ theâ leanestââcylinderâforâtheâspecificâapplication.
7.âDuringânormalâoperation,âmaintainâtheâfollowingârecommendedâtemperatureâlimits:
a.âCylinderâheadâtemperatureâââlimitâlistedâinâtheâLycomingâOperatorâsâManual.
b.â Oilâ temperatureâ ââ limitâ listedâ inâ theâ LycomingââOperatorâsâManual.
8. For maximum service life, maintain the following rec-ommended limits for continuous cruise operation:
a. Engine power settingâââ65% of rated or less.
b. Cylinder head temperatures ââ400Ë F. or below.
c. Oil temperature ââ165Ë F. ââ220Ë F.
C. LEANING THE TURBOCHARGED LYCOMING POWER PLANT
1.âTheâcylinderâheadâtemperatureâ(CHT)âandâturbineâinletâtem-peratureâ(TIT)âgagesâareârequiredâinstrumentsâforâleaningâwithâturbochargingâbyâLycoming.âEGTâprobesâonâindividualâcylindersâshouldânotâbeâusedâforâleaning.
2.âDuringâmanualâ leaning,â theâmaximumâallowableâTITâforâaâparticularâengineâmustânotâbeâexceeded.âCheckâtheâPOH/AFMâorâtheâLycomingâOperatorâsâManualâtoâdetermineâtheseâtemperaturesâandâfuel-flowâlimits.
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3.âMaintainingâengineâtemperatureâlimitsâmayârequireâadjust-mentsâtoâfuelâflow,âcowlâflapsâorâairspeedâforâcooling.
4.âAllânormalâtakeoffs,âwithâturbochargedâpowerâplants,âmustâbeâatâfull-richâmixtureâregardlessâofâairportâelevation.
5.âIfâmanualâleaningâofâtheâmixtureâisâpermittedâatâtakeoff,âclimbâpowerâorâhigh-performanceâcruise,â itâwillâbeâspecifiedâinâ theâPOH/AFMâandâwillâlistârequiredârangesâforâfuelâflow,âpowerâset-tingsâandâtemperatureâlimitations.
6. Leaning to best economy mixture.
a.âSetâmanifoldâpressureâandâRPMâforâtheâdesiredâcruiseâpowerâsettingâperâtheâaircraftâPOH/AFM.
b.âLeanâslowlyâinâsmallâsteps,âwhileâmonitoringâinstrumen-tation,âtoâpeakâTITâorâmaximumâallowableâTIT,âwhicheverâoccursâfirst.
7. Leaning to best power mixture.
Beforeâleaningâtoâbestâpowerâmixture,âitâisânecessaryâtoâestablishâaâTITâreferenceâpoint.âThisâisâaccomplishedâasâfollows:
a.âSetâmanifoldâpressureâandâRPMâforâtheâhighestâcruiseâpowerâsettingâwhereâleaningâtoâbestâeconomyâisâpermittedâperâtheâaircraftâPOH/AFM.
b.â Leanâ slowlyâ inâ smallâ stepsâ untilâ peakâ TITâ orâ max-imumâ allowableâTITâ isâ reached.â Recordâ peakâTITâ asâ aââreferenceâpoint.
c.âDeductâ125ËâF.âfromâthisâreference,âandâthusâestablishâtheâTITâtemperatureâforâbestâpower-mixtureâoperation.
d.âReturnâtheâmixtureâtoâfull-rich,âandâadjustâmanifoldâpres-sureâandâRPMâforâtheâdesiredâcruiseâconditions.
e.â Leanâ mixtureâ toâ theâ TITâ temperatureâ forâ bestââpower/mixtureâoperationâestablishedâinâstepâc.
8.âDuringânormalâoperation,âmaintainâtheâfollowingâlimits:
a.âEngineâpowerâsettingâââratingâ listedâ inâ theâLycomingâOperatorâsâManual.
b.âCylinderâheadâtemperatureâââlimitâlistedâinâtheâLycomingâOperatorâsâManual.
c.âOilâtemperatureâââlimitâlistedâinâtheâLycomingâOperatorâsâManual.
d.âTurbineâinletâtemperatureâââlimitâlistedâinâtheâLycomingâOperatorâsâManual.
9. For maximum service life, maintain the following recom-mended limits for continuous operation.
a.âEngineâpowerâsettingâââ65%âofâratedâorâless.
b.âCylinderâheadâtemperaturesâââ400ËâF.âorâbelow.
c.âOilâtemperatureâââ165ËâF.âââ220ËâF.
d.âTurbineâinletâtemperatureâââmaintainâ100ËâF.âonârichâsideâofâmaximumâallowable.â
D. LEANING THE SUPERCHARGED LYCOMING POWER PLANTS
1.â Allâ takeoffsâ withâ superchargedâ powerâ plantsâ mustâ beâ atââfull-richâmixtureâregardlessâofâtheâairportâelevation.
2.âIfâmanualâleaningâofâtheâmixtureâisâpermittedâatâclimbâpower,âitâwillâbeâspecifiedâinâtheâPOH/AFMâandâwillâlistârequiredârangesâforâfuelâflow,âpowerâsettingsâandâtemperatureâlimitations.
3.âRecommendedâstandardâcruiseâpowerâforâ theâsuperchargedâengineâisâ65%.âAtâ65%âpowerâorâless,âthisâtypeâofâengineâmayâbeâleanedâasâdesiredâasâlongâasâtheâengineâoperatesâsmoothly,âandâtemperaturesâandâpressuresâareâwithinâmanufacturerâsâprescribedâlimits.
4.âTheâexhaustâgasâtemperatureâ(EGT)âgageâisâaâhelpfulâinstru-mentâforâleaningâtheâsuperchargedâengineâatâcruiseâpowerâwithâaâmanualâmixtureâcontrol.
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This Article Now Incorporates Material From âA Special On Fuel Managementâ Which Has Been Eliminated
VariousâLycomingâFlyerâarticlesâhaveâemphasizedâproperâleaningâatâtheâmanufacturerâsârecommendedâcruiseâpower.âBeforeâdelvingâintoâtheâsavingsâtoâbeâobtainedâbyâleaning,âitâmayâbeâappropriateâtoâagainâreviewâthoseâfactorsâthatâaffectâleaningâatâcruise.
First,âweâmustâknowâthatâcruiseâpowerâforâLycomingânormallyâaspiratedâenginesâisâgenerallyâconsideredâtoâbeâ55%âtoâ75%âofâtheâmaximumâpowerâforâwhichâtheâengineâisârated.âAtâtheseâpowerâset-tings,âtheâengineâmay be leaned at any altitude.âThereâhasâbeenâconfusionâaboutâtheâreferenceâtoânotâleaningâbelowâ5000-feetâden-sityâaltitude.âRememberâthatâthisâreferenceâonlyâappliesâtoâthoseâpowerâsettingsâaboveâtheâcruiseârangeâââthoseânormallyâusedâforâtakeoffâandâclimb.âOnceâcruiseâpowerâhasâbeenâset,âleaningâtoâbestâeconomyâshouldâbeâstandardâprocedureâasâdamageâtoâtheâengineâwillânotâoccurâfromâleaningâatâcruiseâpowerâsettings.
Inâ thisâarticle,âweâwillâexpandâourâdiscussionâofâ leaningâandâexplainâ(1)âhowâitâsavesâdollars,âandâ(2)âhowâitâaidsâsafeâflight.âInâaâpracticalâapproachâtoâourâsubject,âletâsâlookâcloselyâatâtheâchartâprintedâbelow:
Leaning the normally aspirated, direct-drive Lycoming engine at cruise vs. full rich at 4,000-feet density altitude, 75% power.
â EngineâModelâ AirplaneâModel
300 HP Piper Cherokee 300
Fullâ Best Economy Hours Hours
â Richâ (PeakâEGT)â Richâ Lean
â 19+âgals.â 15.6âgals.â 4.2âhrs.â 5.1âhrs.ââ
â EngineâModelâ AirplaneâModel
250 HP Piper Aztec
Full Best Economy Hours Hours
â Richâ (PeakâEGT)â Richâ Lean
â 16.2âgals.â 13.6âgals.â 4.3âhrs.â 5.1âhrs.ââ
â EngineâModelâ AirplaneâModel
180 HP Cessna Cardinal
Full Best Economy Hours Hours
â Richâ (PeakâEGT)â Richââ Lean
â 11.9âgalsâ .9.7âgals.â 4.1âhrs.â 5.1âhrs.
Toâputâtheâcostâofâoperatingâatâaâfull-richâmixtureâsettingâduringâcruiseâflightâintoâperspective,âletâusâassumeâthatâtheâcostâofâavia-tionâgasolineâisâ$4.00âperâgallon.âInâeachâcase,âitâisâonlyâneces-saryâtoâmultiplyâtheâdifferenceâinâgallonsâburnedâatââFullâRichââvs.ââBestâEconomyââtimesâtheâfuelâprice.âTheânumberâobtainedâwillâbeâtheâamountâsavedâeachâhourâofâflightâbyâoperatingâatâbestâeconomyâduringâcruise.âUsingâtheâexamplesâabove,âtheseâareâtheâsavingsâforâeachâofâthoseâaircraftâandâengines:
Aircraft Fuel-burn difference Fuel-cost savings
Cherokeeâ300â 3.4âgallonsâXâ$4.00â =â$13.60âperâhr.
Aztecâ 5.2âgallonsâXâ$4.00â =â$20.80âperâhr.â
Cardinalâ 2.2âgallonsâXâ$4.00â =â$8.80âperâhr.
Whileâweâareâonâaâdiscussionâofâunnecessaryâcostsâofâoperation,âanotherâ importantâ factorâ isâ theâdamageâoftenâdoneâ toâengineâaccessoriesâbyâoperatingâatâfullârichâatâcruiseâpower.âEnginesâoperatingâatâ fullâ richâ inâcruiseâ tendâ toâbeârough,âresultingâ inâshakingâengineâaccessoriesâandâengineâmounts,âtherebyâconsid-erablyâreducingâtheirâlifeâandâoftenâresultingâinâexpensiveâearlyâreplacement.âAâproperlyâleanedâengineâatâcruiseâpowerâisâaâsmoothâengineâââandâwillâsaveâmoney.
InâearlierâissuesâofâtheâFlyer,âweâhaveâbeenâtellingâallâconcernedâaboutâtheâbenefitsâtoâtheâsparkâplugâofâproperâleaningâatâcruiseâpower.âThatâ informationâcanâbeâ repeatedâ inâ thisâdiscussion,âbecauseâitâhelpsâtoâillustrateâourâpointâonâsavingâdollars.âProperâleaningâatâcruiseâhelpsâpreventâsparkâplugâfouling.âTheâmainte-nanceâcostâtoâremoveâandâcleanâsparkâplugsâcanâbeâreducedâbyâgoodâleaningâtechniques.âFrequentâcleaningâofâsparkâplugsâreducesâtheirâ lifeâandârequiresâearlyâreplacement.âFurthermore,âbadlyâfouledâsparkâplugsâcouldâalsoâbecomeâaâsafety-of-flightâproblem.
Forâaâveryâinterestingâsafety-of-flightâitem,âletâsâlookâatâtheâchartâagain.âNoticeâtheâdifferenceâinâhoursâofâflightâatâfullârichâvs.âleanâatâcruise.âInâtheâillustrationâofâtheâ180âHPâengine,âthereâisâoneâfullâadditionalâhourâofâflightâwhenâproperlyâleaned.âTheâotherâenginesâprovideânearlyâanâadditionalâhourâofâflightâtimeâwhenâleanedâtoâbestâeconomyâduringâcruise.âEfficientâfuelâmanagementâisâaâveryârealââsafety-ofâ-flightâfact.
Theseâareâsomeâofâtheâmoreâimportantâfactsâthatâillustrateâhowâproperâleaningâatâcruiseâpowerâaidsâsafeâflightâââandâsavesâdollars.
Someâpilotsâhaveâdemonstratedâaâlackâofâunderstandingâwithâregardâtoâtheâoperationâofâtheâdirect-drive,âfixed-pitch,ânormallyâaspiratedâpowerâplants.âWhenâaâpowerâchartâisâprovided,âitâwillâindicateâthatâasâtheâairplaneâisâflownâatâdifferentâaltitudesâaboveâseaâlevel,âitâisâneces-saryâtoâuseâaâhigherâRPMâforâadequateâcruiseâperformanceâwithâanâincreaseâinâaltitude.âAâtypicalâexampleâmightâbeâtheâO-360,â180âHPâLycomingâpowerâplant.âTheâpowerâchartâbyâtheâairframeâmanufac-turerâforâthisâfixed-landingâgearâaircraftâlistsâ75%âpowerâatâ7,500âfeetâatâ2675âRPMâ(noâmanifoldâpressureâgageâinâtheirâairplane).âTheâpilotâ
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whoâdoesânotâunderstandâtheâprinciplesâofâoperationâinâtheâthinâairâatâaltitudeâmayâobserveâthatâred-lineâtakeoffâRPMâisâ2700âRPM,âandâisâthenâreluctantâtoâleanâeitherâforâcruiseâorâclimbâdespiteâtheâaltitudeâbecauseâheâisâpullingâalmostâtheâsameâRPMâasâatâtakeoff.
However,âtheâpilotâcanâandâshouldâleanâtheâengineâatâtheseâalti-tudesâdespiteâtheâhighâRPM,âforâtheâhorsepowerâisâdownâtoâ75%âbecauseâofâtheâthinnerâair.âOnâtheâotherâhand,âwithâanyâdirect-driveânormallyâaspiratedâLycomingâengine,â theâpilotâcanâandâshouldâleanâtheâmixtureâatâanyâaltitudeâasâlongâasâtheâaircraftâisâinâcruiseâconfigurationâatâ75%âpowerâorâless.
Letâsâ lookâatâ theâairframeâmanufacturerâsâpowerâchartâforâ theââO-360,â180âHPâengine,âandâobserveâ theâgradualâ increaseâ inâRPMârequiredâwithâ theâ increaseâ inâaltitude,âbutâmaintainingâ75%âforâcruiseâatâeachâaltitude.âWhatâtheâchartâwillânotâshowâhereâisâthatâforâflightâaboveâ7500âfeet,âitâisânotâpossibleâtoâachieveâ75%âpowerâwithâaânormallyâaspiratedâengineâ (meaningânotââturbochargedâorâsupercharged).
POWER CHART
Percent Endurance on
Altitude RPM of H. P. 59 gals. fuel
â 2500â 2550ââ75%â 4.8âhours
â 3500â 2575ââ75%ââ 4.8âhours
â 4500â 2600ââ75%â 4.8âhours
â 5500â 2625ââ75%â 4.8âhours
â 6500â 2650ââ75%â 4.8âhours
â 7500â 2675ââ75%â 4.8âhours
BecauseâthereâareâaâwideâvarietyâofâLycomingâenginesâinâopera-tion,âtheâparagraphsâbelowâmayâbeâhelpfulâinâunderstandingâtheâdifferentâmodesâofâoperationârequiredâwhenâoperatingâeachâtypeâatâtakeoffâandâclimbâpowerâsettings.âTheâPilotâsâOperatingâHandbookâforâtheâaircraftâinâwhichâtheâenginesâareâinstalledâshouldâbeâtheâfinalâauthorityâasâtoâhowâtheâengineâshouldâbeâoperated.
DIRECT-DRIVE ENGINES
Mostâ normallyâ aspiratedâ enginesâ areâ ratedâ atâ fullâ powerâforâ takeoffâ andâ climbâ indefinitely,â providedâ engineâ tem-peraturesâandâpressuresâareâwithinâ theâgreenâarcâareaâofâ theâengineâ instruments.â Extraâ fuel,â sensibleâ airspeedâ andâ cowlâflaps,â ifâ available,â areâ allâ helpfulâ inâ keepingâ cylinderâ headâtemperaturesâwithinâdesiredâ limitsâduringâ takeoffâorâ climb.âClimbârequirementsâmayâvary;âforâexample,âonâaâwarmâdayâwithâtheâairplaneâcloseâ toâgrossâweight,âandâaâdirect-driveâengineâwithâaâfixed-pitchâprop,â theâpilotâwillâneedâfullâ throttleâallâ theâwayâ toâcruiseâaltitude.âTheâsameâairplaneâonâaâcoldâdayâandââlightlyâ-loadedâmayânotârequireâfullâpowerâforâclimb.âAfterâfullââ
throttleâatâtakeoff,âtheâpilotâmayâwantâtoâreduceâpowerâ100âorâ200âRPMâandâstillânotâseeâperformanceâsuffer.
Thoseâdirect-driveânormallyâaspiratedâenginesâwithâaâpropâgov-ernorâareâalsoâratedâindefinitelyâatâfullâpower,âandâtheâmanualsâallârecommendâfullâpowerâforâtakeoff,âbutâspecifyâaâsmallâreductionâinâpower,âgenerallyâtoâ85%âpowerâclimb.âStudyâtheâspecificâairplaneâPilotâsâOperatingâHandbookâforâdetailedâpowerâsettings.
GEARED, TURBOCHARGED AND SUPERCHARGED ENGINES
Turningâtoâtheâmoreâcomplexâpowerâplantsâsuchâasâtheâgeared,âtur-bochargedâandâsuperchargedâmodels,âtheâmanualsâareâquiteâspecificâinâtheirâdescriptionâofâtakeoffâandâclimbâtechniques.âOurâgearedâandâsuperchargedâpowerâplantsâhaveâaâlimitâofâfiveâminutesâatâtakeoffâpower.âHowever,âitâisâadvisableâtoâthrottleâpowerâtoâtheârecommendedâclimbâpowerâasâstipulatedâinâtheâmanualâasâsoonâasâtakeoffâobstruc-tionsâhaveâbeenâclearedâandâproperâairspeedâattained.
TheâturbochargedâLycomingsâ(includingâtheâTIGO-541-Eâseries)âdoânotâhaveâaâfive-minuteâlimitâatâtakeoffâpower.âHowever,âtheâmanualâclearlyâstipulatesâaâreductionâtoâaâproperâclimbâpowerâwhenâclearâofâobstacles,âwhenâclimbâspeedâhasâbeenâestablished,âandâwhenâcylinderâhead,âoilâandâturbineâinletâtemperaturesâareâwithinâlimits.âDueâtoâtheâmoreâcompleteâengineâinstrumentationâinâtheâairplane,âtheâmanualsâallowâsomeâleaningâatâclimb,âbutâonlyâwithâtheâengineâinstrumentsâreadingâwithinâspecifiedâlimitsâlistedâinâtheâairplaneâmanual.
Theâmoreâcomplexâpowerâplantsâ (geared,â superchargedâandâturbocharged)âdemandâsmooth,âcarefulâoperationâofâtheâthrottleâatâallâ times,âparticularlyâatâhighâpower,âbutâespeciallyâwhenââenginesâandâoilâareânotâupâ toânormalâoperatingâ temperaturesâsuchâ asâ forâ theâ initialâ takeoff.â Overboostâ orâ erraticâ engineâoperationâwillâ resultâ fromâabruptâmovementsâofâ theâ throttle.ââAllâsuperchargedâandâturbochargedâenginesâmustâuseâfull-richâmixtureâforâallâtakeoffsâregardlessâofâfieldâelevation.
Sinceâsoâmanyâoperatorsâofâourâenginesâfrequentlyâaskâusâaboutâtheâuseâofâanâexhaustâgasâ temperatureâwithâourâpowerâplants,âperhapsâweâshouldâexamineâtheâsystemâandâseeâhowâitârelatesâtoâfuelâmanagement.
OneâofâtheâbetterâpublicationsâdescribingâtheâEGTâthatâweâhaveâseenâwasâputâoutâbyâAlcorâInc.,âP.âO.âBoxâ792222âofâSanâAntonio,âTexasâ78279-2222.âThisâexcellentâbookletâ isâ titled,ââEGTâandâCombustionâAnalysisâinâaâNutshell,ââandâisâavailableâfreeâonâlineâatâwww.alcorinc.com.
AnâEGTâsystemâisânotâaâcomplexâorâexpensiveâitemâtoâinstall.âTheâmoreâeconomicalâkitâconsistsâbasicallyâofâtheâgage,âwiringâandâ probeâ (seeâ illustration).âTheâ systemâ generatesâ itsâ ownââelectricityâtoâoperateâtheâinstrument.
L y c o m i n g F l y e r ďż˝ ďż˝
INSTALLATION INFORMATION
Theâmechanicâmustâcarefullyâfollowâtheâinstallationâinstructionsâconcerningâplacingâtheâprobeâinâtheâexhaustâstack.âIfâitâisâcloserâthanâ1â½â"âtoâtheâcylinderâhead,âprobeâlifeâwillâbeâlimited,âorâifâtooâfarâdownâtowardâtheâendâofâtheâexhaustâstack,âtheâresponseâonâtheâgageâwillâbeâslow.âShouldâthereâbeâdoubtâconcerningâinâwhichâstackâaâsingleâprobeâisâtoâbeâinstalled,âthatâinformationâmayâbeâavailableâfromâtheâairframeâdealerâsâserviceâdepartment.âTheâoperatorâmightâdesireâtheâmoreâexpensiveâinstallationâofâprobesâinâallâcylinders,âthereforeâtheâaccompanyingâgageâwillâgenerallyâhaveâaâselectorâswitchâforâindividualâreadingsâonâallâcylinderâexhaustâstacks.âAgain,âitâisâmostâimportantâthatâtheâinstallationâinstructionsâareâcarefullyâfollowedâinâorderâtoâgetâreliableâreadings.
INTERPRETING THE SYSTEM
Mostâofâ theâEGTâmanufacturersâhaveâstandardizedâonâgageââincrementâmarkingsâofâ25ËâFâ(seeâillustration).âAâfewâEGTâmanu-facturersâwillâgoâfurtherâandâshowâtheâtemperatureârangeâonâtheâgageâasâ1200ËâFâtoâ1700ËâF.
Theâsimpleâgageâshownâinâtheâillustrationâisâquiteâsatisfactoryâforâtheâlessâcomplexâengines.âAnâadvantageâofâtheâEGTâoverâtheâcylinderâheadâtemperatureâgageâisâoneâofâanâalmostâimmediateâresponseâtoâmanualâmovementâofâtheâmixtureâcontrol,âasâlongâasâitâisânotâaârapidâmovementâofâtheâcontrol.âRememberâthatâtheâpeakâorâpointâofâmaximumâneedleâdeflectionâofâtheâEGTâgageâisâtheâbasicâreferenceâforâfuelâmanagement.âIfâanâoperatorâhasâexperimentedâwithâtheâEGTâatâtheâengineâmanufacturerâsârecommendedâcruiseâpower,âheâobservesâthatâgradualâleaningâdoesâresultâinâpeakâEGT.âTheâlocationâofâpeakâEGTâonâtheâgageâwillâalsoâvaryâwithâdif-ferentâpowerâsettings,âchangesâinâaltitudeâandâchangeâinâambientâtemperature.
FromâpeakâEGT,âeitherâincreasingâorâdecreasingâtheâfuelâflowâcausesâaâdecreaseâinâEGT.âWhenâricherâthanâpeakâEGTâcoolingâoccursâbecauseâthereâisâexcessâfuel,âandâwhenâleanerâthanâpeak,âcoolingâoccursâbecauseâthereâisâexcessâair.
PeakâEGTâwithâaâ float-typeâcarburetedâengineâ isâ frequentlyââaâvagueâpointâbecauseâofâ lessâefficientâdistributionâ(thanâfuelâinjection)â toâ theâindividualâcylindersâbyâthisâ typeâofâmeteringââdevice.âAsâaâresult,âfloat-typeâcarburetedâenginesâtendâtoâoperateâ
smootherâatâ+25Ëâtoâ+50ËâFâonâtheârichâsideâofâpeakâEGT.âWhereas,âtheâfuel-injectedâenginesâatâ250âHPâandâhigherâwillâprovideâaâmoreâpreciseâpeak,âandâthereforeâtheâEGTâsystemâisâlikewiseâaâmoreâpreciseâmethodâofâfuelâmanagementâwithâfuelâinjection.
DEFINITION OF PEAK EGT
AâsimpleâdefinitionâofâpeakâEGTâisâgivenâusâbyâengineeringâasâtheâchemicallyâcorrectâmixtureâofâfuelâandâairâwhichâgivesâ100%âutilizationâofâallâ theâfuelâandâallâ theâair.âRemember,âweâsaidâearlierâ thatâatâmixturesâleanerâthanâpeakâEGT,âthereâisâexcessâair,âandâatâricherâmixtures,âexcessâfuel.âOperationâatâpeakâEGT,âparticularlyâonâlongâflights,âcanâbeâanâadvantageânotâonlyâforâpurposesâofâincreasedârange,âbutâthereâisâlessâlikelihoodâofâsparkâplugâfoulingâasâwell.
Donâtâbeâsurprisedâ toâseeâvariationsâ inâ temperatureâbetweenâindividualâcylindersâwhereâthereâisâaâprobeâforâeveryâcylinder.âItâ isâfairlyâtypicalâtoâseeâanâaverageâ100ËâFâvariationâwithâfuelâinjection,âandâasâmuchâasâ200ËâFâvariationâwithâaâ float-typeâcarburetor.âTheâlatterâ(carburetor)âvariationâtendsâtoâbeâgreaterâbecauseâfuel/airâdistributionâisânotâasâgoodâasâwithâfuelâinjec-tion.âInâcoldâoutsideâairâtemperatureâflightâconditions,âtheâmix-tureâdistributionâisâpoorerâforâbothâfuel-injectedâandâcarburetedâengines.âHowever,âwithâtheâfloat-typeâcarburetorâoperatingâinâbelow-freezingâambientâ temperatures,â theâfuel/airâdistributionâisâdefinitelyâworsened,âresultingâinânoticeableâvariationsâinâtem-peratureâbetweenâindividualâexhaustâstacks.
Itâ isâalsoâimportantâtoâunderstandâthatâleaningâtoâroughnessâatâtheâengineâmanufacturerâsârecommendedâcruiseâpowerâisânotâanâindicationâofâdetonation,âbutâindicatesânormalâcharacteristicsâofâdistributionâtoâtheâindividualâcylinders.âTheâroughnessâindicatesâthatâtheâleanestâcylinderâhasâbecomeâsoâlean,âitâisâbeginningâtoâmiss.âThisâisâtypicalâofâanâengineâwithâaâfloat-typeâcarburetor.âDamage,âtoâanâengineâfromâleaningâdoesânotâoccurâatâtheâmanu-facturerâsârecommendedâcruiseâpower,âbutâtakesâplaceâatâhigherâthanâcruiseâpower.
Asâfarâasâtheâpilotâ isâconcerned,âoperatingâonâtheâleanâsideâofâpeakâEGTâcanâonlyâbeâaccomplishedâwithâfuel-injectedâenginesâofâatâleastâ250âHPâorâhigherâbecauseâtheâfuelâflowsâinâtheâlowerâhorsepowerâenginesâareâsoâsmall.âItâisnâtâpossibleâwithâfloat-typeâcarburetorsâbecauseâofâtheâfuel/airâdistributionâproblem.âInâanyâcase,âleaning past the peak is not recommended.
LIMITATIONS OF POWER AT PEAK EGT
Lycomingâ allowsâ leaningâ toâ peakâ EGTâ atâ 75%â powerâ andâbelowâ onâ ourâ direct-driveâ normallyâ aspiratedâ engines.â Weâlimitâ operationâ atâ peakâ EGTâ onâ ourâ geared,â superchargedââpowerâplantsâatâ65%âpowerâorâbelow.âWithâLycomingâturbochargedâengines,âwhereâtheâEGTâgageâisâusedâtoâinterpretâturbineâinletâtem-peratureâ(TIT),âtheâmaximumâallowableâTITâspecifiedâinâtheâPOHâshouldânotâbeâexceededâwhenâattemptingâtoâfindâaâpeakâtemperatureâbyâmanualâleaning.âWhereâaâcylinderâheadâtemperatureâisâalsoâavail-able,âtheâoperatorâshouldâalwaysâcross-checkâtheâheadâtemperatureâasâaâroutineâprocedureâwhenâleaning,âandârememberâthatâwheneverâCHTâreachesâtheâmaximumâbeforeâreachingâpeakâEGT,âthenâCHTâratherâthanâEGTâshouldâdictateâtheâlimitâofâallowableâleaning.â
�� L y c o m i n g F l y e r
BEST ECONOMY MIXTURE
BestâeconomyâmixtureâasâitârelatesâtoâtheâEGTâsystemâbeginsâatâpeak.âForâallâpracticalâpurposesâwithâLycomingâengines,âpeakâEGTâisârightâatâtheâedgeâofâbestâeconomyâmixture,âandâisâourâonlyâpracticalâpointâofâreferenceâinâtheâbestâeconomyâmixtureârange.âAtâtheâmanufacturerâsârecommendedâcruiseâpower,âpeakâEGTâcausesâaâslightâlossâofâhorsepowerâusuallyâreflectedâinâtwoâorâthreeâmilesâperâhourâofâairspeed.âIfâtheâpilotâattemptsâtoâgoâleanerâthanâpeakâEGTâ(withâfuelâinjectionâonly),âtheâpowerâdecreasesârapidlyâasâfuelâflowâdecreases.
BEST POWER MIXTURE
Bestâpowerâmixture,âorâsometimesâ termedâmaximumâpowerârange,âasâdepictedâonâ theâEGTâgage,â isâ inâ theâ rangeâofâplusââ100ËâFâonâtheârichâsideâofâpeak.âBestâpowerâmixtureâwillâprovideâfastestâ indicatedâairspeedâforâaâcruiseâpowerâsetting,âalthoughâitâisâgenerallyânotâconsideredâaâpracticalâeconomicâmixtureâforâcruiseâpurposes.âHowever,âbestâpowerâmixtureâgenerallyâprovidesâaâsafeâamountâofâfuelâforâaâpowerâsettingâhigherâthanâtheâengineâmanufacturerâsâ recommendedâcruise,âexceptâ thatâneededâforâtakeoffâpower.
Again,âweâ repeatâ thatâmaximumâ leaningâ (peakâEGT)âdoesânotâdamageâanâengineâatâ theâengineâmanufacturerâsâ recom-mendedâcruiseâpower.âDamageâisâcausedâbyâmaximumâleaningâatâhigherâthanârecommendedâcruiseâpowerâwhereâtheâmanualsâdoânotâspellâitâoutâorâallowâit,âandâwhenâtheâaircraftâdoesânotâhaveâaâcompleteâsetâofâreliableâengineâinstrumentsâtoâprotectâtheâpowerâplants.âExcessiveâ leaningâunderâ theâ latterâ highâpowerâconditionsâcanâcauseâdetonationâand/orâpreignitionâandââpossibleâengineâfailure.
IfâweâwereâtoâsumâupâtheâmajorâadvantagesâofâanâEGTâtoâtheâoperator,âtheyâareâasâfollows:
1.âSavesâfuelâââanâeconomyâaid.
2.ââAidsâproperâmixtureâcontrolâââmoreâpreciseâfuelââmanagement.
3.âHelpsâincreaseârange.
4.âDetectsâsomeâtypesâofâengineâtroubles.
5.âAidsâpeakâengineâperformanceâatâcruise.
6.âHelpsâpreventâsparkâplugâfouling.
7.âFitsâanyâGeneralâAviationâpistonâaircraftâengine.
