MULTIENGINE FLIGHTThis chapter is devoted to the factors associated withthe operation of small multiengine airplanes. For thepurpose of this handbook, a “small” multiengine air-plane is a reciprocating or turbopropeller-poweredairplane with a maximum certificated takeoff weightof 12,500 pounds or less. This discussion assumes aconventional design with two engines—one mountedon each wing. Reciprocating engines are assumedunless otherwise noted. The term “light-twin,”although not formally defined in the regulations, isused herein as a small multiengine airplane with amaximum certificated takeoff weight of 6,000 poundsor less.

There are several unique characteristics of multiengineairplanes that make them worthy of a separate class rat-ing. Knowledge of these factors and proficient flightskills are a key to safe flight in these airplanes. Thischapter deals extensively with the numerous aspects ofone engine inoperative (OEI) flight. However, pilotsare strongly cautioned not to place undue emphasison mastery of OEI flight as the sole key to flyingmultiengine airplanes safely. The inoperative engineinformation that follows is extensive only becausethis chapter emphasizes the differences between flyingmultiengine airplanes as contrasted to single-engineairplanes.

The modern, well-equipped multiengine airplane canbe remarkably capable under many circumstances. But,as with single-engine airplanes, it must be flown pru-dently by a current and competent pilot to achieve thehighest possible level of safety.

This chapter contains information and guidance on theperformance of certain maneuvers and procedures insmall multiengine airplanes for the purposes of flighttraining and pilot certification testing. The finalauthority on the operation of a particular make andmodel airplane, however, is the airplane manufacturer.Both the flight instructor and the student should beaware that if any of the guidance in this handbook con-flicts with the airplane manufacturer’s recommendedprocedures and guidance as contained in the FAA-approved Airplane Flight Manual and/or Pilot’sOperating Handbook (AFM/POH), it is the airplanemanufacturer’s guidance and procedures that takeprecedence.

GENERALThe basic difference between operating a multiengineairplane and a single-engine airplane is the potentialproblem involving an engine failure. The penalties forloss of an engine are twofold: performance and control.The most obvious problem is the loss of 50 percentof power, which reduces climb performance 80 to 90percent, sometimes even more. The other is the con-trol problem caused by the remaining thrust, whichis now asymmetrical. Attention to both these factorsis crucial to safe OEI flight. The performance andsystems redundancy of a multiengine airplane is asafety advantage only to a trained and proficientpilot.

TERMS AND DEFINITIONSPilots of single-engine airplanes are already familiarwith many performance “V” speeds and their defini-tions. Twin-engine airplanes have several additionalV speeds unique to OEI operation. These speeds aredifferentiated by the notation “SE”, for single engine.A review of some key V speeds and several new Vspeeds unique to twin-engine airplanes follows.

• VR – Rotation speed. The speed at which backpressure is applied to rotate the airplane to a take-off attitude.

• VLOF – Lift-off speed. The speed at which theairplane leaves the surface. (Note: some manu-facturers reference takeoff performance data toVR, others to VLOF.)

• VX – Best angle of climb speed. The speed atwhich the airplane will gain the greatest altitudefor a given distance of forward travel.

• VXSE – Best angle-of-climb speed with oneengine inoperative.

• VY – Best rate of climb speed. The speed atwhich the airplane will gain the most altitude fora given unit of time.

• VYSE – Best rate-of-climb speed with one engineinoperative. Marked with a blue radial line onmost airspeed indicators. Above the single-engineabsolute ceiling, VYSE yields the minimum rate ofsink.

• VSSE – Safe, intentional one-engine-inoperativespeed. Originally known as safe single-engine

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speed. Now formally defined in Title 14 of theCode of Federal Regulations (14 CFR) part 23,Airworthiness Standards, and required to beestablished and published in the AFM/POH. It isthe minimum speed to intentionally render thecritical engine inoperative.

• VMC – Minimum control speed with the criticalengine inoperative. Marked with a red radial lineon most airspeed indicators. The minimum speedat which directional control can be maintainedunder a very specific set of circumstances outlinedin 14 CFR part 23, Airworthiness Standards.Under the small airplane certification regulationscurrently in effect, the flight test pilot must be ableto (1) stop the turn that results when the criticalengine is suddenly made inoperative within 20°of the original heading, using maximum rudderdeflection and a maximum of 5° bank, and (2)thereafter, maintain straight flight with notmore than a 5° bank. There is no requirement inthis determination that the airplane be capableof climbing at this airspeed. VMC onlyaddresses directional control. Further discus-sion of VMC as determined during airplane cer-tification and demonstrated in pilot trainingfollows in minimum control airspeed (VMC)demonstration. [Figure 12-1]

Figure 12-1. Airspeed indicator markings for a multiengineairplane.

Unless otherwise noted, when V speeds are given inthe AFM/POH, they apply to sea level, standard dayconditions at maximum takeoff weight. Performancespeeds vary with aircraft weight, configuration, andatmospheric conditions. The speeds may be stated instatute miles per hour (m.p.h.) or knots (kts), and theymay be given as calibrated airspeeds (CAS) or indi-cated airspeeds (IAS). As a general rule, the newer

AFM/POHs show V speeds in knots indicated airspeed(KIAS). Some V speeds are also stated in knots cali-brated airspeed (KCAS) to meet certain regulatoryrequirements. Whenever available, pilots should oper-ate the airplane from published indicated airspeeds.

With regard to climb performance, the multiengineairplane, particularly in the takeoff or landing con-figuration, may be considered to be a single-engineairplane with its powerplant divided into two units.There is nothing in 14 CFR part 23 that requires amultiengine airplane to maintain altitude while inthe takeoff or landing configuration with one engineinoperative. In fact, many twins are not required todo this in any configuration, even at sea level.

The current 14 CFR part 23 single-engine climbperformance requirements for reciprocating engine-powered multiengine airplanes are as follows.

• More than 6,000 pounds maximum weightand/or VSO more than 61 knots: the single-engine rate of climb in feet per minute (f.p.m.) at5,000 feet MSL must be equal to at least .027VSO

2. For airplanes type certificated February 4,1991, or thereafter, the climb requirement isexpressed in terms of a climb gradient, 1.5 per-cent. The climb gradient is not a direct equiva-lent of the .027 VSO

2 formula. Do not confuse thedate of type certification with the airplane’smodel year. The type certification basis of manymultiengine airplanes dates back to CAR 3 (theCivil Aviation Regulations, forerunner of today’sCode of Federal Regulations).

• 6,000 pounds or less maximum weight and VSO61 knots or less: the single-engine rate of climbat 5,000 feet MSL must simply be determined.The rate of climb could be a negative number.There is no requirement for a single-enginepositive rate of climb at 5,000 feet or any otheraltitude. For light-twins type certificatedFebruary 4, 1991, or thereafter, the single-engine climb gradient (positive or negative) issimply determined.

Rate of climb is the altitude gain per unit of time, whileclimb gradient is the actual measure of altitude gainedper 100 feet of horizontal travel, expressed as a per-centage. An altitude gain of 1.5 feet per 100 feet oftravel (or 15 feet per 1,000, or 150 feet per 10,000) is aclimb gradient of 1.5 percent.

There is a dramatic performance loss associated withthe loss of an engine, particularly just after takeoff.Any airplane’s climb performance is a function ofthrust horsepower which is in excess of that required

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for level flight. In a hypothetical twin with each engineproducing 200 thrust horsepower, assume that the totallevel-flight thrust horsepower required is 175. In thissituation, the airplane would ordinarily have a reserveof 225 thrust horsepower available for climb. Loss ofone engine would leave only 25 (200 minus 175) thrusthorsepower available for climb, a drastic reduction.Sea level rate-of-climb performance losses of at least80 to 90 percent, even under ideal circumstances, aretypical for multiengine airplanes in OEI flight.

OPERATION OF SYSTEMSThis section will deal with systems that are generallyfound on multiengine airplanes. Multiengine airplanesshare many features with complex single-engine air-planes. There are certain systems and features coveredhere, however, that are generally unique to airplaneswith two or more engines.

PROPELLERSThe propellers of the multiengine airplane may out-wardly appear to be identical in operation to theconstant-speed propellers of many single-engineairplanes, but this is not the case. The propellers ofmultiengine airplanes are featherable, to minimizedrag in the event of an engine failure. Dependingupon single-engine performance, this feature oftenpermits continued flight to a suitable airport followingan engine failure. To feather a propeller is to stopengine rotation with the propeller blades streamlinedwith the airplane’s relative wind, thus to minimizedrag. [Figure 12-2]

Feathering is necessary because of the change in para-site drag with propeller blade angle. [Figure 12-3]When the propeller blade angle is in the featheredposition, the change in parasite drag is at a minimumand, in the case of a typical multiengine airplane, theadded parasite drag from a single feathered propelleris a relatively small contribution to the airplane totaldrag.

At the smaller blade angles near the flat pitch position,the drag added by the propeller is very large. At thesesmall blade angles, the propeller windmilling at highr.p.m. can create such a tremendous amount of drag thatthe airplane may be uncontrollable. The propeller wind-milling at high speed in the low range of blade anglescan produce an increase in parasite drag which may beas great as the parasite drag of the basic airplane.

As a review, the constant-speed propellers on almostall single-engine airplanes are of the non-feathering,oil-pressure-to-increase-pitch design. In this design,increased oil pressure from the propeller governordrives the blade angle towards high pitch, low r.p.m.

In contrast, the constant-speed propellers installedon most multiengine airplanes are full feathering,

counterweighted, oil-pressure-to-decrease-pitchdesigns. In this design, increased oil pressure from thepropeller governor drives the blade angle towards lowpitch, high r.p.m.—away from the feather blade angle.In effect, the only thing that keeps these propellersfrom feathering is a constant supply of high pressureengine oil. This is a necessity to enable propeller feath-ering in the event of a loss of oil pressure or a propellergovernor failure.

FullFeathered

90°HighPitch

LowPitch

Figure 12-2. Feathered propeller.

Change inEquivalentParasite

Drag

Propeller Blade Angle

0 15 30 45 60 90

PROPELLER DRAG CONTRIBUTION

WindmillingPropeller

StationaryPropeller Feathered

Position

Flat Blade Position

Figure 12-3. Propeller drag contribution.

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The aerodynamic forces alone acting upon a wind-milling propeller tend to drive the blades to low pitch,high r.p.m. Counterweights attached to the shank ofeach blade tend to drive the blades to high pitch, lowr.p.m. Inertia, or apparent force called centrifugal forceacting through the counterweights is generally slightlygreater than the aerodynamic forces. Oil pressure fromthe propeller governor is used to counteract the coun-terweights and drives the blade angles to low pitch,high r.p.m. A reduction in oil pressure causes the r.p.m.to be reduced from the influence of the counterweights.[Figure 12-4]

To feather the propeller, the propeller control isbrought fully aft. All oil pressure is dumped from thegovernor, and the counterweights drive the propellerblades towards feather. As centrifugal force acting onthe counterweights decays from decreasing r.p.m.,additional forces are needed to completely feather theblades. This additional force comes from either aspring or high pressure air stored in the propellerdome, which forces the blades into the feathered posi-tion. The entire process may take up to 10 seconds.

Feathering a propeller only alters blade angle and stopsengine rotation. To completely secure the engine, thepilot must still turn off the fuel (mixture, electric boostpump, and fuel selector), ignition, alternator/generator,and close the cowl flaps. If the airplane is pressurized,

there may also be an air bleed to close for the failedengine. Some airplanes are equipped with firewallshutoff valves that secure several of these systemswith a single switch.

Completely securing a failed engine may not be neces-sary or even desirable depending upon the failuremode, altitude, and time available. The position of thefuel controls, ignition, and alternator/generatorswitches of the failed engine has no effect on aircraftperformance. There is always the distinct possibilityof manipulating the incorrect switch under conditionsof haste or pressure.

To unfeather a propeller, the engine must be rotatedso that oil pressure can be generated to move thepropeller blades from the feathered position. Theignition is turned on prior to engine rotation with thethrottle at low idle and the mixture rich. With thepropeller control in a high r.p.m. position, the starteris engaged. The engine will begin to windmill, start,and run as oil pressure moves the blades out offeather. As the engine starts, the propeller r.p.m.should be immediately reduced until the engine hashad several minutes to warm up; the pilot shouldmonitor cylinder head and oil temperatures.

Should the r.p.m. obtained with the starter be insuffi-cient to unfeather the propeller, an increase in airspeed

CounterweightAction

Aerodynamic Force

Hydraulic Force

High-pressure oil enters the cylinder through the center of the propeller shaft and piston rod. The propeller control regulates the flow of high-pressure oil from a governor.

A hydraulic piston in the hub of the propeller is connected to each blade by a piston rod. This rod is attached to forks that slide over the pitch-change pin mounted in the root of each blade.

The oil pressure moves the piston toward the front of the cylinder, moving the piston rod and forks forward.

The forks push the pitch-change pin of each blade toward the front of the hub, causing the blades to twist toward the low-pitch position.

A nitrogen pressure charge or mechanical spring in the front of the hub opposes the oil pressure, and causes the propeller to move toward high-pitch.

Counterweights also cause the blades to move toward the high-pitch and feather positions. The counter-weights counteract the aerodynamic twisting force that tries to move the blades toward a low-pitch angle.

Nitrogen Pressure or SpringForce, and Counterweight Action

Figure 12-4. Pitch change forces.

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from a shallow dive will usually help. In any event, theAFM/POH procedures should be followed for theexact unfeathering procedure. Both feathering andstarting a feathered reciprocating engine on the groundare strongly discouraged by manufacturers due to theexcessive stress and vibrations generated.

As just described, a loss of oil pressure from the pro-peller governor allows the counterweights, springand/or dome charge to drive the blades to feather.Logically then, the propeller blades should featherevery time an engine is shut down as oil pressure fallsto zero. Yet, this does not occur. Preventing this is asmall pin in the pitch changing mechanism of thepropeller hub that will not allow the propeller bladesto feather once r.p.m. drops below approximately800. The pin senses a lack of centrifugal force frompropeller rotation and falls into place, preventing theblades from feathering. Therefore, if a propeller is tobe feathered, it must be done before engine r.p.m.decays below approximately 800. On one popularmodel of turboprop engine, the propeller blades do,in fact, feather with each shutdown. This propeller isnot equipped with such centrifugally-operated pins,due to a unique engine design.