AlthoughâuseâofâtheâEGTâhasâtheâadvantagesâlistedâabove,âfromâaâpilotâsâpointâofâview,âthereâareâalsoâsomeâpossibleâdisadvantages.âPoorâmixtureâdistributionâtoâtheâcylindersâ(particularlyâinâcar-buretedâengines)âisâtheâprimaryâreasonâforâtheseâdisadvantages.âTheâEGTâprobeâisâtoâbeâinstalledâinâtheâleanestâcylinder,âbutâthisâchangesâwithâaltitudeâandâpowerâsetting,â thereforeâmakingâ itâveryâdifficult,âorâperhapsâimpossible,âtoâchooseâaâbestâcylinderâforâprobeâinstallation.âWithoutâanâEGTâinstallation,âtheâpilotâcanâeasilyâleanâusingâtheâleanestâcylinderâofâaâcarburetedâengineâbyâsimplyâleaningâtoâfindâengineâroughnessâfromâtheâfirstâ indica-tionâofââleanâmisfire,ââandâthenâricheningâtheâmixtureâtoâsmoothâengineâoperation.
Theâpilotâmustâalsoârealizeâthatâevenâwithâaâfuel-injectedâengine,âthereâwillâbeâvariationsâinâfuelâflow.âUtilizingâanâEGTâwithâprobesâinâeachâexhaustâstackâ(sometimesâcalledâaâcombustionâanalyzer)âwillâshowâtheseâvariations.âTryingâtoâinterpretâtheâvariationsâinâtemperatureâshownâforâeachâcylinderâhasâcausedâsomeâpilotsâtoâsuspectâproblemsâwithâtheirâengineâwhenâitâhasâbeenâoperatingânormally.âSometimesâtooâmuchâknowledgeâcanâbeâaâproblem.
Finally,â theâEGTâsystemâmustâbeâ inâperfectâworkingâorderâ toâgiveâaccurateâreadings.âTheâprobesâinâtheâexhaustâsystemâwillâdeteriorateâwithâageâandâcontinuousâuse.âThisâoftenâcausesâtheâgageâtoâreadâaâ temperatureâthatâ isânotâaccurate,âandâthereforeâaâpeakâreadingâthatâisânotâreachedâsoonâenough.âThisâresultsâinâoverleaningâtoâtheâleanâsideâofâpeakâwhereâoperationâisânotârecom-mended.âFrequentâmaintenanceâtoâensureâthatâtemperatureâprobesâareâinâgoodâconditionâwillâreduceâtheâpossibilityâofâinaccuracies,âbutâtheâpilotâcannotâdetermineâtheâaccuracyâofâthisâratherâcriticalâreadingâduringâoperation.
Theâexhaustâgasâtemperatureâsystem,âwhenâwellâmaintainedâandâthoroughlyâunderstood,âcanâbeâanâaidâinâproperâleaningâatâcruiseâpowerâwithâfuel-injectedâpowerâplants.âItâisâhopedâthatâthisâinfor-mationâwillâhelpâtheâoperatorsâofâLycomingâenginesâachieveâtheâbestâpossibleâengineâefficiencyâthroughâuseâofâtheâEGTâsystem.
â
Pilotsâfrequentlyâaskâusâforâinformationâandâguidanceâconcerningâlandingsâandâtakeoffsâfromâhigh-elevationâairports.âOurâreferenceâpointâinâthisâdiscussionâwillâbeâbasedâonâdensityâaltitude.âTheâdiscussionâalsoârequiresâ thatâweâtreatâseparatelyâoperationâofânormallyâaspirated,âturbochargedâandâsuperchargedâenginesâatâhigh-elevationâairports.
NORMALLY ASPIRATED
Theânormallyâaspiratedâengineâperformsâandâreactsâtoâdensityâaltitude.âAsâanâexample,â thisâ typeâofâpowerâplantâatâ takeoffâfromâanâairportâwithâanâ indicatedâaltitudeâofâ3,000âfeet,âbutâwithâanâambientâ temperatureâatâ85ËâF,âwouldâhaveâaâdensityâaltitudeâofâmoreâthanâ5,000âfeet.âTheâengineâwouldâlackâsomeâ20âtoâ25%âofâitsâpowerâandâalsoâprobablyârunâroughâbecauseâofâaârichâmixtureâonâtheâgroundâatâfullârich.âTherefore,âtheâtypicalânormallyâaspiratedâdirect-driveâengineârequiresâtheâmixtureâbeâleanedâonâtheâgroundâforâefficientâ takeoffâperformanceâwhereâairportsâareâ5,000âfeetâ(densityâaltitude)âorâhigher.âTheâover-richâconditionâisâsomethingâtheâpilotâcanâcompensateâforâbyâleaning.âHowever,âtheâhigher-densityâaltitudeâwithâitsâthinnerâairâcannotâbeâcompensatedâforâwithâaânormallyâaspiratedâengineâunlessâaâsuperchargerâorâturbochargerâunitâisâaddedâtoâtheâpowerâplant.ââThus,âatâdensityâaltitudesâofâ5,000â-â6,000âfeet,âtheâpilotâofâaânor-mallyâaspiratedâengineâhasâavailableâtoâhimâapproximatelyâ75%âofâtheâengineâpower,âandâmustâplanâhisâtakeoffâaccordinglyâafterâsettingâtheâmixture.
L y c o m i n g F l y e r ��
PROCEDURE FOR LEANING
1.âTheâfixed-pitchâpropellerâââleanâtoâmaximumâRPMâatâfullâthrottleâpriorâ toâ takeoffâwhereâairportsâareâ5,000âfeetâdensityâaltitudeâorâhigher.âLimitâoperationâatâfullâthrottleâonâtheâgroundâtoâaâminimumâtime.
2.âTheâdirect-driveânormallyâaspiratedâengineâwithâaâpropâgov-ernorâbutâwithoutâaâfuel-flowâgage,âsetâthrottleâatâfullâpowerâandâleanâmixtureâatâmaximumâRPMâwithâsmoothâoperationâofâtheâengineâasâaâdecidingâfactor.
3.âWithâfuelâinjection,âifâtheâpowerâplantâhasâaâmarkedâfuel-flowâgage,â thenâsetâmixtureâinâaccordanceâwithâinstructionsâonâtheâfuel-flowâgageâand/orâ inâaccordanceâwithâtheâairplaneâPilotâsâOperatingâHandbook.
4.âPressureâcarburetorâââAllâLycomingâenginesâequippedâwithâBendixâPSâcarburetorsâhaveâanâautomaticâmixtureâcontrolâwhichâdoesânotârequireâleaningâforâtakeoff.
5.âTurbochargedâandâsuperchargedâenginesâââAllâtakeoffsâmustâbeâatâfull-richâmixture,âbecauseâtheâengineâisâbroughtâbackâtoâseaâlevelâhorsepowerâwhichâdoesânotâpermitâleaning.
DESCENT
Regardlessâofâtheâfieldâelevationâwhereâtheâpilotâintendsâtoâland,âtheâdescentâfromâcruiseâaltitudeâtoâtrafficâpatternâaltitudeâshouldâbeâmadeâwithâtheâengineâleanedâforâsmoothâengineâoperation.âLowâelevationâfieldsâ(belowâ5,000âfeetâdensityâaltitude)âwillârequireâthatâ theâmixtureâbeâmovedâtoâfullârichâinâ theââbeforeâ landingâchecklist.ââLandingâatâairportsâaboveâ5,000âfeetâdensityâaltitude,âtheâmixtureâmustâbeâleanedâtoâsmoothâengineâoperationâduringâtrafficâpatternâflightâandâlanding;âotherwise,âtheâengineâmayâstopâonâtheârunwayâbecauseâofâexcessiveârichness.
TO INCREASE POWERâââfirst,âenrichâmixture,âincreaseâRPM,âthenâfollowâwithâthrottle.
TO DECREASE POWERâââfirst,âreduceâthrottle,âreduceâRPM,âandâthenâadjustâmixture.
INCREASING POWERâââenrichâmixtureâfirstâtoâensureâpro-tectingâtheâengineâagainstâdamageâfromâhigherâpowerâwhenâpreviouslyâleanedâoutâforâaâlowerâpowerâsetting.
Next,â increaseâRPMâbecauseâ inâsomeâmodelsâ theâengineâandâpropellerâwouldâhaveâundesirableâpressureâandâstressesâwithâaâhighâmanifoldâpressureâandâlowerâRPM.
Then,âfollowâwithâtheâappropriateâmanifoldâpressure,ânowâthatâtheâmixtureâandâRPMâhaveâbeenâcorrectlyâsetâtoâaccommodateâtheâincreasedâthrottle.
DECREASING POWER â ââ Mostâ modelsâ ofâ ourâ enginesârequireâtheâbasicâprocedureâforâdecreaseâofâpowerâbyâretardingâthrottle,â followedâbyâRPM.âHowever,âweâdoâhaveâanâexcep-
tionâinâseveralâolderâmodelsâofâourâgearedânormallyâaspiratedâpowerâplants,âsuchâasâ theâGO-480âandâGO-435âseries.â Inâ theâclimbâconfiguration,âweârecommendedâfullâthrottleâthroughoutâtheâclimbâforâ internalâ fuelâcoolingâwithâRPMâreductionsâ ini-tiallyâtoâ3000âRPMâandâthenâ2750âRPMâforâprolongedâclimb.ââTurbochargedâandâsuperchargedâenginesârequireâcarefulâapplica-tionâofâtheâbasicâpowerâsequencesâasâoutlinedâinâtheâbeginning.âItâisâalsoâpossibleâtoâcreateâanâoverboostâconditionâonâtheseâenginesâbyâgoingâtoâtakeoffâmanifoldâpressureâatâcruiseâRPM,âsuchâasâmightâtakeâplaceâinâanâunexpectedâgo-around.âTheâstressesâandâpressuresâonâpropâandâengineâwouldâcreateâaâthreatâtoâboth.
Aâletterâreceivedâhereâatâ theâfactoryâaskedâaâquestionâweâhaveâheardâquiteâoften:
âIsâ itâaâfact,âorâ isâ itâ fiction,â thatâenginesâwithâconstantâspeedâpropsâ shouldâ notâ useâ powerâ settingsâ whereâ inchesâ ofâ mer-curyâexceedâRPMâinâhundreds?âIâamâreferring,âofâcourse,â toâânon-turbochargedâenginesâinâgeneralâ.â
Theâanswerâ toâ thisâquestionâ isâeasilyâ foundâ inâcruiseâpowerâchartsâofâ theâairframeâPilotâsâOperatingâHandbook.âWhateverâtheâcombinationsâofâRPMâandâMPâlistedâinâtheâchartsâââtheyâhaveâ beenâ flightâ testedâ andâ approvedâ byâ theâ airframeâ andââpowerâplantâengineers.âTherefore,âifâthereâareâpowerâsettingsâsuchâasâ2100âRPMâandâ24"âMPâinâtheâpowerâchart,âtheyâareâapprovedâforâuse.
Theâ confusionâ overâ so-calledâ âsquaredââ powerâ settingsââ(i.e.,â2400âxâ24"âMP),âappearsâtoâhaveâbeenâaâcarry-overâfromâsomeâmodelsâofâ theâoldâradialâenginesâwhichâwereâvulnerableâtoâexcessiveâbearingâwearâwhereâanâMPâhigherâthanââsquaredââwasâused.âMoreâpressureâonâtheâbearingsâwithâtheâhigherâthanââsquaredââMPâwasâtheâcauseâofâtheirâproblem.âHowever,âchangesâinâdesign,âmetalsâandâlubricantsâpermitâchangesâinâoperationâinâtheâmoreâmodernâflat-opposedâpowerâplants.
LetâsâlookâatâtheâpowerâchartsâinâaâcoupleâofâtheâPilotâsâOperatingâHandbooksâofâtwoâdifferentâaircraftâmanufacturers,âbutâwhereâbothâareâusingâtheâfour-cylinderâ200âHPâLycomingâengine.
CessnaâsâModelâ177âRG,âusingâtheâLycomingâIO-360-A1B6D,âinâtheâcruiseârangeâatâ6,000âfeet,âlistsâaâcruiseâpower-settingârangeâatâthatâaltitudeâofâanywhereâfromâ2100âRPMâtoâ2500âRPMâwithâvariationsâallâtheâwayâfromâ18"âMPâtoâ24"âMP.âTheyâlistâaârecom-mendedâpower-settingâforâ66%âpowerâatâ2100âRPMâatâ24"âMP.
TheâPiperâArrow,âpoweredâbyâ theâLycomingâIO-360-Câseriesââengine,â listsâ theâfollowingâcruiseâpowerâsettingsâatâ6,000âfeetâinâ theirâ chartâ atâ65%âpowerâatâ fullâ throttleâ (aboutâ23"âMP)ââxâ2100âRPM.
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THE COMPLETE CHART FOR ��% POWER IS SHOWN AS FOLLOWS:
Altitude 2100 RPM 2400 RPM
â SLâ 25.9âMPâ 22.9âMP
â 1,000â 25.6âMPâ 22.7âMP
â 2,000â 25.4âMPâ 22.5âMP
â 3,000â 25.1âMPâ 22.2âMP
â 4,000â 24.8âMPâ 22.0âMP
â 5,000â F.âT.âMPâ 21.7âMP
â 6,000â F.âT.âMPâ 21.5âMP
âAfterâstudyingâtheâpowerâchart,âtheâpilotâwouldâundoubtedlyâthenâaskâwhatâcombinationâofâRPMâandâMPâwouldâbeâbestâtoâuseâatâcruise.âWeârecommendâtheâpilotâ tryâtheâvariousâcombinationsâofferedâbyâtheâpowerâchartâoverâaâfive-minuteâperiodâwhenâflyingâinâsmoothâair,âandâuseâtheâlistedâRPMâandâMPâcombinationâwhichâgaveâtheâleastâvibrationâandâtheâlowestânoiseâlevel.
Inâadditionâtoâtheâquieterâandâsmootherâconsideration,âlowerâRPMâmeansâlowerâfrictionâHP.âThisâreducedâlossâofâhorsepowerâdueâtoâfrictionâalsoâtranslatesâtoâslightlyâimprovedâfuelâeconomy.
TheâPilotâsâOperatingâHandbookâisâtheâbasicâreferenceâforâtheâpilotâasâthisâsubjectâillustrates.
Theâhighâpriceâofâaviationâfuelâisâcausingâaircraftâownersâandâpilotsâtoâreviewâtheirâoperationsâinâsearchâofâwaysâtoâkeepâoperatingâcostsâdown.âThoseâoperatingâaircraftâwithâcontrollableâpropellersâhaveâbeenârequestingâinformationâonâcruiseâoperationâinâtheâlowâRPMârangeâââ1800âorâ1900âRPMâforâexample.âTheânumberâofâqueriesâreceivedâindicatesâaâgreatâdealâofâinterest,âandâthereforeâitâseemsâappropriateâtoâshareâtheâinformationâonâthisâsubjectâwithâallâofâourâreaders.
TheâLycomingâEngineâOperatorâsâManualâ hasâperformanceâcurvesâ applicableâ toâ eachâ engineâ series.âTheâ curveâ forâ theââIO-540-Kâseries,â300-horsepowerâengineâ isâprintedâhereâasâaâreferenceâforâ thisâarticle.âTheâcurveâdoesâprovideâdataâonâ theâmaximumâmanifoldâpressureâ (MP),âwhichâmayâbeâusedâwithâanyâparticularâRPMâatâseaâ levelâandâatâaltitude.âTheâ limitingâmanifoldâpressureâlineâclearlyârestrictsâhighâmanifoldâpressuresâwithâ low-RPMâsettings.âThereâ isâaâgoodâreasonâforâ this;âhighâmanifoldâpressureâandâlowâRPMâisâsimilarâtoâallowingâyourâauto-mobileâtoâlugâuphillâinâfourthâgear.âTheâpingingâyouâhearâinâyourââautomobileâtellsâyouâthatâdetonationâisâoccurring,âandâyouâshouldâshiftâdownâtoâaâlowerâgear.âInâanâaircraft,âdetonationâisânotâlikelyâtoâbeâheardâasâdamageâoccursâinâtheâengine,âandâitâisâthenâtooâlateâforâpreventiveâmeasures.âForâthisâreason,âengineâoperationâshouldâbeâwithinâ theâ limitationsâestablishedâ inâ theâPilotâsâOperatingâHandbookâ(POH).
Althoughâthereâareârestrictions,âitâisâquiteâapparentâthatâoperationâisâpossibleâinâtheâ1800âtoâ1900âRPMârange.âLowerâRPMâwillâresultâinâless-frictionâhorsepowerâwithâaâresultantâfuelâsavings,âbutâmostâofâtheâfuel-flowâreductionâexperiencedâwillâbeâtheâresultâofâaâmuchâlowerâpowerâsettingâandâthereforeâreducedâperformance.âThisâraisesâaâquestionâaboutâtheâamountâofâbenefitâinâtermsâofâcostâsavingsâthatâmightâactuallyâbeâachievedâbyâusingâtheâlowerâRPMâsettingsâforâcruise.
Oneâofâtheâfirstâconsiderationsâofâlow-RPMâcruiseâisâthatâpowerâsettingsâthisâlowâshouldânotâbeâusedâduringâtheâengineâbreak-inâperiod.âDuringâtheâbreak-inâperiod,ânormalâclimbâpowerâasâspeci-fiedâinâtheâPilotâsâOperatingâHandbookâshouldâbeâused.âToâseatâtheâpistonâringsâinâaânewâorâoverhauledâengine,âcruiseâtheâaircraftâatâ65%âtoâ75%âpowerâforâtheâfirstâ50âhours,âorâuntilâoilâconsump-tionâhasâstabilized.âLowâpowerâforâbreak-inâmayâresultâinâglazedâcylinderâwallsâandâhighâoilâconsumptionâthatâcanâonlyâbeâcuredâbyâcylinderâremovalâandârehoning.
Thereâareâsomeâotherâconsiderationsâofâlow-powerâcruiseâopera-tion.âLowâmanifoldâpressures,âbelowâanâarbitraryâpointâofâperhapsâ18"âforâcontinuousâcruise,âmayâcauseâexcessiveâoilâusageâandâoilâbuildupâinâtheâvalveâguidesâwhichâcouldâleadâtoâstickingâvalves.
Particularlyâduringâcold-weatherâoperation,â low-powerâopera-tionâmayâallowâbothâtheâoilâandâcylinderâheadâtemperaturesâtoâfallâbelowâtheânormalârange.âThisâisâdetrimentalâtoâgoodâengineâhealth.âOilâtemperatureâinâparticularâshouldâbeâmaintainedâbetweenââ165ËâFâandâ220ËâFâtoâachieveâmaximumâserviceâlife.âAtâlowerâtemperatures,âtheâmoistureâwhichâgathersâasâaâresultâofâcombustionâwillânotâvaporizeâandâbeâexpelled.âThisâcanâcauseâdilutionâofâtheâoilâwhichâdetractsâfromâitsâlubricatingâproperties.
TheâPilotâsâOperatingâHandbookâforâeachâaircraftâprovidesâaâvarietyâofâpowerâsettingsâthatâmostâoftenâshowâ2100âorâ2200âRPMâasâtheâminimumâforâcruise.âTheâtableâshownâhereâisâforâtheâIO-540-Kâseriesâengineâwhichâwasâillustratedâinâtheâcurveâshownâearlier.âUsingâthatâcurve,ânoteâthatâcruiseâflightâatâ6,000âfeetâusingâ1900âRPMâwouldâbeâ limitedâ toâapproximatelyâ55%âofâpowerâwithâmanifoldâpressureâsetâatâ24".âAsâshownâinâtheâcurve,â24"âofâMPâisâveryânearâtheâlimitingâmanifoldâpressureâlineâandâthereforeâcloseâtoâtheâmaximumâavailable.
Quiteâfrequently,âsomeoneâwillâaskâifâtheâengineâwillâlastâlongerâifâitâisârunâatâaâslowerâRPMâsetting.âTheâanswerâmustâbeâqualified.âOperationâatâtheârecommendedâcruiseâRPMâsettingsâshouldâallowâtheâengineâtoâreachâTBOâifâitâhasâregularâoilâchanges,âisâoperatedâwithinânormalâtemperatureârangesâandâisâwellâcaredâforâbyâpilotsâandâmaintenanceâpersonnel.âLongerâengineâlifeâmayâbeâexpectedâfromâmostâenginesâwhenâtheâoperatorâisâwillingâtoâsacrificeâmax-imumâperformanceâforâconservativeâcruiseâoperationâinâtheâ60%âtoâ65%âpowerârange.âForâmanyâengines,âtheseâpowerâsettingsâareâachievedâatâ2100âorâ2200âRPMâratherâthanâtheâ1800âorâ1900âRPMâmentionedâearlierâinâthisâdiscussion.
Inâsummary,âitâisâpossibleâtoârunâanâengineâatâcruiseâusingâ1800âorâ1900âRPM.âAâcurveâ fromâ theâEngineâOperatorâsâManualâshouldâbeâconsultedâtoâensureâthatâmanifoldâpressureâlimitsâareânotâexceeded.â Inâ reality,â theâ recommendationsâofâ theâPilotâsââOperatingâHandbookâprovideâtheâbestâguidanceâforâoperationâofâanââaircraft/engineâcombination,âandâthereforeâtheârecommendationsâandâlimitationsâofâtheâPOHâshouldâbeâobserved.
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SEAâLEVELâANDâALTITUDEâPERFORMANCEâCURVEâ-âIO-540-K,â-L,â-M,â-S
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POWERâTABLEâSETTINGâââ
LYCOMINGâMODELâIO-540-K,â-L,â-MâSERIES,â300âHPâENGINE
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â
â
Theâgasolineâengineâoperatesâonâaâfuel/airâmixtureâthatâisâignitedâbyâtheâsparkâplugs.âEnginesâdoânotârunâwhenâanyâofâtheseâele-mentsâareâmissing.âPilotsâknowâpositivelyâthatâtheyâmustârefuelâtheâaircraftâonâaâregularâbasisâifâtheyâwantâtoâflyâwithoutâincident,âbutâtheâpossibilityâofâlosingâtheâairâpartâofâtheâfuel/airâmixtureâisânotâalwaysâconsideredâandâunderstoodâasâwellâasâitâshouldâbe.âPerhapsâtheâpersonalâexperienceâofâseveralâ individuals,âandâsomeâfactsâaboutâinduction-systemâicingâcanâbeâusedâtoâhelpâFlyerâreadersâavoidâanâaccidentâcausedâbyâlackâofâairâforâtheirâengines.
Rememberâthatâanyâmaterialâthatâreducesâorâcutsâoffâtheâflowâofâairâinâtheâinductionâsystemâhasâtheâpotentialâtoâcauseâaâlossâofâpower.âAâmaterialâfailureâofâtheâairâfilterâisâoneâproblemâwhichâisâreportedâallâtooâoften.âTheâfilterâisâveryânecessaryâtoâkeepâdirtâoutâofâtheâengine;âitâmustâbeâinspectedâfrequentlyâandâshouldâbeâchangedâonâsomeâregularâschedule.âAâfilterâwhichâisâseveralâyearsâoldâandâhasâfilteredâtheâairâduringâhundredsâofâhoursâofâoperationâmayâbeâtired.âOneâpilotâreportedâthatâonâturn-upâofâtheâengineâbeforeâtakeoff,âheâcouldânotâgetâtheâstaticâRPMâthatâhisâengineâandâfixed-pitchâpropellerâshouldâhaveâproduced.âHeâwiselyâelectedâtoâreturnâtoâtheâlineâandâhaveâtheâengineâinspected.âTheâairâfilterâhadâpulledâlooseâfromâitsâsupportingâframeâandâwasâlodgedâinâtheâintakeâsystemâwhereâitâwasâcuttingâoffâtheâairâsupply.
Ifâthisâincidentâhadâoccurredâinâflight,âtheâengineâwouldâpossiblyânotâhaveâbeenâproducingâenoughâpowerâ toâmaintainâaltitude.âDependingâonâtheâparticularâairframe,âthereâareâsomeâoptionsâwhichâmightâbeâutilizedâtoâregainâsomeâofâtheâlostâpower.âAnââalternateâairâsystemâorâcarburetorâheatâsystemâisâdesignedâintoâtheâinductionâsystemâprimarilyâtoâcombatâinductionâicing,âbutâuseâofâtheseâsystemsâmayâpossiblyâhelpâwhenâintakeâairâisâblockedâbyâotherâforeignâmaterials.âInâsomeâcases,âjustâleaningâtheâmixtureâmayâhelpâtoâregainâaâlittleâofâtheâlostâpower.
Severalâyearsâago,âthereâwasâaâreportedâlossâofâengineâpowerâinâheavyârain.âInâthatâcase,âaâpaperâairâfilterâwasâbeingâused.âWhenâsaturatedâwithâwater,â theâpaperâfilterâelementâbecameâswollenâsoâthatâairflowâwasâimpeded.âInâthisâcase,âtheâuseâofâcarburetorâheatâtoâbypassâtheâfilterâandâreleaningâtoâachieveâaâbetterâfuel/airâmixtureâwereâsuccessfulâtacticsâthatâkeptâtheâaircraftâflyingâuntilâaâsafe,âon-airportâlandingâcouldâbeâmade.âWeâshouldâkeepâinâmindâthatâitâisânotâtheâingestionâofâwaterâthroughâtheâengineâthatâcausesâaâseriousâlossâofâpower;âitâisâtheâreducedâairflow.
Someâpilotsâbelieveâ thatâfuel-injectedâenginesâareâ immuneâtoâinductionâicing.âThisâ isânotâso.âAlthoughâtheâpilotâflyingâwithâaâfuel-injectedâengineâdoesânotâhaveâtheâsameâthreatâofâicingâatâtheâventuriâasâthoseâwithâaâcarburetor,ârain,âsnow,âslushâandâcoldâtemperaturesâmayâcauseâaâblockageâ(impact ice)âtoâairâflowâinâotherâpartsâofâtheâinductionâsystem.
Asâanâexample,âtheâpilotâofâaâfuel-injectedâsingleâreportedâflyingâatâ11,000âfeetâinâlightâdrizzle.âTheâtemperatureâwasâslightlyâaboveâ
freezingâandâwaterâ readilyâranâoffâ theâwindscreen.âAlthoughâthisâwouldâseemâtoâbeâaâno-problemâsituation,âtheâengineâstartedâtoâloseâpower.âAfterâconsiderationâofâtheâavailableâoptions,âtheâmanualâalternateâairâsystemâwasâactivated.âTheâengineâimmedi-atelyâregainedâpower,âandâflightâwasâcontinuedâtoâtheâhome-baseâdestination.âAfterâlanding,âtheâaircraftâwasâtakenâintoâtheâhangerâforâexamination.âItâwasâfoundâthatâtheâairâfilterâwasâcoveredâwithâaâlayerâofâiceâthatâhadâcutâoffâtheâairflow.âThisâisânotâanâisolatedâorâunusualâcase.âWhenâwaterâisânearâfreezing,âmovementâofâtheâwaterâmoleculesâmayâsometimesâcauseâinstantaneousâfreezing.âThisâglazingâoverâofâtheâairâfilterâisâaâknownâphenomenaâwhichâpilotsâshouldâexpectâandâbeâreadyâtoâcopeâwith.âAgain,âbypassingâtheâblockageâofâimpactâiceâbyâuseâofâalternateâairâprovedâtoâbeâaâsuccessfulâtacticâforâthisâpilot.
Theâmostâsubtleâandâinsidiousâofâtheâairflowâblockageâpossibilitiesâisâprobablyârefrigeration ice,âknownâmoreâcommonlyâasâcarbu-retorâice,âthatâformsâinâtheâvicinityâofâtheââbutterflyââorâthrottleâplate.âUnfortunately,â thereâareâmanyâpilotsâwhoâareânotâfullyâawareâofâwhatâcarburetorâiceâcanâdoâorâwhatâtoâdoâaboutâitâwhenâitâdoesâoccur.âAnâindicationâofâthisâareâstatementsâmadeâbyâpilotsâinvolvedâinâpower-lossâaccidentsâwhoâhaveâsaidâthatâtheyâtriedâcarburetorâheat,âfoundâitâdidânotâwork,âandâthenâreturnedâtheâcon-trolâtoâtheâcoldâposition.âCarburetorâheatâdoesânotâprovideâinstantâreliefâwhenâappliedâafterâiceâhasâformedâinâtheâcarburetor.âOnceâ
Rewritten and combined with article âInduction Icingâ
CARBURETORâICE
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heatâisâapplied,âitâshouldâbeâleftâonâuntilâengineâpowerâreturns.âLeftâuncorrected,âiceâaccumulationâinâtheâcarburetorâmayâcauseâcompleteâengineâstoppage.
Everyâ pilotâ whoâ fliesâ anâ aircraftâ poweredâ byâ aâ carburetedââengineâshouldâbeâthoroughlyâeducatedâaboutâcarburetorâice.âTheyâshouldâknowâthatâunderâmoistâconditionsâ(aârelativeâhumidityâofâ50%âtoâ60%âisâmoistâenough),âcarburetorâiceâcanâformâwithâanyâoutsideâairâtemperatureâfromâ20Ëâtoâ90ËâF.âItâisâmostâlikelyâinâtheâ30Ëâtoâ60ËâFârange.âTemperaturesâinâtheâcarburetorâcanâdropâ60Ëâtoâ70ËâFâ(refrigeratorâeffect)âasâaâresultâofâfuelâvaporizationâandâtheâcarburetorâventuriâeffect.âItâalsoâhappensâthatâcarburetorâiceâformsâmoreâreadilyâwhenâtheâengineâ isâoperatedâinâ theâ lowerâpowerârange.âItâwillâformâwhileâtaxiing,âandâthisâmakesâitâveryâimportantâtoâcheckâengineâpowerâbeforeâtakeoffâandâtoâremoveâtheâiceâifânecessary.âCareâshouldâbeâtakenâtoâavoidâdustyâorâdirtyâconditionsâwhenâutilizingâcarburetorâheatâonâtheâground.
Next,âitâisâimperativeâthatâtheâpilotârecognizeâcarburetorâiceâwhenâitâformsâduringâflight.âTheâlossâofâpowerâthatâoccursâwillâcauseâaâreductionâofâRPMâwhenâflyingâwithâaâfixed-pitchâpropeller,âandâaâlossâofâmanifoldâpressureâwhenâaâcontrollable-pitchâpropellerâisâused.âInâeitherâcase,âaâlossâofâaltitudeâorâairspeedâwillâoccur.âTheseâsymptomsâmayâsometimesâbeâaccompaniedâbyâvibrationâorâengineâroughness.âInâanyâcase,âitâ isâaâgoodâideaâtoâconsiderâcarburetorâiceâasâtheâcauseâofâanyâunexplainedâpowerâlossâduringâcruiseâflight.
Onceâaâpowerâ lossâ isânoticedâbyâ theâpilot,â immediateâactionâshouldâbeâtakenâtoâeliminateâiceâwhichâhasâalreadyâformedâinâtheâcarburetor,âandâ toâpreventâ furtherâ iceâ formation.âThisâ isââaccomplishedâbyâapplyingâfullâcarburetorâheatâwhichâwillâinitiallyâcauseâaâfurtherâlossâofâpowerâ(perhapsâasâmuchâasâ15%)âandâpos-sibly,âengineâroughness.âTheâadditionalâpowerâlossâisâcausedâbyâtheâheatedâairâthatâisâbeingâdirectedâintoâtheâinductionâsystem.âHeatedâairâmakesâtheâmixtureâricherâandâalsoâmeltsâtheâiceâwhichâthenâgoesâ throughâ theâengineâasâwater.âTheâ throttleâmayâbeâadvancedâandâtheâmixtureâmayâbeâleanedâtoâhelpâgetâsomeâofâtheâlostâpowerâback,âbutâimmediatelyâafterâtheâapplicationâofâcarbu-retorâheat,âtheâpilotâmustâbeâpatientâandâkeepâtheâairplaneâflyingâuntilâtheâiceâhasâcompletelyâmeltedâandânormalâpowerâreturns.âHowâlongâthisâwillâtakeâdependsâonâtheâseverityâofâtheâicing,âbutâtheâpilotâshouldâexpectâaâdelayâofâ30âsecondsâtoâseveralâminutes.âUnderâtheâcircumstances,â thisâperiodâofâtimeâwillâbeâstressfulâandâalwaysâseemsâlongerâthanâitâreallyâis,âbutâtheâknowledgeableâpilotâwillânotâretreatâfromâuseâofâcarburetorâheat.âCarburetorâheatâshouldâremainâinâtheâhotâpositionâuntilâpowerâreturns.
Inâ conditionsâ whereâ carburetorâ iceâ isâ likelyâ toâ form,â theââpilotâmayâuseâheatâduringâcruiseâtoâpreventâtheâformationâofâiceâinâ theâcarburetor.â Itâ isâalsoâappropriateâ toâuseâfullâcarburetorâheat,â ifâneeded,â toâpreventâicingâwhenâoperatingâatâ lowâpowerâforâ instrumentâapproaches,âorâforâflightâ inâ theâtrafficâpattern.ââUnlessâtheâaircraftâisâequippedâwithâaâcarburetorâairâtemperatureâ(CAT)âgage,âandâveryâfewâgeneralâaviationâaircraftâare,âuseâofâfullâcarburetorâheatâisârecommended.âAnâunknownâamountâofâpartialâheatâcanâactuallyâcauseâinductionâiceâ inâ theâfloat-typeâcarburetor.âThisâmayâoccurâwhenâmoistureâinâcrystalâformâinâtheââincomingâairâthatâwouldâordinarilyâpassâthroughâtheâinductionâ
systemâwithoutâanyâproblemâisâmeltedâbyâtheâpartialâheat.âThisâmoistureâthenâfreezesâwhenâitâcomesâinâcontactâwithâtheâcoldâmetalâofâtheâthrottleâplate.
Wheneverâcarburetorâheatâisâusedâinâtheâlandingâconfiguration,âandâaâgo-aroundâorâ touch-and-goâtakesâplace,â thereâareâsomeâimportantâstepsâforâtheâpilotâtoâremember.âTheâthrottleâmustâbeâadvanced,âandâtheâcarburetorâheatâleverâplacedâinâtheâcoldâposi-tion.âTheâorderâinâwhichâtheseâstepsâareâaccomplishedâisânotâtooâimportant,âbutâbothâmustâbeâdone.âLeavingâtheâcarburetorâheatâonâduringâaâgo-aroundâwillâresultâinâaâlossâofâpowerâthatâcouldâbeâcriticalâatâlowâaltitudeâandâlowâairspeed.
DoânotâuseâcarburetorâheatâforâtakeoffâorâclimbâwithâaâLycomingâengineâasâ itâ isânotânecessary,âandâ itâmayâbringâonâdetonationâandâpossibleâengineâdamage.âAnâexceptionâtoâ thisâruleâmightâbeâjustifiedâinâextremelyâcold-weatherâconditionsâsuchâasâthoseâfoundâinâtheâArctic,âandâtheseâconditionsârequireâaâspecialâknowl-edgeâtoâaccommodateâoperationâunderâsuchâextremeâconditions.
Aâreviewâofâtheâmaterialâdiscussedâinâthisâarticleâshouldâhelpâpilotsâcopeâwithâreductionâofâengineâpowerâwhenâitâisâcausedâbyâlossâofâintakeâairâforâcombustion.âAâthoroughâunderstandingâofâtheâairâintakeâsystemâandâtheâknowledgeâtoâcompetentlyâdealâwithâinduc-tionâicingâareâessentialâtoâsafeâflightâinâgeneralâaviationâaircraft.âPilotsâareâencouragedâtoâenhanceâtheâsafetyâofâtheirâflyingâbyâknowingâwhatâtoâexpectâandâwhatâstepsâtoâtakeâwhenâtheâairflowâtoâtheâengineâisâcutâoffâforâanyâreason.
Aânoteâ thatâcameâinâ theâmailâ fromâaâFlyerâ readerâ includedâaâsuggestionâthatâwentâsomethingâlikeâthis,ââHowâaboutâanâarticleâdealingâmoreâextensivelyâwithâ theâcold-startâproblem?ââThisâsuggestionâwasâaâgoodâoneâasâitâprovidedâanâopportunityâtoâshareâinformationâaboutâaâvarietyâofâcold-weatherâconsiderationsâtoâhelpâgetâtheâengineâstartedâandâtoâkeepâitâoperatingâduringâcold-weatherâconditions.â
Althoughâtheâsuggestionâmadeâinâtheâfirstâparagraphâwasâaimedâatâhelpingâwithâcold-weatherâstarting,âthisâarticleâhasâbeenâexpandedâtoâincludeâtipsâandâinformationâonâpreflight,âstarting,â in-flightâsafetyâandâengineâoperationalâconsiderations.âKeepâinâmindâthatâthisâmaterialâdealsâwithânormalâcold-weatherâoperationâexperi-encedâatâtemperaturesâtoâ-25ËâF,âandânotâtheâextremelyâlowâtem-peraturesâthatâmayâbeâfoundâinâArcticâregions.âOperationâinâthoseâregionsâmayârequireâmoreâspecializedâknowledge.
Letâsâstartâwithâtheâgeneralâhealthâofâtheâengine.âWhenâattemptingâaâstartâunderâadverseâconditions,âitâisâimperativeâthatâtheâengineâbeâ wellâ maintainedâ andâ inâ excellentâ operatingâ condition.âSparkâplugsâandâmagnetoâpointsâshouldâbeâproperlyâgappedâandâreadyâ toâ functionâeffectively.â Inâadditionâ toâ theâ ignitionâsystem,âtheâproperâfunctioningâofâotherâsystemsâsuchâasâinduction,ââpriming,âexhaustâandâcarburetorâheatâcanâhaveâanâeffectâonâtheâstartingâandâoperationâofâtheâengine.
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Regularâmaintenanceâshouldâincludeâhavingâtheâheatingâsystemâcheckedâforâ leaks.âThisâcold-weatherâ tipâ isâworthyâofâaâsepa-rateâ littleâsentenceâallâ itsâownâââremember,âyouâcanâtâsmellââcarbonâmonoxide.
Inâcoldâweather,âpreheatâisâanotherâfactorâthatâmustâbeâconsid-eredâpriorâtoâstartingâtheâengine.âThereâareâspecificâguidelinesâinâLycomingâserviceâinstructionsâwhichâestablishâwhenâpreheatâshouldâbeâused,âbutâhowâmuch,âorâ theâmethodâofâpreheatâ isâgenerallyâleftâtoâtheâgoodâjudgmentâofâtheâpilotâorâmaintenanceâpersonâdoingâtheâpreheating.âUseâofâtheâheatedâdipâstickâisânotârecommendedâbyâLycoming,âalthoughâmostâotherâmethodsâareâconsideredâtoâbeâsatisfactory.âForâmostâLycomingâmodels,âpreheatâshouldâbeâappliedâanytimeâtemperaturesâareâatâ10ËâFâorâlower.âTheâexceptionâtoâthisâruleâisâtheâ76âseriesâmodelsâthatâincludeâtheâO-320-H,âandâtheâO/LO-360-E.âTheseâenginesâshouldâbeâpreheatedâwhenâtemperaturesâareâbelowâ20ËâF.âItâisârecommendedâthatâtheseâguidelinesâbeâfollowedâevenâwhenâmulti-viscosityâoilâ isâbeingâused.âInâadditionâtoâhardâstarting,âfailureâtoâpreheatâtheâentireâengineâandâoilâsupplyâsystemâasârecommendedâmayâresultâinâminorâamountsâofâabnormalâwearâtoâinternalâengineâparts,âandâeventuallyâtoâreducedâengineâperformanceâandâshortenedâTBOâtime.
Waterâisâoneâofâtheâmostâlikelyâcontaminantsâofâaviationâgaso-line.âTheâengineâwillânotârunâonâwater,âandâalthoughâweâmayâgetâawayâwithâsmallâamountsâofâmoistureâinâtheâfuelâduringâwarmâweather,âflightâintoâfreezingâtemperaturesâmakesâanyâamountâofâmoistureâinâtheâfuelâsystemâveryâcritical.âEvenâaâtinyâbubbleâofâmoistureâmayâfreezeâinâtheâfuelâlineâandâtotallyâcutâoffâtheâflowâofâfuel.âTwoâstepsâshouldâbeâtakenâtoâavoidâthisâproblem.âFirst,âavoidâwaterâcontaminationâifâpossible.âKeepâfuelâ tanksâfullâ toâpreventâcondensation,âandâbeâsureâfuelâcapsâdoânotâallowâleakageâifâtheâaircraftâisâparkedâoutsideâinârainâorâsnow.âSecond,âlookâforâcontaminationâbeforeâeveryâflightâbyâreligiouslyâdrainingâfuelâtanksâandâsumps.
Ifâ flightâ isâplannedâforâbadâweather,â theâpreflightâ inspectionâshouldâincludeâobservationâofâtheâreliefâopeningâinâtheâengineâbreatherâtubeâsoâthatâanyâfreezingâofâmoistureâatâtheâendâofâtheâbreatherâwillânotâresultâinâaâlossâofâengineâoil.â(SeeââTheâWhistleâSlotââinâthisâbook.)
Onceâonâboardâ theâaircraft,âcheckâ theâfuel-selectorâvalveâforâfreedomâofâmovement.âItâmayâbeâfrozenâfastâ(thisâhasâhappened),âandâyouâdâbetterâfindâoutâwhileâstillâonâtheâground.
Mostâofâtheâtime,âweâthinkâofâstartingâanyâengineâasâaâveryâsimpleâprocess.âJustâengageâtheâstarter,âandâlistenâforâtheâengineâtoâstartâpurring.âUnfortunately,âwhenâtheâweatherâ turnsâcold,â itâ isânotâalwaysâthatâsimple.âWhenâdealingâwithâaâreciprocatingâaircraftâengine,âitâmayâbeâessentialâtoâgetâaâstartâonâtheâfirstâtryâinâorderâtoâavoidâicingâoverâtheâsparkâplugsâandâmakingâanâimmediateâstartâimpossible.âInâorderâtoâachieveâaâstartâonâtheâfirstâtry,âthereâareâaânumberâofâfactorsâtoâbeâconsidered.âThoseâfactorsâwillâbeâdiscussedâinâtheâfollowingâparagraphs.
Althoughâitâmightâbeâgoodâprocedureâtoâuseâanâexternalâpowerâsourceâforâstartingâduringâveryâcoldâweather,âmostâofâusâexpectâourâbatteryâtoâdoâtheâjob.âWeâshouldârememberâthatâtheâbatteryâisâhandicappedâbyâcoldâweather.âParticularlyâwhenâaâsingle-viscosityâoilâisâbeingâused,âtheâcolderâtheâtemperature,âtheâmoreâcrankingâ
energyârequired.âCombineâthisâwithâreducedâbatteryâoutputâatâlowerâtemperatures,âandâitâcanâbeâaâseriousâhandicap.
Whileâonâtheâsubjectâofâbatteries,ârememberâthatâfreezingâtem-peraturesâprovideâaâperfectâopportunityâtoâdestroyâanâaircraftâbat-tery.âTheâbatteryâwithâaâfullâchargeâsurvivesânicely,âbutâoneâthatâisâdischargedâwillâfreeze.âOnceâthisâhappens,âtheâproblemâcanâonlyâbeâremediedâbyâreplacingâtheâbattery,âsoâitâisâveryâworthwhileâtoâtakeâpreventiveâmeasures.âShouldâtheâbatteryâbeârunâdownâduringâanâattemptâtoâstart,âdoânotâleaveâit;âgetâitâchargedâimmediately.âAndâfinally,âbeâabsolutelyâcertainâthatâtheâmasterâswitchâisâalwaysâOFFâwhileâtheâaircraftâisâparkedâbetweenâflights.âIfâleftâon,âtheâbatteryâwillâdischargeâandâfreeze.âTheseâratherâminorâmistakesâcanâbeâquiteâexpensive.
Oilâisâanotherâfactorâtoâbeâconsideredâinâtheâcold-weatherâstartingâprocess.âAllâoilsâareâaffectedâbyâtemperatureâandâtendâtoâthickenâasâtheâtemperatureâdrops.âTheâengineâmayâbeâreluctantâtoâturnâoverâwhenâtheâoilâisâstiff;âaâsummerâweightâoilâisânotâsuitableâinâcoldâweather.âItâisâalsoâtheâconditionâwhichâbringsâoutâtheâprimaryâadvantageâofâmultiviscosityâoilsâandâofâpreheating.âBecauseâmulti-viscosityâoilsâareâthinnerâ(lowerâviscosity),âtheyâallowâtheâengineâtoâbeâturnedâoverâmoreâeasily.âTheâeasierâandâquickerâoilâflowâalsoâpromotesâfasterâlubricationâofâinternalâengineâpartsâwhenâtheâengineâdoesâstart.âSinceâtheâproperâoilâviscosityâisâsoâimportantâinâallâaspectsâofâengineâstartingâandâoperation,âtheârecommendationsâofâoilâgradeâvs.âtemperatureârangeâshownâinâLycomingâServiceâInstructionâNo.â1014âshouldâbeâfollowed.
Probablyâ theâmostâ importantâ factorâ inâstartingâanâengineâ isâachievingâaâ fuel/airâmixtureâ thatâ isâsatisfactoryâforâcombus-tion.âSinceâtheâengineâusuallyâstartsâveryâeasily,âmanyâpilotsâareâunawareâofâorâignoreâtheâchangeâofâstartingâprocedureâneededâtoâsuccessfullyâstartâunderâvaryingâtemperatureâconditions.âInâwarmâweather,âtheâairâisâlessâdense,âandâthereforeâmustâbeâmixedâwithâaâlesserâamountâofâfuelâthanâinâcoldâweather.âInâadditionâtoâthis,âinâwarmâweather,âtheâfuelâwillâvaporizeâreadilyâandâmakeâstartingâeasier.âSimplyâstated,âasâtemperaturesâgoâdownâitâbecomesâmoreâandâmoreâimportantâ thatâweâhaveâaâplanâforâprimingâthatâwillâachieveâtheâcorrectâfuel/airâmixture.
Whenâ primingâ aâ carburetedâ engine,â theâ pilotâsâ planâ mustâconsiderâtheâtemperature,âtheânumberâofâcylindersâwhichâhaveâprimingâlinesâinstalled,âandâtheânumberâofâstrokesâofâtheâprimerâneededâtoâproduceâtheâcorrectâfuel/airâmixture.âTheâprimerâlinesâareâorderedâorâinstalledâbyâtheâairframeâmanufacturerâandânotâallâaircraftâareâconfiguredâtheâsame.âSomeâaircraftâhaveâactuallyâbeenâproducedâwithâonlyâoneâcylinderâbeingâprimed,âandâtheseâenginesâareâextremelyâhardâtoâstartâinâcoldâweather.âTheânumberâofâcylindersâthatâareâprimedâmustâbeâconsideredâsinceâtheâtotalâfuelâdeliveredâbyâtheâprimerâwillâbeâdividedâandâsentâtoâtheseâcylinders.âAsâtheâairâbecomesâcolderâandâdenser,âtheâamountâofâprimeâusedâmustâbeâincreased,âbutâtheânumberâofâstrokesâtoâbeâusedâshouldâbeâplannedâasâaâresultâofâsomeâtrialâandâerrorâexperimentationâforâeachâaircraftâaâpilotâflies.âWhenâtheâcor-rectânumberâofâprimerâstrokesâforâeachâtemperatureârangeâhasâbeenâestablished,âtheâengineâwillâusuallyâstartâveryâquickly.âWeâmayâfindâthatâanâengineâstartsâeasilyâwhenâoneâstrokeâofâ theâprimerâisâusedâinâtheâ60Ëârange,âtwoâstrokesâinâtheâ50Ëârange,âthreeâstrokesâinâtheâ40Ëârange,âetc.âThisâisâanâexampleâofâtheâ
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trialâandâerrorâweâmightâuseâtoâestablishâtheânumberâofâprimerâstrokesâ toâuseâunderâ anyâparticularâ temperatureâ condition.
Whileâdiscussingâtheâprimingâofâanâengine,âthereâhaveâbeenâsitu-ationsâwhereâprimerâlinesâbecomeâclogged.âThisâmakesâengineâstartingâdifficultâandânegatesâanyâtrialâandâerrorâexperimentationâthatâmayâhaveâbeenâdone.âWhenâmaintenanceâisâdoneâonâanâaircraftâbeforeâtheâstartâofâwinter,âitâmayâbeâwiseâtoâhaveâthoseâprimerâlinesâcheckedâtoâensureâthatâfuelâwillâflowâthroughâthem.
Theâamountâofâfuelâneededâtoâachieveâtheâcorrectâfuel/airâmixtureâforâstartingâaâfuel-injectedâengineâisâcontrolledâbyâtimingâratherâthanânumberâofâprimerâstrokes.âWithâtheâelectricâfuelâpumpâon,âmovingâtheâmixtureâcontrolâ toâtheârichâpositionâallowsâfuelâtoâflowâtoâtheâcylinders.âForâcold-weatherâstarting,âitâmayâbeâneces-saryâtoâkeepâtheâmixtureâcontrolâinârichâsomewhatâlongerâthanâinâwarmâweather.
Theâfuelâpartâofâtheâfuel/airâmixtureâmayâbeâtheâpartâweâhaveâtheâmostâcontrolâoverâduringâtheâengineâstart,âbutâkeepâinâmindâthatâtheâamountâofâthrottleâopeningâdoesâhaveâanâeffectâonâtheâairâ thatâisâpumpedâthroughâtheâengine.âJustâasâweâcompensateâforâcold/denseâairâbyâaddingâmoreâfuelâforâstart,âitâmayâalsoâbeâappropriateâtoâreduceâtheâairâpartâofâtheâmixtureâwhenâtheâtem-peratureâisâveryâcold.âForâexample,âifâtheâthrottleâisânormallyâsetâopenâone-halfâinchâforâwarmâweatherâstarting,âitâmayâbeâhelpfulâtoâreduceâthisâtoâone-quarterâinchâinâcoldâweather.âAgain,âitâwillârequireâsomeâexperimentationâtoâdetermineâwhatâ isâneededâtoâachieveâtheâcorrectâfuel/airâmixtureâforâanyâparticularâaircraftâatâanyâtemperatureârange.
Whenâanâengineâdoesânotâstartâeasily,â itâcanâbeâfrustrating.âOfâcourse,â thisâcanâoccurâatâanyâ timeâofâ theâyear,âandâ itâ isâveryâtemptingâtoâjustâkeepâgrindingâawayâwithâtheâstarterâinâanâattemptâtoâgetâitâgoing.âShouldâthisâhappenâtoâyou,âRELAX.âTakeâcareâofâ thatâstarter,âorâ itâmayâfail.âTheâgeneralâ ruleâ forâstartersâ isâthatâ theyâshouldâonlyâbeâoperatedâforâshortâperiods,âandâthenâallowedâ toâcool.â Ifâengineâstartâhasânotâoccurredâafterâ threeâ10-secondâperiodsâofâoperationâwithâaâpauseâbetweenâeach,âaââfive-minuteâcoolingâoffâperiodâisârequired.âWithoutâthisâtimeâlimitâforâoperationâandâanâadequateâcoolingâoffâperiod,âtheâstarterâwillâoverheatâandâisâlikelyâtoâbeâdamagedâorâtoâfailâcompletely.
Theâpreviousâparagraphsâhaveâaddressedâseveralâissuesâthatârelateâtoâtheâcold-weatherâpreflightâandâtheâcold-weatherâstart.âThereâareâotherâcold-weatherâ itemsâthatâshouldâbeâconsideredâinâtheâoperationâofâtheâengine.
Assumingâtheâengineâhasâkickedâoff,âcheckâforâanâ indicationâofâoilâpressure.âLearnâ theâcharacteristicsârelativeâ toâresponseâofâoilâpressureâ indicationsâofâyourâaircraft/engineâcombina-tion.âOnâmostâ single-engineâ aircraft,â anâ almostâ immediateââresponseâisânoted.âOnâtwin-engineâaircraft,âtheâresponseâmayâbeââmuchâ slower.â Onâ someâ twins,â theâ oilâ pressureâ mayâ goâ up,ââandâduringâwarm-up,âmayâdropâagainâforâaâshortâperiodâofâtime,ââthenâagainâriseâtoânormal.âAllâcasesâmentionedâmayâbeânormal,ââbutâ theâ importantâ thingâisâ toâknowâwhatâ toâexpectâfromâyourââaircraft/engineâcombination.
Afterâstart,âdoânotâidleâengineâbelowâ1000âRPM.âItâsânotâgoodâpracticeâtoâidleâenginesâbelowâ1000âRPMâatâanyâtime.âThisâisâparticularlyâtrueâduringâcoldâweatherâtoâpreventâleadâfoulingâofâsparkâplugs.â(ExceptionâââPiperâPressurizedâNavajo)
Now,âhereâsâaâtipâforânoviceâpilots.âWhenâsettingâupâforâcruiseâconfiguration,âbeâprecise,âreadâyourâinstrumentsâandârememberâwhatâyouâread.âExample:âIfâyouâdecideâonâ22"âofâmanifoldâpres-sure,âsetâitârightâonâ22.âIfâtheâRPMâisâtoâbeâ2350,âmakeâitâ2350.âSelectâanâaltitude.âTrimâtheâaircraftâtoâholdâthatâselectedâaltitude.âNoteâairspeed.âNow,âifâanythingâchanges,âbarringâturbulentâair,âitâhasâtoâbeâaâchangeâinâpower.âPerhapsâitâisâcarburetorâorâinduction-airâicing.âSupposeâyouâpickedâupâaâbitâofâcarburetorâice,âandâtheâengineâsuffersâaâslightâpowerâloss.âThereâwillâbeâaâslightâdropâinâmanifoldâpressure,âaâlossâinâairspeed,âandâtheâaircraftâwillâwantâtoâloseâaltitude,âandâifâyouâholdâaltitude,âyouâllâfindâbackâpressureâonâtheâwheelâisârequired.âTherefore,âevenâthoughâyouâdidnâtâdiscoverâtheâpowerâlossâthroughâinstrumentâscanning,âyouâllâgetâaâwarningâthroughâtheââheavyââwheelâorâstick.
Duringâflightâinâveryâlowâtemperatures,âexerciseâconstantâspeedâpropsâaboutâeveryâ30âminutesâtoâhelpâpreventâcongealingâofâoilâinâtheâpropâdome.
Shouldâoneâengineâofâaâtwin,âforâanyâreason,âindicateâtheâpropâmustâbeâfeathered,âdonâtâtarryâtooâlongâwithâreducedâpowerâinâveryâcoldâweather.âAtâreducedâpower,âtheâoilâmayâcongealâmakingâfeatheringâanâimpossibility.
Aâtipâforâeveryâpilot,âdonâtârunâoneâsetâofâfuelâtanksânearlyâdryâbeforeâswitchingâtanks.âSwitchâwithâplentyâofâfuelâremainingâinâtheâtanksâfirstâused.âThisâisââmoneyâinâtheâbank,ââshouldâyouâfindâtheâselectorâvalveâfrozen.
Althoughâcarburetorâiceâisânotânecessarilyâaâwintertimeâphenomena,âaâcheckâofâcarburetorâheatâshouldâbeâmadeâduringâtheâengineârun-up.âGenerallyâspeaking,âweâcanâsayâthatâcarburetorâheatâshouldâneverâbeâusedâforâtakeoff,âbutâthereâisâoneâexception.âThisâexceptionâoccursâwhenâoperatingâinâtemperaturesâsoâcoldâthatâapplicationâofâcarburetorâheatâproducesâaâriseâinâRPM.âMostâpilotsâwillâneverâfindâthemselvesâinâcircumstancesâwhichârequireâuseâofâcarburetorâheatâforâtakeoffâandâclimb;âthoseâwhoâflyâcarburetedâenginesâwillâalmostâcertainlyâhaveâoccasionâtoâuseâcarburetorâheatâduringâcruiseâorâletâdown.âUseâofâtheâfull-hotâorâfull-coldâpositionâisârecommended.âAnâintermediateâsettingâshouldâonlyâbeâselectedâifâtheâaircraftâisâequippedâwithâaâcarburetorâairâtemperatureâ(CAT)âgage.
Engineâoperatingâtemperatureâisâanotherâ itemâthatâ isânotâusu-allyâgivenâenoughâconsiderationâ inâcoldâweather.âWeâusuallyâareâveryâcautiousâaboutâhighâoilâtemperatureâwhichâweâknowâisââdetrimentalâtoâgoodâengineâhealth,âwhileâaâlowâoilâtemperatureâisâeasierâtoâaccept.âTheâdesiredâoilâtemperatureârangeâforâLycomingâenginesâisâfromâ165Ëâtoâ220ËâF.âIfâtheâaircraftâhasâaâwinteriza-tionâkit,â itâ shouldâbeâ installedâwhenâoperatingâ inâoutsideâairâtemperaturesâ(OAT)âthatâareâbelowâtheâ40Ëâtoâ45ËâFârange.âIfânoâwinterizationâkitâisâsuppliedâandâtheâengineâisânotâequippedâwithâaâthermostaticâbypassâvalve,âitâmayâbeânecessaryâtoâimproviseâaâmeansâofâblockingâoffâaâportionâofâtheâairflowâtoâtheâoilâcooler.âKeepingâtheâoilâtemperatureâaboveâtheâminimumârecommendedâtemperatureâ isâ aâ factorâ inâ engineâ longevity.âLowâoperatingââtemperaturesâdoânotâvaporizeâtheâmoistureâthatâcollectsâinâtheâoilâasâtheâengineâbreathesâdampâairâforânormalâcombustion.âWhenâminimumârecommendedâoilâ temperaturesâareânotâmaintained,âoilâshouldâbeâchangedâmoreâfrequentlyâthanâtheânormallyârec-ommendedâ50-hourâchangeâcycle.âThisâisânecessaryâinâorderâtoâeliminateâtheâmoistureâthatâcollectsâandâcontaminatesâtheâoil.
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Andâ finally,â power-offâ letdownsâ shouldâ beâ avoided.â Thisâisâ especiallyâ applicableâ toâ cold-weatherâ operationsâ whenââshock-coolingâofâtheâcylinderâheadsâisâlikely.âItâisârecommendedâthatâcylinderâheadâ temperatureâchangeânotâexceedâ50ËâF.âperâminute.âPlanâahead,âreduceâpowerâgraduallyâandâmaintainâsomeâpowerâthroughoutâtheâdescent.âAlsoâkeepâtheâfuel/airâmixtureâleanedâoutâduringâtheâdescent.âIfâanâexhaustâgasâtemperatureâgageâisâinstalledâwithâaânormallyâaspiratedâengine,âkeepâitâpeakedâtoâensureâtheâgreatestâpossibleâengineâheatâforâ theâpowerâsettingâselected;âforâaâ turbochargedâinstallation,â leanâtoâpeakâduringâdescentâunlessâotherwiseâ specifiedâ inâ theâPilotâsâOperatingâHandbook,âorâunderâconditionsâwhereâtheâlimitingâturbineâinletâtemperatureâwouldâbeâexceeded.
Exposureâtoâsnow,âfrostâandâcoldâweatherâwhileâflyingârequiresâtheâconsiderationâofâmanyâfactors,âbothâairframeâandâengineârelated.âThisâdiscussionâdealsâwithâissuesârelatingâtoâtheâengine.âWhileâthereâmayâbeâotherâissues,âthoseâitemsâwhichâareâaskedâaboutâmostâ frequentlyâhaveâbeenâdiscussed.âSaferâ flyingâandâlongerâengineâlifeâcouldâresultâfromâcarefulâconsiderationâofâtheâmaterialâaddressed.
TheâfatalâcrashâofâaâlightâtwinâinâwhichâaâflightâinstructorâandâanâapplicantâforâaâmultiengineâratingâwereâkilledâpromptedâtheâNTSBâtoâissueâanâurgentâwarningâtoâallâpilotsâsimulatingâanâengine-outâconditionâonâmultiengineâairplanes.âTheâBoardâsâ investigationârevealedâthatâsomeâflightâinstructorsâdoâuseâtheâfuelâselectorâorâtheâmixtureâcontrolâtoâshutâdownâanâengineâtoâtestâaâmultiengineâapplicant.âAlthoughâthisâisâaârecommendedâprocedure,âtheâurgentâwarningâwasâaimedâatâflightâinstructorsâwhoâwereâusingâthisâpro-cedureâatâaltitudesâtooâlowâforâcontinuedâsafeâflight.
TheâNTSBâobservedâthatâuseâofâsuchâproceduresâatâtrafficâpatternâaltitudesâmayânotâpermitâ instructorsâenoughâtimeâtoâovercomeâpossibleâerrorsâonâtheâpartâofâtheâapplicant.âTheârecommenda-tionâbyâtheâNTSBâmeansâthatâallâsimulatedâengine-outâoperationâatâtheâlowerâaltitudesâshouldâbeâaccomplishedâbyâretardingâtheâthrottle,âandâthisâshouldâbeâdoneâslowlyâandâcarefullyâtoâavoidâengineâdamageâorâfailure.
Manyâflightâinstructorsâdownâthroughâtheâyearsâusedâtheâtech-niqueâofâabruptlyâcuttingâanâengineâwithâaâmultiengineâcan-didateâ toâ testâhisâemotionalâ reactionâandâ judgmentâwithâ thisââextremeâtechnique.âBigâradialâpistonâenginesâwithâshort,âstubbyââcrankshaftsâ couldâ tolerateâ theâ abruptâ technique.â However,ââflat-opposedâpistonâenginesâwithâ theirâ longâcrankshaftsâandââattachedâcounterweightsâcouldânotâasâ readilyâ takeâ theâabuseâofâsuddenlyâsnappingâaâthrottleâshut,âparticularlyâatâ takeoffâorâclimbâpower.âUseâofâtheâlatterâtechniqueâwouldâtendâtoâdetuneââcrankshaftâcounterweightsâandâcouldâpossiblyâresultâ inâaânastyâengineâfailure.
Sinceâitâwasâcommonâtechniqueâbyâflightâ instructorsâtoâtermi-nateâpowerâabruptlyâtoâsimulateâanâengineâpowerâloss,âweâhadâtoâprotectâ theâengine.âAsâaâresult,âweâpublishedâinâourâEngineââOperatorâsâManualâandâinâServiceâBulletinâNo.â245,âtheârecom-mendationâ thatâ ifâ theâpowerâwasâabruptlyâ terminated,â itâmustâbeâaccomplishedâwithâtheâmixtureâcontrol.âOfâcourse,âthisâwasââintendedâ forâ theâ higherâ altitudesâ whereâ aâ completeâ engineââshut-downâcouldâbeâconductedâsafely.âTheâstudentâwasâtoâiden-tifyâtheâdeadâengineâbyâretardingâthatâthrottleâtoâaboutâ12"âMPâtoâsimulateâzeroâthrust,âorâsimilarâtoâhavingâtheâpropâfeathered.âAtâthatâpoint,âtheâinstructorâcouldâimmediatelyâreturnâtheâmixtureâtoââanâengine-operatingâcondition,âandâpowerâwouldâbeâavailableââifâneeded.
Inâourâpublications,âweâthenâexplainedâtheâreasonâforâusingâtheâmix-tureâtoâabruptlyâterminateâpower.âByâputtingâtheâmixtureâcontrolâinâidleâcutoffâpositionâwithâtheâthrottleâinâaânormalâopenâorâoperatingâposition,âtheâpilotâmerelyâcutâoffâtheâfuel,âbutâallowedâtheâairâtoâcon-tinueâtoâfillâtheâcylindersâwithâresultingânormalâcompressionâforcesâthatâareâsufficientâtoâcushionâtheâdecelerationâofâtheâengineâandâpreventâtheâdetuningâofâtheâcrankshaftâcounterweights.