An unfeathering accumulator is an optional device thatpermits starting a feathered engine in flight without theuse of the electric starter. An accumulator is any devicethat stores a reserve of high pressure. On multiengineairplanes, the unfeathering accumulator stores a smallreserve of engine oil under pressure from compressedair or nitrogen. To start a feathered engine in flight,the pilot moves the propeller control out of thefeather position to release the accumulator pressure.The oil flows under pressure to the propeller hub anddrives the blades toward the high r.p.m., low pitchposition, whereupon the propeller will usually beginto windmill. (On some airplanes, an assist from theelectric starter may be necessary to initiate rotationand completely unfeather the propeller.) If fuel andignition are present, the engine will start and run.For airplanes used in training, this saves much elec-tric starter and battery wear. High oil pressure fromthe propeller governor recharges the accumulatorjust moments after engine rotation begins.

PROPELLER SYNCHRONIZATIONMany multiengine airplanes have a propeller synchro-nizer (prop sync) installed to eliminate the annoying“drumming” or “beat” of propellers whose r.p.m. areclose, but not precisely the same. To use prop sync, thepropeller r.p.m. are coarsely matched by the pilot andthe system is engaged. The prop sync adjusts the r.p.m.of the “slave” engine to precisely match the r.p.m. ofthe “master” engine, and then maintains that relation-ship. The prop sync should be disengaged when thepilot selects a new propeller r.p.m., then re-engaged

after the new r.p.m. is set. The prop sync should alwaysbe off for takeoff, landing, and single-engine opera-tion. The AFM/POH should be consulted for systemdescription and limitations.

A variation on the propeller synchronizer is the pro-peller synchrophaser. Prop sychrophase acts muchlike a synchronizer to precisely match r.p.m., but thesynchrophaser goes one step further. It not onlymatches r.p.m. but actually compares and adjusts thepositions of the individual blades of the propellers intheir arcs. There can be significant propeller noise andvibration reductions with a propeller synchrophaser.From the pilot’s perspective, operation of a propellersynchronizer and a propeller syncrophaser are verysimilar. A synchrophaser is also commonly referred toas prop sync, although that is not entirely correctnomenclature from a technical standpoint.

As a pilot aid to manually synchronizing thepropellers, some twins have a small gauge mountedin or by the tachometer(s) with a propeller symbolon a disk that spins. The pilot manually fine tunesthe engine r.p.m. so as to stop disk rotation, therebysynchronizing the propellers. This is a useful backupto synchronizing engine r.p.m. using the audiblepropeller beat. This gauge is also found installedwith most propeller synchronizer and synchrophasesystems. Some synchrophase systems use a knob forthe pilot to control the phase angle.

FUEL CROSSFEEDFuel crossfeed systems are also unique to multiengineairplanes. Using crossfeed, an engine can draw fuelfrom a fuel tank located in the opposite wing.

On most multiengine airplanes, operation in the cross-feed mode is an emergency procedure used to extendairplane range and endurance in OEI flight. There area few models that permit crossfeed as a normal, fuelbalancing technique in normal operation, but these arenot common. The AFM/POH will describe crossfeedlimitations and procedures, which vary significantlyamong multiengine airplanes.

Checking crossfeed operation on the ground with aquick repositioning of the fuel selectors does nothingmore than ensure freedom of motion of the handle. Toactually check crossfeed operation, a complete, func-tional crossfeed system check should be accomplished.To do this, each engine should be operated from itscrossfeed position during the runup. The enginesshould be checked individually, and allowed to run atmoderate power (1,500 r.p.m. minimum) for at least 1minute to ensure that fuel flow can be established fromthe crossfeed source. Upon completion of the check,each engine should be operated for at least 1 minute atmoderate power from the main (takeoff) fuel tanks toreconfirm fuel flow prior to takeoff.

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This suggested check is not required prior to everyflight. Infrequently used, however, crossfeed lines areideal places for water and debris to accumulate unlessthey are used from time to time and drained using theirexternal drains during preflight. Crossfeed is ordinar-ily not used for completing single-engine flights whenan alternate airport is readily at hand, and it is neverused during takeoff or landings.

COMBUSTION HEATERCombustion heaters are common on multiengineairplanes. A combustion heater is best described asa small furnace that burns gasoline to produceheated air for occupant comfort and windshielddefogging. Most are thermostatically operated, andhave a separate hour meter to record time in servicefor maintenance purposes. Automatic overtemperatureprotection is provided by a thermal switch mounted onthe unit, which cannot be accessed in flight. Thisrequires the pilot or mechanic to actually visuallyinspect the unit for possible heat damage in order toreset the switch.

When finished with the combustion heater, a cooldown period is required. Most heaters require that out-side air be permitted to circulate through the unit for atleast 15 seconds in flight, or that the ventilation fan beoperated for at least 2 minutes on the ground. Failureto provide an adequate cool down will usually trip thethermal switch and render the heater inoperative untilthe switch is reset.

FLIGHT DIRECTOR/AUTOPILOTFlight director/autopilot (FD/AP) systems are commonon the better-equipped multiengine airplanes. Thesystem integrates pitch, roll, heading, altitude, andradio navigation signals in a computer. The outputs,called computed commands, are displayed on a flightcommand indicator, or FCI. The FCI replaces theconventional attitude indicator on the instrumentpanel. The FCI is occasionally referred to as a flightdirector indicator (FDI), or as an attitude directorindicator (ADI). The entire flight director/autopilotsystem is sometimes called an integrated flight con-trol system (IFCS) by some manufacturers. Othersmay use the term “automatic flight control system(AFCS).”

The FD/AP system may be employed at three differentlevels.

• Off (raw data).

• Flight director (computed commands).

• Autopilot.

With the system off, the FCI operates as an ordinaryattitude indicator. On most FCIs, the command barsare biased out of view when the flight director is off.

The pilot maneuvers the airplane as though the systemwere not installed.

To maneuver the airplane using the flight director, thepilot enters the desired modes of operation (heading,altitude, nav intercept, and tracking) on the FD/APmode controller. The computed flight commands arethen displayed to the pilot through either a single-cueor dual-cue system in the FCI. On a single-cue system,the commands are indicated by “V” bars. On adual-cue system, the commands are displayed ontwo separate command bars, one for pitch and onefor roll. To maneuver the airplane using computedcommands, the pilot “flies” the symbolic airplaneof the FCI to match the steering cues presented.

On most systems, to engage the autopilot the flightdirector must first be operating. At any time thereafter,the pilot may engage the autopilot through the modecontroller. The autopilot then maneuvers the airplaneto satisfy the computed commands of the flightdirector.

Like any computer, the FD/AP system will only dowhat it is told. The pilot must ensure that it has beenproperly programmed for the particular phase of flightdesired. The armed and/or engaged modes are usuallydisplayed on the mode controller or separate annunci-ator lights. When the airplane is being hand-flown, ifthe flight director is not being used at any particularmoment, it should be off so that the command bars arepulled from view.

Prior to system engagement, all FD/AP computer andtrim checks should be accomplished. Many newersystems cannot be engaged without the completion ofa self-test. The pilot must also be very familiar withvarious methods of disengagement, both normal andemergency. System details, including approvals andlimitations, can be found in the supplements sectionof the AFM/POH. Additionally, many avionics manu-facturers can provide informative pilot operatingguides upon request.

YAW DAMPERThe yaw damper is a servo that moves the rudder inresponse to inputs from a gyroscope or accelerometerthat detects yaw rate. The yaw damper minimizesmotion about the vertical axis caused by turbulence.(Yaw dampers on sweptwing airplanes provideanother, more vital function of damping dutch rollcharacteristics.) Occupants will feel a smoother ride,particularly if seated in the rear of the airplane, whenthe yaw damper is engaged. The yaw damper shouldbe off for takeoff and landing. There may be additionalrestrictions against its use during single-engine opera-tion. Most yaw dampers can be engaged independentlyof the autopilot.

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ALTERNATOR/GENERATORAlternator or generator paralleling circuitry matchesthe output of each engine’s alternator/generator so thatthe electrical system load is shared equally betweenthem. In the event of an alternator/generator failure,the inoperative unit can be isolated and the entireelectrical system powered from the remaining one.Depending upon the electrical capacity of the alter-nator/generator, the pilot may need to reduce theelectrical load (referred to as load shedding) whenoperating on a single unit. The AFM/POH will containsystem description and limitations.

NOSE BAGGAGE COMPARTMENTNose baggage compartments are common on multiengineairplanes (and are even found on a few single-engineairplanes). There is nothing strange or exotic about anose baggage compartment, and the usual guidanceconcerning observation of load limits applies. Theyare mentioned here in that pilots occasionally neglectto secure the latches properly, and therein lies thedanger. When improperly secured, the door will openand the contents may be drawn out, usually into thepropeller arc, and usually just after takeoff. Even whenthe nose baggage compartment is empty, airplaneshave been lost when the pilot became distracted by theopen door. Security of the nose baggage compartmentlatches and locks is a vital preflight item.

Most airplanes will continue to fly with a nose bag-gage door open. There may be some buffeting fromthe disturbed airflow and there will be an increase innoise. Pilots should never become so preoccupiedwith an open door (of any kind) that they fail to flythe airplane.

Inspection of the compartment interior is also animportant preflight item. More than one pilot has beensurprised to find a supposedly empty compartmentpacked to capacity or loaded with ballast. The towbars, engine inlet covers, windshield sun screens, oilcontainers, spare chocks, and miscellaneous smallhand tools that find their way into baggage compart-ments should be secured to prevent damage fromshifting in flight.

ANTI-ICING/DEICINGAnti-icing/deicing equipment is frequently installed onmultiengine airplanes and consists of a combination ofdifferent systems. These may be classified as eitheranti-icing or deicing, depending upon function. Thepresence of anti-icing and deicing equipment, eventhough it may appear elaborate and complete, does notnecessarily mean that the airplane is approved forflight in icing conditions. The AFM/POH, placards,and even the manufacturer should be consulted forspecific determination of approvals and limitations.

Anti-icing equipment is provided to prevent ice fromforming on certain protected surfaces. Anti-icingequipment includes heated pitot tubes, heated or non-icing static ports and fuel vents, propeller blades withelectrothermal boots or alcohol slingers, windshieldswith alcohol spray or electrical resistance heating,windshield defoggers, and heated stall warning liftdetectors. On many turboprop engines, the “lip”surrounding the air intake is heated either electricallyor with bleed air. In the absence of AFM/POH guidanceto the contrary, anti-icing equipment is actuated prior toflight into known or suspected icing conditions.

Deicing equipment is generally limited to pneumaticboots on wing and tail leading edges. Deicing equip-ment is installed to remove ice that has already formedon protected surfaces. Upon pilot actuation, the bootsinflate with air from the pneumatic pumps to break offaccumulated ice. After a few seconds of inflation, theyare deflated back to their normal position with theassistance of a vacuum. The pilot monitors the buildupof ice and cycles the boots as directed in theAFM/POH. An ice light on the left engine nacelleallows the pilot to monitor wing ice accumulation atnight.

Other airframe equipment necessary for flight in icingconditions includes an alternate induction air sourceand an alternate static system source. Ice tolerantantennas will also be installed.

In the event of impact ice accumulating over normalengine air induction sources, carburetor heat (carbu-reted engines) or alternate air (fuel injected engines)should be selected. Ice buildup on normal inductionsources can be detected by a loss of engine r.p.m. withfixed-pitch propellers and a loss of manifold pressurewith constant-speed propellers. On some fuel injectedengines, an alternate air source is automaticallyactivated with blockage of the normal air source.

An alternate static system provides an alternate sourceof static air for the pitot-static system in the unlikelyevent that the primary static source becomes blocked.In non-pressurized airplanes, most alternate staticsources are plumbed to the cabin. On pressurized air-planes, they are usually plumbed to a non-pressurizedbaggage compartment. The pilot must activate thealternate static source by opening a valve or a fitting inthe cockpit. Upon activation, the airspeed indicator,altimeter, and the vertical speed indicator (VSI) will beaffected and will read somewhat in error. A correctiontable is frequently provided in the AFM/POH.

Anti-icing/deicing equipment only eliminates ice fromthe protected surfaces. Significant ice accumulationsmay form on unprotected areas, even with proper useof anti-ice and deice systems. Flight at high angles of

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attack or even normal climb speeds will permit signifi-cant ice accumulations on lower wing surfaces, whichare unprotected. Many AFM/POHs mandate minimumspeeds to be maintained in icing conditions. Degradationof all flight characteristics and large performance lossescan be expected with ice accumulations. Pilots shouldnot rely upon the stall warning devices for adequate stallwarning with ice accumulations.

Ice will accumulate unevenly on the airplane. It willadd weight and drag (primarily drag), and decreasethrust and lift. Even wing shape affects ice accumu-lation; thin airfoil sections are more prone to iceaccumulation than thick, highly-cambered sections.For this reason certain surfaces, such as the horizontalstabilizer, are more prone to icing than the wing. Withice accumulations, landing approaches should be madewith a minimum wing flap setting (flap extensionincreases the angle of attack of the horizontal stabilizer)and with an added margin of airspeed. Sudden and largeconfiguration and airspeed changes should be avoided.

Unless otherwise recommended in the AFM/POH, theautopilot should not be used in icing conditions.Continuous use of the autopilot will mask trim andhandling changes that will occur with ice accumula-tion. Without this control feedback, the pilot may notbe aware of ice accumulation building to hazardouslevels. The autopilot will suddenly disconnect when itreaches design limits and the pilot may find the airplanehas assumed unsatisfactory handling characteristics.

The installation of anti-ice/deice equipment on air-planes without AFM/POH approval for flight into icingconditions is to facilitate escape when such conditionsare inadvertently encountered. Even with AFM/POHapproval, the prudent pilot will avoid icing conditionsto the maximum extent practicable, and avoid extendedflight in any icing conditions. No multiengine airplaneis approved for flight into severe icing conditions, andnone are intended for indefinite flight in continuousicing conditions.

PERFORMANCE AND LIMITATIONSDiscussion of performance and limitations requires thedefinition of several terms.

• Accelerate-stop distance is the runway lengthrequired to accelerate to a specified speed (eitherVR or VLOF, as specified by the manufacturer),experience an engine failure, and bring the air-plane to a complete stop.