However,âanyâpracticeâofâsimulatedâengine-outâconditionâatâlowâaltitudesâshouldâbeâbestâaccomplishedâbyâaâslowâretardationâofâtheâthrottleâinâaccordanceâwithâtheâNTSBârecommendation.âThisâcarefulâtechniqueâwillâprotectâtheâengine,âandâatâtheâsameâtime,âprovideâforâinstantâpowerâifâitâisâneeded.
âAlthoughâ theâ smal lerâ four-cyl inderâ enginesâ ofâ theââlow-compression,âlow-horsepowerâvarietyâdoânotâgenerallyâuseâaâcylinderâheadâ temperatureâgage,â theâhigherâpowered,âmoreâcomplexâpowerâplantsârequireâaâcylinderâheadâtemperatureâgageâinâorderâtoâpreventâunwittingâabuseâbyâtheâpilot.â
If head temperatures are higher than normal during flight, it should not be ignored, because there is some reason for it. Itâmayâbeâcausedâbyâhotâambientâtemperatures,âaâleanâfuelâmeteringâdeviceâatâhigherâthanâcruiseâpower,âbadâbafflesâorâleakingâcowling,âorâmalfunctioningâofâ theâ ignitionâsystem.âEvenâoldâandâ tiredâengineâmountsâthatâallowâtheâengineâtoâsagâslightlyâmayâcauseâaâchangeâinâtheâairflowâpatternâandâanâabnormalâincreaseâinâCHT.âItâisâalsoâpossibleâthatâaâmechanicalâproblemâmayâbeâdevelopingâinâtheâengine.
Whenâhigherâthanânormalâcylinderâheadâtemperaturesâareâshowingâonâtheâgage,âtheâpilotâshouldâtakeâstepsâtoâbringâtheâtemperaturesâdownâtoâtheânormalâoperatingârangeâinâorderâtoâkeepâtheâremainingâflightâsafe.âHeadâtemperaturesâmayâbeâreducedâby:
1.âEnrichingâtheâmixture
2.âAdjustingâcowlâflaps
3.âReducingâpower
4.âAnyâcombinationâofâtheâabove
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Weâsuggestâ thatâ inâorderâ toâhelpâ theâmechanicâdiagnoseâ theâproblem,âtheâpilotâorâsomeâmemberâofâtheâcrewâshouldâmakeâaâwrittenârecordâofâtheâengineâinstrumentâreadingsâduringâtheâaboveâflightâconditionâandâpresentâitâtoâtheâmaintenanceâpeople.
Aâfirstâstepâinâdiagnosingâabnormalâcylinderâheadâtemperaturesâwouldâbeâensuringâthatâtheâgagesâareâprovidingâaccurateâreadings.âIfâtheyâare,âtheâmechanicâcanâthenâproceedâtoâcheckâengineâbafflesâthatâmayâhaveâdeteriorated,âproperâflowâofâ theâfuelâmeteringâdevice,âandâthenâotherâmoreâtime-consumingâchecksâforâignitionâorâmechanicalâmalfunction.
Theâcylinderâheadâtemperatureâgageâ(CHT)âhelpsâtheâpilotâpro-tectâhisâengineâagainstâtheâthreatâofâexcessiveâheat.âMostâGeneralâAviationâaircraftâ takeâtheâCHTâoffâ theâhottestâsingleâcylinderâofâtheâfour-âsix-âorâeight-cylinderâpowerâplantsâdeterminedâbyâextensiveâflightâtests.âOptionalâinstallationsâofferâreadingsâfromâallâcylinders.âInâLycomingâengines,âallâcylindersâareâdrilledâtoâaccommodateâaâCHTâbayonet-typeâthermocouple.
Someâoperatorsâ inâ theâ fieldâhaveâbeenâusingâ aâ sparkâplugââgasket-typeâ installationâ inâorderâ toâgetâ cylinderâheadâ tem-peratureâreadings.âLycomingâEngineeringâdoesânotâcurrentlyââapproveâ thisâmethodâofâdeterminingâCHT.âNotâonlyâ isâ theâmethodâ lessâaccurateâ thanâ theâ recommendedâ thermocoupleâtype,âbutâtheâtemperatureâreadingsâdifferânoticeablyâfromâtheâapprovedâinstallations.
Minimumâin-flightâCHTâshouldâbeâ150ËâFâ(65ËâC),âandâmaximumâinâmostâdirect-driveânormallyâaspiratedâLycomingâenginesâ isââ500ËâFâ(260ËâC).âSomeâofâourâhigher-poweredâmoreâcomplexââenginesâhaveâaâmaximumâlimitâofâ475ËâFâ(245ËâC).âAlthoughâtheseâareâminimumâandâmaximumâlimits,âtheâpilotâshouldâoperateâhisâorâherâengineâatâmoreâreasonableâtemperaturesâinâorderâtoâachieveâtheâexpectedâoverhaulâlifeâofâtheâpowerâplant.âInâourâmanyâyearsâofâbuildingâengines,âtheâenginesâhaveâbenefitedâduringâcontinuousâoperationâbyâkeepingâCHTâbelowâ400ËâFâinâorderâtoâachieveâbestâlifeâandâwearâofâtheâpowerâplant.âInâgeneral,âitâwouldâbeânormalâduringâall-yearâoperations,âinâclimbâandâcruiseâtoâseeâheadâtem-peraturesâinâtheârangeâofâ350ËâFâtoâ435ËâF.
Ifâanâengineâhasâbayonetâprobesâinâallâcylinders,âitâisânotâunusualâtoâseeâvariationsâinâCHTâreadingsâonâfuel-injectedâenginesâofâ100ËâFâbetweenâcylinders,âandâasâmuchâasâ150ËâFâonâenginesâwithâfloat-typeâcarburetors.âWithâtheâlatter,âanâimportantâcauseâofâtheâvariationâisâtheâkindâofâdistributionâofâfuelâandâairâtoâtheâindividualâcylinders.âOtherâinfluencesâonâCHTâareâsuchâitemsâasâcylinderâbaffles,âcowling,âcowlingâflaps,âlocationâofâengineâaccessoriesâand,âofâcourse,âmanualâcontrolâofâfuelâmixture.
ItâisâveryâimportantâthatâtheâCHTâprobesâbeâcheckedâonâaâregularâbasis.âWhenâtheseâbayonetâprobesâdeteriorate,âtheyâtendâtoâgiveâreadingsâthatâareâlessâthanâtheâactualâtemperatureâofâtheâcylinderâhead.âThisâcanâresultâinâoperationâaboveâtheârecommendedâmax-imumâtemperatureâwithoutâtheâpilotâevenâknowingâit.
OperatorsâfrequentlyâaskâaboutâtheâdifferenceâbetweenâtheâCHTâandâEGTâ(exhaustâgasâtemperature)âsystems,âandâtheirâmeaningâtoâtheâpilotâduringâoperationâofâtheâengineâorâengines.âTheâEGTâprobeâisâinstalledâinâaâdifferentâlocationâfromâtheâCHT,âorâaboutâfourâ inchesâ fromâtheâcylinderâheadâdownâ theâexhaustâ stack.âAlthoughâtheâEGTâhasâsomeâtroubleshootingâability,â itâ isâpri-marilyâaâfuel-managementâinstrument.âOnâtheâotherâhand,âtheâCHTâisâanâengineâinstrumentâdesignedâtoâprotectâtheâpowerâplantâagainstâitsâenemy,âexcessiveâheat.
Theâpresent-dayâpistonâengineâinstrumentsâusedâinâtheâtypicalâgeneralâaviationâairplaneâareânotâprecisionâ laboratoryâ instru-ments.âWeâexcludeâtheâturbineâandâjet-poweredâaircraftâfromâthisâdiscussionâandâwillâconsiderâonlyâpistonâengines,ârecognizingâthatâ theâmoreâexpensiveâpressurizedâtwin-engineâmodelsâmayâalsoâbeâexceptions.
Nevertheless,âtheâpurposeâofâthisâbriefâpresentationâisâaâpracticalâapproachâtoâinterpretingâtheâreadingsâofâyourâengineâinstrumentsâinâaccomplishingâaâsafeâandâefficientâflight.âIf,âforâexample,âyouâwereâtoâobserveâanâirregularâreadingâofâoneâengineâinstrument,âitâcallsâforâaâcross-checkâonâallâotherâinstruments,âandânotârelyingâonâoneâinstrumentâasâaâbasisâforâaâdecisionâaffectingâflight.
Sinceâtheâengineâisâdependentâonâfuel,âweâconsiderâtheâgasolineâgageâasâaârelatedâengineâinstrument.âIfâpilotsâareâgoingâtoâattemptâtoâstretchâtheirâflightârangeâcloseâtoâlimits,âtheyâshouldâbeâawareâofâtheâerrorsâinâtheâgagesâvs.âtheâactualâusableâfuel.âSomeâmodernâsingle-engineâaircraftâhaveâhadâtheâgasâgageâshowâseveralâgallonsâremaining,âwhenâinâreality,â theâ tankâwasâempty.âOthersâhaveâindicatedâaâspecificânumberâofâgallonsâwhenâfilled,âbutâactuallyâtheâtankâheldâseveralâgallonsâlessâthanâindicated.
Therefore,â inâplanningâforâeachâflight,ârememberâthatâgeneralâaviationâengineâinstrumentsâareânotâprecisionâlaboratoryâtypes,âsoâcross-check,âandâgiveâyourselfâanâextraâmarginâforâsafety.
Anâimportantâpartâofâtheâengine-startingâprocedureâisâtheâprimingâtechnique.âOfâcourse,âtheâPilotâsâOperatingâHandbookâwillâspecifyâtheâstepsâinâstartingâaâspecificâmodelâengine.âHowever,âsomeâofâtheâpilotâhandbooksâmayânotâexplainâwhyâcertainâproceduresâareâusedâinâtheâstartingâprocess.
Primingâcanâbeâbestâaccomplishedâwithâanâengineâprimingâsystem,âasâopposedâtoâuseâofâtheâthrottle.âTheâprimerâpumpsâextraâfuelâdirectlyâintoâtheâcylinderâintakeâportâorâinductionâsystem.âSomeâfloat-typeâandâpressureâcarburetorsâalsoâprovideâaâsupplementalâsourceâofâpriming.âLycomingâenginesâofâmoreâthanâ118âHPâhaveâaâthrottleâpumpâwhichâcanâbeâusedâforâprimingâunderâmoderateâambientâtemperatureâconditionsâwhileâturningâtheâengineâwithâtheâstarter.
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Pilotsâshould,âhowever,âbeâadvisedâthatâexcessiveâthrottleâprimingâcanâcauseâfloodingâofâtheâcarburetorâandâairbox,âandâresultâ inâaâfireâinâtheâinductionâsystemâorâonâtheâoutsideâwhereâtheâfuelâdrainsâoverboard.âIfâtheâoperatorâfloodsâtheâengineâbyâpumpingâtheâthrottleâandâhasâaâfire,âitâisâpossibleâtoâhandleâsuchâaâfireâinâtheâearlyâstagesâbyâcontinuingâtoâturnâtheâengineâwithâtheâstarter,âtherebyâsuckingâ theâ fireâbackâ intoâ theâengine.âFurthermore,ââifâthereâisâanyâfireâonâtheâoutsideâofâtheâengine,âifâtheâengineâstarts,âthereâisâaâgoodâchanceâitâwillâblowâoutâtheâexternalâfire.
Ifâ thereâ isâ floodingâofâ theâengineâwithoutâaâfire,â theâoperatorâshouldâopenâtheâthrottleâfullâandâcloseâtheâmixture;â(seeâOperatorâsâHandbookâonâmixture)âturnâtheâengineâoverâseveralâtimesâwithâtheâstarterâtoâclearâit;âthenâbeginâagainâwithâaânormalâstartâroutine.
MostâLycomingâ fuel-injectedâenginesâareâsimplyâprimedâbyâturningâtheâfuelâboostâpumpâon,âopeningâtheâmixtureâbrieflyâtoâfullârich,âandâcrackingâtheâthrottle.âAnyâpumpingâofâtheâthrottleâisâineffectiveâuntilâtheâengineâbeginsâtoâfire.
FUEL CONTAMINATION â Water (says the FAA) is the principal contamination of aviation fuel. For a safe flight, carefully drain fuel sumps at each preflight.
Asâ anâ engineâ manufacturer,â weâ areâ frequentlyâ askedâ aboutâtheâproperâuseâofâ theâfuelâboostâpumpâwithâourâpowerâplants.âAlthoughâweâcanâtâpretendâ toâbeâanâexpertâonâ theâfuelâboostâpumpâitself,âweâhaveâsomeâpositiveârecommendationsâconcerningâitsâuseâwithâourâengines.âWhereâaâboostâpumpâisâprovidedâbyâtheâairframeâmanufacturer,âandâtheâairframeâPilotâsâOperatingâHandbookâhasâaâlimitedâtreatmentâofâtheâuseâofâtheâfuelâboostâpump,âperhapsâ thisâdiscussionâcanâprovideâtheânecessaryâfuelâboostâpumpâinformationâforâtheâpilotâinâorderâtoâoperateâhisâorâherââengineâasâsafelyâasâpossible.
Itâisânecessaryâtoâsupplyâtheâengineâwithâaâsteady,âuninterruptedâflowâofâfuelâforâallâoperatingâconditions.âEntrappedâair,âtempera-tureâchanges,âpressureâdrops,âagitationâinâtheâfuelâlinesâandâotherâfactorsâaffectâtheâreleaseâofâairâandâvaporâfromâtheâfuelâsystem.âUnderâsomeâcircumstancesâwhereâanâengine-mountedâfuelâpumpâisâprovided,âitâmayânotâbeâableâtoâpumpâaâcontinuousâfuelâsupplyâfreeâofâexcessiveâvapor.
Anâeffectiveâcontinuousâfuelâsupplyâisâprovidedâbyâuseâofâtheâfuelâboostâpump.âAsâaâgeneralârecommendation,âtheâfuelâboostâpumpâshouldâbeâusedâwithâLycomingâenginesâinâallâconditionsâwhereâthereâisâanyâpossibilityâofâexcessiveâvaporâformation,âorâwhenâaâtemporaryâcessationâofâfuelâflowâwouldâintroduceâundesirableâhazards.âTheâconditionsâunderâwhichâLycomingârecommendsâoperationâofâtheâfuelâboostâpumpâareâasâfollows:
1.âEveryâtakeoff.
2.âClimbâafterâtakeoffâunlessâPilotâsâOperatingâHandbookâsaysââitâisânotânecessary.
3.âWhenâswitchingâfuelâselectorsâfromâoneâseparateâfuelâtankââ âtoâanother,âtheâfuelâboostâpumpâshouldâbeââonââinâtheânewââ âtankâuntilâtheâoperatorâisâassuredâthereâwillâbeânoâinterruptionâofâtheâfuelâflow.
4.âEveryâlandingâapproach.
5.âAnyâtimeâtheâfuelâpressureâisâfluctuating,âandâtheâengineâisââ ââaffectedâbyâtheâfluctuation.
6.âHotâweather,âhotâengineâgroundâoperationâwhereâfuelâvaporâââproblemsâcauseâerraticâengineâoperation.
7.âSomeâGeneralâAviationâaircraftârequireâtheâuseâofâtheâfuelââ âboostâpumpâduringâhigh-altitudeâflight.âThisâwillâbeâspelledââ âoutâinâtheâPilotâsâOperatingâHandbook.
8.âIfâtheâengine-mountedâfuelâpumpâfails.
Ifâtheâfuelâboostâpumpâisâusedâduringâgroundâoperation,âdonâtâfailâtoâcheckâtheâconditionâofâtheâengine-mountedâfuelâpumpâbeforeâtakeoffâbyâturningâtheâboostâpumpâoffâbriefly,âandâthenâbackââonââforâtakeoff.âIfâtheâengine-mountedâpumpâhasâfailed,âitâwouldâbeâsaferâtoâknowâthatâonâtheâgroundâratherâthanâinâtheâairâwhenâtheâfuelâboostâpumpâisâturnedââoff.â
Whenâinâdoubt,âdoâtheâsafestâthingâandâuseâtheâfuelâboostâpumpâwithâLycomingâengines.âDonâtâbeââstingyââwithâtheâboostâpump.âInâmostâcases,âtheyâlastâtheâoverhaulâlifeâofâtheâengine,âandâareâthenâexchangedâorâoverhauledâthemselves.âASâAâREMINDER,âtheâairframeâPilotâsâOperatingâHandbookâisâtheâauthorityâifâboostâpumpâinformationâisâspelledâoutâinâit.
Suddenâcoolingâisâdetrimentalâtoâtheâgoodâhealthâofâtheâpistonâaircraftâengine.âLycomingâServiceâInstructionâ1094Dârecommendsâaâmaximumâtemperatureâchangeâofâ50ËâFâperâminuteâtoâavoidâshock-coolingâofâtheâcylinders.
Operationsâ thatâ tendâ toâ induceâ rapidâ engineâ cooldownâ areââoftenâassociatedâwithâaâfastâletdownâandâreturnâtoâtheâfieldâafterâdroppingâparachutistsâorâaâgliderâtow.âThereâareâoccasionsâwhenâAirâTrafficâControlâalsoâcallsâforâfastâdescentsâthatâmayâleadâtoâsuddenâcooling.
Theâengineâproblemsâthatâmayâbeâexpectedâwhenâpilotsâconsis-tentlyâmakeâfastâletdownsâwithâlittleâorânoâpowerâinclude:
1.âExcessivelyâwornâringâgroovesâaccompaniedâbyâbrokenârings.
2.âCrackedâcylinderâheads.
3.âWarpedâexhaustâvalves.
4.âBentâpushrods.
5.âSparkâplugâfouling.
Generallyâspeaking,âpilotsâholdâtheâkeyâtoâdodgingâtheseâprob-lems.â Theyâ mustâ avoidâ fastâ letdownsâ withâ veryâ lowâ powerââ(high-cruiseâRPMâandâlowâmanifoldâpressure),âalongâwithârichâ
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mixturesâthatâcontributeâtoâsuddenâcooling.âItâisârecommendedâthatâpilotsâmaintainâatâleastâ15"âMPâorâhigher,âandâsetâtheâRPMâatâtheâlowestâcruiseâposition.âThisâshouldâpreventâringâflutterâandâtheâproblemsâassociatedâwithâit.
Letdownâspeedâshouldânotâexceedâhighâcruiseâspeedâorâapproxi-matelyâ1,000âfeetâperâminuteâofâdescent.âKeepingâdescentâandâairspeedâwithinâ theseâ limitsâwillâhelpâ toâpreventâ theâsuddenâcoolingâ thatâ mayâ resultâ inâ crackedâ cylinderâ heads,â warpedââexhaustâvalvesâandâbentâpushrods.
Theâmixtureâsettingâalsoâhasâanâeffectâonâengineâcooling.âToâreduceâsparkâplugâfoulingâandâkeepâtheâcylinderâcoolingâwithinâtheârecommendedâ50Ëâper-minuteâlimit,â theâmixtureâshouldâbeâleftâatâtheâleanâsettingâusedâforâcruiseâandâthenârichenedâgradu-allyâduringâdescentâfromâaltitude.âTheâleanâmixture,âmaintainingâsomeâpowerâandâusingâaâsensibleâairspeedâshouldâachieveâtheâmostâefficientâengineâtemperaturesâpossible.
Theâoperatingâtechniquesârecommendedâinâthisâarticleâareâworthâconsiderationâasâtheyâwillâbeâaâpositiveâstepâtowardâsavingâdol-larsâthatâmightâbeâspentâonâmaintenance.âWhateverâtheâcircum-stances,âpilotsâmustâplanâtheirâflightâoperationsâsoâthatâtheâpoten-tialâdamageâcausedâbyâsuddenâengineâcoolingâcanâbeâavoided.â
Knowledgeâgainedâfromâtheâexperienceâofâothersâisâusuallyâtheâeasyâwayâtoâlearn.âInâtheâcaseâofâstickingâvalvesâthatâmayâdamageâanâengineâorâcauseâitâtoâfail,âitâisâsurelyâbestâifâtheâknowledgeâisânotâacquiredâfirsthand.âTheâexperienceâofâothersâisârelatedâinâtheâfollowingâparagraphs.
Oneâofâ theâ regionalâ serviceâmanagersâhereâatâ theâLycomingâfactoryâ indicatedâ thatâhisâexperienceâoverâ theâyearsâ includedâworkingâonâenginesâwithâstickingâvalves.âHeâcommentedâthatâtheâengineâwillâalmostâalwaysâprovideâaâwarningâbyârunningâveryâroughâatâstart-up.âAsâ theâengineâwarmsâup,â itâmayâ thenâsmoothâoutâafterâaâfewâsecondsâandârunânormally,âbutâtheâini-tialâroughnessâisâaâwarningâthatâpreventiveâmaintenanceâactionââisârequired.
Justâaâfewâdaysâafterâtheseâcommentsâwereâmade,âaâconversationâwithâanâaircraftâownerâconfirmedâthatâ theâregionalâmanagerâsâcommentsâwereârightâonâtarget.âThisâisâtheâstoryâwhichâtheâaircraftâownerârelated.
Anâaircraftâhadâbeenâpurchasedârecently,âandâtheâownerâflewâitâtoâaltitudeâinâtheâvicinityâofâhisâhomeâairportâtoâsatisfyâhimselfâofâtheâaircraftâcapabilityâtoâflyâoverâmountainousâterrainâduringâaâplannedâvacationâtrip.âContentâthatâtheâaircraftâandâengineâwereâcapableâofâmeetingâhisârequirements,âtheâvacationâtripâwasâundertaken.âAllâwentâsmoothlyâonâtheâfirstâ300-mileâlegâofâtheâtripâwhichâendedâwithâaâplannedâovernightâstop.
Whenâ theâengineâwasâstartedâ theânextâday,â itâwasâvery,âveryârough,âbutâsmoothedâoutâandâranânormallyâafterâaâshortâtime.âWithâtheâengineârunningâsmoothly,âtheâvacationâtripâcontinuedâtoâitsââ
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destination.âTheâaircraftâwasâthenâtiedâdownâandânotâoperatedâuntilâitâwasâtimeâforâtheâreturnâtripâââaâperiodâofâaboutâoneâweek.
Asâtheâengineâwasâstartedâforâtheâreturnâtrip,âitâagainâgaveâindica-tionsâthatâaâvalveâwasâmomentarilyâstickingâ...âitâranâveryâroughâforâseveralâseconds,âbutâthenâsmoothedâout.âWithâtheâengineârunningâsmoothlyâagain,âtheâreturnâtripâwasâstarted.âAfterâoneâtoâtwoâhoursâofâflightâatâaltitude,âoverâmountainousâterrain,âtheâengineâranâveryâroughâagainâforâaâshortâperiodâofâtime,âandâthenâsmoothedâout.âTheâpilotâdecidedâtoâlandâatâtheânearestâairport.
Examinationâofâtheâengineârevealedâaâconsiderableâamountâofâoilâleakage.âTheâcauseâââaâvalveâwhichâhadâstuckâsolidlyâandâcausedâtheâpushrodâtoâbend.âThisâbendingârupturedâtheâpushrodâshroudâtubeâandâallowedâoilâtoâescape.âThisâisâaâclassicâexampleâofâtheâdamageâthatâstickingâvalvesâcanâcause.
Theâ lessonâ toâbeâ learnedâ isâquiteâsimple.âDoânotâneglectâ theâwarningâsigns.âPerhapsâtheâexperienceârelatedâhereâwillâallowâothersâtoârecognizeâaârough-runningâengineâatâstart-upâasâaâpos-sibleâindicationâofâstickingâvalves.âTheânextâstepâisâtoâtakeâimme-diateâactionâtoâpreventâdamage.
Althoughâ thereâmayâbeâanâoccasionalâexception,â itâ isâalmostâalwaysâanâexhaustâvalveâ thatâsticks.âToâpreventâ furtherâvalveâstickingâandâ toâreduceâ theâpossibilityâofâdamage,âallâexhaustâvalveâguidesâshouldâbeâcleanedâofâanyâcarbon,âvarnishâorâotherâcontaminationâbuildup.âThisâ isâaccomplishedâbyâreamingâ theâguidesâtoâtheirâoriginalâsizeâasâspecifiedâinâLycomingâPublicationâSSPâ1776,âTableâofâLimits.âTheâ latestâ revisionâofâLycomingâServiceâInstructionâ1425âprovidesârecommendationsâtoâreduceâtheâpossibilityâofâvalveâsticking.â Inâparticular,âPartâ IIIâofâ theâinstructionâgivesâaâprocedureâforâreamingâvalveâguidesâthatâcanâbeâaccomplishedâwithoutâremovingâtheâengineâfromâtheâaircraftâorâtheâcylindersâfromâtheâengine.
Consideringâthatâtheâproperlyâtimedâsequenceâofâvalveâopeningâandâclosingâisâessentialâtoâefficientâandâreliableâengineâoperation.âAnytimeâthoseâvalvesâstickâforâanyâreason,âitâisâaâseriousâproblem.âTherefore,âtheâpurposeâofâthisâarticleâisâtoâprovideâourâreadersâwithâsomeâinsightâintoâthisâproblemâalongâwithâmethodsâtoâhelpâavoidâit.
Theâspaceâbetweenâtheâcontinuouslyâmovingâvalveâstemâandâitsâstationaryâvalveâguideâisâextremelyâcritical.âNoteâthatâtheâamountâofâclearanceâcanâbeâaffectedâbyâhighâtemperatures,âengineâclean-linessâandâextendedâperiodsâofâengineâ inactivity.âChangesâ inâvalve-to-guideâclearanceâcanâoccurâduringâtheâcourseâofâengineâoperation.âInâotherâwords,âaâstickingâorâbrokenâvalveâmayânotâbeâtheâfaultâofâtheâengine.âItâisâpossibleâtoâpromoteâvalveâsticking,âandâthereâareâactionsâthatâcanâbeâtakenâtoâreduceâorâeliminateâtheâpossibilityâofâ thisâphenomena.âTheseâactionsâwillâaffectâengineâcooling,âfuelâmanagementâandâinternalâengineâcleanliness.
Engineâcleanlinessâisâaâprimaryâconsiderationâthatâ isâaffectedâbyâmanyâmaintenanceâandâoperationalâprocedures.âProperâfilterâmaintenanceâisâoneâsuchâitem.âTheâinductionâairâfilterâisâtheâfirstâ
lineâofâdefenseâinâkeepingâdirtâandâabrasivesâfromâenteringâtheâengine.âToâpreventâdirtâfromâenteringâtheâengine,âtheâfilterâmustâformâaâgoodâsealâwithâtheâfilterâholder,âandâtheâinductionâsystemâshouldâbeâfreeâofâairâleaks.âTheâairâfilterâshouldâbeâcleanedâorâchangedâonâaâregularâbasis.âInâextremelyâdustyâconditions,âaâfilterâchangeâcouldâbeânecessaryâasâfrequentlyâasâeveryâfewâhoursâofâoperation.
Theâsecondâ lineâofâdefenseâagainstâdirtâandâabrasivesâ isâ theââfull-flowâoilâfilterâthatâisâstandardâwithâmostâLycomingâenginesânowâbeingâproduced.âOlderâenginesâwereâmanufacturedâwithâaâpressureâscreen,âbutâmayâbeâconvertedâtoâaâfull-flowâfilterâforâmoreâeffectiveâcleaningâofâtheâoil.âLycomingâServiceâPublicationâSSP-885-2âprovidesâinformationâandâinstructionsâneededâforâthisâconversion.
Anotherâcontributorâtoâaâvarietyâofâengineâproblems,âincludingâvalveâsticking,âisâfrequentâlongâperiodsâofâinactivity.âAnâengineâshouldâbeâflownâregularlyâtoâstayâinâtiptopâcondition.âTheâoilâinâtheâsumpâcollectsâresidueâfromâcombustionâsuchâasâmoisture,âacidâandâleadâsludge.âFlyingâtheâaircraftâ tendsâ toâheatâ theâoilâenoughâtoâvaporizeâ theâmoistureâandâhelpâeliminateâsomeâofâtheseâcontaminants,âbutâanâengineâ thatâ isânotâflownâwillâcol-lectâmoisture,âacidsâandâgumsâwhichâmayâcontributeâtoâcorro-sionâandâtoâvalve-trainâproblems.âInâadditionâtoâfrequentâflight,âtheseâcontaminantsâareâalsoâeliminatedâ fromâ theâengineâbyâchangingâ theâoil.âLycomingâServiceâBulletinâNo.â480âmakesâtheseâ recommendationsâ forâenginesâoperatingâunderânormalââ(non-dusty)âconditions:
a.â50-hourâintervalâoilâchangeâandâfilterâreplacementâforâallâenginesâusingâaâfull-flowâfiltrationâsystem.
b.â25-hourâ intervalâoilâchangeâandâscreenâcleaningâforâallââenginesâemployingâaâpressure-screenâsystem.
c.âAâtotalâofâfourâmonthsâmaximumâbetweenâoilâchangesâforâeitherâofâtheâsystemsâdiscussedâunderâa.âandâb.,âevenâifâtheâengineâisâânotâflown.
Reportsâfromâaircraftâownersâcontinueâtoâindicateâthatâtrouble-freeâoperationâthroughâTBOâisâmostâoftenâobtainedâwithâenginesâsubjectedâ toâ frequentâoilâchangeâ intervals.âAbsurdâasâ itâmayâseem,âanâengineâwhichâdoesânotâflyâregularlyâshouldâhaveâtheâoilâchangedâatâmoreâfrequentâflightâtimeâintervalsâthanâoneâthatâdoesâflyâregularly.
Preventingâaâbuildupâofâcontaminantsâ isâ justâasâ importantâasâeliminatingâthoseâthatâdoâform.âAvoidingâlongâperiodsâofâgroundâoperationâisâaâvitalâstepâsinceâmoistureâcanâenterâtheâbreather,âbutâwillânotâvaporizeâwhenâtheâoilâisânotâheatedâtoânormalâoper-atingâtemperatures.âGroundârunningâalsoâinvolvesâaâslightlyârichâmixtureâwhichâcontributesâtoâtheâformationâofâleadâsludgeâinâtheâoil.âDuringâflight,â theâdepositâofâ leadâsludgeâinâtheâoilâcanâbeâminimizedâbyâproperâleaning.
Althoughâsomeâexcessâfuelâisârequiredâforâengineâcoolingâduringâhigh-powerâoperation,âproperâleaningâatâcruise-powerâsettingsâwillâpromoteâcompleteâburningâofâtheâfuelâand,âtherefore,âaâminimumâofâleadâsludgeâdepositedâinâtheâoil.âThisâisâimportantâsinceâleadâsludgeâisânotâfilteredâout,âbutâisâremovedâbyâchangingâtheâoil.âTheâairframeâmanufacturerâsârecommendationsâandâlimitationsâforâleaningâshouldâbeâobserved,âbutâitâmayâbeâbeneficialâtoâbeâawareâ
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thatâwhenâpermittedâbyâtheâPilotâsâOperatingâHandbook,âleaningâtoâpeakâEGTâatâcruise-powerâsettingsâwillâproduceâcompleteâburningâofâtheâfuel/airâmixtureâforâbestâeconomyâandâreductionâofâcombustion-relatedâcontaminants.
Havingâ touchedâonâfuelâmanagementâandâmaintenanceâ itemsârequiredâ toâkeepâanâengineâcleanâ internally,â theâ finalâ factorâaffectingâpotentialâvalveâstickingâisâengineâoperatingâtempera-ture.âSomeâoperatingâproceduresâalreadyâdiscussedâalsoâhaveâanâeffectâonâengineâtemperature.âProlongedâengineâgroundârun-upâatâhigh-powerâsettings,âforâexample,âcanâcauseâengineâoverheatingâorâhotâspotsâsinceâcoolingâairflowâisânotâalwaysâadequateâwhenâtheâaircraftâisâstationary.
Sinceâproperâengineâoperatingâtemperaturesâfallâwithinâaâmin-imumâandâmaximumârange,âitâisâimportantâtoâconsiderâallâaspects.âItâmustâbeâemphasizedâthatâbaffles designed to direct cooling air over the cylinders must be maintained in good condition. Theyâplayâanâextremelyâimportantârole.âIfâtheseâbafflesâdeteriorateâorâareâinstalledâsoâthatâcoolingâairâisânotâadequatelyâcontainedâandâdirected,âhotâspotsâwhichâpromoteâaâleadâorâcarbonâbuildupâmayâoccur.âDuringâhotâweatherâinâparticular,âthoseâbafflesâorâductsâthatâdirectâcoolingâairâthroughâtheâoilâcoolerâmustâalsoâbeâmaintainedâinâgoodâcondition.
Theâpilot,âasâwellâasâmaintenanceâpersonnel,âwillâplayâanâimpor-tantâroleâinâensuringâthatâengineâoperatingâtemperaturesâdoânotâpromoteâvalveâsticking.âAsâmentionedâearlier,âgroundârunningâfarâinâexcessâofâtheâtimeânecessaryâforâengineâwarm-upâshouldâbeâavoided.âAlsoâtoâbeâconsideredâisâcontinuousâoperationâatâveryâlowâaircraftâspeedsâthatâmayânotâgenerateâtheâmostâefficientâflowâofâcoolingâairâoverâtheâengine.âThisâlackâofâeffectiveâcoolingâairâmayâcauseâsomeâareasâofâtheâengineâtoâbeâexcessivelyâhot,âandâthereforeâhaveâanâeffectâonâanyâcontaminantsâthatâareâinâtheâoil.âTheâformationâofâdepositsâisâpromoted,âwithâtheâexhaustâvalveâguideâareaâ theâmostâ likelyâ toâbeâaffected.âTheâresultâofâ theseâdepositsâmayâbeâaâstuckâorâstickingâvalve.
Theâotherâendâofâtheâspectrumâcontrollableâbyâtheâpilotâisâexces-sivelyârapidâcooldownâofâanâengineâ thatâhasâbeenârunningâatânormalâoperatingâ temperatures.âLycomingâenginesâareâmadeâwithâvariousâmetalsâthatâexpandâandâcontractâatâdifferentâratesâwhenâexposedâtoâheatâorâcold.âItâisâpoorâtechniqueâtoââchopââtheâpowerâfromâcruiseâorâhigherâpowerâsettingsâtoâidleâandâthenâstartâaârapidâletdownâwhichâdevelopsâexcessiveâcoolingâairflowâoverâtheâengine.âItâ isâalwaysâbestâtoâreduceâpowerâinâincrementsâsoâthatâengineâtemperatureâchangesâwillâoccurâgradually.âItâisâalsoâbeneficialâtoâcontinueâtheâengineâcoolingâprocessâafterâlandingâbyâensuringâthatâseveralâminutesâofâengineâoperationâatâ800âtoâ1200âRPMâareâallowedâbeforeâshutdown.âAtâlargeâairports,âthisâisâusuallyâaccomplishedâbyâ theâ timeâtaxiâ toâ theâparkingâareaâisâcompleted.âAtâairportsâwhereâclearingâtheârunwayâputsâ theââaircraftâinâtheâparkingâarea,âaâshortâperiodâofâadditionalâoperationâinâtheâ800âtoâ1200âRPMârangeâpriorâtoâengineâshutdownâwillâallowâtemperaturesâtoâstabilize.
Aâlogicalâquestionâafterâthisâlongâseriesâofâthingsâtoâdoâandâthingsânotâ toâdoâmightâbeâthis,ââIsâ thereâanyâwayâtoâtellâ ifâaâvalveâisâstickingâbeforeâseriousâdamageâoccurs?ââThereâareâsometimesâwarningâsignsâthatâshouldâbeâinvestigated.âAlthoughâthereâmayâbeâotherâcauses,âanâintermittentâhesitationâorâmissâinâtheâengineâ
mayâbeâanâindicationâthatâcarbonâorâotherâsimilarâcontaminantsâhaveâbuiltâupâ insideâ theâvalveâguideâcausingâ theâvalveâstemâtoâdragâinsteadâofâmovingâfreely.âTheseâcontaminantsâshouldâbeâremovedâbyâreamingâtheâguideâtoâ theâsizeâspecifiedâinâ theââLycomingâTableâofâLimitsâ(SSPâ1776).âTheâprocedureâtoâbeâusedâwhenâreamingâtoâremoveâvalveâguideâdepositâbuildupâisâfoundâinâLycomingâServiceâInstructionâ1425.âKnownâasââtheâoldâropeâtrickââtoâmanyâA&Pâmechanics,âthisâvalveâguideâreamingâpro-cedureârestoresâvalveâstemâtoâguideârunningâclearanceâandâcanâbeâaccomplishedâwithoutâremovingâtheâengineâfromâtheâaircraft.
Toâsummarize,âproceduresâ toâreduceâvalveâstickingâwillâalsoâreduceâtheâprobabilityâofâadditionalâengineâdamageâwhichâmayâcauseâlossâofâpowerâandâtheâneedâforâcostlyârepairs.âTheseâproce-duresâmayâbeâreducedâtoârelativelyâsimpleâterms:âTheâmaintenanceâandâoperationalâproceduresânecessaryâtoâavoidâstickingâvalvesâareâthoseâthatâkeepâtheâengineâcleanâinternallyâandâwhichâcauseâitâtoârunâwithinâproperâoperatingâtemperatureâranges.âTheâitemsâdiscussedâaboveâshouldâserveâasâaâguideâforâA&Pâmechanicsâandâforâpilots.
Theseâareâsomeâofâ theâmoreâcommonâquestionsâaskedâatâourâserviceâhanger:
QUESTION: Doâ yourâ new,â rebuiltâ orâ overhauledâ enginesârequireâaâbreak-inâperiodâthatâconsistsâofâcruiseâatâlow-powerâsettings?
ANSWER: Definitelyânot.âFlyâthemâasâyouâwouldâaâhigh-timeâengine.â Inâ fact,â so-calledââslowââ flyingâmayâhaveâharmfulâeffects.âTheâringsâmayânotâseatâproperlyâresultingâinâhigherâthanânormalâoilâconsumption.
QUESTION: Atâwhatârateâofâoilâconsumptionâdoesâcontinuedâoperationâofâtheâengineâbecomeâaâhazard?
ANSWER: Generallyâ speaking,âwhenâ theâoilâ consumptionâreachesâoneâquartâperâhour,âcorrectiveâactionâshouldâbeâtaken.âHowever,âmaximumâpermissibleâforâeachâparticularâengineâisâlistedâinâtheâengineâoperatorâsâmanual.
QUESTION: Whatâareâtheâdangersâofâoperatingâanâengineâwithâhighâoilâconsumption?
ANSWER: Whenâexcessiveâamountsâofâoilâgetâpastâtheârings,âthereâisâdangerâofâtheâringâstickingâorâbreakingâwithâaâdramaticâriseâ inâoilâ consumption.âThenâoilâ soakedâcarbonâ formsâatâaâfastârate.âAtâtheâsameâtime,âtheâpresenceâofâoilâinâtheâcombus-tionâchamberâhasâtheâeffectâofâloweringâtheâoctaneâratingâofâtheâfuel.âOperatingâtemperaturesâgoâup.âWeâhaveânowâsetâupâconditionsâinvitingâdetonationâand/orâpreignition.
QUESTION: IfâIâcanâtâgetâaviationâfuel,âmayâIâuseâautomotiveâfuelâifâoctaneâratingâisâequalâorâhigher?
ANSWER: No.âAsâanâengineâmanufacturer,âevenâ theâuseâofâautomotiveâfuelâwhereâanâSTCâhasâbeenâissuedâisâconsideredâriskyâandâisânotârecommended.âThereâareâ4âorâ5âgoodâreasonsâ
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andâallâareâimportant.âTheyâcanâbeâsummedâupâinâthreeâwordsâââpotentialâengineâfailure.
QUESTION: Whatâ isâ theâmostâcommonâcauseâofâprematureââengineâwear?
ANSWER: Dirtâ inâ theâ airâ enteringâ theâ engineâ throughâ theâcarburetorâorâinjectorâdueâtoâworn-outâairâfilter,âtornâinductionâhosesâorâbrokenâairâboxes,âandâthenâbeingâcarriedâthroughâtheâengineâbyâtheâoil.
QUESTION: Doesâ theâspacerâbetweenâ theâpropellerâandâ theââengineâserveâanyâpurposeâotherâthanâstreamliningâtheânacelle?
ANSWER: Yes.âInâmanyâcases,âmovingâtheâpropellerâforward,âwhichâ increasesâ theâclearanceâbetweenâpropellerâandâcowl,âincreasesâpropellerâefficiencyâandâreducesânacelleâvibration.
QUESTION: Inâ someâ cases,âweânoteâ aâminorâ discrepancyâbetweenâtheâengineâoperatorâsâmanualâandâtheâairplaneâPilotâsâOperatingâHandbook.âWhichâoneâshouldâbeâfollowed?
ANSWER: TheâairframeâPilotâsâOperatingâHandbook.âForâvariousâreasons,âafterâtheâengineâisâinstalledâinâtheâairframe,âoperationalâtechniquesâmayâbeâalteredâorâcertainârestrictionsâmayâbeâplacedâonâtheâengine.âAâsimpleâexampleâwouldâbeâaâplacardârestrictingâcontinuousâoperationâinâaâcertainâRPMârange.
QUESTION: Iâ flyâ anâ aircraftâ equippedâ withâ aâ fixed-pitchââpropeller.âDuringâcruise,âIâmâtoldâtoâkeepâincreasingâtheâRPMâasâmyâcruisingâaltitudeâisâincreased.âSinceâIâflyâprettyâhigh,âinâorderâtoâholdâ65%âpower,âIâfindâtheâRPMâisâmostlyâatâ2550âtoâ2600.âWonâtâthisâhighâRPMâreduceâtheâengineâlife?
ANSWER: No.âTheâhigherâRPMâwonâtâharmâ theâengineâorâreduceâserviceâlife.âRemember,âyouâareâincreasingâtheâRPMâonlyâ toâholdâ theâ sameâpowerâyouâhadâatâaâ lowerâaltitudeâatâsay,â2350âRPM.
QUESTION: Isâ thereâ reallyâ anyâ differenceâ betweenâ goodââautomotiveâoilâandâaviationâoil?
ANSWER: Yes,â indeedâ thereâ is!âDonâtâeverâuseâautomotiveâoilâ inâyourâaircraftâ engine.âTheseâoilsâ areânowâblendedâ forâuseâwithâunleadedâfuels,âandâ theâadditivesâ inâautoâoilâcauseâproblemsâinâanâaircraftâengineâ thatâoperatesâatâmuchâhigherâtemperaturesâ thanâ theâautomobileâengine.âWeâhaveâencoun-teredâenginesâwithâholesâburnedâinâpistonsâdueâtoâtheâuseâofâautomotiveâoilsâthatâhaveâanâashâdepositâcausingâpreignition.âItâseemsâawfullyâhardâtoâconvinceâpeopleâwhoâhaveâhadâgreatâsuccessâwithâtheâoilâusedâinâtheirâcarâthatâitâmayânotâbeâusedâinâtheirâaircraftâengine.
NOTE â Since we have had several questions on fuels and oils, it might be well to mention that we canât think of a quicker way to void your engine warranty than by using anything other than the recommended and FAA-approved aviation fuels and oils.
QUESTION: Whatâ areâ someâ commonâcausesâ ofâ excessiveâoilâ consumptionâotherâ thanâ theâburningâofâoilâ dueâ toâhighââengineâtime?
ANSWER: Buildingâupâofâcrankcaseâpressureâdueâtoââblow-byââcausedâbyâringâwearâmayâresultâ inâoilâbeingâblownâoutâofâ theâbreather.âTheâsameâthingâcanâresultâfromâbrokenâpistonârings.âOilâ
mayâbeâpumpedâoverboardâdueâtoâaâfaultyâvacuumâpumpâorâfaultyâautomotive-typeâfuelâpump.
QUESTION: Myâdealerâadvisedâmeâtoâuseâstraightâmineralâoilâinâmyânewâengineâuntilâitâsââbrokenâin.ââHowâdoâIâknowâwhenâitâsââbrokenâinâ?
ANSWER: Whenâoilâconsumptionâhasâstabilized.âExample:âAfterâcontinuedâcheckingâofâoilâconsumption,âyouâhaveâdeter-minedâtheâengineâisâconsistentlyâusingâoneâquartâinâaâknownânumberâofâhours.âThisâperiodâshouldânotâexceedâ50âhoursâofâoperation.
QUESTION: Iâhaveâproblemsâwithâleadâfoulingâofâsparkâplugs.âWhatâcanâI,âasâaâpilot,âdoâaboutâit?
ANSWER: Severalâ things.â Seeâ thatâ youâ haveâ theâ correctââsparkâ plugsâ thatâ areâ recommendedâ byâ theâ engineâ manu-facturerâsâ charts,â notâ oddballsâ recommendedâ byâ someââwell-meaningâfriend.âAvoidâprolongedâidlingâonâtheâground.âAvoidâpower-offâdescents.âLeanâoutâatâcruiseâandâevenâonâshortâcross-countryâflights.âRotateâplugsâfromâbottomâtoâtopâeveryâ50âhoursâââorâ25âifânecessary.
Combined with âTurbocharging â A Brief Refresherâ
TurbochargingâhasâbeenâaâpartâofâeverydayâoperationsâforâsomeâpilotsâandâAâ&âPâmechanicsâforâmanyâyears.âTheâscienceâofâaddingâaâturbochargerâtoâanâaircraftâengineâandâmakingâthatâsystemâpro-videâaâbonusâinâoperatingâcapabilityâhasâbeenâwellâestablished.âTheâpurposeâofâthisâcombinedâandârewrittenâarticleâisâtoâshareâourâexperienceâandâgiveâaâthoroughârundownâofâwhatâtheâGeneralâAviationâpilotâshouldâknowâaboutâ turbochargedâflat-opposedâpistonâengines.âThroughâaâsoundâbasicâknowledge,âtheâpilotâcanârealizeâmoreâefficientâuseâofâhisâorâherâ turbochargedâengine.
WHY TURBOCHARGE?
Experienceâ hasâ taughtâ usâ thatâ flyingâ highâ andâ fastâ isâ mostâdesirableâonâcross-countryâflights,âandâtheâsmall,â lightweightâandârelativelyâ inexpensiveâ turbochargerâmakesâ thisâpossible.âTurbochargingâtheâflat-opposedâcylinderâaviationâengineâhasâalsoââallowedâcabinâpressurizationâinâgeneralâaviationâaircraft.
Theâ turbochargerâhasâmadeâ itâpossibleâ toâclimbâaboveâmostâofâ theâundesirableâflyingâweatherâ insteadâofâbangingâthroughâtheâpoorâvisibilities,âbumpyâair,âicingâandâslowerâspeedsâofâtheââaltitudesâbelowâ10,000âfeet.âTheâ rareâ lossâofâanâengineâ inâaâtwinâwillânotânecessarilyâresultâinâtheâairplaneâbeingâforcedâtoââdescendâintoâtheâweather,âbutâwillâmeanâmerelyâslowerâflightâwhileâstillâmaintainingâtheâdesired,âsafeâaltitudeâwithâtheâturbochargerâhelpingâtheâengineâtoâproduceâtheâneededâpower.
Withâgreaterâflexibilityâinâchoiceâofâaltitude,âitâisâpossibleâtoâtakeâbetterâadvantageâofâfavorableâwindsâandâavoidâturbulence.
Muchâsaferâflightâforâgeneralâaviationâaircraftâ isânowâpossibleâoverâhighâmountains.
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Theâturbochargedâengineâallowsâtheâpilotâtoâmaintainâsufficientâcruiseâpowerâatâhighâaltitudesâwhereâ thereâ isâ lessâdrag.âThisâmeansâ fasterâ trueâairspeedsâandâ increasedârangeâwithâbetterâfuelâeconomy.âAtâtheâsameâtime,âtheâpowerâplantâhasâflexibilityâandâcanâbeâflownâatâaâ lowâaltitudeâwithoutâgulpingâfuelâ likeââaâthirstyâturbine.
Theâturbochargedâpowerâplantâisâaâblessingâatâhigh-altitudeâairports.âTheânormallyâaspiratedâengineâmayâbeâmarginalâfromâtheseâfields,âbutâturbochargingâwillâprovideâseaâlevelâpowerâandâremoveâtheâaircraftâfromâtheâmarginalâcategoryâatâhigh-altitudeâairports.
Theâ turbochargedâ pistonâ engineâ offersâ theâ advantageâ ofââhigh-altitudeâflightâwithoutâtheâhighâcostâofâaâturbine-poweredâaircraft.âTheâaddedâutilityâandâeconomyâmakeâitâpopularâwithâsmallâbusinessesâandâalsoâwithâsomeâindividuals.
WHAT IS TURBOCHARGING?
Atâ theâriskâofâ insultingâ theâ intelligenceâandâexperienceâ levelâofâ someâreaders,âweâshouldâneverthelessâ review,â forâanyoneâinterestedâinâtheâbasicâprincipleâinvolvedâinâturbocharging,âandââanswerâtheâquestionâââWhatâisâturbocharging?
Thisâreviewâwillâbeâaânontechnicalâexplanationâofâwhatâturbo-chargingâdoesâforâ theâreciprocatingâengine.âAsâyouâknow,â theâaircraftâengineâderivesâitsâpowerâfromâtheâburningâofâaâmixtureâofâfuelâandâair.âAssumingâthatâthisâfuel/airâmixtureâretainsâaâconstantâratio,âtheâamountâofâpowerâtheâengineâdevelopsâwillâbeâdirectlyâproportionalâtoâtheâtotalâmassâofâairâpumpedâthroughâtheâengine.âClimbingâ toâaltitudeâ inâanâaircraftâequippedâwithâaânormallyâaspiratedâengineâprovidesâaâveryârealisticâexample;âasâ theâairâbecomesâlessâandâlessâdenseâwithâaltitude,âtheâengineâisâcapableâofâproducingâlessâandâlessâpowerâasâindicatedâbyâtheâdecreasingârateâofâclimbâandâeventuallyâtheâtotalâinabilityâtoâclimbâhigher.
Inâsimpleâ terms,â theâ turbochargerâprovidesâanâairâpumpâthatâallowsâusâtoâsupplyâtheâengineâwithâdenseâairâ(andâtheâoxygenâneededâforâcombustion)ânotâonlyâatâseaâlevel,âbutâalsoâwhenâoper-atingâinâtheâthinâairâatâaltitude.âTheâpumpâusedâinâaâturbochargerâmayâbeâdescribedâmoreâaccuratelyâasâaâcentrifugalâairâcompressorâthatâ isâmountedâonâaâshaft.âToâpowerâtheâcompressor,â theâhotâexhaustâgasesâthatâareâdischargedâasâwastedâenergyâinâaânormallyâaspiratedâengineâareânowâharnessedâbyâdirectingâthemâthroughâaâturbineâwheelâthatâmightâbeâdescribedâasâaâveryâsophisticatedâwindmill.âTheâturbineâwheelâisâmountedâonâtheâsameâshaftâasâtheâairâcompressorâsoâthatâduringâoperationâtheâcompressorâandâturbineâwillâturnâatâtheâsameâspeed.âTherefore,âasâmoreâexhaustâgasesâ(energy)âareâdirectedâoverâtheâturbine,âbothâwheelsâwillâturnâfasterâandâtheâdensityâofâtheâairâsuppliedâtoâtheâengineâbyâtheâcompressorâwillâincrease.âThisâallowsâtheâengineâtoâproduceâmoreâpower.âTheseâtwoâwheelsâmountedâonâaâshaftâareâenclosedâwithinâhousingsâthatâseparateâandâcontainâtheâtwoâfunctionsâjustâdiscussed;âthisâisâtheâturbocharger.
THE FACTORY TURBOCHARGED ENGINE
Whenâturbochargingâfirstâbecameâpopular,âsomeâcompaniesâusedâconversionâkitsâtoâaddâturbochargersâtoâaâstandardânormallyâaspi-ratedâengine.âTheseâinstallationsârequiredâaâSupplementalâTypeâCertificateâ(STC)âissuedâbyâtheâFAA.âTheâadd-onâsystemsâdidâmeetâwithâsomeâsuccess,âbutâtheâpilotâflyingâwithâtheseâsystemsâcouldâeasilyâcauseâseriousâengineâdamageâwithâjustâaâlittleâcare-lessness.âDamageâcausedâbyâtheseâadd-onâsystemsâwouldânotâbeâcoveredâbyâengineâmanufacturerâwarranty.
Engineâmanufacturersâhaveâbeenâprovidingâaâmatedâturbochargedâengineâpackageâforâbothârotaryâandâfixed-wingâaircraftâforâmanyâyears.âWhenâtheâengineâmanufacturerâcertifiesâsuchâaâpackageââ(eitherâcarburetedâorâfuelâinjected),âitâwillâhaveâseveralâturbocharge-orientedâdesignâfeatures,âandâmanufacturerâwarrantyâwillâapply.
Anâengineâ thatâproducesâmoreâ thanânormalâ seaâ levelâmani-foldâpressureâforâtakeâoffâandâclimbâwillâhaveâbeenâbeefedâupâwithâaâheavierâcrankshaftâforâthisâadditionalâpowerârequirement.âCombustionâchambersâareâprotectedâbyâusingâaâlowerâcompressionâratioâcomparedâtoânormallyâaspiratedâengines.
Asâourâ turbochargedâaircraftâ isâflownâhigher,â theâcompressorâwheelâmustârunâfasterâ toâcompensateâforâ theâ thinnerâair.âOneâproblemâinâcompressingâairâisâthatâitâgetsâhotter.âTherefore,âtheâhigherâweâfly,âtheâfasterâtheâcompressorâmustâturn.âThisâproducesâaâhotterâchargeâtoâtheâcylinders,âusuallyâreflectedâinâhigherâcyl-inderâheadâtemperatures.
Theseâhigherâengineâtemperaturesâmustâreceiveâcarefulâconsid-eration.âEngineâmanufacturersâinstallâexhaustâvalvesâandâguidesâofâspecialâheatâresistantâmetalsâtoâcopeâwithâtheseâtemperatures.âSpecialâoilâsquirtsâ inâ theâcrankcaseâdirectâaâstreamâofâoilâonââpistonsâtoâhelpâcoolâcriticalâareas.
Nowâ hasâ manyâ turbochargedâ engineâ modelsâ whichââareâFAAâcertified.âWithâtheâaddedâfeaturesâincorporatedâtoâcom-pensateâforâadditionalâheatâandâstress,âtheâfactoryâturbochargedâenginesâhaveâprovenâtoâbeâveryâreliableâpowerâplants.
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CONTROLLING TURBOCHARGER SPEED
Turbochargersâinâuseâtodayâmayârunâatâspeedsâupâtoâ110,000âRPM.â
Sinceâtheâspeedâatâwhichâaâturbochargerâmustâoperateâisâdependentâuponâtheâpowerâdesiredâfromâtheâengineâandâtheâdensityâofâtheâairâatâtheâaltitudeâatâwhichâtheâaircraftâisâflying,âitâisânecessaryâtoâprovideâtheâpilotâwithâtheâcapabilityâofâadjustingâturbochargerâspeed.âThisâisâaccomplishedâbyâcontrollingâtheâamountâofâexhaustâgasâthatâisâdirectedâtoâtheâturbineâsideâofâtheâturbocharger.âInâthoseâcasesâwhereâairâofâincreasedâdensityâisânotâneededâfromâtheâturbo-chargerâ(lowâaltitudeâorâlowâpowerârequired),âaâwastegateâinâtheâexhaustâsystemâisâallowedâtoâremainâopen,âandâtheâexhaustâgasâisâventedâaroundâtheâturbineâwheelâandâthroughâtheâwastegateâtoâtheâatmosphere,âveryâmuchâlikeâtheânormallyâaspiratedâengine.âAsâtheâdemandâforâdenseâairâincreases,âtheâwastegateâcanâbeâclosedâtoâaâpositionâthatâwillâforceâtheâproperâamountâofâexhaustâgasâintoâtheâturbineâandâthereforeâspeedâupâtheâcompressorâtoâmeetâtheâcur-rentâdemandâforâdenserâair.âAdjustingâturbochargerâspeedâtoâmeetâchangingâpowerârequirementsâisâaâmatterâofâprovidingânecessaryâcontrolsâoverâtheâwastegate,âandâthereforeâtheâflowâofâexhaustâgas.
AUTOMATIC VS. MANUAL CONTROLS
Controlâofâ theâwastegateâ forâ factory-installedâ turbochargersââisâ accomplishedâ byâ twoâ basicâ methods.â Theseâ areâ manualââcontrolâorâautomaticâcontrol.âManualâcontrolâisâalsoâdividedâintoâtwoâtypes;â theâfixed-bleedâsystemâandâtheâ throttle/wastegateââinterconnect.
Thoseâenginesâutilizingâmanualâ controlâoverâ theâwastegateârequireâ muchâ moreâ pilotâ attentionâ thanâ installationsâ withââautomaticâcontrol.âPilotâworkloadâisâreducedâwithâaâturbochargerâthatâutilizesâanâautomaticallyâcontrolledâwastegateâunit.â
Theâautomaticâcontrollerâadjustsâforâtemperatureâorâpressureâorâboth,âdependingâonâtheâvariousâapplications,âandâpermitsâ theâturbochargerâ toâbeâcontrolledâbyânormalâ throttleâmovements.âTheâautomaticâcontrolâfeatureâisânormallyâsetâatâtheâfactoryâandâshouldânotâbeâtamperedâwithâinâtheâfield.
OPERATION
Bothâtheâmechanicâandâtheâpilotâmustâknowâhowâtoâoperateâtheâspecificâturbochargedâsystemâheâworksâonâorâflies,âsoâthisâinfor-mationâisânotâintendedâasâaâsubstituteâforâtheâEngineâOperatorâsâManualâorâtheâPilotâsâOperatingâHandbook.âTheâtreatmentâhereâisâmoreâgeneral.âButâweâcanâaugmentâthoseâbasicâreferencesâwithâexplanationsâfromâtheâpilotâsâpointâofâview.
Theâmostâpracticalâconsiderationâofâoperationâisâtoâtreatâtheâauto-maticâandâmanualâsystemsâseparately.âHowever,âbeforeâweâdoâthat,âthereâareâaâfewâbasicâhandlingâorâoperationalârequirementsâthatâapplyâtoâbothâsystems.
1.âTheâthrottleâorâ throttlesâmustâbeâoperatedâsmoothlyâorâ theââenginesâwillâsurge,âwhichâisâhardâonâtheâturbochargerâandâtheâengine.âThoseâpilotsâtryingâaâturbochargedâinstallationâforâtheâfirstâtimeâshouldâbeâawareâofâthrottleâsensitivityâandâtheâneedâforâveryâsmoothâthrottleâmovements.âInâcaseâofâtheâmanualâsystems,âtheâturbochargerârequiresâtimeâtoâfollowâthrottleâmovementâsinceâitâmayâoperateâatâspeedsâupâ toâ110,000âRPM.âTheâautomaticâcontrolâsystemsâexperienceâthisâsameâphenomenaâand,âinâaddi-
tion,âallâelementsâofâtheâcontrolâsystemâmustâstabilizeâfollowingâanyâmovementâofâtheâthrottle.âGoodâadviceâisââMoveâtheâthrottleâcontrolsâslowly andâwait.â
2.âThisâadviceâisâalsoâgoodâwhenâleaningâtheâmixtureâsinceâtheâmixtureâsettingâhasâaâgreatâeffectâonâengineâoperatingâtempera-tures.âTheâoperatingâtemperaturesâofâaâturbochargedâengineâwillâbeâsomewhatâhigherâthanâthoseâofâaâsimilarânormallyâaspiratedâengineâbecauseâtheâintakeâairâisâheatedâasâitâisâcompressed;âthisâisâparticularlyâtrueâatâhigherâaltitudesâwhereâtheâcompressorâmustâworkâveryâhardâtoâsupplyâdenseâairâtoâtheâengine.âCylinderâheadâtemperaturesâmayâaverageâ30ËâFâhigherâatâaltitude,âandâsmooth,âsteadyâoperationâofâtheâmixtureâcontrolâwillâensureâthatâturbineâinletâtemperatureâ(TIT)âlimitationsâareânotâexceeded.
3.âPowerâsequenceâisâveryâimportantâwithâtheâturbochargedâââengine.
To increase power â Enrich mixture, increase RPM, then MP
To decrease power â Decrease MP, then RPM
4.âHigh-altitudeâflightsâmeanâhigherâturbineâspeedsâandâhotterâcylinderâheadâtemperatures.âObserveâtheseâtemperatures,âandâstayâwithinâtheâlimitsâprescribedâforâbestâengineâlife.
5.âCruiseâcontrolâatâaltitudeâisâinâaccordanceâwithâtheâspecificâinstructionsâinâtheâairplaneâPilotâsâOperatingâHandbook.
6.âTurbochargedâpowerâplantsârequireâ100âoctaneâaviationâgradeâfuelâasâaâminimum.
THE MANUALLY CONTROLLED TURBOCHARGER
Theâsimplestâformâofâmanualâcontrolâisâtheâfixed-bleedâsystem.âItâdoesânotâ incorporateâaâwastegate,âbutâallowsâsomeâexhaustâgasâtoâcontinuouslyâescapeâthroughâanâorificeâofâpredeterminedâsize.âSizeâofâ theâorificeâestablishesâ theâcriticalâaltitudeâofâ theâengine.âTheâremainderâofâ theâexhaustâgasâ isâusedâ toâ turnâ theâturbochargerâmechanismâanytimeâ theâengineâ isâ running.â Inâthisâsystem,âengineâpowerâ isâadjustedâbyâ theâpositionâofâ theââthrottleâplateâinâtheâcarburetorâorâfuelâinjector,âandâtheâamountâofââexhaustâgasâavailableâtoâturnâtheâturbochargerâisâaâresultâofâtheâpowerâdevelopedâatâanyâparticularâthrottleâsetting.
Lycomingâdevelopedâaâsecondâmanualâsystemâtoâbeâusedâprimarilyâinâsingle-engineâinstallations.âTheâthrottle/wastegateâinterconnectâsystemâusesâpositioningâofâtheâcockpitâthrottleâcontrolâtoâactuateâbothâtheâthrottleâplateâandâtheâturbochargerâwastegate.âTheâdesignâofâthisâmechanismâcausesâaâprogrammedâmovementâofâtheâthrottleâplateâandâwastegate;âtheâthrottleâplateâstartsâtoâmoveâtowardâtheâfull-openâpositionâbeforeâmovementâofâtheâwastegateâaffectsâanyâchangeâinâtheâexhaustâbleedâwhichâwillâcauseâturbochargerâspeedâtoâincrease.âAtâtheâfullyâadvancedâpositionâofâtheâthrottleâcontrol,âtheâthrottleâplateâisâatâfullâopenâandâtheâwastegateâisâclosedâtoâitsâmaximumâdesignâlimit.
Aâpressureâ reliefâ valveâ isâ normallyâ includedâ inâ theâ factoryâdevelopedâsystemâofâeachâmanuallyâcontrolledâ turbochargerââinstallation.âTheâpurposeâofâthisâvalveâisâprotectionâofâtheâengineâinâcaseâofâinadvertentâexcessiveâthrottleâopeningâ(overboost)âbyâtheâpilot.âWithâaâmanuallyâcontrolledâturbochargerâsystem,âtheâpilotâisâtheâcontroller,âandâmustâlimitâthrottleâmovementâtoâkeepâmanifoldâpressureâwithinâtheâlimitâspecifiedâforâtheâengine.