• Accelerate-go distance is the horizontal dis-tance required to continue the takeoff and climbto 50 feet, assuming an engine failure at VR orVLOF, as specified by the manufacturer.

• Climb gradient is a slope most frequentlyexpressed in terms of altitude gain per 100 feetof horizontal distance, whereupon it is stated asa percentage. A 1.5 percent climb gradient is analtitude gain of one and one-half feet per 100 feetof horizontal travel. Climb gradient may also beexpressed as a function of altitude gain per nau-tical mile, or as a ratio of the horizontal distanceto the vertical distance (50:1, for example).Unlike rate of climb, climb gradient is affectedby wind. Climb gradient is improved with aheadwind component, and reduced with a tail-wind component. [Figure 12-5]

• The all-engine service ceiling of multiengineairplanes is the highest altitude at which the air-plane can maintain a steady rate of climb of 100f.p.m. with both engines operating. The airplanehas reached its absolute ceiling when climb isno longer possible.

• The single-engine service ceiling is reachedwhen the multiengine airplane can no longermaintain a 50 f.p.m. rate of climb with one engineinoperative, and its single-engine absolute ceil-ing when climb is no longer possible.

The takeoff in a multiengine airplane should beplanned in sufficient detail so that the appropriateaction is taken in the event of an engine failure. Thepilot should be thoroughly familiar with the airplane’sperformance capabilities and limitations in order tomake an informed takeoff decision as part of the pre-flight planning. That decision should be reviewed asthe last item of the “before takeoff” checklist.

In the event of an engine failure shortly after takeoff,the decision is basically one of continuing flight orlanding, even off-airport. If single-engine climbperformance is adequate for continued flight, andthe airplane has been promptly and correctly con-figured, the climb after takeoff may be continued. Ifsingle-engine climb performance is such that climbis unlikely or impossible, a landing will have to bemade in the most suitable area. To be avoided aboveall is attempting to continue flight when it is notwithin the airplane’s performance capability to doso. [Figure 12-6]

Takeoff planning factors include weight and balance,airplane performance (both single and multiengine),runway length, slope and contamination, terrain andobstacles in the area, weather conditions, and pilotproficiency. Most multiengine airplanes haveAFM/POH performance charts and the pilot shouldbe highly proficient in their use. Prior to takeoff, themultiengine pilot should ensure that the weight andbalance limitations have been observed, the runway

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length is adequate, the normal flightpath will clear obsta-cles and terrain, and that a definitive course of action hasbeen planned in the event of an engine failure.

The regulations do not specifically require that therunway length be equal to or greater than the accel-erate-stop distance. Most AFM/POHs publishaccelerate-stop distances only as an advisory. It

becomes a limitation only when published in thelimitations section of the AFM/POH. Experiencedmultiengine pilots, however, recognize the safetymargin of runway lengths in excess of the bare min-imum required for normal takeoff. They will insiston runway lengths of at least accelerate-stop dis-tance as a matter of safety and good operatingpractice.

50 ftVR / VLOFBrake

Release

Accelerate-Stop Distance

Accelerate-Go Distance

500 ft

VLOFBrakeRelease

5,000 ft

10:1 or 10 Percent Climb Gradient

Figure 12-5. Accelerate-stop distance, accelerate-go distance, and climb gradient.

Figure 12-6. Area of decision.

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VXSEVYSE

Gear Up and Loss of One Engine

Best Rate of ClimbBest Angle of Climb

Decision Area

VR / VLOF

BrakeRelease

ENGINE FAILURE AFTER LIFT-OFF

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The multiengine pilot must keep in mind that theaccelerate-go distance, as long as it is, has onlybrought the airplane, under ideal circumstances, to apoint a mere 50 feet above the takeoff elevation. Toachieve even this meager climb, the pilot had to instan-taneously recognize and react to an unanticipatedengine failure, retract the landing gear, identify andfeather the correct engine, all the while maintainingprecise airspeed control and bank angle as the airspeedis nursed to VYSE. Assuming flawless airmanship thusfar, the airplane has now arrived at a point little morethan one wingspan above the terrain, assuming it wasabsolutely level and without obstructions.

With (for the purpose of illustration) a net 150 f.p.m.rate of climb at a 90-knot VYSE, it will take approxi-mately 3 minutes to climb an additional 450 feet to reach500 feet AGL. In doing so, the airplane will havetraveled an additional 5 nautical miles beyond theoriginal accelerate-go distance, with a climb gradientof about 1.6 percent. A turn of any consequence, suchas to return to the airport, will seriously degrade thealready marginal climb performance.

Not all multiengine airplanes have published acceler-ate-go distances in their AFM/POH, and fewer stillpublish climb gradients. When such information ispublished, the figures will have been determined underideal flight testing conditions. It is unlikely that thisperformance will be duplicated in service conditions.

The point of the foregoing is to illustrate the marginalclimb performance of a multiengine airplane thatsuffers an engine failure shortly after takeoff, evenunder ideal conditions. The prudent multienginepilot should pick a point in the takeoff and climbsequence in advance. If an engine fails before this point,the takeoff should be rejected, even if airborne, for alanding on whatever runway or surface lies essentiallyahead. If an engine fails after this point, the pilot shouldpromptly execute the appropriate engine failure proce-dure and continue the climb, assuming the performancecapability exists. As a general recommendation, if thelanding gear has not been selected up, the takeoffshould be rejected, even if airborne.

As a practical matter for planning purposes, the optionof continuing the takeoff probably does not exist unlessthe published single-engine rate-of-climb performanceis at least 100 to 200 f.p.m. Thermal turbulence, windgusts, engine and propeller wear, or poor technique inairspeed, bank angle, and rudder control can easilynegate even a 200 f.p.m. rate of climb.

WEIGHT AND BALANCEThe weight and balance concept is no different thanthat of a single-engine airplane. The actual execution,however, is almost invariably more complex due to a

number of new loading areas, including nose and aftbaggage compartments, nacelle lockers, main fueltanks, aux fuel tanks, nacelle fuel tanks, and numerousseating options in a variety of interior configurations.The flexibility in loading offered by the multiengineairplane places a responsibility on the pilot to addressweight and balance prior to each flight.

The terms “empty weight, licensed empty weight,standard empty weight, and basic empty weight” asthey appear on the manufacturer’s original weight andbalance documents are sometimes confused by pilots.

In 1975, the General Aviation ManufacturersAssociation (GAMA) adopted a standardized formatfor AFM/POHs. It was implemented by mostmanufacturers in model year 1976. Airplanes whosemanufacturers conform to the GAMA standards utilizethe following terminology for weight and balance:

Standard empty weight+ Optional equipment= Basic empty weight

Standard empty weight is the weight of the standardairplane, full hydraulic fluid, unusable fuel, and fulloil. Optional equipment includes the weight of allequipment installed beyond standard. Basic emptyweight is the standard empty weight plus optionalequipment. Note that basic empty weight includes nousable fuel, but full oil.

Airplanes manufactured prior to the GAMA formatgenerally utilize the following terminology for weightand balance, although the exact terms may vary some-what:

Empty weight+ Unusable fuel= Standard empty weight

Standard empty weight+ Optional equipment= Licensed empty weight

Empty weight is the weight of the standard airplane,full hydraulic fluid and undrainable oil. Unusable fuelis the fuel remaining in the airplane not available tothe engines. Standard empty weight is the emptyweight plus unusable fuel. When optional equipmentis added to the standard empty weight, the result islicensed empty weight. Licensed empty weight,therefore, includes the standard airplane, optionalequipment, full hydraulic fluid, unusable fuel, andundrainable oil.

The major difference between the two formats(GAMA and the old) is that basic empty weightincludes full oil, and licensed empty weight does not.

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Oil must always be added to any weight and balanceutilizing a licensed empty weight.

When the airplane is placed in service, amendedweight and balance documents are prepared by appro-priately rated maintenance personnel to reflect changesin installed equipment. The old weight and balancedocuments are customarily marked “superseded” andretained in the AFM/POH. Maintenance personnel areunder no regulatory obligation to utilize the GAMAterminology, so weight and balance documentssubsequent to the original may use a variety ofterms. Pilots should use care to determine whetheror not oil has to be added to the weight and balancecalculations or if it is already included in the figuresprovided.

The multiengine airplane is where most pilotsencounter the term “zero fuel weight” for the first time.Not all multiengine airplanes have a zero fuel weightlimitation published in their AFM/POH, but many do.Zero fuel weight is simply the maximum allowableweight of the airplane and payload, assuming there isno usable fuel on board. The actual airplane is notdevoid of fuel at the time of loading, of course. This ismerely a calculation that assumes it was. If a zero fuelweight limitation is published, then all weight inexcess of that figure must consist of usable fuel. Thepurpose of a zero fuel weight is to limit load forces onthe wing spars with heavy fuselage loads.

Assume a hypothetical multiengine airplane with thefollowing weights and capacities:

Basic empty weight . . . . . . . . . . . . . . . . .3,200 lb.

Zero fuel weight . . . . . . . . . . . . . . . . . . . .4,400 lb.

Maximum takeoff weight . . . . . . . . . . . . .5,200 lb.

Maximum usable fuel . . . . . . . . . . . . . . . .180 gal.

1. Calculate the useful load:

Maximum takeoff weight . . . . . . . . . . . . .5,200 lb.

Basic empty weight . . . . . . . . . . . . . . . . .-3,200 lb.

Useful load . . . . . . . . . . . . . . . . . . . . . . . .2,000 lb.

The useful load is the maximum combination of usablefuel, passengers, baggage, and cargo that the airplaneis capable of carrying.

2. Calculate the payload:

Zero fuel weight . . . . . . . . . . . . . . . . . . . . 4,400 lb.

Basic empty weight . . . . . . . . . . . . . . . . . -3,200 lb.Payload . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,200 lb.

The payload is the maximum combination of passen-gers, baggage, and cargo that the airplane is capableof carrying. A zero fuel weight, if published, is thelimiting weight.

3. Calculate the fuel capacity at maximum payload(1,200 lb.):

Maximum takeoff weight . . . . . . . . . . . . .5,200 lb.

Zero fuel weight . . . . . . . . . . . . . . . . . . .-4,400 lb.

Fuel allowed . . . . . . . . . . . . . . . . . . . . . . . .800 lb.

Assuming maximum payload, the only weight permit-ted in excess of the zero fuel weight must consist ofusable fuel. In this case, 133.3 gallons.

4. Calculate the payload at maximum fuel capacity(180 gal.):

Basic empty weight . . . . . . . . . . . . . . . . .3,200 lb.

Maximum usable fuel . . . . . . . . . . . . . . .+1,080 lb.

Weight with max. fuel . . . . . . . . . . . . . . .4,280 lb.

Maximum takeoff weight . . . . . . . . . . . . .5,200 lb.

Weight with max. fuel . . . . . . . . . . . . . . .-4,280 lb.

Payload allowed . . . . . . . . . . . . . . . . . . . . .920 lb.

Assuming maximum fuel, the payload is the differencebetween the weight of the fueled airplane and the max-imum takeoff weight.

Some multiengine airplanes have a ramp weight,which is in excess of the maximum takeoff weight. Theramp weight is an allowance for fuel that would beburned during taxi and runup, permitting a takeoff atfull maximum takeoff weight. The airplane mustweigh no more than maximum takeoff weight at thebeginning of the takeoff roll.

A maximum landing weight is a limitation againstlanding at a weight in excess of the published value.This requires preflight planning of fuel burn to ensurethat the airplane weight upon arrival at destination willbe at or below the maximum landing weight. In theevent of an emergency requiring an immediate land-ing, the pilot should recognize that the structuralmargins designed into the airplane are not fullyavailable when over landing weight. An overweightlanding inspection may be advisable—the servicemanual or manufacturer should be consulted.

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Although the foregoing problems only dealt withweight, the balance portion of weight and balanceis equally vital. The flight characteristics of themultiengine airplane will vary significantly withshifts of the center of gravity (CG) within theapproved envelope.

At forward CGs, the airplane will be more stable, witha slightly higher stalling speed, a slightly slowercruising speed, and favorable stall characteristics.At aft CGs, the airplane will be less stable, with aslightly lower stalling speed, a slightly faster cruisingspeed, and less desirable stall characteristics. ForwardCG limits are usually determined in certification byelevator/stabilator authority in the landing round-out. Aft CG limits are determined by the minimumacceptable longitudinal stability. It is contrary to theairplane’s operating limitations and the Code ofFederal Regulations (CFR) to exceed any weightand balance parameter.

Some multiengine airplanes may require ballast toremain within CG limits under certain loading condi-tions. Several models require ballast in the aft baggagecompartment with only a student and instructor onboard to avoid exceeding the forward CG limit.When passengers are seated in the aft-most seats ofsome models, ballast or baggage may be required inthe nose baggage compartment to avoid exceedingthe aft CG limit. The pilot must direct the seating ofpassengers and placement of baggage and cargo toachieve a center of gravity within the approvedenvelope. Most multiengine airplanes have generalloading recommendations in the weight and balancesection of the AFM/POH. When ballast is added, itmust be securely tied down and it must not exceedthe maximum allowable floor loading.

Some airplanes make use of a special weight andbalance plotter. It consists of several movable partsthat can be adjusted over a plotting board on whichthe CG envelope is printed. The reverse side of thetypical plotter contains general loading recommen-dations for the particular airplane. A pencil line plotcan be made directly on the CG envelope imprintedon the working side of the plotting board. This plotcan easily be erased and recalculated anew for eachflight. This plotter is to be used only for the makeand model airplane for which it was designed.

GROUND OPERATIONGood habits learned with single-engine airplanes aredirectly applicable to multiengine airplanes for pre-flight and engine start. Upon placing the airplane inmotion to taxi, the new multiengine pilot will noticeseveral differences, however. The most obvious isthe increased wingspan and the need for even

greater vigilance while taxiing in close quarters.Ground handling may seem somewhat ponderousand the multiengine airplane will not be as nimbleas the typical two- or four-place single-engine airplane.As always, use care not to ride the brakes by keepingengine power to a minimum. One ground handlingadvantage of the multiengine airplane over single-engine airplanes is the differential power capability.Turning with an assist from differential power mini-mizes both the need for brakes during turns and theturning radius.

The pilot should be aware, however, that making asharp turn assisted by brakes and differential powercan cause the airplane to pivot about a stationaryinboard wheel and landing gear. This is abuse forwhich the airplane was not designed and should beguarded against.

Unless otherwise directed by the AFM/POH, allground operations should be conducted with the cowlflaps fully open. The use of strobe lights is normallydeferred until taxiing onto the active runway.

NORMAL AND CROSSWIND TAKEOFF AND CLIMBWith the “before takeoff” checklist complete andair traffic control (ATC) clearance received, the air-plane should be taxied into position on the runwaycenterline. If departing from an airport without anoperating control tower, a careful check forapproaching aircraft should be made along with aradio advisory on the appropriate frequency. Sharpturns onto the runway combined with a rollingtakeoff are not a good operating practice and maybe prohibited by the AFM/POH due to the possibilityof “unporting” a fuel tank pickup. (The takeoff itselfmay be prohibited by the AFM/POH under any circum-stances below certain fuel levels.) The flight controlsshould be positioned for a crosswind, if present.Exterior lights such as landing and taxi lights, andwingtip strobes should be illuminated immediatelyprior to initiating the takeoff roll, day or night. Ifholding in takeoff position for any length of time,particularly at night, the pilot should activate allexterior lights upon taxiing into position.

Takeoff power should be set as recommended in theAFM/POH. With normally aspirated (non-tur-bocharged) engines, this will be full throttle. Fullthrottle is also used in most turbocharged engines.There are some turbocharged engines, however,that require the pilot to set a specific power setting,usually just below red line manifold pressure. Thisyields takeoff power with less than full throttle travel.

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Turbocharged engines often require special consid-eration. Throttle motion with turbocharged enginesshould be exceptionally smooth and deliberate. It isacceptable, and may even be desirable, to hold theairplane in position with brakes as the throttles areadvanced. Brake release customarily occurs after sig-nificant boost from the turbocharger is established. Thisprevents wasting runway with slow, partial throttleacceleration as the engine power is increased. If runwaylength or obstacle clearance is critical, full power shouldbe set before brake release, as specified in the perform-ance charts.

As takeoff power is established, initial attention shouldbe divided between tracking the runway centerline andmonitoring the engine gauges. Many novice multi-engine pilots tend to fixate on the airspeed indicatorjust as soon as the airplane begins its takeoff roll.Instead, the pilot should confirm that both enginesare developing full-rated manifold pressure andr.p.m., and that the fuel flows, fuel pressures, exhaustgas temperatures (EGTs), and oil pressures are matchedin their normal ranges. A directed and purposeful scanof the engine gauges can be accomplished well beforethe airplane approaches rotation speed. If a crosswind ispresent, the aileron displacement in the direction of thecrosswind may be reduced as the airplane accelerates.The elevator/stabilator control should be held neutralthroughout.

Full rated takeoff power should be used for every take-off. Partial power takeoffs are not recommended.There is no evidence to suggest that the life of modernreciprocating engines is prolonged by partial powertakeoffs. Paradoxically, excessive heat and enginewear can occur with partial power as the fuel meteringsystem will fail to deliver the slightly over-richmixture vital for engine cooling during takeoff.

There are several key airspeeds to be noted during thetakeoff and climb sequence in any twin. The first speedto consider is VMC. If an engine fails below VMC whilethe airplane is on the ground, the takeoff must berejected. Directional control can only be maintained bypromptly closing both throttles and using rudder andbrakes as required. If an engine fails below VMC whileairborne, directional control is not possible with theremaining engine producing takeoff power. On take-offs, therefore, the airplane should never be airbornebefore the airspeed reaches and exceeds VMC. Pilotsshould use the manufacturer’s recommended rotationspeed (VR) or lift-off speed (VLOF). If no such speedsare published, a minimum of VMC plus 5 knots shouldbe used for VR.

The rotation to a takeoff pitch attitude is donesmoothly. With a crosswind, the pilot should ensure

that the landing gear does not momentarily touch therunway after the airplane has lifted off, as a side driftwill be present. The rotation may be accomplishedmore positively and/or at a higher speed under theseconditions. However, the pilot should keep in mindthat the AFM/POH performance figures for accelerate-stop distance, takeoff ground roll, and distance to clearan obstacle were calculated at the recommended VRand/or VLOF speed.

After lift-off, the next consideration is to gain alti-tude as rapidly as possible. After leaving the ground,altitude gain is more important than achieving anexcess of airspeed. Experience has shown thatexcessive speed cannot be effectively converted intoaltitude in the event of an engine failure. Altitudegives the pilot time to think and react. Therefore, theairplane should be allowed to accelerate in a shallowclimb to attain VY, the best all-engine rate-of-climbspeed. VY should then be maintained until a safesingle-engine maneuvering altitude, consideringterrain and obstructions, is achieved.

To assist the pilot in takeoff and initial climb profile,some AFM/POHs give a “50-foot” or “50-foot barrier”speed to use as a target during rotation, lift-off, andacceleration to VY.

Landing gear retraction should normally occur after apositive rate of climb is established. SomeAFM/POHs direct the pilot to apply the wheel brakesmomentarily after lift-off to stop wheel rotation priorto landing gear retraction. If flaps were extended fortakeoff, they should be retracted as recommended inthe AFM/POH.

Once a safe single-engine maneuvering altitude hasbeen reached, typically a minimum of 400-500 feetAGL, the transition to an enroute climb speed shouldbe made. This speed is higher than VY and is usuallymaintained to cruising altitude. Enroute climb speedgives better visibility, increased engine cooling, and ahigher groundspeed. Takeoff power can be reduced, ifdesired, as the transition to enroute climb speed ismade.

Some airplanes have a climb power setting publishedin the AFM/POH as a recommendation (or sometimesas a limitation), which should then be set for enrouteclimb. If there is no climb power setting published, it iscustomary, but not a requirement, to reduce manifoldpressure and r.p.m. somewhat for enroute climb. Thepropellers are usually synchronized after the firstpower reduction and the yaw damper, if installed,engaged. The AFM/POH may also recommend leaning

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the mixtures during climb. The “climb” checklistshould be accomplished as traffic and work load allow.[Figure 12-7]

LEVEL OFF AND CRUISEUpon leveling off at cruising altitude, the pilot shouldallow the airplane to accelerate at climb power untilcruising airspeed is achieved, then cruise power andr.p.m. should be set. To extract the maximum cruiseperformance from any airplane, the power settingtables provided by the manufacturer should be closelyfollowed. If the cylinder head and oil temperatures arewithin their normal ranges, the cowl flaps may beclosed. When the engine temperatures have stabilized,the mixtures may be leaned per AFM/POH recommen-dations. The remainder of the “cruise” checklist shouldbe completed by this point.

Fuel management in multiengine airplanes is oftenmore complex than in single-engine airplanes.Depending upon system design, the pilot may need toselect between main tanks and auxiliary tanks, oreven employ fuel transfer from one tank to another.In complex fuel systems, limitations are often foundrestricting the use of some tanks to level flight only,or requiring a reserve of fuel in the main tanks fordescent and landing. Electric fuel pump operation canvary widely among different models also, particularlyduring tank switching or fuel transfer. Some fuelpumps are to be on for takeoff and landing; others areto be off. There is simply no substitute for thorough

systems and AFM/POH knowledge when operatingcomplex aircraft.

NORMAL APPROACH AND LANDINGGiven the higher cruising speed (and frequently, alti-tude) of multiengine airplanes over most single-engineairplanes, the descent must be planned in advance. Ahurried, last minute descent with power at or near idleis inefficient and can cause excessive engine cooling.It may also lead to passenger discomfort, particularlyif the airplane is unpressurized. As a rule of thumb, ifterrain and passenger conditions permit, a maximumof a 500 f.p.m. rate of descent should be planned.Pressurized airplanes can plan for higher descent rates,if desired.

In a descent, some airplanes require a minimum EGT,or may have a minimum power setting or cylinderhead temperature to observe. In any case, combi-nations of very low manifold pressure and highr.p.m. settings are strongly discouraged by enginemanufacturers. If higher descent rates are necessary,the pilot should consider extending partial flaps orlowering the landing gear before retarding the powerexcessively. The “descent” checklist should be initiatedupon leaving cruising altitude and completed beforearrival in the terminal area. Upon arrival in the terminalarea, pilots are encouraged to turn on their landingand recognition lights when operating below10,000 feet, day or night, and especially whenoperating within 10 miles of any airport or in conditionsof reduced visibility.

Figure 12-7.Takeoff and climb profile.

Lift-offPublished VR or VLOF

if not Published,VMC + 5 Knots

Positive Rate - Gear Up Climb at VY

500 ft1. Accelerate to Cruise Climb2. Set Climb Power3. Climb Checklist

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The traffic pattern and approach are typically flown atsomewhat higher indicated airspeeds in a multiengineairplane contrasted to most single-engine airplanes.The pilot may allow for this through an early start onthe “before landing” checklist. This provides time forproper planning, spacing, and thinking well ahead ofthe airplane. Many multiengine airplanes have partialflap extension speeds above VFE, and partial flaps canbe deployed prior to traffic pattern entry. Normally, thelanding gear should be selected and confirmed downwhen abeam the intended point of landing as the down-wind leg is flown. [Figure 12-8]

The Federal Aviation Administration (FAA) recom-mends a stabilized approach concept. To the greatestextent practical, on final approach and within 500 feetAGL, the airplane should be on speed, in trim, con-figured for landing, tracking the extended centerlineof the runway, and established in a constant angle ofdescent towards an aim point in the touchdownzone. Absent unusual flight conditions, only minorcorrections will be required to maintain this approachto the roundout and touchdown.

The final approach should be made with power andat a speed recommended by the manufacturer; if a rec-ommended speed is not furnished, the speed should beno slower than the single-engine best rate-of-climbspeed (VYSE) until short final with the landing assured,but in no case less than critical engine-out minimumcontrol speed (VMC). Some multiengine pilots preferto delay full flap extension to short final with the land-ing assured. This is an acceptable technique with appro-priate experience and familiarity with the airplane.

In the roundout for landing, residual power is gradu-ally reduced to idle. With the higher wing loading ofmultiengine airplanes and with the drag from twowindmilling propellers, there will be minimal float.

Full stall landings are generally undesirable in twins. Theairplane should be held off as with a high performancesingle-engine model, allowing touchdown of the mainwheels prior to a full stall.

Under favorable wind and runway conditions, thenosewheel can be held off for best aerodynamic brak-ing. Even as the nosewheel is gently lowered to therunway centerline, continued elevator back pressurewill greatly assist the wheel brakes in stopping theairplane.

If runway length is critical, or with a strong crosswind,or if the surface is contaminated with water, ice orsnow, it is undesirable to rely solely on aerodynamicbraking after touchdown. The full weight of the air-plane should be placed on the wheels as soon aspracticable. The wheel brakes will be more effectivethan aerodynamic braking alone in decelerating theairplane.

Once on the ground, elevator back pressure should beused to place additional weight on the main wheels andto add additional drag. When necessary, wing flapretraction will also add additional weight to the wheelsand improve braking effectivity. Flap retraction duringthe landing rollout is discouraged, however, unlessthere is a clear, operational need. It should not beaccomplished as routine with each landing.

Some multiengine airplanes, particularly those of thecabin class variety, can be flown through the roundoutand touchdown with a small amount of power. This isan acceptable technique to prevent high sink rates andto cushion the touchdown. The pilot should keep inmind, however, that the primary purpose in landing isto get the airplane down and stopped. This techniqueshould only be attempted when there is a generous

Approaching Traffic Pattern1. Descent Checklist2. Reduce to Traffic Pattern Airspeed and Altitude

Downwind1. Flaps - Approach Position2. Gear Down3. Before Landing Checklist

Base Leg1. Gear-Check Down2. Check for Conflicting Traffic

Final1. Gear-Check Down2. Flaps-Landing Position

Airspeed- 1.3 Vs0 orManufacturers Recommended

Figure 12-8. Normal two-engine approach and landing.

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margin of runway length. As propeller blast flowsdirectly over the wings, lift as well as thrust is produced.The pilot should taxi clear of the runway as soon asspeed and safety permit, and then accomplish the “afterlanding” checklist. Ordinarily, no attempt should bemade to retract the wing flaps or perform other check-list duties until the airplane has been brought to a haltwhen clear of the active runway. Exceptions to thiswould be the rare operational needs discussed above,to relieve the weight from the wings and place it on thewheels. In these cases, AFM/POH guidance should befollowed. The pilot should not indiscriminately reachout for any switch or control on landing rollout. Aninadvertent landing gear retraction while meaning toretract the wing flaps may result.

CROSSWIND APPROACH AND LANDINGThe multiengine airplane is often easier to land in acrosswind than a single-engine airplane due to itshigher approach and landing speed. In any event, theprinciples are no different between singles and twins.Prior to touchdown, the longitudinal axis must bealigned with the runway centerline to avoid landinggear side loads.

The two primary methods, crab and wing-low, aretypically used in conjunction with each other. Assoon as the airplane rolls out onto final approach, thecrab angle to track the extended runway centerline isestablished. This is coordinated flight with adjust-ments to heading to compensate for wind drift eitherleft or right. Prior to touchdown, the transition to asideslip is made with the upwind wing lowered andopposite rudder applied to prevent a turn. The airplanetouches down on the landing gear of the upwind wingfirst, followed by that of the downwind wing, andthen the nose gear. Follow-through with the flightcontrols involves an increasing application of aileroninto the wind until full control deflection is reached.

The point at which the transition from the crab to thesideslip is made is dependent upon pilot familiaritywith the airplane and experience. With high skill andexperience levels, the transition can be made duringthe roundout just before touchdown. With lesser skill

and experience levels, the transition is made atincreasing distances from the runway. Some multi-engine airplanes (as some single-engine airplanes)have AFM/POH limitations against slips in excess ofa certain time period; 30 seconds, for example. This isto prevent engine power loss from fuel starvation asthe fuel in the tank of the lowered wing flows towardsthe wingtip, away from the fuel pickup point. Thistime limit must be observed if the wing-low methodis utilized.