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TheâpilotâshouldâcarefullyâreadâtheâPilotâsâOperatingâHandbookâonâthisâequipment,âandâalsoâgetâaâgoodâcheckoutâbyâaâcompetentâpilotâqualifiedâinâtheâaircraft.âPilotâtechniqueâcautionsâagainstâsuddenâmovementsâofâtheâthrottle,âandârecommendsâinsteadâslowâdeliberateâmovements.âForâ takeoff,â thisârequiresâveryâsmoothââapplicationâofâtheâthrottleâuntilâmanifoldâpressureâindicatesâaboutâtwoâinchesâbelowâtheâmaximumâforâwhichâtheâengineâisârated.âAsâtheâturbochargerâspeedâbuildsâup,âtheâmanifoldâpressureâwillâincreaseâslightlyâtoâtheâmaximumâlimit.âDuringâclimbâatâaâfixed-throttleâcondition,âmanifoldâpressureâwillâdecreaseâatâtheârateâofâapproximatelyâoneâinchâforâeachâthousandâfeet.âAsâengineâpowerâdeteriorates,â theâpilotâslowlyâadvancesâtheâthrottleâtoâmaintainâtheâdesiredâmanifoldâpressureâuntilâ theâfull-throttleâpositionâisâreachedâatâtheâcriticalâaltitude.
Theâpilotâshouldâbeâalertâtoâtheâreactionâofâtheâmanifoldâpressureâinâthisâtypeâofâengineâwhenâleaningâatâcruiseâpower.âAtâaâfixedâRPMâandâthrottleâsetting,âtheâmanifoldâpressureâwillâincreaseâasâtheâmixtureâisâleanedâtoâBestâPower,âandâdecreaseâwhenâfurtherâleanedâtoâBestâEconomy.âTheârecommendedâprocedureâisâthatâatâtheâcompletionâofâtheâleaningâprocedure,âifâ theâmanifoldâpres-sureâisâmoreâthanâoneâinchâfromâtheâbeginningâMPâvalue,âitâisârecommendedâthatâtheâmixtureâbeâreturnedâtoâfullârichâandâtheâMPâadjustedâaccordinglyâsoâthatâtheâleaningâprocedureâproducesâtheâdesiredâmanifoldâpressure.
THE AUTOMATICALLY CONTROLLED SYSTEMS
Ownersâofâenginesâthatâcallâforâmoreâthanâfield-levelâmanifoldâpressureâ toâproduceâratedâpowerâshouldâknowâthatâ theâ turbo-chargerâ isâoperatingâatâallâ timesâwhenâtheâengineâ isârunning.âTheseâenginesâusuallyâhaveâturbochargersâthatâareâcontrolledâbyâautomaticâsystems.
Theâautomaticâsystemsâusedâtoâcontrolâturbochargerâoperationâutilizeâdevicesâ thatâ senseâdifferencesâofâairâpressureâatâvar-iousâpointsâinâtheâinductionâsystem,âandâutilizeâanyâchangesâtoââadjustâtheâoilâpressureâthatâcontrolsâtheâpositionâofâtheâwastegate.ââNotâallâofâtheseâsystemsâareâexactlyâtheâsameâand,âtherefore,âitâisâveryâimportantâthatâtheâpilotâunderstandâexactlyâwhatâmanifoldâpressuresâ toâexpectâwhenâfullâ throttleâ isâappliedâforâ takeoff.
Enginesâsuchâasâ theâLycomingâTIO-541âandâTIGO-541âhaveâcontrollerâsystemsâthatâareâsetâtoâprovideâred-lineâmanifoldâpres-suresâwhenâtheâthrottleâisâfullâopenâforâtakeoff.âOtherâengines,âmanyâofâthoseâinâtheâLycomingâTIO-540âseries,âutilizeâaâdensityâcontrollerâthatâwillâmaintainâaâsetâpowerâoutputâatâfullâthrottleâregardlessâofâvariationsâinâaltitudeâandâinâtemperaturesâaboveâorâbelowâstandard;âasâaâresult,âmanifoldâpressuresâatâfullâ throttleâmayâindicateâseveralâ inchesâaboveâorâbelowâthatâspecifiedâforâstandardâdayâconditions.
Althoughâ theâsystemsâwithâcontrollersâautomaticallyâprotectâagainstâoverboostâatâallânormalâRPMâandâMPâsettings,âitâisâpos-sibleâtoâoverboostâaâturbochargedâengineânevertheless.âAnyâsuddenâstraight-armingâofâtheâthrottles,âparticularlyâonâcoldâengines,âcanâcauseâanâoverboostâconditionâthatâwouldâexceedâtheâred-line.âButâoverboostâcanâalsoâtakeâplaceâevenâthoughâtheâred-lineâMPâhasânotâbeenâexceeded.âThisâoccursâwhereâtheâpilotâmayâhaveâaâlowâRPMâandâveryâhighâMP.âAnâexampleâofâthisâhasâbeenâobservedâwhenâtheâpilotâhasâletâdownâwithâlowâRPM,âthenâonâtheâfinalâapproachâ
executedâaâgo-aroundâwithoutâfirstâadvancingâRPM.âThusâheâcouldâbeâpullingâmaximumâmanifoldâpressureâ(toâred-line)âatâlowâRPM.âThisâwouldâproduceâaâdefiniteâoverboostâcondition,âwithâresultingâheavyâdetonationâandâundesirableâcompressorâsurge.
Theâengineâmanufacturersâhaveâserviceâbulletinsâandâserviceâinstructionsâforâreferenceâifâthisâshouldâhappen.âAâsevereâover-boostâcouldârequireâaâmajorâoverhaulâofâtheâengineâandâreplace-mentâofâtheâcrankshaft.
Ofâcourse,âtheâniceâfeatureâofâtheâautomaticâsystemâforâtheâbusyâpilotâduringâclimbâisâ thatâonceâtheâ throttlesâareâset,â thereâ isâaâminimumâofâadjustmentârequired.âCruiseâhandlingâisâsimilarâtoâtheâotherâsystemsâdescribedâearlier.âDuringâletdown,âthereâisânoâworryâaboutâhighâMPâbecauseâtheâpilotâmerelyâretardsâhisâthrottles,âandâtheâautomaticâsystemâdoesâtheâworkâforâhim.
Sinceâtheâturbochargerâisâoperatingâduringâtakeoff,âallâtakeoffsâatâanyâaltitudeârequireâfull-richâmixtureâbecauseâtheâturbochargerâprovidesâfull-ratedâhorsepower,âandâfull-richâmixtureâisârequiredâforâthatâamountâofâpower.
MAINTENANCE
Maintenanceâ forâallâ theâ turboâsystemsâcoveredâhereâ isâ rela-tivelyâ simple.âTheâdailyâpreflightâmerelyâ callsâ forâ aâ visualââinspectionâpriorâtoâtheâfirstâflight.âLookâatâturboâmountingsâandââconnectionsâforâsecurity,âlubricantâleakageâorâairâleakage.âThereâareâtheâusualâ50-âandâ100-hourâinspectionsâthatâareâbriefâinâwhatâtheyârecommend.âMechanicsâshouldânotâtinkerâwithâtheâsystemâunlessâtheyâhaveâbeenâspecificallyâschooled.âAâveryâimportantârequirementâisâtheânecessityâtoâavoidâdroppingâanyâlooseâitemsâinâtheâinductionâsystem.âTheyâwillâbeâsuckedâupâandâgoâthroughâtheâturbineâwheelâdamagingâitâandâalsoâpossiblyâdamagingâtheâengineâasâwell.âThisâcouldâbecomeâveryâcostly.
Anyâoverboostingâ shouldâbeâenteredâ inâ theâ logbookâbyâ theâpilot.âTheâmechanicâmustâ thenâ referâ toâ theâmanufacturerâsâserviceâpublicationâforâtheânecessaryâactionâtoâtake.âWhenâtheâengineâisâexchangedâorâoverhauled,âtheâturbochargerâshouldâalsoâbeâexchangedâorâoverhauled.
SUMMARY
Turbochargingâtheâflat-opposedâcylinderâpistonâengineâwasâanâinnovationâthatâimprovedâandâexpandedâtheâutilityâofâtheâGeneralâAviationâairplane.âCombiningâcabinâpressurizationâandâengineâturbochargingâfromâtheâsameâcompressorâ includedâasâpartâofâtheâengineâpackage,âprovidesâsimplicity,âwhichâ leadsâ toâ lowâcostâandâ lightâweight.âTheâ turbochargedâpistonâengineâhadâaâgreatâ impactâonâ theâhelicopterâ industry,âparticularlyâ forâuseâinâmountainousâareas.âAltitudeâ testâ flightsâandâfieldâexperi-enceâhaveâindicatedâexcellentâfuelâeconomyâandârangeâwithâtheââaccompanyingâhigherâtrueâairspeeds.
Theâ turbochargerâhasâbeenâquiteâcompatibleâwithâLycomingâpistonâ engines.â Weâ haveâ triedâ toâ giveâ informationâ onâ allâaspectsâofâturbochargingâinâanâeffortâtoâaidâpilotâunderstandingâofâ theâsubject.âThereâ isânoâsubstituteâforâaâgoodâcheckoutâbyâanâ experiencedâ pilot;â andâ forâ specificâ knowledgeâ aboutâyourâaircraft,âbeâsureâ toâ readâ theâairplaneâPilotâsâOperatingâHandbook.âGiveâ theâpowerâplantâandâ turboâ theâmaintenanceâ
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theyârequireâandâtheâcarefulâoperationâtheyâdeserve,âandâtheyâwillâgiveâyouâperformanceâwithâaâ longâandâsatisfactoryâ life.â
Airlineâderegulationâhasâcausedâchanges.âManyâaircraftâpoweredâbyâLycomingâreciprocatingâenginesâareâbeingâusedâinâtheâcom-muterâmarket.âTheseâaircraftâoperateâunderâPartâ135âofâtheâFederalâAirâRegulationsâandâgenerallyâhaveâaâregularâscheduleâwhichâmustâbeâmaintainedâdayâafterâday.âTheâenginesâofâtheseâaircraft,âlikeâthoseâoperatedâforâindividualâorâcorporateâtransportation,âareâexpectedâtoâreachâtheâmanufacturerâsârecommendedâTBOâwhenâoperatedâandâmaintainedâasâspecifiedâ inâ theâPilotâsâOperatingâHandbookâ(POH)âandâappropriateâmaintenanceâpublications.
ManyâcommercialâoperatorsâhaveârequestedâassistanceâandâadviceâonâtheâsubjectâofâoperatingâandâmaintainingâtheirâenginesâinâaâmannerâthatâwillâassistâinâmeetingâregularâschedulesâandâachievingârecommendedâengineâTBO.âInâresponseâtoâtheseârequests,âaâseriesâofâoperatingâtipsâhasâbeenâdevelopedâtoâemphasizeâthatâaâslightlyâmoreâconservativeâandâcautiousâmodeâofâoperationâwillâhelpâtoâincreaseâexpectedâengineâlife.âTheseâtipsâareâdirectedâspecificallyâatâTI0-540-Jâseriesâengines,âbutâ theyâmayâbeâappliedâtoâotherâLycomingâenginesâasâwell.
Individualâorâcorporateâoperatorsâmayâalsoâfindâtheseâtipsâbeneficialâforâensuringâlong,âreliableâengineâoperationalâlife.âConsideringâthis,âitâseemsâappropriateâtoâprintâtheseâsuggestedâoperatingâtipsâforâtheâbenefitâofâallâLycomingâTIO-540-Jâseriesâengineâownersâandâoperators.âTheseâtipsâareâapplicableâwhereâmaximumâengineâserviceâ lifeâ ratherâ thanâmaximumâaircraftâperformanceâ isâ theâprimaryâconsideration.
âTipsâfromâFredââwereâoutlinedâinâaâmemoâwhichâisâreprintedâbelow:
ďż˝. INTRODUCTION:
ThisâmemoâwasâoriginallyâdirectedâatâPartâ135âCommuterâusage,âbutâ anyâoperatorâ ofâLycomingâ turbochargedâ enginesâwhereâlongâengineâserviceâlifeâ isâaâmajorâconsiderationâmayâbenefit.âPowerâsettingsâandâproceduresâwithinâ theânormalâ range,âbutâmoreâconservativeâthanâtheâmaximumâallowableâlimitsâspecifiedâinâ theâPilotâsâOperatingâHandbookâ(POH),âmayâbeâhelpfulâ inâachievingâthisâextendedâengineâlife.âTheâfollowingâsuggestionsâdealâwithâtheâengineâareasâthatâleadâtoâtheânecessityâofâoverhaulâbyââattemptingâtoâminimizeâwearâratesâandâpotentialâcylinderâprob-lems,âandâtoâmaximizeâturboâsystemâandâwastegateâlifeâthroughâchangesâ inâoperationalâprocedures.âEconomicâorâperformanceâconsiderationsâmayârequireâdeviationâfromâidealârecommendationsâwithâtheâpossibleâattendingâlossâofâsomeâofâtheâmaximumâpossibleâengineâserviceâlife.
ďż˝. GROUND OPERATION:
a.â Inâextremelyâcoldâweatherâ (20ËâFâandâcolder),â engineââand/orâoilâpreheatingâshouldâbeâutilizedâtoâminimizeâacceler-atedâcoldâwearâratesâduringâtheâengineâwarm-upâperiod.
b.âAvoidârapidâaccelerationâafterâanyâcoldâstart-up,âandâmakeâeveryâeffortâtoâmaintainâaâconstantâspeedâofâaboutâ1000âRPMâforâseveralâminutesâduringâtheâinitialâwarm-upâperiod.
c.âAdhereâ toâ theâ lubricatingâoilâ recommendationsâforâ theâaverageâambientâairâtemperature,âasâlistedâinâtheâlatestârevi-sionâofâLycomingâServiceâInstructionâNo.â1014.âNoteâthatâSAEâ15W-50âorâ20W-50âall-temperatureâoilâ(MIL-L-22851âSpec)âisâapprovedâforâuseâinâTI0-540âseriesâengines.
d.âOilâtemperatureâindicationsâshouldâregisterâonâtheâaircraftâgageâbeforeâtakeoffâisâattemptedâsoâthatâproblemsâassociatedâwithâunusuallyâhighâoilâpressureâwillâbeâminimized.
e.âAllâpowerâsettingsâmustâalwaysâbeâaccomplishedâslowlyâandâsmoothlyâtoâminimizeâpossibleâdamageâtoâtheâcrankshaftâdynamicâcounterweightâsystem.
f.âTaxiâatâ theâminimumâpowerâsettingârequiredâ toâgetâ theââjobâdone.
ďż˝. TAKEOFF:
a.âPartâthrottleâtakeoffsâshouldâbeâavoided.âTheâfuelâinjectorâmeteringâ jetâ isâ aâ two-holeâ unit,â whichâ isâ interconnectedâwithâ theâ throttle.â Theâ secondaryâ jetâ isâ fullyâ openedâ onlyâatâfull-throttleâconditions.âTheâricherâfuelâflowâsupplementsâengineâ coolingâ andâ detersâ engineâ damagingâ detonation.ââTheâ turbochargerâ controlâ systemâ automaticallyâ seeksâ toâmaintainâaâconstantâdensityâairâ chargeâatâ theâ fuelâ injectorâentrance.âTheâdensityâcontrollerâsettingâshouldâbeâcheckedâroutinelyâ withâ aâ temperatureâ probeâ inâ accordanceâ withââLycomingâCurveâNumberâ13225-C,âasâdescribedâinâdetailâinâtheâlatestârevisionâofâLycomingâServiceâInstructionâNo.â1187.âItâisânormalâforâtheâtakeoffâmanifoldâpressureâlevelâtoâvaryâsig-nificantlyâasâdailyâambientâgroundâlevelâtemperatureâchanges.âNeverâattemptâtoâsetâratedâmanifoldâpressureâbasedâuponâambientâtemperatureâcomparisonâandâinterpolationâwithâtheâvariousâratedâpowerâlevelsâshownâonâLycomingâCurveâNumberâ3216-C.âThatâcurveâisâintendedâonlyâasâanâexplanatoryâcurveâandâshouldânotâbeâusedâforâsettingâmanifoldâpressureâatâratedâconditionsâbelowâcrit-icalâaltitude.âItemsâsuchâasâaâdirtyâairâfilter,âalternateâairâdoorânotâcompletelyâshut,âlooseâragâorâsimilarâforeignâobjectâblockingâtheâairâfilterâwillâaffectâtheâratedâmanifoldâpressureâlevel.âTheâcorrectâdensityâsettingâcanâonlyâbeâobtainedâbyâmonitoringâcompressorâdischargeâtemperatureâandâmanifoldâpressureâsimultaneously.
b.âTheâRPMâshouldâbeâatâ2575âRPMâforâtakeoff,âandâaâfull-richâmixtureâmustâbeâutilized.
ďż˝. CLIMB:
Climbâshouldâbeâaccomplishedâwithâengineâcoolingâinâmind.âCowlâflapsâshouldâalwaysâbeâopenâforâclimb.âAâhigherâthanânormalâclimbâspeedâofâ140âMPHâisârecommendedâtoâaidâcooling.âMaximumânormalâoperatingâpowerâofâ2400âRPM,â40"âHgâmanifoldâpressureâwithâpartialâleaning,âinâaccordanceâwithâtheâPOH,âisâpermissibleâwhereâterrainâorâconditionsâpermit.âAâconservativeâclimbâpowerâsettingâofâ2400âRPM,â35"âHgâmanifoldâpressureâisâalsoârecom-mendedâwhileâmaintainingâcylinderâheadâtemperatureâasâcoolâasâ400ËâFâbyâmanualâleaning.âForâmaximumâengineâserviceâlife,âanâexhaustâgasâtemperatureâofâ1,400ËâFâshouldânotâbeâexceeded.
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ďż˝. CRUISE:
Conservativeâcruiseâpowerâsettingsâwillâalsoâ increaseâengineâserviceâlife.âAâpowerâsettingâofâ2200âRPMâandâ31"âHgâmani-foldâpressureâisârecommendedâforâallâcruiseâflight.âAâmaximumâ1,450ËâFâexhaustâgasâtemperatureâandâmaximumâcylinderâheadâtemperatureâofâ420ËâFâisârecommended.âSlightâenrichmentâorâcowlâflapâopeningâshouldâbeâutilizedâifâtheâcylinderâheadâtemperatureâlevelâcannotâbeâmaintained.âTheâprecedingâconditionsâcorrespondâtoâaâpowerâsettingâofâaboutâ63%âatâ standardâconditionsâandâapproximatelyâbestâpowerâmixtureâstrength.âItâmayâbeânecessaryâtoâ increaseâ theâcruiseâmanifoldâpressureâsettingâonâaâhotâdayâandâtoâdecreaseâtheâcruiseâmanifoldâpressureâonâaâcoldâday.âAsâaâruleâofâthumb,âmodifyâmanifoldâpressureâbyâ1%âforâeachâ10ËâFâvariationâfromâstandardâaltitudeâconditions.âNoteâthatâthisâcruiseâpowerâsettingâisânotârecommendedâforânewâenginesâorâenginesâinâserviceâfollowingâcylinderâreplacementâorâtopâoverhaulâofâoneâorâmoreâcylinders.âUnderâthoseâcircumstances,âtoâassureâtheâproperâringâseating,âcruiseâshouldâbeâatâ65%âtoâ75%âpowerâforâtheâfirstâ50âhoursâofâoperation,âorâuntilâoilâconsumptionâhasâstabilized.
ďż˝. DESCENT:
Rapidâ cooldownâ duringâ initialâ descentâ canâ damageâ theâengine.âGradualâcooldownâ isâpreferable.âTheâdescentâpowerâreductionâ shouldâbeâ accomplishedâ inâ severalâ steps.â Ideally,âtheâdescentâshouldâbeginâbyânosingâ theâaircraftâoverâslightlyâwhileâ engineâ powerâ andâ mixtureâ remainâ atâ theâ cruiseâ set-ting.âTheâaddedâspeedâwillâ initiateâaâgradualâcooldown.âWhenââtheâCHTâhasâstabilized,â reduceâ theâmanifoldâpressureâ toâ25"âHg,â andâ releanâ theâ mixtureâ toâ maintainâ 1,350Ëâ Fâ exhaustâgasâ temperature,âwhichâwillâ preventâ rapidâ cooldown.âAfterâaâperiodâofâatâ leastâoneâminute,âaâ furtherâ reductionâofâman-ifoldâ pressureâ toâ 20"â Hgâ andâ 2000â RPMâ canâ beâ made,ââifâ necessary.âAgain,â mixtureâ shouldâ beâ leanedâ toâ maintainâ1,350ËâFâexhaustâgasâtemperature.âCowlâflapsâshouldânotâbeâusedâasâanâaidâinâslowingâtheâaircraftâduringâdescent.âDescentâpowerââsettingsâ atâ greaterâ thanâ 20"â Hgâ manifoldâ pressureâ shouldââbeâutilizedâforâ theâgreatestâpossibleâ timeâtoâavoidâacceleratedâpistonâringâwear.
ďż˝. LANDING:
a.âFollowingâlanding,â theâminimumânecessaryâ taxiâpowerâwillâ aidâ inâengineâcooldown.âExtendingâ theâground-idleâcoolingâ periodâ reducesâ turbochargerâ temperatureâ andââreducesâtheâtendencyâofâturboâcokingâfollowingâhotâengineâshutdown.âIdeally,âaâfive-minuteâminimumâcoolingâperiodâisâdesirable.âFollowingâlanding,âoptingâforâtheâsecondâturn-offâcanâaidâtheâcooldown.
b.âHigherâthanârequiredâpowerâsettingsâforâgroundâoperationâincreaseâtheâpossibilityâofâdirtâingestionâintoâtheâengine.
SomeâGeneralâAviationâpilotsâmayânotâbeâawareâofâtheânumberâofâdetrimentalâinfluencesâonâtheirâaircraftâenginesâwhichâcanâbeâ
identifiedâasâthievesâofâengineâpower,âandâhowâtheyâcanâcreateâunsafeâflightâconditions.âAsâanâexample,âinâmostâinstances,âtheâmoderateâengineâpowerâlossâthatâoccursâfromâattemptingâaâtakeoffâatâseaâlevelâwhereâaâpilotâhasâinadvertentlyâleftâtheâcarburetorâheatâinâfull-hotâpositionâfromâtheâpreviousâlandingâmayâcauseâaâscareâbutânotânecessarilyâanâaccident.âButâmoveâtheâsituationâtoâaâ5,000âfeetâorâhigherâ(densityâaltitude)âsmallâairport,âagainâforgetâthereâisâfullâcarburetorâheat,âaddâaârichâcarburetorâcondition,âandâtheâsumâtotalâofâtheseâcombinedâpowerâthievesâaddâupâtoâaâtakeoffâorâgo-aroundâaccident.âSimilarly,âaâreviewâofâaccidentsâoverâtheâyearsâshowsâthatâinâmostâcasesâitâhasârarelyâbeenâoneâfactorâresponsibleâforâaâcrash,âbutâratherâoneâsmallâ item,âaddedâtoâanotherâsmallâitem,âaddedâtoâaâthird;âallâofâtheseâsmallâitemsâfinallyâaddâupâtoâaâtotalâbeyondâtheâabilityâofâtheâpilotâtoâcope.âThisâisâhowâaccidentsâhappen.âSoâletâsâidentifyâseveralâofâtheseâpowerâthievesâinâanâeffortâtoâmakeâflightâasâsafeâasâweâcan.
PREVENT POWER LOSS ON TAKEOFF WITH DIRECT-DRIVE ENGINES IN COLD WEATHER
Inâcoolâorâcoldâweather,âpilotsâshouldâtakeâextraâcareâpriorâ toâattemptingâtoâtakeoffâwithâaâcoldâengineâandâcoldâoil,âandâtherebyâpreventâaâ temporaryâpowerâ lossâduringâaâcriticalâpartâofâ theâtakeoff.âColdâorâheavyâoilâcanâandâquiteâoftenâdoesâaffectânormalâoperationâofâtheâhydraulicâlifters.âRememberâthatâaviationâlubri-cantsâareâheavierâwhenâcoldâthanâtheâcommonlyâusedâautomotiveâengineâoilsâandârequireâaâlittleâmoreâtimeâinâwarm-upâtoâobtainânormalâflowâinâorderâ toâfunctionâproperlyâthroughoutâ theâair-cooledâaircraftâengine.
Toâpreventâpossibleâpowerâloss,âaâproperâwarm-upâshouldâbeâcon-ducted.âTheâengineâisâusuallyâwarmâenoughâforâpre-flightâgroundâcheckâinâabove-freezingâtemperaturesâafterâ2âtoâ3âminutesârunningâatâ1000âtoâ1200âRPM.âBelowâfreezingâtemperatures,âtheâwarm-upâperiodâshouldâbeâlonger.âWithâturbochargedâpowerâplants,âcoldâoilâandâcoldâenginesârequireâaâlongerâwarm-upâperiodâtoâassureâproperâcontrollerâoperationâandâtoâpreventâmanifoldâpressureâoverboost.
Afterâtheâaboveârecommendedâwarm-upâperiodâinâcoolâorâcoldâweather,âincludingâmagnetoâandârunupâcheck,âifâtheâoilâpressureâisâconsistentlyâoverâmaximumâred-line,âhaveâaâknowledgeableâmechanicâadjustâoilâpressureâsoâthatâitâdoesânotâexceedâred-lineâatâtakeoffâorâclimbâpowers,âandâyetâitâisâwithinâtheârecommendedâgreenâarcâareaâatâcruise.âColdâweatherâusuallyârequiresâaâlongerâwarm-upâperiod.
Anotherâcauseâofâpowerâlossâunderâtheseâtemperatureâandâflightâconditionsâhasâbeenâtheâuseâofâaâheavier-weightâviscosityâofâoilâthanârecommendedâforâtheâambientâtemperatureâflightâcondition.âAâheavier-weightâoilâthanârecommendedâinâcoolâorâcoldâweatherâwillâhelpâpreventâtheânormalâoperationâofâtheâhydraulicâliftersâandâtherebyâcauseâaâlossâofâpower.
Thus,âtoâpreventâpowerâlossâonâtakeoffâwithâdirect-driveâengines,âselectâtheâproperâweightâofâoilâforâyourâengineâforâcoldâweatherâoperationâMakeâaâcarefulârun-upâpriorâtoâtakeoffâwithâcoldâoilâandâaâcoldâengineâandâobserveâengineâinstruments.âExtendâyourâwarm-upâperiodâinâcoldâweatherâuntilâoilâpressureâisâwithinârec-ommendedâlimits,âorâconsultâaâmechanicâconcerningâaâcompro-miseâadjustment.âIfâinâdoubtâaboutâpowerâoutput,âaâbriefâsmoothâfull-throttleâcheckâisârecommended.
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CARBURETOR HEAT OR ALTERNATE AIR HEAT AS POWER THIEVES
Inâtheâopeningâparagraph,âcarburetorâheatâwasâusedâasâanâexampleâofâaâcauseâofâpowerâloss,âbutâmanyâpilotsâarenâtâsureâtheyâunder-standâtheâreasonâforâit.âFlightâtestsâconductedâwithâaâprecisionâtorqueâmeterâinstalledâhaveâmeasuredâfairlyâaccuratelyâaâlossâofâasâmuchâasâ15%âofâengineâpowerâwhenâfullâalternateâairâorâcarburetorâheatâhaveâbeenâapplied.âAsâaâspecificâexplanation,âthereâisâaâsmallâpowerâlossâwhenâweâuseâheatâbecauseâtheâpilotâhasâswitchedâfromâtheâdirect,âcolderâramâairâtoâanâindirectâcarburetorâheatâmuff,âorâaâsimilarâindirectâsourceâofâwarmâairâwithâanâalternateâwarmâairâsourceâfromâinsideâtheâcowling.âThisâaccountsâforâanâaverageâ3%âpowerâdropâbecauseâofâtheâlossâofâramâair.âTheâmajorâportionâofâtheââengineâpowerâlossâisâcausedâbyâtheâcarburetorâheatâorâalternateâairâheat.âAircraftâenginesâareâcheckedâforâtheirâhorsepowerâoutputâatâaâcorrectedâstandardâtemperatureâofâ59ËâF.âEngineeringâhasâprovidedâaâsimpleâruleâofâthumbâforâtheâeffectâofâheatâonâpower,ââi.e.,âforâeveryâ10ËâFâofâheatâaboveâtheâstandardâ59ËâF,âthereâisâaâ1%âpowerâloss.âSinceâtheâaverageâheatâsourceâonâanâengineâprovidesâatâleastâ100ËâFâofâheatâaboveâstandard,âthisâheatâconditionâcausesâanâaverageâpowerâlossâofâ10%.âOurâmeasurableâtotalâpowerâlossâatâseaâlevelâwithâstandardâconditionsâisâalreadyâupâtoâ13%.
Whenâwarmâairâisâusedâbyâtheâpilot,âtheâmixtureâbecomesâricher,âandâtheâengineâmayâroughenâwithâanotherâslightâpowerâlossâasâaâresult.âInâaddition,âtheâhigherâtheâaltitudeâwithâitsâless-denseâair,â theâgreaterâ theâenrichingâeffectâbecauseâtheâfuel-meteringââdeviceâwillâbecomeâricherâatâaltitudeâandâtheâengineâlessâefficient.âThus,âthereâwillâbeâanotherâsmall,âdifficultâtoâmeasure,âpowerâlossâtoâbeâaddedâtoâtheâ13%âlossâalreadyâaccumulated.
Withâfullâcarburetorâheatâapplied,âmostâfloat-typeâcarburetorsâreactâveryâsluggishlyâorâinefficientlyâonâaâstraight-armâthrottleâtechniqueâduringâaâtouch-and-goâlandingâorâanâabortedâlanding.âInâsomeâcases,â theâfloat-typeâcarburetorâmayârefuseâtoâacceptâtheâthrottleâwhenâitâisâappliedâinâthisâmanner.âAâgradual,âsteadyâapplicationâofâtheâthrottleâisâalwaysâtheâbestâapproach.
Weâshouldâalsoâremindâtheâpilotâthatâwhenâusingâcarburetorâheatâorâalternateâairâheatâatâcruiseâpower,âtoâadjustâtheâmixtureâlean,âotherwiseâtheâmixtureâwillâbeârich.âIfâtheâheatâcausesâanâundesir-ableâpowerâlossâatâcruise,âandâthereâisâthrottleâavailable,âtheâpilotâmayâbringâtheâmanifoldâpressureâupâatâleastâtoâtheâpowerâreadingâbeforeâapplicationâofâheat;âandâifâadditionalâpowerâisâneededâandâavailable,âaddâaâmaximumâofâtwoâinchesâofâMP,âorâ100âRPMâ(fixed-pitchâprop)âaboveâtheâpreviousâpower,âandâthenâadjustâtheâmixture.âItâisâpossibleâtoâcompensateâforâtheâhorsepowerâlossâdueâtoâheatâbyâmeansâofâtheâlatterâtechniqueâifâthrottleâorâRPMâareâavailable.
EFFECTS ON POWER AT A HIGH-ALTITUDE AIRPORT ON A HOT DAY
Toâflyâsafelyâatâaâhigh-altitudeâairportâ (5,000âft.âdensityâalti-tudeâandâabove)âonâaâwarmâweatherâday,âweâmustâconsiderâtheâaerodynamicâ lossâofâefficiencyâonâ theâairplaneâandâpropellerâunderâtheseâconditions,âandâtheâpowerâlossâeffectâonâtheâengine.âAâgoodââruleâofâ thumbââforâ theâpilotâ toâ rememberâ isâââforâeachâthousandâfeetâaboveâseaâ level,â theâ takeoffârunâ increasesâapproximatelyâ25%.âInâtheâcaseâofânormallyâaspiratedâenginesâ(notâ turbochargedâorâsupercharged),âatâanâaltitudeâofâ10,000âfeet,â aboutâone-halfâofâ availableâengineâhorsepowerâ isâ lost.