Some multiengine pilots prefer to use differentialpower to assist in crosswind landings. The asym-metrical thrust produces a yawing moment littledifferent from that produced by the rudder. Whenthe upwind wing is lowered, power on the upwindengine is increased to prevent the airplane fromturning. This alternate technique is completelyacceptable, but most pilots feel they can react tochanging wind conditions quicker with rudder andaileron than throttle movement. This is especiallytrue with turbocharged engines where the throttleresponse may lag momentarily. The differentialpower technique should be practiced with aninstructor familiar with it before being attemptedalone.

SHORT-FIELD TAKEOFF AND CLIMBThe short-field takeoff and climb differs from thenormal takeoff and climb in the airspeeds and initialclimb profile. Some AFM/POHs give separateshort-field takeoff procedures and performancecharts that recommend specific flap settings and air-speeds. Other AFM/POHs do not provide separateshort-field procedures. In the absence of such specificprocedures, the airplane should be operated only asrecommended in the AFM/POH. No operations shouldbe conducted contrary to the recommendations in theAFM/POH.

On short-field takeoffs in general, just after rotationand lift-off, the airplane should be allowed to acceler-ate to VX, making the initial climb over obstacles atVX and transitioning to VY as obstacles are cleared.[Figure 12-9]

Figure 12-9. Short-field takeoff and climb.

VX

VY

50 ft

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When partial flaps are recommended for short-fieldtakeoffs, many light-twins have a strong tendency tobecome airborne prior to VMC plus 5 knots. Attemptingto prevent premature lift-off with forward elevatorpressure results in wheelbarrowing. To prevent this,allow the airplane to become airborne, but only a fewinches above the runway. The pilot should be preparedto promptly abort the takeoff and land in the event ofengine failure on takeoff with landing gear and flapsextended at airspeeds below VX.

Engine failure on takeoff, particularly with obstruc-tions, is compounded by the low airspeeds and steepclimb attitudes utilized in short-field takeoffs. VX andVXSE are often perilously close to VMC, leaving scantmargin for error in the event of engine failure as VXSEis assumed. If flaps were used for takeoff, the enginefailure situation becomes even more critical due to theadditional drag incurred. If VX is less than 5 knotshigher than VMC, give strong consideration to reducinguseful load or using another runway in order toincrease the takeoff margins so that a short-fieldtechnique will not be required.

SHORT-FIELD APPROACH AND LANDINGThe primary elements of a short-field approach andlanding do not differ significantly from a normalapproach and landing. Many manufacturers do notpublish short-field landing techniques or performancecharts in the AFM/POH. In the absence of specificshort-field approach and landing procedures, theairplane should be operated as recommended in theAFM/POH. No operations should be conductedcontrary to the AFM/POH recommendations.

The emphasis in a short-field approach is on configu-ration (full flaps), a stabilized approach with a constantangle of descent, and precise airspeed control. As partof a short-field approach and landing procedure,some AFM/POHs recommend a slightly slower thannormal approach airspeed. If no such slower speed ispublished, use the AFM/POH-recommended normalapproach speed.

Full flaps are used to provide the steepest approachangle. If obstacles are present, the approach should beplanned so that no drastic power reductions arerequired after they are cleared. The power should besmoothly reduced to idle in the roundout prior totouchdown. Pilots should keep in mind that the pro-peller blast blows over the wings, providing some liftin addition to thrust. Significantly reducing power justafter obstacle clearance usually results in a sudden,high sink rate that may lead to a hard landing.

After the short-field touchdown, maximum stoppingeffort is achieved by retracting the wing flaps, addingback pressure to the elevator/stabilator, and applyingheavy braking. However, if the runway length permits,the wing flaps should be left in the extended positionuntil the airplane has been stopped clear of the runway.There is always a significant risk of retracting the land-ing gear instead of the wing flaps when flap retractionis attempted on the landing rollout.

Landing conditions that involve either a short-field,high-winds or strong crosswinds are just about the onlysituations where flap retraction on the landing rolloutshould be considered. When there is an operationalneed to retract the flaps just after touchdown, it mustbe done deliberately, with the flap handle positivelyidentified before it is moved.

GO-AROUNDWhen the decision to go around is made, the throttlesshould be advanced to takeoff power. With adequateairspeed, the airplane should be placed in a climb pitchattitude. These actions, which are accomplishedsimultaneously, will arrest the sink rate and place theairplane in the proper attitude for transition to aclimb. The initial target airspeed will be VY, or VX ifobstructions are present. With sufficient airspeed, theflaps should be retracted from full to an intermediateposition and the landing gear retracted when there isa positive rate of climb and no chance of runwaycontact. The remaining flaps should then beretracted. [Figure 12-10]

Figure 12-10. Go-around procedure.

Retract RemainingFlaps

Positive Rateof Climb, Retract

Gear, Climbat VY

500'Cruise Climb

Timely Decision toMake Go-Around Apply Max Power

Adjust Pitch Attitudeto Arrest Sink Rate

Flaps toIntermediate

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If the go-around was initiated due to conflicting trafficon the ground or aloft, the pilot should maneuver to theside, so as to keep the conflicting traffic in sight. Thismay involve a shallow bank turn to offset and then par-allel the runway/landing area.

If the airplane was in trim for the landing approachwhen the go-around was commenced, it will soon requirea great deal of forward elevator/stabilator pressure as theairplane accelerates away in a climb. The pilot shouldapply appropriate forward pressure to maintain thedesired pitch attitude. Trim should be commenced imme-diately. The “balked landing” checklist should bereviewed as work load permits.

Flaps should be retracted before the landing gear fortwo reasons. First, on most airplanes, full flaps producemore drag than the extended landing gear. Secondly,the airplane will tend to settle somewhat with flapretraction, and the landing gear should be down in theevent of an inadvertent, momentary touchdown.

Many multiengine airplanes have a landing gear retrac-tion speed significantly less than the extension speed.Care should be exercised during the go-around not toexceed the retraction speed. If the pilot desires toreturn for a landing, it is essential to re-accomplish theentire “before landing” checklist. An interruption to apilot’s habit patterns, such as a go-around, is a classicscenario for a subsequent gear up landing.

The preceding discussion of go-arounds assumes thatthe maneuver was initiated from normal approachspeeds or faster. If the go-around was initiated from alow airspeed, the initial pitch up to a climb attitude mustbe tempered with the necessity of maintaining adequateflying speed throughout the maneuver. Examples ofwhere this applies include go-arounds initiated from thelanding roundout or recovery from a bad bounce as wellas a go-around initiated due to an inadvertent approachto a stall. The first priority is always to maintain controland obtain adequate flying speed. A few moments oflevel or near level flight may be required as the airplaneaccelerates up to climb speed.

REJECTED TAKEOFFA takeoff can be rejected for the same reasons a takeoffin a single-engine airplane would be rejected. Once thedecision to reject a takeoff is made, the pilot shouldpromptly close both throttles and maintain directionalcontrol with the rudder, nosewheel steering, andbrakes. Aggressive use of rudder, nosewheel steering,and brakes may be required to keep the airplane onthe runway. Particularly, if an engine failure is notimmediately recognized and accompanied byprompt closure of both throttles. However, the pri-mary objective is not necessarily to stop the airplanein the shortest distance, but to maintain control ofthe airplane as it decelerates. In some situations, it

may be preferable to continue into the overrun areaunder control, rather than risk directional control loss,landing gear collapse, or tire/brake failure in anattempt to stop the airplane in the shortest possibledistance.

ENGINE FAILURE AFTER LIFT-OFFA takeoff or go-around is the most critical time to suf-fer an engine failure. The airplane will be slow, closeto the ground, and may even have landing gear andflaps extended. Altitude and time will be minimal.Until feathered, the propeller of the failed engine willbe windmilling, producing a great deal of drag andyawing tendency. Airplane climb performance will bemarginal or even non-existent, and obstructions maylie ahead. Add the element of surprise and the need fora plan of action before every takeoff is obvious.

With loss of an engine, it is paramount to maintainairplane control and comply with the manufacturer’srecommended emergency procedures. Complete fail-ure of one engine shortly after takeoff can be broadlycategorized into one of three following scenarios.

1. Landing gear down. [Figure 12-11] If theengine failure occurs prior to selecting the land-ing gear to the UP position, close both throttlesand land on the remaining runway or overrun.Depending upon how quickly the pilot reacts tothe sudden yaw, the airplane may run off theside of the runway by the time action is taken.There are really no other practical options. Asdiscussed earlier, the chances of maintainingdirectional control while retracting the flaps (ifextended), landing gear, feathering the propeller,and accelerating are minimal. On some airplaneswith a single-engine-driven hydraulic pump,failure of that engine means the only way toraise the landing gear is to allow the engine towindmill or to use a hand pump. This is not aviable alternative during takeoff.

2. Landing gear control selected up, single-engine climb performance inadequate.[Figure 12-12] When operating near or abovethe single-engine ceiling and an engine failure isexperienced shortly after lift-off, a landing mustbe accomplished on whatever essentially liesahead. There is also the option of continuingahead, in a descent at VYSE with the remainingengine producing power, as long as the pilotis not tempted to remain airborne beyond theairplane’s performance capability. Remainingairborne, bleeding off airspeed in a futileattempt to maintain altitude is almost invariablyfatal. Landing under control is paramount. Thegreatest hazard in a single-engine takeoff isattempting to fly when it is not within the per-

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formance capability of the airplane to do so. Anaccident is inevitable.

Analysis of engine failures on takeoff reveals a veryhigh success rate of off-airport engine inoperativelandings when the airplane is landed under control.Analysis also reveals a very high fatality rate in stall-spin accidents when the pilot attempts flight beyondthe performance capability of the airplane.

As mentioned previously, if the airplane’s landing gearretraction mechanism is dependent upon hydraulicpressure from a certain engine-driven pump, failureof that engine can mean a loss of hundreds of feet ofaltitude as the pilot either windmills the engine toprovide hydraulic pressure to raise the gear or raisesit manually with a backup pump.

3. Landing gear control selected up, single-engine climb performance adequate. [Figure12-13] If the single-engine rate of climb isadequate, the procedures for continued flightshould be followed. There are four areas ofconcern: control, configuration, climb, andchecklist.

• CONTROL— The first consideration followingengine failure during takeoff is control of the air-plane. Upon detecting an engine failure, aileronshould be used to bank the airplane and rudderpressure applied, aggressively if necessary, tocounteract the yaw and roll from asymmetricalthrust. The control forces, particularly on therudder, may be high. The pitch attitude for VYSEwill have to be lowered from that of VY.

Figure 12-11. Engine failure on takeoff, landing gear down.

If Engine Failure Occurs ator Before Lift-off, Abort theTakeoff.

If Failure of Engine Occurs After Lift-off:1. Maintain Directional Control2. Close Both Throttles

Figure 12-12. Engine failure on takeoff, inadequate climb performance.

Liftoff

Engine FailureDescend at VYSE

Land Under ControlOn or Off Runway

Over Run Area

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At least 5° of bank should be used, if necessary,to stop the yaw and maintain directional control.This initial bank input is held only momentarily,just long enough to establish or ensure direc-tional control. Climb performance suffers whenbank angles exceed approximately 2 or 3°, butobtaining and maintaining VYSE and directionalcontrol are paramount. Trim should be adjustedto lower the control forces.

• CONFIGURATION—The memory items fromthe “engine failure after takeoff” checklist[Figure 12-14] should be promptly executed toconfigure the airplane for climb. The specificprocedures to follow will be found in theAFM/POH and checklist for the particular air-plane. Most will direct the pilot to assume VYSE,set takeoff power, retract the flaps and landinggear, identify, verify, and feather the failedengine. (On some airplanes, the landing gear isto be retracted before the flaps.)

The “identify” step is for the pilot to initiallyidentify the failed engine. Confirmation on theengine gauges may or may not be possible,depending upon the failure mode. Identificationshould be primarily through the control inputsrequired to maintain straight flight, not theengine gauges. The “verify” step directs the pilotto retard the throttle of the engine thought to havefailed. No change in performance when the sus-pected throttle is retarded is verification that thecorrect engine has been identified as failed. Thecorresponding propeller control should bebrought fully aft to feather the engine.

• CLIMB—As soon as directional control is estab-lished and the airplane configured for climb, thebank angle should be reduced to that producingbest climb performance. Without specificguidance for zero sideslip, a bank of 2° andone-third to one-half ball deflection on theslip/skid indicator is suggested. VYSE is main-tained with pitch control. As turning flightreduces climb performance, climb should bemade straight ahead, or with shallow turns toavoid obstacles, to an altitude of at least 400feet AGL before attempting a return tothe airport.

Obstruction ClearanceAltitude or Above

At 500' or Obstruction Clearance Altitude:7. Engine Failure Checklist Circle and Land

3. Drag - Reduce - Gear, Flaps4. Identify - Inoperative Engine5. Verify - Inoperative Engine6. Feather - Inoperative Engine

If Failure of Engine Occurs After Liftoff:1. Maintain Directional Control - VYSE, Heading, Bank into Operating Engine2. Power - Increase or Set for Takeoff

Figure 12-13. Landing gear up—adequate climb performance.

Figure 12-14.Typical “engine failure after takeoff” emergencychecklist.

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ENGINE FAILURE AFTER TAKEOFF

Airspeed . . . . . . . . . . . . . . . . . . . Maintain VYSE

Mixtures . . . . . . . . . . . . . . . . . . . RICHPropellers . . . . . . . . . . . . . . . . . .HIGH RPMThrottles . . . . . . . . . . . . . . . . . . . FULL POWERFlaps . . . . . . . . . . . . . . . . . . . . . . . UPLanding Gear . . . . . . . . . . . . . . . UPIdentify . . . . . . . . . . . . . . . . . . . . Determine failed

engineVerify Close throttle of

failed enginePropeller . . . . . . . . . . . . . . . . . . . FEATHERTrim Tabs . . . . . . . . . . . . . . . . . . . ADJUSTFailed Engine . . . . . . . . . . . . . . . SECUREAs soon as practical . . . . . . . . . . LAND

Bold - faced items require immediate action and are to be accomplished from memory.

. . . . . . . . . . . . . . . . . . . . . . . .

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• CHECKLIST—Having accomplished thememory items from the “engine failure aftertakeoff” checklist, the printed copy should bereviewed as time permits. The “securing failedengine” checklist [Figure 12-15] should then beaccomplished. Unless the pilot suspects anengine fire, the remaining items should beaccomplished deliberately and without unduehaste. Airplane control should never be sacrificedto execute the remaining checklists. The priorityitems have already been accomplished frommemory.

Figure 12-15. Typical “securing failed engine” emergencychecklist.

Other than closing the cowl flap of the failed engine,none of these items, if left undone, adversely affectsairplane climb performance. There is a distinct possibilityof actuating an incorrect switch or control if the proce-dure is rushed. The pilot should concentrate on flyingthe airplane and extracting maximum performance. IfATC facilities are available, an emergency should bedeclared.

The memory items in the “engine failure after takeoff”checklist may be redundant with the airplane’s existingconfiguration. For example, in the third takeoff scenario,the gear and flaps were assumed to already be retracted,yet the memory items included gear and flaps. This isnot an oversight. The purpose of the memory items isto either initiate the appropriate action or to confirmthat a condition exists. Action on each item may notbe required in all cases. The memory items alsoapply to more than one circumstance. In an enginefailure from a go-around, for example, the landinggear and flaps would likely be extended when thefailure occurred.

The three preceding takeoff scenarios all include thelanding gear as a key element in the decision to land orcontinue. With the landing gear selector in the DOWNposition, for example, continued takeoff and climb isnot recommended. This situation, however, is not jus-tification to retract the landing gear the moment theairplane lifts off the surface on takeoff as a normal

procedure. The landing gear should remain selecteddown as long as there is usable runway or overrunavailable to land on. The use of wing flaps for takeoffvirtually eliminates the likelihood of a single-engineclimb until the flaps are retracted.

There are two time-tested memory aids the pilot mayfind useful in dealing with engine-out scenarios. Thefirst, “Dead foot–dead engine” is used to assist in iden-tifying the failed engine. Depending on the failuremode, the pilot won’t be able to consistently identifythe failed engine in a timely manner from the enginegauges. In maintaining directional control, however,rudder pressure will be exerted on the side (left or right)of the airplane with the operating engine. Thus, the“dead foot” is on the same side as the “dead engine.”Variations on this saying include “Idle foot–idleengine” and “Working foot–working engine.”

The second memory aid has to do with climb perform-ance. The phrase “Raise the dead” is a reminder thatthe best climb performance is obtained with a veryshallow bank, about 2° toward the operating engine.Therefore, the inoperative, or “dead” engine should be“raised” with a very slight bank.

Not all engine power losses are complete failures.Sometimes the failure mode is such that partial powermay be available. If there is a performance loss whenthe throttle of the affected engine is retarded, the pilotshould consider allowing it to run until altitude and air-speed permit safe single-engine flight, if this can bedone without compromising safety. Attempts to save amalfunctioning engine can lead to a loss of the entireairplane.

ENGINE FAILURE DURING FLIGHTEngine failures well above the ground are handleddifferently than those occurring at lower speeds andaltitudes. Cruise airspeed allows better airplane con-trol, and altitude may permit time for a possiblediagnosis and remedy of the failure. Maintainingairplane control, however, is still paramount.Airplanes have been lost at altitude due to apparentfixation on the engine problem to the detriment offlying the airplane.

Not all engine failures or malfunctions are catastrophicin nature (catastrophic meaning a major mechanicalfailure that damages the engine and precludes furtherengine operation). Many cases of power loss arerelated to fuel starvation, where restoration of powermay be made with the selection of another tank. Anorderly inventory of gauges and switches may revealthe problem. Carburetor heat or alternate air can beselected. The affected engine may run smoothly on justone magneto or at a lower power setting. Altering the

SECURING FAILED ENGINE

Mixture . . . . . . . . . . . . . . . . . . . . . . . IDLE CUT OFFMagnetos . . . . . . . . . . . . . . . . . . . . . OFFAlternator . . . . . . . . . . . . . . . . . . . . . OFFCowl Flap . . . . . . . . . . . . . . . . . . . . . CLOSEBoost Pump . . . . . . . . . . . . . . . . . . . . OFFFuel Selector . . . . . . . . . . . . . . . . . . OFFProp Sync . . . . . . . . . . . . . . . . . . . . . OFFElectrical Load . . . . . . . . . . . . . . . . . . . ReduceCrossfeed . . . . . . . . . . . . . . . . . . . . . Consider

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mixture may help. If fuel vapor formation is suspected,fuel boost pump operation may be used to eliminateflow and pressure fluctuations.

Although it is a natural desire among pilots to save anailing engine with a precautionary shutdown, theengine should be left running if there is any doubt as toneeding it for further safe flight. Catastrophic failureaccompanied by heavy vibration, smoke, blisteringpaint, or large trails of oil, on the other hand, indicatea critical situation. The affected engine should befeathered and the “securing failed engine” checklistcompleted. The pilot should divert to the nearest suit-able airport and declare an emergency with ATC forpriority handling.

Fuel crossfeed is a method of getting fuel from a tankon one side of the airplane to an operating engine onthe other. Crossfeed is used for extended single-engineoperation. If a suitable airport is close at hand, there isno need to consider crossfeed. If prolonged flight on asingle-engine is inevitable due to airport non-avail-ability, then crossfeed allows use of fuel that wouldotherwise be unavailable to the operating engine. Italso permits the pilot to balance the fuel consumptionto avoid an out-of-balance wing heaviness.

AFM/POH procedures for crossfeed vary widely.Thorough fuel system knowledge is essential if cross-feed is to be conducted. Fuel selector positions and fuelboost pump usage for crossfeed differ greatly amongmultiengine airplanes. Prior to landing, crossfeedshould be terminated and the operating engine returnedto its main tank fuel supply.

If the airplane is above its single-engine absoluteceiling at the time of engine failure, it will slowlylose altitude. The pilot should maintain VYSE to min-imize the rate of altitude loss. This “drift down” ratewill be greatest immediately following the failureand will decrease as the single-engine ceiling isapproached. Due to performance variations causedby engine and propeller wear, turbulence, and pilottechnique, the airplane may not maintain altitudeeven at its published single-engine ceiling. Any furtherrate of sink, however, would likely be modest.

An engine failure in a descent or other low powersetting can be deceiving. The dramatic yaw and per-formance loss will be absent. At very low powersettings, the pilot may not even be aware of a failure.If a failure is suspected, the pilot should advance bothengine mixtures, propellers, and throttles significantly,to the takeoff settings if necessary, to correctly identifythe failed engine. The power on the operative enginecan always be reduced later.

ENGINE INOPERATIVE APPROACHAND LANDINGThe approach and landing with one engine inoperativeis essentially the same as a two-engine approach andlanding. The traffic pattern should be flown at similaraltitudes, airspeeds, and key positions as a two-engineapproach. The differences will be the reduced poweravailable and the fact that the remaining thrust isasymmetrical. A higher-than-normal power settingwill be necessary on the operative engine.

With adequate airspeed and performance, the landinggear can still be extended on the downwind leg. Inwhich case it should be confirmed DOWN no laterthan abeam the intended point of landing. Performancepermitting, initial extension of wing flaps (10°, typi-cally) and a descent from pattern altitude can also beinitiated on the downwind leg. The airspeed should beno slower than VYSE. The direction of the traffic pat-tern, and therefore the turns, is of no consequence asfar as airplane controllability and performance areconcerned. It is perfectly acceptable to make turnstoward the failed engine.

On the base leg, if performance is adequate, the flapsmay be extended to an intermediate setting (25°, typi-cally). If the performance is inadequate, as measuredby a decay in airspeed or high sink rate, delay furtherflap extension until closer to the runway. VYSE is stillthe minimum airspeed to maintain.

On final approach, a normal, 3° glidepath to a landingis desirable. VASI or other vertical path lighting aidsshould be utilized if available. Slightly steeperapproaches may be acceptable. However, a long, flat,low approach should be avoided. Large, sudden powerapplications or reductions should also be avoided.Maintain VYSE until the landing is assured, then slowto 1.3 VSO or the AFM/POH recommended speed. Thefinal flap setting may be delayed until the landing isassured, or the airplane may be landed with partialflaps.

The airplane should remain in trim throughout. Thepilot must be prepared, however, for a rudder trimchange as the power of the operating engine is reducedto idle in the roundout just prior to touchdown. Withdrag from only one windmilling propeller, the airplanewill tend to float more than on a two-engine approach.Precise airspeed control therefore is essential, especiallywhen landing on a short, wet and/or slippery surface.

Some pilots favor resetting the rudder trim to neutralon final and compensating for yaw by holding rudderpressure for the remainder of the approach. This elim-inates the rudder trim change close to the ground as

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the throttle is closed during the roundout for landing.This technique eliminates the need for groping for therudder trim and manipulating it to neutral during finalapproach, which many pilots find to be highly dis-tracting. AFM/POH recommendations or personalpreference should be used.

Single-engine go-arounds must be avoided. As a prac-tical matter in single-engine approaches, once the air-plane is on final approach with landing gear and flapsextended, it is committed to land. If not on the intendedrunway, then on another runway, a taxiway, or grassyinfield. The light-twin does not have the performanceto climb on one engine with landing gear and flapsextended. Considerable altitude will be lost whilemaintaining VYSE and retracting landing gear andflaps. Losses of 500 feet or more are not unusual. If thelanding gear has been lowered with an alternate meansof extension, retraction may not be possible, virtuallynegating any climb capability.

ENGINE INOPERATIVE FLIGHT PRINCIPLESBest single-engine climb performance is obtained atVYSE with maximum available power and minimumdrag. After the flaps and landing gear have beenretracted and the propeller of the failed engine feath-ered, a key element in best climb performance isminimizing sideslip.

With a single-engine airplane or a multiengine airplanewith both engines operative, sideslip is eliminatedwhen the ball of the turn and bank instrument is cen-tered. This is a condition of zero sideslip, and theairplane is presenting its smallest possible profile tothe relative wind. As a result, drag is at its minimum.Pilots know this as coordinated flight.

In a multiengine airplane with an inoperative engine,the centered ball is no longer the indicator of zerosideslip due to asymmetrical thrust. In fact, there is noinstrument at all that will directly tell the pilot theflight conditions for zero sideslip. In the absence of ayaw string, minimizing sideslip is a matter of placingthe airplane at a predetermined bank angle and ballposition. The AFM/POH performance charts for sin-gle-engine flight were determined at zero sideslip. Ifthis performance is even to be approximated, the zerosideslip technique must be utilized.

There are two different control inputs that can be usedto counteract the asymmetrical thrust of a failedengine: (1) yaw from the rudder, and (2) the horizontalcomponent of lift that results from bank with theailerons. Used individually, neither is correct. Usedtogether in the proper combination, zero sideslip andbest climb performance are achieved.

Three different scenarios of airplane control inputs arepresented below. Neither of the first two is correct.They are presented to illustrate the reasons for the zerosideslip approach to best climb performance.

1. Engine inoperative flight with wings level andball centered requires large rudder input towardsthe operative engine. [Figure 12-16] The result isa moderate sideslip towards the inoperativeengine. Climb performance will be reduced bythe moderate sideslip. With wings level, VMC willbe significantly higher than published as there isno horizontal component of lift available to helpthe rudder combat asymmetrical thrust.

Figure 12-16. Wings level engine-out flight.

Rudder Force

YawString

Fin EffectDue to Sideslip

Slipstream

Wings level, ball centered, airplane slips toward dead engine.Results: high drag, large control surface deflections required,and rudder and fin in opposition due to sideslip.

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2. Engine inoperative flight using ailerons alonerequires an 8 - 10° bank angle towards the oper-ative engine. [Figure 12-17] This assumes norudder input. The ball will be displaced welltowards the operative engine. The result is alarge sideslip towards the operative engine.Climb performance will be greatly reduced bythe large sideslip.

3. Rudder and ailerons used together in the propercombination will result in a bank of approxi-mately 2° towards the operative engine. Theball will be displaced approximately one-thirdto one-half towards the operative engine. The

result is zero sideslip and maximum climb per-formance. [Figure 12-18] Any attitude otherthan zero sideslip increases drag, decreasingperformance. VMC under these circumstanceswill be higher than published, as less than the5° bank certification limit is employed.

The precise condition of zero sideslip (bank angle andball position) varies slightly from model to model, andwith available power and airspeed. If the airplane isnot equipped with counter-rotating propellers, it willalso vary slightly with the engine failed due to P-factor.The foregoing zero sideslip recommendations apply to

YawString

Excess bank toward operating engine, no rudder input.Result: large sideslip toward operating engine and greatlyreduced climb performance.

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Rudder Force

YawString

Bank toward operating engine, no sideslip. Results: muchlower drag and smaller control surface deflections.

Figure 12-17. Excessive bank engine-out flight. Figure 12-18. Zero sideslip engine-out flight.

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reciprocating engine multiengine airplanes flown atVYSE with the inoperative engine feathered. The zerosideslip ball position for straight flight is also the zerosideslip position for turning flight.

When bank angle is plotted against climb performancefor a hypothetical twin, zero sideslip results in the best(however marginal) climb performance or the least rateof descent. Zero bank (all rudder to counteract yaw)degrades climb performance as a result of moderatesideslip. Using bank angle alone (no rudder) severelydegrades climb performance as a result of a largesideslip.

The actual bank angle for zero sideslip varies amongairplanes from one and one-half to two and one-halfdegrees. The position of the ball varies from one-thirdto one-half of a ball width from instrument center.

For any multiengine airplane, zero sideslip can be con-firmed through the use of a yaw string. A yaw string isa piece of string or yarn approximately 18 to 36 inchesin length, taped to the base of the windshield, or to thenose near the windshield, along the airplane centerline.In two-engine coordinated flight, the relative wind willcause the string to align itself with the longitudinal axisof the airplane, and it will position itself straight up thecenter of the windshield. This is zero sideslip.Experimentation with slips and skids will vividly displaythe location of the relative wind. Adequate altitude andflying speed must be maintained while accomplishingthese maneuvers.

With an engine set to zero thrust (or feathered) and theairplane slowed to VYSE, a climb with maximum poweron the remaining engine will reveal the precise bankangle and ball deflection required for zero sideslip andbest climb performance. Zero sideslip will again beindicated by the yaw string when it aligns itself ver-tically on the windshield. There will be very minorchanges from this attitude depending upon theengine failed (with noncounter-rotating propellers),power available, airspeed and weight; but withoutmore sensitive testing equipment, these changes aredifficult to detect. The only significant differencewould be the pitch attitude required to maintain VYSEunder different density altitude, power available, andweight conditions.