Weâcanâcreateâaâpracticalâ flightâproblemâforâ theâpilotâwhoâisâfacedâwithâaâhigh-elevationâfieldâtakeoff.âAtâDenver,âColorado,âwhereâ theâfieldâelevationâ indicatedâonâ theâairplaneâaltimeterâisâ5,000âft.,â theâpilotâshouldâconsultâ theâdensityâaltitudeâchartâforâtakeoffâandâmustâknowâthatâtheâpublishedâperformanceâcri-teriaâofâanâaircraftâisâgenerallyâbasedâonâstandardâatmosphericâconditionsâ (temperatureâ 59Ëâ F,â pressureâ 29.92"â ofâ mercuryâatâseaâ level).â Inâcheckingâ theâdensityâchartâandâapplyingâ theââambientâtemperatureâofâaâsummerâdayâofâ80ËâF,âtheâcarefulâpilotâwillânoteâthatâtheâdensityâaltitudeâisâactuallyâ7,500âfeet,âandâtheâtakeoffâdistanceâatâ thisâdensityâaltitudeâwillâbeâ2.3â timesâ theâseaâlevelâtakeoffârollâshownâinâtheâPilotâsâOperatingâHandbook.
TheâsameâpilotâflyingâtoâLaramie,âWyoming,âforâtheânextâlandingâandâsubsequentâtakeoff,âmightâmeetâtheâfollowingâtypicalâflightâconditions.
Theâfieldâelevationâisâ7,276âfeet,âandâwithâanâambientâtemperatureâofâ60ËâF,â theâactualâdensityâaltitudeâwillâbeâ9,300âfeet,âwithâaâtakeoffârollâ2.9âtimesâtheâseaâlevelâtakeoff.âFurthermore,âtheâpilotâmustârememberâââtheâhigherâtheâambientâtemperatureâindicates,âtheâhigherâtheâdensityâaltitudeâbecomes.âAtâthisâelevation,âtheâpilotâofânormallyâaspiratedâaircraftâenginesâshouldâconsiderâtakeoffsâinâtheâcoolâtemperaturesâofâearlyâmorningâorâeveningâhours,âratherâthanâduringâtheâhotâhoursâofâtheâday.
Summingâupâ theâspecificâflightâconditionâ justâdiscussed,â theâpilotâmustârememberâââwhenâtheâtemperatureâbecomesâhigherâthanâstandardâ (59ËâF),â theâdensityâofâ theâairâ isâ reducedâandâaerodynamicallyâaffectsâoverallâ airplaneâperformance.âTheâhorsepowerâoutputâofâ theâengineâisâdecreasedâbecauseâitsâfuelâairâmixtureâintakeâisâreduced.âTheâpropellerâdevelopsâlessâthrustâbecauseâtheâbladesâareâlessâefficient.âTheâwingsâdevelopâlessâliftâbecauseâtheâlessâdenseâatmosphereâexertsâlessâforceâonâtheâwingsâasâairfoils.âAsâaâresult,âtheâtakeoffâdistanceâisâincreasedâandâtheâclimbâperformanceâreduced.
Inâorderâtoâcopeâwithâhigh-elevationâairportâtakeoffsâwithânor-mallyâaspiratedâengines,âwheneverâtheâdensityâaltitudeâisâ5,000âfeetâorâhigher,âtheâpilotâmustâcompensateâonâtheâgroundâbeforeâtakeoff.âWithâaâdirect-driveâengineâandâaâfixed-pitchâpropeller,ârunâtheâengineâupâtoâtakeoffâRPMâandâleanâtheâmixtureâuntilâaâmaximumâRPMâisânoted;âleaveâmixtureâatâ thatâpositionâandâaccomplishâtheâtakeoff.âIfâtheâengineâhasâaâgovernor,ârunâitâupâtoâtakeoffâRPM,âandâthenâleanâuntilâtheâengineâsmoothsâoutâandâgivesâ theâ indicationâofâmaximumâpower.âAtâ5,000âft.âdensityâaltitudeâorâhigher,âtheâavailableâhorsepowerâhasâbeenâreducedâsoâthatâleaningâasâdescribedâwillânotâdamageâaâhealthyâengine.âIfâanâEGTâsystemâisâavailable,âleanâtoâ+100ËâFâonâtheârichâsideâofâpeakâEGTâonâaâdirect-driveânormallyâaspiratedâLycomingâengine.
Allâturbochargedâorâsuperchargedâenginesâmustâuseâfullârichâforâtakeoffâatâanyâelevationâairport.âThisâincludesâeitherâmanuallyâoperatedâturbosâorâtheâautomaticâtype.
IGNITION SYSTEM POWER ROBBERS
Thereâareâseveralâpossibilitiesâwherebyâtheâignitionâsystemâcanâbeâtheâcauseâofâpowerâlossâinâtheâengine.âThereâisâaâpowerâlossâofâapproximatelyâ3%âwithâaâsingleâdeadâmagnetoâorârunningâonâoneâmag.âInâfixed-wingâaircraft,âifâtheâpilotâlostâaâmagnetoâinâflightâ
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itâmightânotâbeâaâseriousâsituationâtoâcompleteâtheâflightâsafelyâprovidedâotherâpowerârobbersâdidnâtâbeginâtoâaddâtoâtheâproblem.âButâinâtheâcaseâofâtheârotary-wingâaircraft,â itâcouldâbeâseriousâduringâtakeoff,âhover,âorâlandingâbecauseâthereâareâtheâregularâinroadsâonâpowerâââsuchâasâoperationâofâtheâtailârotor,âtheâcoolingâfan,âtheâalternator,âtheâtransmissionâandâalsoâpowerâlossâfromâanyâexcessiveârotorâbladeâtrimâtabâpositionâbeyondâtheâmanufacturerâsârecommendation.âTherefore,âmagnetoâmaintenanceâreallyâ isâaâcriticalâitemâonârotor-wingâaircraft.
Otherâpowerâlossâinfluencesâinâtheâignitionâsystemâincludeâwornâorâfouledâsparkâplugsâthatâtendâtoâprovideâaâweakâspark.âLikewise,âdeterioratedâmagnetoâpointsâwillâhaveâsomeâpowerâlossâinfluence.âWeâhaveâalsoâlearnedâtheâdifficultâwayâthatâold,âwornâorâcrackedâ(insulation)âignitionâharnessesâcanâcauseâaâlossâofâpower,âparticu-larlyâatâaltitude.âIfâthisâisâsuspected,âitâcanâbeâcheckedâbyâmeansâofâaâharnessâtester.
Weâ knowâ thatâ magnetoâ timing,â eitherâ earlyâ orâ late,â hasâ aâdetrimentalâ influenceâ onâ power.â Soundâ maintenanceâ canâeliminateâtheseâproblems.âButâcomingâbackâtoâsparkâplugs,âtheâcorrectâplugâisâmostâimportantâforâefficientâengineâoperation,âandââLycomingâServiceâ Instructionâ1042â isâ theâofficialâ referenceâsource.âMaintenanceâmustâalsoâbeâcarefulâthatâlong-reachâplugsâareâusedâonlyâinâthoseâcylindersâdesignatedâbyâanâareaâofâyellowâpaintâ inâ theâfinâareaâbetweenâ theâsparkâplugâandârockerâbox.âCylindersâdesignedâforâshort-reachâplugsâmayâbeâeitherâgray,âblueâorâunpaintedâinâthisâarea.âIfâtheâwrongâlengthâplugâisâusedâinâtheâcylinder,âitâwillâcauseâaâlossâofâpowerâandâperhapsâpreignitionâorâdetonation.
ChampionâSparkâPlugâCompanyâpublishedâaâbulletinâwarningâthatâoneâdirtyâharnessâterminalâ(cigarette)âorâcontaminatedâplugâbarrelâcanâ robâanâaircraftâengineâofâ twoâhorsepowerâduringâtakeoff.âWhenâdirtâandâmoistureâareâallowedâtoâaccumulateâonâtheâcigaretteâorâsparkâplugâbarrelâinsulator,âconnectorâwellâflashoverâcanâoccurâresultingâ inâplugâmisfire.âTheâhigh-voltageâcurrentâwillâtakeâtheâeasyâpathâtoâgroundâratherâthanâsparkâbetweenâtheâfiring-endâelectrodeâgap.âCigarettes,âharnessâ terminals,âsealsâandâsparkâplugâbarrelsâshouldâbeâkeptâcleanâandâdry.âWhenâciga-rettesâareâclean,âdoânotâtouchâthemâasâtheâmoistureâonâfingersâisâenoughâtoâcontaminateâthemâagain.âReplacingâtheseâpartsâandâpiecesâatâ reasonableâperiodsâ isâ inexpensiveâ insuranceâagainstâpowerâthieves.âWhenâtheâlatterâareâatâwork,âsharpâperformanceâandâeconomyâareâlost.
INDUCTION SYSTEM LEAKS
Ifâtheâintakeâpipesâareâlooseâatâeitherâend,âleakageâthatâleansâtheâmixtureâwillâtakeâplaceâandâcauseâaâpowerâloss.âItâcouldâbeâcriticalâinâtheâtakeoffâorâclimbâpowerâranges.âInâmostâengines,âtheâleakageâcanâbeâdetectedâbyâobservingâfuelâdyeâevidenceâatâtheâleakageâarea.âAnyâtimeâthisâconditionâisâdiscovered,âitâmustâbeâremediedâbeforeâtheâaircraftâisâflownâagain.
Inâthoseâenginesâusingâaâcarburetor,âweâhaveâobservedâpowerâlossâeffectsâfromâwornâairâboxesâwhereâtheâcarburetorâheatâflapperâvalveâinâtheâairâboxâremainsâpartlyâopen.âWhenâtheâoutsideâairâtemperatureâisâaboveâ59ËâF,âthisâmalfunctionâcanâcreateâaâsneakyâpowerâloss,âparticularlyâatâhigherâthanâcruiseâpower.
BLOW-BY AND COMPRESSION LOSS
Anotherâpowerâlossâconditionâisâthatâofâblow-byâââorâoilâblowingâbyâtheâpistonâringsâandâgettingâintoâtheâcombustionâchamberâinâmoreâ thanâdesirableâamounts.â Itâoccursâwithâbrokenâorâwornâpistonârings,âscoredâcylinderâwallsâandâbell-mouthedâexhaustâvalveâguides.âOilâinâtheâcombustionâchamberâfoulsâsparkâplugsâandâreducesâtheirâefficiency.âItâalsoâlowersâtheâoctaneâratingâofâtheâfuelâandâcausesâaâlossâofâpower,âparticularlyâatâtakeoffâorâclimb.âIfâtheâengineâisânotâcloseâtoâitsânormalâoverhaulâlife,âthenâaâtopâoverhaulâwouldâbeâinâorderâ ifâmoreâthanâoneâcylinderâshowedâthisâcondition.
Powerâ lossâ fromâvalveâ leakageâmayânotâbeânoticeableâ toâ theâpilotâwhileâinâflight.âIfâanâexhaustâvalveâbecomesâburnedâandââdeterioratedâatâ theâedgeâofâ theâhead,â itâmayâcauseâanâengineâmissâinâflight.âButâleakingâintakeâvalvesâareâdifficultâtoâdetectâduringâflight.âTheâlatterâeitherâgetâirregularlyâseatedâandâcauseâaâcompressionâloss,âorâtheyâcanâalsoâcauseâaâlossâifâtheyâgetâtulipedâfromâpreignition.âAâgoodâdifferentialâcompressionâcheckâwillâpickâupâmostâofâtheseâdiscrepanciesâexceptâforâsomeâoccasionsâofâbrokenârings.âHowever,âanyâoilâinâtheâcombustionâchamberâfromâbrokenâringsâwould,âinâaddition,âcallâforâaâvisualâinspectionâwithâaâborescopeâorâaâgooseneckâlight.
SUMMARY:
Weâcanâtâlistâallâtheâmanyâpower-robbingâfactorsâhere,âbutâweâhaveâtriedâtoâlistâtheâimportantâones,âalongâwithârecommendationsâonâhowâtoâcopeâwithâthem.âAgain,âweâwantâtoâremindâallâconcernedâofâtheâdangerousâdifferenceâbetweenâanâengineâproblemâwhereâbothâsparkâplugsâfailâtoâfireâinâaâcylinder,âwhichâisâimmediatelyâobvious,âasâcomparedâwithâtheâsmallâpowerâlossâproblemâthatâisânotâasâobvious.âTheâpowerâthievesâtakeâpowerâawayâinâsmallâquantitiesâperâcylinderâuntilâseveralâofâthemâhappenâtoâoccurâatâtheâsameâtime,âreachingâseriousâproportionsâandâaâdefiniteâunsafeâflightâcondition.âBeâawareâââdonâtâbecomeâaâvictimâofâpowerâthieves!
TheâFAAâhasâpublishedâaâpamphletâentitledââWetâAirââ thatâenlightensâtheâpilotâconcerningâthisâpotentialâdangerâtoâengineâpower.âScientistsâ stateâ thatâweâcanâdismissâanyâappreciableââeffectâofâdampnessâinâtheâairâonâtheâefficiencyâofâtheâwingâinâliftingâandâtheâpropellerâinâthrusting.âButâtheyâsayâtheâeffectâofâwaterâvaporâorâhighâhumidityâonâengineâpowerâoutputâcanâbeâsignificant,âandâshouldâbeâtakenâintoâconsiderationâwhenâplanningâtakeoffsâinâmuggyâorâhighlyâhumidâweather.
Theâpamphletâexplainsâtheâpowerâlossâbyâpointingâoutâthatâwithâwaterâvaporâpresent,âthereâisâlessâairâenteringâtheâengine.âSecondly,âthisâcreatesâanâexcessiveâenrichmentâbecauseâtheâfuelâamountâisâtheâsame,âbutâtheâamountâofâairâisâless.âFurthermore,âtheâwaterâvaporâslowsâtheâburningâwhichâslightlyâaffectsâpower,âbutâoffersânoâcoolingâvalueâtoâtheâengine.
FAAârecommendsâaâroughâruleâofâthumbâisâtoâkeepâhigh-moistureâcontentâinâmind,âandâsuggestsâtheâpilotâconsultâhisâPilotâsâOperatorâHandbookâforâtakeoffâdistances,âandâaddâanotherâ10%âforâtheâpossibleâ
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effectsâofâengineâpowerâlossâdueâtoâwaterâvaporâonâaâmuggyâday.âTheâpilotâcanâeasilyâidentifyâaâhighâwaterâvaporâconditionâbyâtheâmuggy,âhot,âstickyâfeelingâinâthisâkindâofâweather.âTheâhigherâtheâambientâtemperature,âtheâgreaterâtheâwaterâvaporâcontentâinâtheâair,âi.e.,âatâ96ËâF,âtheâwaterâvaporâcontentâwillâbeâeightâtimesâasâgreatâasâatâ42ËâF.âTheâwrite-upâalsoâstatesâthatâtheâeffectâofâwaterâvaporâonâsupercharged,âfuel-injectedâpistonâenginesâisâsubstantiallyâtheâsameâasâtheâeffectâonâotherâpistonâengines.ââFuel-injectionâsystemsâmeterâfuelâonâtheâbasisâofâaâgivenâvolumeâofâgasâenteringâtheâcombustionâchamber,âwhetherâtheâgasâisâairâorâwaterâvapor,âjustâasâtheâcarburetorâdoes.âItâcannotâdiscriminateâbetweenâcombustiblesâandânoncombustibles.â
Pilotsâshouldâbeâalertâtoâtheâeffectâofâwetâairâonâtheâperformanceâofâtheirâengine.
Weâhaveâfirmâevidenceâthatâenginesânotâflownâfrequentlyâmayânotâachieveâtheânormalâexpectedâoverhaulâ life.âEnginesâflownâonlyâoccasionallyâdeteriorateâmuchâmoreârapidlyâthanâthoseâthatâflyâconsistently.âPilotsâhaveâasked,ââWhatâreallyâhappensâtoâanâengineâwhenâitâsâflownâonlyâoneâorâtwoâtimesâperâmonth?ââAnâaircraftâengineâflownâthisâinfrequentlyâusuallyâaccumulatesârustâandâcorrosionâinternally.âThisârustâandâcorrosionâisâoftenâfoundâwhenâanâengineâisâtornâdown.âSomeâoperatorsâareârunningâtheâenginesâonâ theâgroundâinâanâattemptâ toâpreventârustâbetweenâinfrequentâflights.âThisâmayâharmâratherâthanâhelpâtheâengineâifâ theâoilâ temperatureâisânotâbroughtâupâtoâapproximatelyâ165ËâF,âbecauseâwaterâandâacidsâfromâcombustionâwillâaccumulateâinâ theâengineâoil.âTheâoneâbestâwayâtoâgetâoilâ temperatureâ toâ165ËâFâisâtoâflyâtheâaircraft.âDuringâflight,âtheâoilânormallyâgetsâhotâenoughâtoâvaporizeâtheâwaterâandâmostâacidsâandâeliminateâthemâfromâtheâoil.âIfâtheâengineâisâmerelyâgroundârun,âtheâwaterâaccumulatedâinâtheâoilâwillâgraduallyâturnâtoâacid,âwhichâisâalsoâundesirable.âProlongedâgroundârunningâinâanâattemptâtoâbringâoilâtemperatureâupâisânotârecommendedâbecauseâofâinadequateâcoolingâ thatâmayâresultâ inâhotâ spotsâ inâ theâcylinders,âbakedâandâdeterioratedâ ignitionâharnessâandâbrittleâoilâ sealsâwhichâcauseâoilâleaks.âPullingâonâengineâthroughâbyâhandâifâitâhasânotâbeenârunâforâaâweekâorâmoreâisâNOTârecommended,âandâcanâresultâinâincreasedâwear.âReferâtoâLycomingâServiceâLetterâL180.ââIfâtheâengineâisâflownâsoâinfrequentlyâthatâitâdoesânotâaccumulateâtheâoperatingâhoursârecommendedâforâanâoilâchangeâ(25âhoursâforâaâpressure-screenâsystemâandâ50âhoursâforâaâfull-flowâfilterâsystem),âthenâtheâoilâshouldâbeâchangedâatâfour-monthâintervalsâtoâeliminateâwaterâandâacids.
TaleâNumberâOneââââThe most likely time for an engine failure to occur is at the first power reduction after take-off.â
Everyâindividualâwhoâpilotsâanâaircraftâhasâprobablyâheardâthisâ
statementâatâsomeâtime.âIsâitâaâtrueâstatement?âWeâwillâventureâaâguessâandâsayâthatâperhapsâitâmayâhaveâbeenâatâsomeâtimeâinâtheâdistantâpast.
Severalâyearsâago,âthisâquestionâwasâaskedâofâmeâandâitâ ledâtoâquestioningâsomeâFAAâemployeesâandâaânumberâofâotherâpilotsâaboutâwhereâtheâjustificationâforâthisâstatementâmightâbeâfound.âAfterâseveralâweeksâofâpokingâintoâthisâsubject,â itâwasâfinallyânecessaryâtoâconcludeâthatâweâcouldâfindânoâjustificationâââthatâitâwasâsimplyâanââOldâWivesââTale.â
AâletterâwhichârecentlyâcameâfromâaâFlyerâreaderâtakesâthisâoneâstepâfurther.âFirst,âitâappearsâthatâthereâareâmanyâwhoâcontinueâtoârepeatâthisâtale.âThisâcausedâourâreaderâtoâdelveâintoâtheâsubjectâaâlittleâdeeperâââperhapsâaâlittleâmoreâscientificallyâthanâIâdid.âOurâreaderâstudiedâaâcomputerâreadoutâwhichâhadâdataâonâincidentsâofâengineâfailureâoverâaârecentâthree-yearâperiod.âBasedâonâtheâmaterialâinâthatâreport,âthisâreaderâconcludedâthatâengineâfailuresâduringâtakeoffâareâquiteârare,âandâthatâfailuresâduringâcruiseâareâfarâmoreâcommon.âThisâdoesâseemâlogicalâsinceâtheâenginesâofâfixed-wingâaircraftârunâaâmajorityâofâtheirâoperatingâlifeâinâtheâcruise-powerârange.
Ourâreaderâalsoâhadâaâveryâbelievableâ theoryâaboutâhowâthisâtaleâmayâhaveâgottenâstarted.âHeâwrote,ââItâseemsâlikelyâtoâmeâthatâ thisâ ideaâgotâstartedâwhenâtwin-engineâflightâ instructorsâwouldâsimulateâanâengineâoutâduringâ takeoffââârightâaboutâtheâtimeâtheâstudentâputâhisâhandâonâtheâpropâcontrolâtoâreduceââpower.âGradually,âtheâideaâwasâpropagatedâthatâthisâwasâtheâmostâlikelyâtimeâforâanâengineâfailure,âwhenâinârealityâitâwasâaâlikelyâtimeâforâanâinstructorâtoâsimulateâaâfailure.â
Fromâ theseâ twoâ searchesâ forâ justificationâ ââ withâ noneâbeingâ foundâ inâ eitherâ case,â Iâ believeâ itâ isâ fairâ toâ concludeâthatâ âtheâ ideaâ ofâ anâ engineâ failureâ beingâ mostâ likelyâ toâoccurâ atâ theâ firstâ powerâ reductionâ afterâ takeoffââ is,â inâfact,â anâ oldâ wivesââ tale.â Forâ theâ sakeâ ofâ safety,â letsâ stopârepeatingâ thisâ falseâ taleâ andâ startâ promotingâ theâ ideaâ thatâweâshouldâbeâ readyâ toâdealâwithâpowerâ failureâatâanyâ time.
Aâsecondâoldâwivesââtaleâisâstillâbeingâpromotedâbyâsomeâindi-viduals.âThisâtaleâinvolvesâtheâconstant-speedâpropellerâandâgoesâlikeâthis:ââThe RPM in hundreds should not be exceeded by the manifold pressure in inches of mercury.â Referredâtoâasâaââsquaredâpowerâsettingââ(i.e.,â2400âRPMâxâ24"âofâMP),âitâappearsâthatâthisâtaleâmayâbeâtheâresultâofâaâcarryoverâfromâsomeâmodelsâofâtheâoldâradialâenginesâwhichâwereâvulnerableâtoâbearingâwearâatâhighâpowerâsettings.âChangesâinâengineâdesign,âalongâwithâimprovedâmetalsâandâlubricants,âpermitâchangesâinâtheâoperationâofâmodernâflat,âopposed-cylinderâpowerâplants.
AnyâpilotâwhoâbelievesâthatâsquaredâpowerâsettingsâcontinueâtoâbeânecessaryâshouldâbeâurgedâtoâreadâandâunderstandâtheâinformationâinâtheâPilotâsâOperatingâHandbookâ(POH).âWhileâthereâareâlimitsâtoâtheâpowerâwhichâshouldâbeâtakenâfromâmostâengines,âparticu-larlyâthoseâwhichâareâturbocharged,âtheâcombinationsâofâRPMâandâMPâlistedâinâtheâpowerâchartsâofâtheâPOHâhaveâbeenâflightâtestedâandâapprovedâbyâtheâairframeâandâpowerâplantâengineers.âForâexample,âifâtheâPOHâchartâlistsâ2200âRPMâandâ26"âofâMPâasâanâapprovedâpowerâsetting,âpilotsâshouldânotâbeâapprehensiveâaboutâusingâthatâsettingâifâitâmeetsâtheirâneeds.
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Isnâtâitâstrangeâthatâsomeâbitsâofâinformationâcomeâtoâbeâbelievedâbyâlargeâsegmentsâofâaâpopulationâevenâwhenâtheyâareâuntrue?âTheâtwoâissuesâdiscussedâaboveâareâgoodâexamples.âWillâitâeverâbeâpossibleâtoâgetâallâofâourâfellowâpilotsâtoârejectâtheâtwoâfalseâideasâoutlinedâhere?âLetâsâkeepâtrying.
Sparkâplugâfoulingâinâyourâaircraftâengineâmayâbeâaâproblem.âLycomingâServiceâLetterâL192âprovidesâinformationâthatâmayâbeâveryâhelpfulâinâreducingâsparkâplugâfouling.âToâaidâourâreaders,âtheâentireâ textâofâ theâ latestârevisionâtoâServiceâLetterâL192âisâprintedâhere:
âInâmanyâcases,âsparkâplugâfoulingâresultingâfromâtheâtetraethylâleadâ(TEL)âinâaviationâfuelsâcanâbeâreducedâorâeliminatedâbyâproperâoperatingâtechniques.
âTheâproblemâofâleadâfoulingâarisesâwhenâlowâengine-operatingâtemperaturesâcoupledâwithâaârichâmixtureâpreventâtheâcompleteâvaporizationâofâtheâTEL.âUnderâtheseâconditions,âleadâdepositsâcanâformâinâ theâsparkâplugâelectrodes,âcausingâmisfiring.âByâestablishingâandâmaintainingâproperâengine-operatingâtempera-tures,âtheâTELâcanâbeâkeptâproperlyâvaporizedâandâpassâoutâtheâexhaustâsystem.
âHowever,â theâChampionâSparkâPlugâCompanyâhasâdesignedâaâsparkâplugâwhichâwillâreduceâorâeliminateâtheâeffectsâofâleadâfouling.âTheâsparkâplugâREM-37-BYâcanâbeâusedâinâtheâfollowingâengines:âO-235;âO-320;âIO-320-B,â-F,âAIO-320;âLIO-320-B;âIO-320-A,â-D,â-E;âAEIO-320;âHIO-360-B;âHO-360;âO-360-A,â-C,â-E,â-F;âIO-360-B,â-E,â-F;âAEIO-360-B,â-H;âO-360-B,â-D;âIVO-360;âVO-360-A,âB.
âForâ operatorsâ experiencingâ leadâ fouling,â theâ followingââoperatingârecommendationsâareâmade:
1.âByâuseâofâtheâsparkâplugârecommendationâcharts,âbeâcertainâtheâproperâplugsâareâinstalled.âDoânotâsimplyâreplaceâtheâsameâpartânumberâofâthoseâremoved.âAâpreviousâmechanicâmayâhaveâinstalledâtheâwrongâplugs.âReferenceâlatestâeditionâofâServiceâInstructionâNo.â1042.
2.âRotateâtopâandâbottomâsparkâplugsâeveryâ25âtoâ50âhours.âTopâplugsâscavengeâbetterâthanâtheâbottomâones.
3.âProperâadjustmentâofâtheâidleâspeedâ(600âtoâ650âRPM)âfuelâmixture,âandâmaintenanceâofâtheâinductionâairâsystem,âwillâensureâsmoothâengineâoperationâandâeliminateâexcessivelyârichâfuel/airâmixturesâatâidleâspeeds.âThisâwillâminimizeâtheâseparationâofâtheânon-volatileâcomponentsâofâtheâhigh-leadedâaviationâfuelsâgreatlyâretardingâtheâdepositionârate.
4.âTheâengineâshouldâbeâoperatedâatâengineâspeedsâbetweenâ1000âandâ1200âRPMâafterâstartingâandâduringâ theâ initialâwarm-upâperiod.âAvoidâprolongedâclosed-throttle,âidle-engineâspeedâopera-tionâ(whenâpossible).âAtâengineâspeedsâfromâ1000âtoâ1200âRPM,âtheâsparkâplugâcoreâtemperaturesâareâhotâenoughâtoâactivateâtheâleadâscavengingâagentsâcontainedâinâtheâfuelâwhichâretardsâtheâformationâofâtheâleadâsaltâdepositsâonâtheâsparkâplugsâandâexhaustâ
valveâstems.âAvoidârapidâengine-speedâchangesâafterâstart-up,âandâuseâonlyâtheâpowerâsettingsârequiredâtoâtaxi.
5.âAfterâaâfloodedâstart,âslowlyârunâtheâengineâtoâhighâpowerââtoâburnâoffâharmfulâ leadâdeposits,â thenâreturnâ theâengineâ toâânormalâpower.
â6.âKeepâengineâoperatingâtemperaturesâinâtheânormalâoperatingârange.âTooâmanyâpeopleâthinkâtheâlowerâtheâtemperatures,â theâbetter.âKeepâcylinderâheadâ temperaturesâ inânormalâoperatingârangeâbyâuseâofânormalâpowerâandâproperâleaning.âUseâoilâcoolerâbafflesâtoâkeepâoilâtemperatureâupâinâwinter.
7.âUseânormalârecommendedâleaningâtechniquesâatâcruiseâcondi-tionsâregardlessâofâaltitudeâandâreleanâtheâmixtureâwithâapplicationâofâalternateâairâorâcarburetorâheat.âIfâaircraftâisâusedâasâaâtrainer,âscheduleâcross-countryâoperationâwheneverâpossible.
8.âRapidâengineâcooldownâfromâlow-powerâaltitudeâchanges,âlow-powerâlandingâapproachâand/orâengineâshutdownâtooâsoonâafterâlandingâorâgroundârunsâshouldâbeâavoided.
9.âPriorâtoâengineâshutdown,âtheâengineâspeedâshouldâbeâmain-tainedâbetweenâ1000âandâ1200âRPMâuntilâ theâoperatingâtem-peraturesâhaveâstabilized.âAtâthisâtime,âtheâengineâspeedâshouldâbeâincreasedâtoâapproximatelyâ1800âRPMâforâ15âtoâ20âseconds,âthenâreducedâtoâ1000âtoâ1200âRPMâandâshutâdownâimmediatelyâusingâtheâmixtureâcontrol.â
PaulâMcBride,âaâformerâLycomingâemployeeâwidelyâknownâasââMr.âLycoming,ââ likesâ toâ tellâ theâstoryâofâ theâMooneyâownerâwhoseâpreownedâLycomingâIO-360-poweredâsingleâwouldnâtâgetâupâtoâtheâspecifiedâmaximumâRPMâsettingâofâ2700.âAfterâanâadjustmentâatâaâshop,âtheâengineâdidâobtainâ2700âRPMâonâtheâgage,âbutâtheâpowerâplantâfailedâinâflightâshortlyâthereafter.â
Afterâaâsafeâemergencyâlanding,âCanadianâauthoritiesâtookâoverâandâfoundâ thatâaâconnectingâ rodâhadâfailed.âContributingâ toâtheâfailureâwasâaâmanifoldâpressureâgageâthatâwasâreadingâtwoââinchesâlowââânotâanâunusualâerror,âaccordingâtoâMcBrideâââbutâmoreâimportantly,âtheâtachometerâthatâwasâreadingâ500âRPMâtooâlow.âTheâerrorâmeantâthatâtheâengineâhadâbeenâturningâatâ3200âRPM,âaâfactorâthatâultimatelyâledâtoâtheâfailure.â
TheâpointâofâMcBrideâsâstoryâisânotâtoâtryâtoâassignâblame,âbutâtoâaccentâ theâdangersâofâhavingâblindâfaithâinâtheâaccuracyâofâengineâ instruments.âManyâownersâhaveâsuchâfaith:âMcBrideârecallsâseeingâenginesâthatâhadâbeenâoverhauledâthreeâorâmoreâtimes,âwithâownersâreinstallingâtheâoriginalâengineâinstrumentsâeachâ time.âLycomingââstronglyâârecommendsâgettingâengineâinstrumentsâcalibratedâannuallyâ(seeâSIâ1094D,âFuelâMixtureâLeaningâProcedures,âandâSSPâ400,âOperatingâRecommendationsâforâtheâTIO-540-AE2Aâengine).âItâsâimportantâtoânoteâthatâengineâgagesâareânotâconsideredâpartâofâtheâengineâproper.âInâfact,âFAA-
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approvedâdataâcoveringâtheâverificationâandâcalibrationâofâ theâinstrumentationâisâtheâresponsibilityâofâtheâairframeâmanufac-turer,ânotâtheâengineâmaker.