If a yaw string is attached to the airplane at the timeof a VMC demonstration, it will be noted that VMCoccurs under conditions of sideslip. VMC was notdetermined under conditions of zero sideslip duringaircraft certification and zero sideslip is not part of aVMC demonstration for pilot certification.

To review, there are two different sets of bank anglesused in one-engine-inoperative flight.

• To maintain directional control of a multiengineairplane suffering an engine failure at low speeds(such as climb), momentarily bank at least 5°,and a maximum of 10° towards the operativeengine as the pitch attitude for VYSE is set. Thismaneuver should be instinctive to the proficientmultiengine pilot and take only 1 to 2 seconds toattain. It is held just long enough to assure direc-tional control as the pitch attitude for VYSE isassumed.

• To obtain the best climb performance, the air-plane must be flown at VYSE and zero sideslip,with the failed engine feathered and maximumavailable power from the operating engine. Zerosideslip is approximately 2° of bank toward theoperating engine and a one-third to one-half balldeflection, also toward the operating engine. Theprecise bank angle and ball position will varysomewhat with make and model and poweravailable. If above the airplane’s single-engineceiling, this attitude and configuration will resultin the minimum rate of sink.

In OEI flight at low altitudes and airspeeds such as theinitial climb after takeoff, pilots must operate the airplaneso as to guard against the three major accident factors:(1) loss of directional control, (2) loss of performance,and (3) loss of flying speed. All have equal potential tobe lethal. Loss of flying speed will not be a factor,however, when the airplane is operated with due regardfor directional control and performance.

SLOW FLIGHTThere is nothing unusual about maneuvering duringslow flight in a multiengine airplane. Slow flight maybe conducted in straight-and-level flight, turns, in theclean configuration, landing configuration, or at anyother combination of landing gear and flaps. Pilotsshould closely monitor cylinder head and oil temper-atures during slow flight. Some high performancemultiengine airplanes tend to heat up fairly quicklyunder some conditions of slow flight, particularly inthe landing configuration.

Simulated engine failures should not be conducted dur-ing slow flight. The airplane will be well below VSSEand very close to VMC. Stability, stall warning or stallavoidance devices should not be disabled whilemaneuvering during slow flight.

STALLSStall characteristics vary among multiengine airplanesjust as they do with single-engine airplanes, andtherefore, it is important to be familiar with them. Theapplication of power upon stall recovery, however,has a significantly greater effect during stalls in a

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twin than a single-engine airplane. In the twin, anapplication of power blows large masses of air fromthe propellers directly over the wings, producing asignificant amount of lift in addition to the expectedthrust. The multiengine airplane, particularly at lightoperating weights, typically has a higher thrust-to-weight ratio, making it quicker to accelerate out of astalled condition.

In general, stall recognition and recovery training intwins is performed similar to any high performancesingle-engine airplane. However, for twins, all stallmaneuvers should be planned so as to be completed atleast 3,000 feet AGL.

Single-engine stalls or stalls with significantly morepower on one engine than the other should not beattempted due to the likelihood of a departure fromcontrolled flight and possible spin entry. Similarly,simulated engine failures should not be performed dur-ing stall entry and recovery.

POWER-OFF STALLS (APPROACH AND LANDING)Power-off stalls are practiced to simulate typicalapproach and landing scenarios. To initiate a power-offstall maneuver, the area surrounding the airplaneshould first be cleared for possible traffic. The airplaneshould then be slowed and configured for an approachand landing. A stabilized descent should be established(approximately 500 f.p.m.) and trim adjusted. The pilotshould then transition smoothly from the stabilizeddescent attitude, to a pitch attitude that will induce astall. Power is reduced further during this phase, andtrimming should cease at speeds slower than takeoff.

When the airplane reaches a stalled condition, therecovery is accomplished by simultaneously reducingthe angle of attack with coordinated use of the flightcontrols and smoothly applying takeoff or specifiedpower. The flap setting should be reduced from full toapproach, or as recommended by the manufacturer.Then with a positive rate of climb, the landing gear isselected up. The remaining flaps are then retracted as aclimb has commenced. This recovery process shouldbe completed with a minimum loss of altitude, appro-priate to the aircraft characteristics.

The airplane should be accelerated to VX (if simulatedobstacles are present) or VY during recovery and climb.Considerable forward elevator/stabilator pressure willbe required after the stall recovery as the airplane accel-erates to VX or VY. Appropriate trim input should beanticipated.

Power-off stalls may be performed with wings level, orfrom shallow and medium banked turns. When recov-ering from a stall performed from turning flight, the

angle of attack should be reduced prior to leveling thewings. Flight control inputs should be coordinated.

It is usually not advisable to execute full stalls inmultiengine airplanes because of their relatively highwing loading. Stall training should be limited toapproaches to stalls and when a stall condition occurs.Recoveries should be initiated at the onset, or decay ofcontrol effectiveness, or when the first physicalindication of the stall occurs.

POWER-ON STALLS (TAKEOFF AND DEPARTURE)Power-on stalls are practiced to simulate typicaltakeoff scenarios. To initiate a power-on stallmaneuver, the area surrounding the airplane shouldalways be cleared to look for potential traffic. Theairplane is slowed to the manufacturer’s recommendedlift-off speed. The airplane should be configured in thetakeoff configuration. Trim should be adjusted for thisspeed. Engine power is then increased to that recom-mended in the AFM/POH for the practice of power-onstalls. In the absence of a recommended setting, useapproximately 65 percent of maximum availablepower while placing the airplane in a pitch attitude thatwill induce a stall. Other specified (reduced) powersettings may be used to simulate performance at highergross weights and density altitudes.

When the airplane reaches a stalled condition, therecovery is made by simultaneously lowering theangle of attack with coordinated use of the flightcontrols and applying power as appropriate.

However, if simulating limited power available forhigh gross weight and density altitude situations, thepower during the recovery should be limited to thatspecified. The recovery should be completed with aminimum loss of altitude, appropriate to aircraft char-acteristics.

The landing gear should be retracted when a positiverate of climb is attained, and flaps retracted, if flapswere set for takeoff. The target airspeed on recovery isVX if (simulated) obstructions are present, or VY. Thepilot should anticipate the need for nosedown trim asthe airplane accelerates to VX or VY after recovery.

Power-on stalls may be performed from straight flightor from shallow and medium banked turns. Whenrecovering from a power-on stall performed from turn-ing flight, the angle of attack should be reduced priorto leveling the wings, and the flight control inputsshould be coordinated.

SPIN AWARENESSNo multiengine airplane is approved for spins, andtheir spin recovery characteristics are generally very

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poor. It is therefore necessary to practice spin avoid-ance and maintain a high awareness of situations thatcan result in an inadvertent spin.

In order to spin any airplane, it must first be stalled. Atthe stall, a yawing moment must be introduced. In amultiengine airplane, the yawing moment may begenerated by rudder input or asymmetrical thrust. Itfollows, then, that spin awareness be at its greatestduring VMC demonstrations, stall practice, slowflight, or any condition of high asymmetrical thrust,particularly at low speed/high angle of attack. Single-engine stalls are not part of any multiengine trainingcurriculum.

A situation that may inadvertently degrade into a spinentry is a simulated engine failure introduced at aninappropriately low speed. No engine failure shouldever be introduced below safe, intentional one-engine-inoperative speed (VSSE). If no VSSE is published, useVYSE. The “necessity” of simulating engine failuresat low airspeeds is erroneous. Other than trainingsituations, the multiengine airplane is only operatedbelow VSSE for mere seconds just after lift-off orduring the last few dozen feet of altitude in preparationfor landing.

For spin avoidance when practicing engine failures,the flight instructor should pay strict attention to themaintenance of proper airspeed and bank angle as thestudent executes the appropriate procedure. Theinstructor should also be particularly alert during stalland slow flight practice. Forward center-of-gravitypositions result in favorable stall and spin avoidancecharacteristics, but do not eliminate the hazard.

When performing a VMC demonstration, the instructorshould also be alert for any sign of an impending stall.The student may be highly focused on the directionalcontrol aspect of the maneuver to the extent thatimpending stall indications go unnoticed. If a VMCdemonstration cannot be accomplished under existingconditions of density altitude, it may, for training pur-poses, be done utilizing the rudder blocking techniquedescribed in the following section.

As very few twins have ever been spin-tested (noneare required to), the recommended spin recoverytechniques are based only on the best informationavailable. The departure from controlled flight maybe quite abrupt and possibly disorienting. The direc-tion of an upright spin can be confirmed from the turnneedle or the symbolic airplane of the turn coordinator,if necessary. Do not rely on the ball position or otherinstruments.

If a spin is entered, most manufacturers recommendimmediately retarding both throttles to idle, applying

full rudder opposite the direction of rotation, andapplying full forward elevator/stabilator pressure (withailerons neutral). These actions should be taken as nearsimultaneously as possible. The controls should thenbe held in that position. Recovery, if possible, will takeconsiderable altitude. The longer the delay from entryuntil taking corrective action, the less likely that recov-ery will be successful.

ENGINE INOPERATIVE—LOSS OFDIRECTIONAL CONTROL DEMONSTRATIONAn engine inoperative—loss of directional controldemonstration, often referred to as a “VMC demon-stration,” is a required task on the practical test for amultiengine class rating. A thorough knowledge ofthe factors that affect VMC, as well as its definition,is essential for multiengine pilots, and as such anessential part of that required task. VMC is a speedestablished by the manufacturer, published in theAFM/POH, and marked on most airspeed indicatorswith a red radial line. The multiengine pilot mustunderstand that VMC is not a fixed airspeed under allconditions. VMC is a fixed airspeed only for the veryspecific set of circumstances under which it wasdetermined during aircraft certification. [Figure 12-19]

In reality, VMC varies with a variety of factors asoutlined below. The VMC noted in practice anddemonstration, or in actual single-engine operation,could be less or even greater than the publishedvalue, depending upon conditions and technique.

In aircraft certification, VMC is the sea level calibratedairspeed at which, when the critical engine is suddenlymade inoperative, it is possible to maintain control ofthe airplane with that engine still inoperative and thenmaintain straight flight at the same speed with an angleof bank of not more than 5°.

The foregoing refers to the determination of VMC under“dynamic” conditions. This technique is only used byhighly experienced flight test pilots during aircraft cer-tification. It is never to be attempted outside of thesecircumstances.

In aircraft certification, there is also a determination ofVMC under “static,” or steady-state conditions. If thereis a difference between the dynamic and static speeds,the higher of the two is published as VMC. The staticdetermination is simply the ability to maintain straightflight at VMC with a bank angle of not more than 5°. Thismore closely resembles the VMC demonstration requiredin the practical test for a multiengine class rating.

The AFM/POH-published VMC is determined with the“critical” engine inoperative. The critical engine is the

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engine whose failure has the most adverse effect ondirectional control. On twins with each engine rotatingin conventional, clockwise rotation as viewed from thepilot’s seat, the critical engine will be the left engine.

Multiengine airplanes are subject to P-factor just assingle-engine airplanes are. The descending propellerblade of each engine will produce greater thrust thanthe ascending blade when the airplane is operatedunder power and at positive angles of attack. Thedescending propeller blade of the right engine is alsoa greater distance from the center of gravity, andtherefore has a longer moment arm than the descend-ing propeller blade of the left engine. As a result,failure of the left engine will result in the mostasymmetrical thrust (adverse yaw) as the rightengine will be providing the remaining thrust.[Figure 12-19]

Many twins are designed with a counter-rotating rightengine. With this design, the degree of asymmetricalthrust is the same with either engine inoperative. Noengine is more critical than the other, and a VMCdemonstration may be performed with either enginewindmilling.

In aircraft certification, dynamic VMC is determinedunder the following conditions.

• Maximum available takeoff power. VMCincreases as power is increased on the operatingengine. With normally aspirated engines, VMC ishighest at takeoff power and sea level, anddecreases with altitude. With turbochargedengines, takeoff power, and therefore VMC,remains constant with increases in altitude up tothe engine’s critical altitude (the altitude where

the engine can no longer maintain 100 percentpower). Above the critical altitude, VMCdecreases just as it would with a normally aspi-rated engine, whose critical altitude is sea level.VMC tests are conducted at a variety of altitudes.The results of those tests are then extrapolated toa single, sea level value.

• Windmilling propeller. VMC increases withincreased drag on the inoperative engine. VMC ishighest, therefore, when the critical engine pro-peller is windmilling at the low pitch, highr.p.m. blade angle. VMC is determined with thecritical engine propeller windmilling in thetakeoff position, unless the engine is equippedwith an autofeather system.

• Most unfavorable weight and center-of-gravityposition. VMC increases as the center of gravityis moved aft. The moment arm of the rudder isreduced, and therefore its effectivity is reduced,as the center of gravity is moved aft. At the sametime, the moment arm of the propeller blade isincreased, aggravating asymmetrical thrust.Invariably, the aft-most CG limit is the mostunfavorable CG position. Currently, 14 CFRpart 23 calls for VMC to be determined at themost unfavorable weight. For twins certifi-cated under CAR 3 or early 14 CFR part 23,the weight at which VMC was determined wasnot specified. VMC increases as weight isreduced. [Figure 12-20]

• Landing gear retracted. VMC increases whenthe landing gear is retracted. Extended landinggear aids directional stability, which tends todecrease VMC.

Figure 12-19. Forces created during single-engine operation.

C L C L

D2D1

ArmArm

InoperativeEngine

InoperativeEngine

OperativeEngine

OperativeEngine

(Critical Engine)

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• Wing flaps in the takeoff position. For mosttwins, this will be 0° of flaps.

• Cowl flaps in the takeoff position.

• Airplane trimmed for takeoff.

• Airplane airborne and the ground effect negli-gible.

• Maximum of 5° angle of bank. VMC is highlysensitive to bank angle. To prevent claims ofan unrealistically low VMC speed in aircraftcertification, the manufacturer is permitted touse a maximum of a 5° bank angle toward theoperative engine. The horizontal component oflift generated by the bank assists the rudder incounteracting the asymmetrical thrust of theoperative engine. The bank angle works in themanufacturer’s favor in lowering VMC.

VMC is reduced significantly with increases in bankangle. Conversely, VMC increases significantly withdecreases in bank angle. Tests have shown that VMCmay increase more than 3 knots for each degree ofbank angle less than 5°. Loss of directional controlmay be experienced at speeds almost 20 knots abovepublished VMC when the wings are held level.

The 5° bank angle maximum is a regulatory limitimposed upon manufacturers in aircraft certification.The 5° bank does not inherently establish zero sideslipor best single-engine climb performance. Zero sideslip,and therefore best single-engine climb performance,occurs at bank angles significantly less than 5°. Thedetermination of VMC in certification is solely con-cerned with the minimum speed for directional controlunder a very specific set of circumstances, and has

nothing to do with climb performance, nor is it theoptimum airplane attitude or configuration for climbperformance.

During dynamic VMC determination in aircraft certi-fication, cuts of the critical engine using the mixturecontrol are performed by flight test pilots whilegradually reducing the speed with each attempt. VMCis the minimum speed at which directional controlcould be maintained within 20° of the original entryheading when a cut of the critical engine was made.During such tests, the climb angle with both enginesoperating was high, and the pitch attitude followingthe engine cut had to be quickly lowered to regainthe initial speed. Pilots should never attempt todemonstrate VMC with an engine cut from highpower, and never intentionally fail an engine atspeeds less than VSSE.

The actual demonstration of VMC and recovery in flighttraining more closely resembles static VMC determi-nation in aircraft certification. For a demonstration,the pilot should select an altitude that will allowcompletion of the maneuver at least 3,000 feet AGL.The following description assumes a twin withnoncounter-rotating engines, where the left engineis critical.

With the landing gear retracted and the flaps set to thetakeoff position, the airplane should be slowed toapproximately 10 knots above VSSE or VYSE(whichever is higher) and trimmed for takeoff. For theremainder of the maneuver, the trim setting should notbe altered. An entry heading should be selected andhigh r.p.m. set on both propeller controls. Power on theleft engine should be throttled back to idle as the rightengine power is advanced to the takeoff setting. Thelanding gear warning horn will sound as long as a

Figure 12-20. Effect of CG location on yaw.

A

B

InoperativeEngine

OperativeEngine

B x R = A x T

InoperativeEngine

OperativeEngine

A

R

B

R

T T

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throttle is retarded. The pilots should continue to care-fully listen, however, for the stall warning horn, if soequipped, or watch for the stall warning light. The leftyawing and rolling moment of the asymmetrical thrustis counteracted primarily with right rudder. A bankangle of 5° (a right bank, in this case) should also beestablished.

While maintaining entry heading, the pitch attitude isslowly increased to decelerate at a rate of 1 knot persecond (no faster). As the airplane slows and controleffectivity decays, the increasing yawing tendencyshould be counteracted with additional rudder pres-sure. Aileron displacement will also increase in orderto maintain 5° of bank. An airspeed is soon reachedwhere full right rudder travel and a 5° right bank canno longer counteract the asymmetrical thrust, and theairplane will begin to yaw uncontrollably to the left.

The moment the pilot first recognizes the uncontrol-lable yaw, or experiences any symptom associatedwith a stall, the operating engine throttle should besufficiently retarded to stop the yaw as the pitchattitude is decreased. Recovery is made with a minimumloss of altitude to straight flight on the entry heading atVSSE or VYSE, before setting symmetrical power. Therecovery should not be attempted by increasing poweron the windmilling engine alone.

To keep the foregoing description simple, there wereseveral important background details that were notcovered. The rudder pressure during the demonstrationcan be quite high. In certification, 150 pounds of forceis permitted before the limiting factor becomes rudderpressure, not rudder travel. Most twins will run out ofrudder travel long before 150 pounds of pressure isrequired. Still, it will seem considerable.

Maintaining altitude is not a criterion in accom-plishing this maneuver. This is a demonstration ofcontrollability, not performance. Many airplanes willlose (or gain) altitude during the demonstration. Beginthe maneuver at an altitude sufficient to allow completionby 3,000 feet AGL.

As discussed earlier, with normally aspirated engines,VMC decreases with altitude. Stalling speed (VS),however, remains the same. Except for a few models,published VMC is almost always higher than VS. Atsea level, there is usually a margin of several knotsbetween VMC and VS, but the margin decreases withaltitude, and at some altitude, VMC and VS are thesame. [Figure 12-21]

Should a stall occur while the airplane is under asym-metrical power, particularly high asymmetrical power,a spin entry is likely. The yawing moment inducedfrom asymmetrical thrust is little different from that

induced by full rudder in an intentional spin in theappropriate model of single-engine airplane. In thiscase, however, the airplane will depart controlledflight in the direction of the idle engine, not in thedirection of the applied rudder. Twins are not requiredto demonstrate recoveries from spins, and their spinrecovery characteristics are generally very poor.

Where VS is encountered at or before VMC, the depar-ture from controlled flight may be quite sudden, withstrong yawing and rolling tendencies to the invertedposition, and a spin entry. Therefore, during a VMCdemonstration, if there are any symptoms of animpending stall such as a stall warning light or horn,airframe or elevator buffet, or rapid decay in controleffectiveness, the maneuver should be terminatedimmediately, the angle of attack reduced as the throttleis retarded, and the airplane returned to the entryairspeed. It should be noted that if the pilots arewearing headsets, the sound of a stall warning hornwill tend to be masked.

The VMC demonstration only shows the earliest onsetof a loss of directional control. It is not a loss of con-trol of the airplane when performed in accordance withthe foregoing procedures. A stalled condition shouldnever be allowed to develop. Stalls should never beperformed with asymmetrical thrust and the VMCdemonstration should never be allowed to degrade intoa single-engine stall. A VMC demonstration that isallowed to degrade into a single-engine stall with highasymmetrical thrust is very likely to result in a loss ofcontrol of the airplane.

An actual demonstration of VMC may not be possibleunder certain conditions of density altitude, or withairplanes whose VMC is equal to or less than VS. Underthose circumstances, as a training technique, a demon-stration of VMC may be safely conducted by artificiallylimiting rudder travel to simulate maximum availablerudder. Limiting rudder travel should be accomplishedat a speed well above VS (approximately 20 knots).

Den

sity

Alti

tude

Indicated Airspeed

StallOccurs

First

YawOccurs First

RecoveryMay BeDifficult

Altitude WhereVMC = Stall Speed

Engine-OutPower-OnStall Speed (VS)

VMC

Figure 12-21. Graph depicting relationship of VMC to VS.

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The rudder limiting technique avoids the hazards ofspinning as a result of stalling with high asymmetricalpower, yet is effective in demonstrating the loss ofdirectional control.

The VMC demonstration should never be performedfrom a high pitch attitude with both engines operatingand then reducing power on one engine. The precedingdiscussion should also give ample warning as to whyengine failures are never to be performed at low air-speeds. An unfortunate number of airplanes and pilotshave been lost from unwarranted simulated enginefailures at low airspeeds that degenerated into loss ofcontrol of the airplane. VSSE is the minimum airspeedat which any engine failure should be simulated.

MULTIENGINE TRAINING CONSIDERATIONSFlight training in a multiengine airplane can be safelyaccomplished if both the instructor and the student arecognizant of the following factors.

• No flight should ever begin without a thoroughpreflight briefing of the objectives, maneuvers,expected student actions, and completion stan-dards.

• A clear understanding must be reached as to howsimulated emergencies will be introduced, andwhat action the student is expected to take.

The introduction, practice, and testing of emergencyprocedures has always been a sensitive subject.Surprising a multiengine student with an emergencywithout a thorough briefing beforehand has no placein flight training. Effective training must be carefullybalanced with safety considerations. Simulated enginefailures, for example, can very quickly become actualemergencies or lead to loss of the airplane whenapproached carelessly. Pulling circuit breakers canlead to a subsequent gear up landing. Stall-spin acci-dents in training for emergencies rival the number ofstall-spin accidents from actual emergencies.

All normal, abnormal, and emergency procedures canand should be introduced and practiced in the airplaneas it sits on the ground, power off. In this respect, theairplane is used as a cockpit procedures trainer (CPT),ground trainer, or simulator. The value of this trainingshould never be underestimated. The engines do nothave to be operating for real learning to occur. Uponcompletion of a training session, care should be takento return items such as switches, valves, trim, fuel selec-tors, and circuit breakers to their normal positions.

Pilots who do not use a checklist effectively will be ata significant disadvantage in multiengine airplanes.Use of the checklist is essential to safe operation of

airplanes and no flight should be conducted withoutone. The manufacturer’s checklist or an aftermarketchecklist for the specific make, model, and model yearshould be used. If there is a procedural discrepancybetween the checklist and AFM/POH, then theAFM/POH always takes precedence.

Certain immediate action items (such as the responseto an engine failure in a critical phase of flight) shouldbe committed to memory. After they are accomplished,and as work load permits, the pilot should verify theaction taken with a printed checklist.

Simulated engine failures during the takeoff groundroll should be accomplished with the mixture control.The simulated failure should be introduced at a speedno greater than 50 percent of VMC. If the student doesnot react promptly by retarding both throttles, theinstructor can always pull the other mixture.

The FAA recommends that all in-flight simulatedengine failures below 3,000 feet AGL be introducedwith a smooth reduction of the throttle. Thus, theengine is kept running and is available for instant use,if necessary. Throttle reduction should be smoothrather than abrupt to avoid abusing the engine and pos-sibly causing damage. All inflight engine failures mustbe conducted at VSSE or above.

If the engines are equipped with dynamic crankshaftcounterweights, it is essential to make throttle reductionsfor simulated failures smoothly. Other areas leading todynamic counterweight damage include high r.p.m. andlow manifold pressure combinations, overboosting, andpropeller feathering. Severe damage or repetitive abuseto counterweights will eventually lead to engine failure.Dynamic counterweights are found on larger, morecomplex engines—instructors should check withmaintenance personnel or the engine manufacturer todetermine if their engines are so equipped.

When an instructor simulates an engine failure, thestudent should respond with the appropriate memoryitems and retard the propeller control towards theFEATHER position. Assuming zero thrust will be set,the instructor should promptly move the propellercontrol forward and set the appropriate manifoldpressure and r.p.m. It is vital that the student be keptinformed of the instructor’s intentions. At this pointthe instructor may state words to the effect, “I have theright engine; you have the left. I have set zero thrustand the right engine is simulated feathered.” Thereshould never be any ambiguity as to who is operatingwhat systems or controls.

Following a simulated engine failure, the instructorshould continue to care for the “failed” engine just asthe student cares for the operative engine. If zero thrust

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is set to simulate a feathered propeller, the cowl flapshould be closed and the mixture leaned. An occasionalclearing of the engine is also desirable. If possible,avoid high power applications immediately followinga prolonged cool-down at a zero-thrust power setting.The flight instructor must impress on the student mul-tiengine pilot the critical importance of feathering thepropeller in a timely manner should an actual enginefailure situation be encountered. Awindmilling propeller,in many cases, has given the improperly trainedmultiengine pilot the mistaken perception that thefailed engine is still developing useful thrust, resultingin a psychological reluctance to feather, as featheringresults in the cessation of propeller rotation. The flightinstructor should spend ample time demonstratingthe difference in the performance capabilities of theairplane with a simulated feathered propeller (zerothrust) as opposed to a windmilling propeller.

All actual propeller feathering should be performed ataltitudes and positions where safe landings on estab-lished airports could be readily accomplished.Feathering and restart should be planned so as to becompleted no lower than 3,000 feet AGL. At certainelevations and with many popular multiengine trainingairplanes, this may be above the single-engine serviceceiling, and level flight will not be possible.

Repeated feathering and unfeathering is hard on theengine and airframe, and should be done only asabsolutely necessary to ensure adequate training. TheFAA’s practical test standards for a multiengine classrating requires the feathering and unfeathering of onepropeller during flight in airplanes in which it is safe todo so.

While much of this chapter has been devoted to theunique flight characteristics of the multiengine air-plane with one engine inoperative, the modern,well-maintained reciprocating engine is remarkablyreliable. Simulated engine failures at extremely lowaltitudes (such as immediately after lift-off) and/orbelow VSSE are undesirable in view of the non-existentsafety margins involved. The high risk of simulatingan engine failure below 200 feet AGL does not warrantpracticing such maneuvers.

For training in maneuvers that would be hazardous inflight, or for initial and recurrent qualification in anadvanced multiengine airplane, a simulator trainingcenter or manufacturer’s training course should be

given consideration. Comprehensive training manualsand classroom instruction are available along with sys-tem training aids, audio/visuals, and flight trainingdevices and simulators. Training under a wide varietyof environmental and aircraft conditions is availablethrough simulation. Emergency procedures that wouldbe either dangerous or impossible to accomplish in anairplane can be done safely and effectively in a flighttraining device or simulator. The flight training deviceor simulator need not necessarily duplicate the spe-cific make and model of airplane to be useful. Highlyeffective instruction can be obtained in trainingdevices for other makes and models as well as generictraining devices.

The majority of multiengine training is conducted infour to six-place airplanes at weights significantly lessthan maximum. Single-engine performance, particu-larly at low density altitudes, may be deceptively good.To experience the performance expected at higherweights, altitudes, and temperatures, the instructorshould occasionally artificially limit the amount ofmanifold pressure available on the operative engine.Airport operations above the single-engine ceiling canalso be simulated in this manner. Loading the airplanewith passengers to practice emergencies at maximumtakeoff weight is not appropriate.

The use of the touch-and-go landing and takeoff inflight training has always been somewhat controversial.The value of the learning experience must be weighedagainst the hazards of reconfiguring the airplane fortakeoff in an extremely limited time as well as the lossof the follow-through ordinarily experienced in a fullstop landing. Touch and goes are not recommendedduring initial aircraft familiarization in multiengineairplanes.

If touch and goes are to be performed at all, the studentand instructor responsibilities need to be carefullybriefed prior to each flight. Following touchdown, thestudent will ordinarily maintain directional controlwhile keeping the left hand on the yoke and the righthand on the throttles. The instructor resets the flapsand trim and announces when the airplane has beenreconfigured. The multiengine airplane needs consid-erably more runway to perform a touch and go than asingle-engine airplane. A full stop-taxi back landing ispreferable during initial familiarization. Solo touchand goes in twins are strongly discouraged.

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