Inâbetweenâoverhauls,â itâsâupâ toâ theâpilotâ inâcommandâorâ theâmaintenanceâshopâtoâspotâcalibrationâerrors.âAviationâmaintenanceâtechnicians,âasâpartâofâaâ100-hr.âorâannualâ inspection,âshouldâscanâ theâgagesâ forâproperâoperationâduringâaâpre-inspectionâârun-up.â Ifâ thereâsâ aâ problem,â gagesâ and/orâ sensorâ unitsââwouldâ likelyâbeâswappedâoutâorâsentâoutâ toâanâavionicsâshopâorâ repairâ facilityâ forâ recalibrationâorâ fixes.âOnceâ theâsystemâisâreturned,âLycomingârecommendsâthatâ theâgage,âsensorâandâinterconnectâwiringâbeâcalibratedâbyâaâqualifiedâtechnicianâorâagencyâbeforeâflight.
Ofâtheâtypicalâengineâinstrumentsâââtachometers,âoilâtempera-tureâgages,âoilâpressureâgages,âcylinderâheadâtemperatureâgages,ââexhaustâ gasâ temperature,â manifoldâ pressureâ gagesâ andââturbineâ inletâ temperatureâprobesâforâ turbochargedâenginesââââtachometersâareâ theâmostânotoriousâ forâbeingâoutâofâcalibra-tion,âsaysâMcBride.âCalibrationâerrorsâasâsmallâasâ5%âorâ10%âinâRPMâreadingââwillâgreatlyâincreaseâtheâloadâonâtheâpropellerâandâtheâengineâbearingsâduringâoperation,ââheâsays.âEvenâoff-the-shelfâ instrumentsâareânotâbeyondâreproach.âMcBrideâsaysâoneâmaintenanceâfacilityâownerâtoldâhimâthatâheâdâonceâtestedâfiveâtachometersâoffâtheâshelfâandâfoundâthatâeachâwasâindicatingâaboutââ150âRPMâlow.âThatâsâanâerrorâofâmoreâthanâ5%âofâtheâcruiseâRPMâofâmanyâengines.â
Anâ instrumentâ expertâ withâ Keystoneâ Instrumentsâ inâ LockâHaven,âPennsylvania,âsaysâanâinstallationâerrorâasâinnocuousâasâcuttingâaâtachometerâcableâÂź-inchâtooâlongâcanâcauseâtheâinstru-mentâtoâreadâ500âtoâ600âRPMâfast;âworseâyet,âusingâtheâwrongâcableâcanâdamageâtheâtach.âUsuallyâthough,âheâsaysâproblemsâariseâwhenâ theâ insideâofâ theâgageâgetsâdirtyâandâneedsâ toâbeâcleaned.âEitherâway,âoperatorsâareâ requiredâ toâsendâgagesâ toâanâauthorizedâmaintenanceâfacilityâforârepairsâorârecalibration,ââaccordingâtoâKeystone.
Figuringâoutâwhetherâgagesâareâcalibratedâcorrectlyâinâtheâfieldâisâsometimesâobvious,âsometimesânotâââaâlaâtheâMooneyâmishap.âAnâoilâtemperatureâgage,âforâinstance,âshouldâreadâtheâambientâtemperatureâbeforeâtheâengineâisâstarted.âManifoldâpressure,âtoo,âshouldâmatchâtheâambientâpressureâbeforeâstart.â
Someâgagesâcanâbeâoperationallyâverifiedâonâtheâcheapâbyâaâlocalâmaintenanceâshop.âBenâVisser,âanâaviationâcolumnistâandâformerâShellâOilâchemist,ârecommendsâcheckingâoilâtemperatureâgagesâbyâplacingâtheâsendingâunitâinâaâpanâofâoilâsittingâonâaâhotâplate.âUsingâaâthermometer,âVisserâsaysâtoâheatâtheâoilâtoâ180ËâFâthenâtoâmarkâtheâgageâwithâaâpermanentâmarker,âregardlessâofâwhetherâtheâgageâhasâtemperaturesâprintedâonâtheâface.â
Whyâ180Ë?âVisserâexplainsâ thatâ theâpeakâoilâ temperatureâ inâaânormallyâaspiratedâengineâisâtypicallyâ50ËâFâhigherâthanâtheâtem-peratureâofâtheâoilâinâtheâsump,âtheâlocationâofâtheâsensor.âTheâpeakâtemperatureâinâaâturbochargedâengineâisâaboutâ70âtoâ75ËâFâhotterâthanâtheâindicatedâtemperature.âHeâsaysâtheâtypicalââgreenâbandââonâanâoilâtemperatureâgageârangesâfromâ120ËâFâtoâ245ËâF.
Byâcalibratingâ theâgageâandâoperatingânearâ theâ180Ëâpointâ inâcruise,âVisserâsaysâtheâoilâtemperatureâatâtheâhottestâpointâinâtheâengineâwillâexceedâ212ËâF,âboilingâoffâanyâwaterâthatâhasâaccu-
mulatedâinâtheâoil.âByâconsistentlyâoperatingâbelowâtheâboilingâpoint,âVisserâsaysâwaterâandâacidâcanâbuildâupâinâtheâcrankcase,âleadingâtoârustâandâcorrosionâandâreducedâengineâlife.âKeystoneâsometimesâchecksâitsâoilâ temperatureâgagesâbyâimmersingâtheâsendingâunitsâinâboilingâwaterâtoâverifyâtheâgageâreadsâ212ËâF.â
Theâarrivalâofâsolid-stateâintegratedâavionicsâandâliquid-crystalâdisplaysâforâtheâcockpit,âwhileâeliminatingâtheâabilityâtoâstrikeâaâlineâonâaâgageâface,âwillâundoubtedlyâboostâreliabilityâandâread-abilityâofâengineâgages.âPopularâsystemsâlikeâBlueâMountainââAvionicsââEFIS/Oneââglassââcockpitâ forâexperimentalâaircraftâallowsâanâoperatorâ toâdisplayâasâmanyâasâ16âdifferentâengineâgagesâon-screen,âwhetherâtheâinputâfromâeachâisâvoltage,âdiffer-entialâvoltage,âresistanceâorâthermocouple.âCalibratingâtheâunitâisâârelativelyâsimple,âtooâââitâhasâaâspecialâscreenâthatâallowsâtheâoperatorâtoâviewâandâmodifyâtheâsetupâandâcalibrationâinformationâforâeachâsensor.
TheâflowâofâoilâthroughâaâLycomingâreciprocatingâaircraftâengineâisâknownâtoâbeâaânecessaryâfunctionâduringâtheâoperationâofâtheâengine.âPilotsâareâoftenânotâatâallâconcernedâaboutâhowâthisâfunc-tionâoccurs,âasâlongâasâtheâoilâpressureâandâoilâtemperatureâindica-torsâshowâaâproperâreading.âAâ&âPâmechanics,âonâtheâotherâhand,âoftenâneedâtoâknowâhowâtheâsystemâworksâandâwhatâpartsâcontrolâtheâflowâofâoilâduringâvariousâphasesâofâoperation.âBecauseâofâtheâlargeânumberâofâcallsâconcerningâthisâsubject,âwhichâareâreceivedâbyâLycomingâServiceâSpecialists,âweâcanâbeâsureâthatâthereâareâmanyâwhoâdoânotâhaveâaâgoodâunderstandingâofâtheâoilâsystem.
ItâisânotâsurprisingâthatâmanyâAâ&âPâmechanicsâdoânotâhaveâaâfirmâgraspâonâtheâoperationâofâtheâoilâsystem.âThereâisâroomâforâconfusionâsinceâthereâareâtwoâbasicâsystemsâandâseveralâvariationsâonâeachâofâthese.
Exceptâ forâ theâ screens,â filterâ andâ oilcooler,â theâ flowâ ofâ oilâthroughâtheâengineâisâcompletelyâpre-determinedâbyâtheâdesignedââengine-runningâclearancesâandâbyâtheâpassagesâwhichâareâdrilledâinâtheâcrankcaseâandâaccessoryâhousingâduringâengineâmanufac-ture.âThisâflowâofâoilâservesâthreeâpurposes.âFirst,â itâ lubricates,âbutâcoolingâtheâengineâbyâcarryingâawayâtheâheatâgeneratedâbyâcombustionâisâaâsecondâpurpose,âwhichâisâoftenâjustâasâimportant.âManyâengines,âparticularlyâthoseâwhichâareâturbocharged,âhaveâoilâsquirtsâinâeachâcylinderâwhichâareâdesignedâtoâdirectâcoolingâoilâonâtheâbackâsideâofâtheâpiston.âAndâfinally,âtheâoilâcleansâtheâengineâbyâpickingâupâdirtâandâdepositingâitâinâtheâscreensâorâfilter,âorâbyâkeepingâthatâdirtâinâsuspensionâuntilâtheâoilâisâchanged.
Theâoilâwhichâhasâdoneâ itsâ lubricating,âcoolingâandâcleaningâflowsâbyâgravityâbackâtoâtheâoilâsump.âFromâtheâsump,âtheâoilâpumpâpullsâtheâoilâthroughâtheâsuctionâscreen.âThisâscreenâwillâfilterâoutâ largeâparticlesâofâcarbon,âdirtâorâmetal.âTheâpumpâthenâforcesâ theâoilâ throughâoneâofâ theâ twoâbasicâsystems.â Inâeachâofâtheâtwoâbasicâsystems,âthereâisâaâvalveâwhichâforcesâtheâoilâ throughâtheâoilâcoolerâwhenâtheâvalveâisâseated,âorâallowsâ
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theâoilâtoâbypassâtheâcoolerâwhenâtheâvalveâisâopen.âLycomingâenginesâwereâoriginallyâequippedâwithâaâbypassâvalveâwhichâwasâcontrolledâbyâaâspring.âReferredâtoâasâaâspringâandâplungerâtype,âitâfunctionedâasâaâresultâofâtheâamountâofâpressureâinâtheâoilâsystem.âTheâspring-controlledâbypassâsystemâwasâsupersededâbyâaâsystemâcontrolledâbyâaâThermostaticâOilâCoolerâBypassâwhichâreactsâtoâoilâtemperatureâchanges.
Operationâofâtheâspring-controlledâbypassâsystemâisâtheâresultâofâthickâoilâwhichâcausesâanâincreaseâinâdifferentialâpressureâacrossâtheâbypassâvalveâandâcausesâtheâbypassâvalveâtoâbeâopen,âthusâbypassingâtheâoilâcooler.âAsâtheâoilâwarmsâup,âoilâviscosityâandâpressureâinâtheâsystemâareâreduced,âallowingâtheâbypassâvalveâtoâcloseâandâforcingâoilâflowâthroughâtheâoilâcooler.âAlthoughâtheâbypassâvalveâhelpsâ theâengineâ toâwarmâupâmoreâquicklyâbyâroutingâcoldâoilâaroundâtheâoilâcooler,â itsâprimaryâfunctionâisâforâsystemâsafety;âshouldâtheâoilâcoolerâbecomeâpluggedâforâanyâreason,âsystemâpressureâwillâriseâandâtheâdifferentialâpres-sureâacrossâtheâbypassâvalveâwillâagainâcauseâtheâvalveâtoâopen.ââThisâby-passesâtheâoilâcoolerâandâpreventsâaâpossibleâruptureâofâtheâcoolerâandâlossâofâtheâoil.
TheâThermostaticâOilâCoolerâBypassâValveâwasâdesignedâ toâprovideâbetterâcontrolâofâtheâengineâoilâtemperatureâwhileâalsoâmaintainingâtheâsafetyâofâtheâoilâsystemâbyâbypassingâoilâaroundâanâoilâcoolerâwhichâisâpluggedâforâanyâreason.âTheâthermostaticâoilâcoolerâbypassâvalveâmayâbeâusedâonâenginesâwhichâuseâtheâpressure-screenâsystemâandâonâenginesâwhichâhaveâaâfull-flowâoilâfilter.âForâmostâengineâmodels,âanâoilâfilterâalsoârequiresâanâoilâfilterâadapter.âWhileâtheâoilâisâcold,âthisâsystemâallowsâoilâtoâflowâthroughâtheâoilâfilterâwithoutâpassingâthroughâtheâoilâcooler.âAsâoilâtemperatureârisesâtoâapproximatelyâ180ËâF,âtheâvalveâclosesâandâforcesâtheâoilâtoâpassâthroughâtheâoilâcooler.âTheâoilâthenâreturnsâtoâtheâaccessoryâhousingâwhereâitâisâroutedâthroughâtheâoilâfilterâadapter,âtheâfilterâandâthenâagainâthroughâtheâfilterâadapter,âacces-soryâhousingâandâfinallyâintoâtheâcrankcase.
Theâoilâfilterâisâanotherâpartâofâtheâsystemâwhereâblockageâcouldâcauseâseriousâproblems.âForâthisâreason,âanâoilâfilterâbypassâisâbuiltâintoâtheâoilâfilterâadapter,âorâinâtheâcaseâofâenginesâutilizingâaâdualâmagneto,âintoâtheâaccessoryâhousing.âTheseâbypassâvalvesâareâbuilt-inâsafetyâfeaturesâwhichâactivateâasâaâresultâofâexcessiveâpressureâinâtheâoilâfilter.âTheâoilâfilterâbypassâisânotâadjustable.
Oilâ entersâ theâ crankcaseâ ofâ mostâ Lycomingâ enginesâ nearâtheâ topâofâ theârightârearâcylinderâwhereâ itâpassesâ throughâtheââpressure-reliefâvalve.âThereâareâ threeâ typesâofâpressure-reliefâvalve.âWithâeitherâ theâshortâorâ longâdomeâvalve,âpressureâ isâadjustedâbyâremovingâtheâdomeâandâaddingâorâdeletingâwashersâwhichâareâlocatedâunderâtheâcontrollingâspring.âThereâisâalsoâaâthirdâstyleâofâpressure-reliefâvalveâwhichâmayâbeâadjustedâwithâtheâtwistâofâaâwrenchâorâscrewdriver.
Anâindividualâlookingâforâtheâpressure-screenâhousingâmayânotâfindâexactlyâwhatâheâorâsheâisâlookingâforâsinceâthereâareâtwoâ
possibleâvariations.âTheâhousingâforâtheâpressureâscreenâmayâhaveâoneâholeâfacingâtheârearâofâ theâengine.âThisâhousingâisâusedâonâenginesâincorporatingâaâspringâandâplungerâtoâcontrolâoilâflow,âandâtheâsingleâholeâwillâbeâusedâforâoilâtemperatureâprobe.âAnotherâstyleâofâpressure-screenâhousingâhasâtwoâholesâfacingâ theârearâofâ theâengine.âTheâsmallâholeâ isâusedâforâoilâtemperatureâbulbâconnection,âandâaâThermostaticâOilâCoolerâBypassâValveâisâinstalledâinâtheâlargeâhole.
Evenâmoreâattentionâtoâdetailâmayâbeârequiredâwhenâanâoilâfilterâisâinstalled.âTheâpressure-screenâhousingâmustâbeâremovedâandâoil-filterâadapterâinstalledâinâitsâplace.âWithâtheâoil-filterâadapterâinstalled,âeitherâaâspring-controlledâbypassâvalveâ installedâ inâtheâaccessoryâhousingâjustâaboveâtheâadapter,âorâaâthermostaticââbypassâvalveâ installedâ inâ theâbottomâofâ theâadapterâmayâbeâusedâtoâcontrolâoilâflowâtoâtheâoilâcooler.âBecauseâofâtheâbetterââoil-temperatureâcontrol,âuseâofâtheâthermostaticâoilâcoolerâbypassâvalveâisâpreferredâbyâLycoming.âForâenginesâshippedâfromâtheâfac-toryâwithâanâoilâfilter,âandârequiringâanâoilâcoolerâinâtheâaircraftâinstallation,âitâ isâstandardâprocedureâforâLycomingâtoâsupplyâaâthermostaticâbypassâvalve.âTheâholeâinâ theâaccessoryâhousingâwhichâisâprovidedâforâaâspring-controlledâbypassâvalveâisâcappedâwithâaâplug.âAâholeâonâtheâtopâofâtheâadapterâisâprovidedâforâtheâoilâtemperatureâbulb.
Aâpossibleâvariationâ toâ theâ flowâofâoilâwhichâmayâbeâ foundâwithâaâLycomingâengine.âSomeâairframeâmanufacturersâhaveâutilizedâ smallâ engineâ modelsâ withoutâ anâ oilâ cooler.â Atâ theârequestâofâ theseâairframeâmanufacturers,â theseâenginesâareânotâmachinedâtoâaccommodateâanâoilâcooler.âIndividualsâwhoâacquireâtheseâenginesâforâuseâinâtheirâhome-builtâaircraftâmayâneedâanâoilâcoolerâtoâkeepâtemperaturesâwithinâoperatingâlimits.âThisâcanâbeâaccomplishedâbyâutilizingâanâadapterâââLycomingâpartânumberâ62418.âUtilizationâofâ thisâadapterâwillâallowâtheââengineâtoâbeâusedâandâtheâoilâtoâbeâcooled,âbutâthereâareâlimita-tions.âAnâoilâfilterâcannotâbeâinstalled,âandâonlyâtheâone-holeâpressure-screenâhousingâcanâbeâused.âThisâlimitsâtheâsystemâtoâuseâasâaâspring-controlledâoilâcoolerâbypassâvalveâwhichâisâinstalledâinâtheâadapter.
Thereâareâseveralâbitsâofâinformationâwhichâmayâbeâhelpfulâtoâthoseâwhoâhaveânowâacquiredâaâbetterâunderstandingâofâ theââLycomingâengineâoilâ system.âLycomingâServiceâ Instructionâ1008Bâgivesâ instructionsâ forâ installationâofâ aâThermostaticââOilâCoolerâBypassâValveâonâenginesâwhichâhaveâaâpressure-screenâhousingâandânoâfilter.âSpecialâServiceâPublicationâ(SSP)â885-2âgivesâinstructionâforâtheâinstallationâofâengine-mountedâoilââfilterâkits.âAndâfinally,âaâkitâ(Numberâ05K21437)âforâaâremotelyâmountedâoilâfilterâhasâbeenâdeveloped.â
TheâServiceâSpecialistsâatâtheâLycomingâfactoryâreceiveâmanyâcallsâaboutâ theâoilâ systemâandâ itsâmanyâpossibleâvariations.âTheâmaterialâpresentedâhereâisâintendedâtoâhelpâanswerâmanyâofâthoseâquestions.
L y c o m i n g F l y e r �9
Checkâyourâknowledgeâofâaircraftâenginesâwithâtheââquestionsâbelow.
A. Multiple Choice. Circle the one best answer.
1.âInâcomparisonâtoâfuel-injectionâsystems,âfloat-typeââââcarburetorâsystemsâareâgenerallyâconsideredâtoâbe
a.âequallyâsusceptibleâtoâicingâasâaâfuel-injectionâunit.
b.âlessâsusceptibleâtoâicingâthanâaâfuel-injectionâunit.
c.âsusceptibleâtoâicingâonlyâwhenâvisibleâmoistureâisâpresent.
d.âmoreâsusceptibleâtoâicingâthanâaâfuel-injectionâunit.
2.âTheâbasicâpurposeâofâadjustingâtheâfuel/airâmixtureâcontrolâatâaltitudeâisâto
a.âincreaseâtheâfuel/airâratioâforâflyingâatâaltitude.
b.âdecreaseâtheâfuelâflowâinâorderâtoâcompensateâforâdecreasedâairâdensity.
c.âincreaseâtheâamountâofâfuelâinâtheâmixtureâtoâcompensateâforâtheâdecreaseâinâpressureâandâdensityâofâtheâair.
d.âdecreaseâtheâamountâofâfuelâinâtheâmixtureâinâorderâtoâcompensateâforâincreasedâairâdensity.
3.âIfâtheâengineâofâanâairplaneâisâpermittedâtoâidleâforâaâlongâperiodâofâtimeâwhileâonâtheâground,
a.âaâhydraulicâlockâmayâdevelopâinâoneâorâmoreâcylinders.
b.âtheâleanâmixtureâmayâcauseâtheâengineâtoâmissâorâquit.
c.âtheâresultâmayâbeâanâexcessivelyâhighâoilâpressure.
d.âtheâsparkâplugsâmayâbecomeâfouled.
4.âAssumeâthatâonâyourârun-upâatâanâairportâwhereâtheâelevationâisâ6,000âfeetâMSL,âyouânoteâaâslightâengineâroughnessâthatâ isâânotâ significantlyâ affectedâbyâ theâmagnetoâ checkâbutâ growsâworseâduringâtheâcarburetorâheatâcheck.âUnderâ theseâcircum-stances,âwhichâofâ theâ followingâwouldâbeâyourâmostâ logicalââinitialâaction?
a.âcheckâtoâseeâthatâtheâmixtureâcontrolâisâinâtheâfull-richâposition.
b.âreduceâmanifoldâpressureâtoâcontrolâdetonation.
c.âcheckâtheâresultsâobtainedâwithâaâleanerâsettingâofâtheâmixtureâcontrol.
d.âtaxiâbackâtoâtheâflightâlineâforâaâmaintenanceâcheck
5.âWithâregardâtoâtheâuseâofâaviationâgasoline,âwhichâstatementâisâtrue?
a.âuseâofâaâlower-than-specifiedâgradeâofâfuelâmayâresultâinâaâreducedâpowerâoutputâbutâisâusuallyâlessâharmfulâthanâhigher-ratedâfuel.
b.âuseâofâtheânextâhigher-than-specifiedâgradeâofâfuelâisââ âpermissibleâifâtheâspecifiedâgradeâofâfuelâisânotâavailable.
c.âuseâofâtheânextâlower-than-specifiedâgradeâofâfuelâisâper-missibleâifâtheâspecifiedâgradeâofâfuelâisânotâavailable.
d.âuseâofâaâhigher-than-specifiedâgradeâofâfuelâusuallyâresultsâinâlower-than-normalâcylinderâheadâtemperatures.
6.âIfâtheâgradeâofâfuelâusedâinâanâaircraftâengineâisâlowerâthanââ âspecifiedâforâtheâengine,âitâwillâmostâlikelyâcause
a.âanâincreaseâinâpowerâwhichâcouldâoverstressâinternalâengineâcomponents.
b.âdetonation.
c.âlowerâcylinderâheadâtemperatures.
d.âaânon-uniformâmixtureâofâfuelâandâairâinâtheâcylinders.
7.âWhichâstatementâ isâ trueâregardingâaircraftâenginesâthatâareâequippedâwithâaâfuel-injectionâsystemâinsteadâofâaâcarburetor?
a.âvaporâlocksâduringâgroundâoperationsâonâhotâdaysâareâlessâaptâtoâoccurâwithâfuelâinjection.
b.âaâdisadvantageâofâfuelâinjectionâisâtheâdifficultyââ ââexperiencedâinâcold-weatherâstarting.
c.âslowâthrottleâresponseâisâoneâofâtheâdisadvantagesâofââfuelâinjection.
d.âfuelâinjectionâprovidesâbetterâfuelâmanagementâandâfuelââdistributionâtoâtheâengine.
8.âTheâpresenceâofâcarburetorâice,âinâanâairplaneâequippedâwithâaâfixed-pitchâpropeller,âcanâbeâverifiedâbyâapplyingâcarburetorâheatâandânoting
a.âaâdecreaseâinâRPMâandâthenâaâgradualâincreaseâinâRPM.
b.âaâdecreaseâinâRPMâandâthenâaâconstantâRPMâindication.
c.âanâ immediateâ increaseâ inâRPMâwithânoâfurtherâchangeââinâRPM.
d.âanâincreaseâinâRPMâandâthenâaâgradualâdecreaseâinâRPM.
9.âIfâtheâengineâoilâtemperatureâandâcylinderâheadâtemperatureâgagesâhaveâexceededâtheirânormalâoperatingârange,âyouâmayâhaveâbeen
a.âoperatingâwithâhigher-than-normalâoilâpressure.
b.âusingâfuelâthatâhasâaâhigher-than-specifiedâfuelârating.
c.âoperatingâwithâtooâmuchâpowerâandâwithâtheâmixtureâsetâtooâlean.
d.âoperatingâwithâtheâmixtureâsetâtooârich.
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10.âWhatâchangeâoccursâinâtheâfuel/airâmixtureâwhenâcarburetorâheatâisâapplied?
a.âtheâfuel/airâmixtureâbecomesâleaner.
b.âtheâfuel/airâmixtureâbecomesâricher.
c.ânoâchangeâoccursâinâtheâfuel/airâmixture.
d.âaâdecreaseâinâRPMâresultsâfromâtheâleanâmixture.
11.âForâmaximumâengineâlifeâandâtrouble-freeâoperation,âengineâbreak-inâduringâtheâfirstâ25âtoâ50âhoursâofâengineâoperationâshouldâbeâaccomplishedâby
a.âlimitingâtakeoffâpowerâtoâfiveâminutesâperâflightâandââusingâ65%âpowerâmaximumâforâcruise.
b.ârunningâtheâengineâcontinuouslyâatâ65%âtoâ75%âpowerââ ââwithâfullâpowerâorâmaximumâpowerâavailableâforâclimb.
c.âusingâlessâthanâ100%âpowerâforâtakeoffâandâcruisingâatââ ââ75%âpowerâorâbelow.
d.ârunningâtheâengineâatâ1200âRPMâforâatâleastâ20âminutesâbeforeâtheâfirstâtakeâoffâofâtheâday.
12.âTheâfull-flowâoilâfilterâisâveryâusefulâinâkeepingâanâengineâclean,âbutâitâwillânotâfilterâout
a.âwater.
b.âacids.
c.âleadâsludge.
d.âallâofâtheâabove.
13.âForâaircraftâwithâanâEGTâgage,âaâgoodââruleâofâthumbââforâmostâgeneralâaviationâenginesâatâcruiseâisâtoâleanâto
a.â50ËâonâleanâsideâofâpeakâEGT.
b.âPeakâEGT.
c.â50ËâonârichâsideâofâpeakâEGT.
d.â100ËâonârichâsideâofâpeakâEGT.
14.âWithâhighârelativeâhumidity,âcarburetorâicingâmayâbeâexpectedâwithinâwhichâofâtheâfollowingâranges?
a.â32Ëâtoâ59ËâF.
b.â0Ëâtoâ15ËâF.
c.â20Ëâtoâ90ËâF.
d.â0Ëâtoâ59ËâF.
15.âAnâaircraftâengineâwhichâdevelopsâlessâandâlessâpowerâfromâtheâpointâofâtakeoffâtoâtheâserviceâceilingâisâsaidâtoâbe
a.âsupercharged.
b.ânormallyâaspirated.
c.âturbocharged.
d.âsuperâcritical.
16.âIfâfullâcarburetorâheatâisâusedâduringâcruiseâforâtheâpreven-tionâofâcarburetorâice,âsomeâofâtheâ15%âofâpowerâlossâincurredâmayâbeâregainedâby
a.âenrichingâtheâmixture.
b.âsquaringâtheâpowerâsetting.
c.âapplyingâoneâpumpâofâtheâprimerâeveryâ15âminutes.
d.âleaningâtheâmixture.
17.âTheâfinalâauthorityâregardingâoperationâofâtheâgeneralââaviationâaircraftâengineâis
a.âengineâoperatorâsâmanualâprovidedâbyâtheâengineââ âââmanufacturer.
b.âPilotâsâOperatingâHandbookâprovidedâbyâtheâairframeââ ââmanufacturer.
c.âaviationâcircularsâdistributedâbyâtheâFAA.
d.âyourâlocalâfixed-baseâoperator.
18.âUseâofâpartialâheatâtoâpreventâcarburetorâicingâisârecom-mendedâonlyâifâtheâaircraftâhas
a.âaâcarburetorâairâtemperatureâgageâââCAT.
b.âaâcylinderâheadâtemperatureâgageâââCHT.
c.âanâexhaustâgasâtemperatureâgageâââEGT.
d.âanâoutsideâairâtemperatureâgageâââOAT.
B. Supply the best answer to the following essay questions:
1.â Explainâ whyâ aerobaticsâ orâ invertedâ flightâ shouldâ notâ beâattemptedâunlessâtheâengineâhasâbeenâmodifiedâforâthisâtypeâofâflying.
2.âListâtwoâpurposesâofâengineâoil.
3.âWhatâareâtheâtwoâFAA-approvedâoilsâforâgeneralâaviation?
4.âWhenâoperatingâatâtheâmanufacturerâsârecommendedâcruiseâpower,âatâwhatâaltitudesâmayâleaningâbeâaccomplished?
5.âOfâwhatâsignificanceâisâtheâ5,000âfeetâdensityâaltitudeârefer-enceâpointâforânormallyâaspiratedâengines?
6.âWhatâcausesâengineâroughnessâwhenâleaningâanâengineââusingâaâfloat-typeâcarburetorâatârecommendedâcruiseâpower?
7.âTheâExhaustâGasâTemperatureâ(EGT)âsystemâisâmoreâpreciseâasâaâfuelâmanagementâinstrumentâwithâwhichâofâtheâfollowing?
a.âFloat-typeâcarburetor.
b.âFuelâinjection.
8.âHowâcanâdamageâtoâanâengineâtakeâplaceâasâaâresultâofââleaning?
9.âWhatâimportantâconsiderationâbyâtheâpilotâforâhisâengineâmustâtakeâplaceâwithâaânormallyâaspiratedâengineâatâairportsâwhereâtheâdensityâaltitudeâisâ5,000âfeetâorâhigher?
10.âListâtwoâtypesâofâinductionâice.
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ANSWERS TO QUESTIONS
A. Multiple choice response
1.âdâ 7.âdâ 13.âc
2.âbâ 8.âaâ 14.âc
3.âdâ 9.âcâ 15.âb
4.âcâ 10.âbâ 16.âd
5.âbâ 11.âbâ 17.âb
6.âbâ 12.âdâ 18.âa
B. Essay response
1.âLossâofâengineâoilâoutâtheâbreatherâcanâcauseâengineâdamageâorâfailure.
2.âa.âLubricateâmovingâparts.
âb.âAidâinternalâcoolingâofâtheâengine.
3.âa.âStraightâmineral.
âb.âAshlessâDispersant.
4.âAtâanyâaltitude.
5.âItâisâaâclimbâreferenceâpointâforânormallyâaspiratedâpowerâplants.âClimbâfromâseaâlevelâthroughâ5,000âfeetâ(someâCessnasâmayâuseâ3,000âfeet)âshouldâbeâfullârich.âContinuedâclimbâbeyondâ5,000âfeetâ(3,000âfeetâforâsomeâCessnas)âshouldâuseâsomeâleaningâtoâimproveââengineâefficiency.
6.âTheâroughnessâisânotâdetonationâatârecommendedâcruiseâpower.âTheâleanestâcylinderâinâtheâless-than-perfectâdistributionâpatternâisâcuttingâout.âOperationâinâtheâroughnessâareaâisânotâacceptable.
7.âb.âFuelâinjection.
8.âDamageâtoâanâengineâfromâleaningâtakesâplaceâatâhigherâthanârecommendedâcruiseâpowerâasâdetonationâwhereâanâaircraftâdoesânotâhaveâtheânecessaryâengineâinstrumentsâtoâindicateâtheâpowerâplantâisâbeingâabused.
9.âRequiresâproperâleaningâforâsafest,âefficientâperformanceââatâtakeoff.
10.âTwoâtypesâofâinductionâice:
a.âImpactâiceâââtypicallyâonâtheâairâfilter.
b.âRefrigerationâiceâââformsâinâtheâfloat-typeâcarburetor.
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