Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by...

8
'/! ' i. JJ O O (8 November 1996 St. Louis has launched into the current Program Year with lots of energy and plans for informative, interesting, and useful programs for all members. Already we have hosted presen- tations dealing with Smart Structures, UFO's, the JASSM program, and the affordability initia- tives of JDAM. Donn Gruensfelder is once again preparing for his annual Tour-de-force in the "Pi- lots Super Safety Seminar"* to be held in January 1997. The local members who are affiliated with the AIAA Nation Technical Committee (TC's) have been contacted and told to promote our Section as host site for future conferences and seminars. The St. Louis visitors and convention bureau has been contacted and is assisting us in prepa- ration of proposals to offer the TC's, showing why St. Louis is an ideal place to host large, annual meetings. Planning and executing these meetings take a lot of time and effort, but the payoff is worth it. More of our members will be able to attend the conferences if held locally, and many more will be able to deliver papers at the conference. Our Student Chapters also benefit from being able to attend a locally held National Conference. These meetings are booked several years in advance (Just like the Olympics), so the advanced "Marketing" the Council is doing now begins to payoff in 1999 and later years. If you are interested in helping land and plan for one or more of these please feel free to contact me at 314/ 234.6483 or e-mail at [email protected]. Once again your Section is underwriting Pam Luetkemeyer's effort in decorating a Christmas Tree to be auctioned off at a charity gala benefiting autistic children. This is one activity of providing service to our community stemming from Dianne Cheng's service projects committee. Our hats are off to Bill Bernzott and Dick Pinkert for Leading last year's young member and public policy committees to Third and Second place Awards in the AIAA large section category Nation- ally. Each of the committee chairs put in a lot of effort representing our Section and it's great to see that effort recognized. Please feel free to contact any section chair and offer your services. With YOU, we can sweep the awards table next time around! s Supersonic Propellers by John M. Leonard upersonic propellers interest developed in have a tip Mach number as high as 1.89 due to the high rotational speed. Flying at Mach 0.8 with a supersonic prop would produce a tip Mach number slightly in excess of Mach 2. A correlation of aircraft maximum velocity ver- sus the engine horsepower for 150 propeller driven fighters, mostly of WWII vintage, is shown in Figure 1. Flight velocity increases with horsepower up to about 1500 hp; thereaf- ter, more power does not result in additional speed. Shock waves on the transonic and continued on page 2 the early 50's with the advent of turbo- prop engines coupled with speed limitations of traditional propellers. Several aircraft had pushed their propeller tips through the sound barrier during dives. For example, in August of 1943 an instrumented P-47C reached a Mach number of 0.86 in a dive from about 33,000 feet (Ref. 1). Assuming a 13 foot diam- eter conventional prop turning at 1260 rpm, the tip Mach number would be approximately 1.15. However, a static supersonic prop would

Transcript of Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by...

Page 1: Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate

'/!

' i.JJ

OO

(8

November 1996

St. Louis has launched into the currentProgram Year with lots of energy and plans

for informative, interesting, and useful programsfor all members. Already we have hosted presen-tations dealing with Smart Structures, UFO's,the JASSM program, and the affordability initia-tives of JDAM. Donn Gruensfelder is once againpreparing for his annual Tour-de-force in the "Pi-lots Super Safety Seminar"* to be held in January1997.

The local members who are affiliated with theAIAA Nation Technical Committee (TC's) havebeen contacted and told to promote our Sectionas host site for future conferences and seminars.The St. Louis visitors and convention bureauhas been contacted and is assisting us in prepa-ration of proposals to offer the TC's, showingwhy St. Louis is an ideal place to host large,annual meetings. Planning and executing thesemeetings take a lot of time and effort, but thepayoff is worth it. More of our members will beable to attend the conferences if held locally, andmany more will be able to deliver papers at theconference. Our Student Chapters also benefit

from being able to attend a locally held NationalConference. These meetings are booked severalyears in advance (Just like the Olympics), so theadvanced "Marketing" the Council is doing nowbegins to payoff in 1999 and later years. If you areinterested in helping land and plan for one or moreof these please feel free to contact me at 314/234.6483 or e-mail at [email protected].

Once again your Section is underwriting PamLuetkemeyer's effort in decorating a ChristmasTree to be auctioned off at a charity gala benefitingautistic children. This is one activity of providingservice to our community stemming from DianneCheng's service projects committee.

Our hats are off to Bill Bernzott and DickPinkert for Leading last year's young member andpublic policy committees to Third and Second placeAwards in the AIAA large section category Nation-ally. Each of the committee chairs put in a lot ofeffort representing our Section and it's great to seethat effort recognized. Please feel free to contactany section chair and offer your services. WithYOU, we can sweep the awards table next timearound! •

sSupersonic Propellers

by John M. Leonard

upersonic propellers interest developed in have a tip Mach number as high as 1.89 due tothe high rotational speed. Flying at Mach 0.8with a supersonic prop would produce a tipMach number slightly in excess of Mach 2. Acorrelation of aircraft maximum velocity ver-sus the engine horsepower for 150 propellerdriven fighters, mostly of WWII vintage, isshown in Figure 1. Flight velocity increaseswith horsepower up to about 1500 hp; thereaf-ter, more power does not result in additionalspeed. Shock waves on the transonic and

continued on page 2

the early 50's with the advent of turbo-prop engines coupled with speed limitations oftraditional propellers. Several aircraft hadpushed their propeller tips through the soundbarrier during dives. For example, in Augustof 1943 an instrumented P-47C reached aMach number of 0.86 in a dive from about33,000 feet (Ref. 1). Assuming a 13 foot diam-eter conventional prop turning at 1260 rpm,the tip Mach number would be approximately1.15. However, a static supersonic prop would

Page 2: Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate

continued from page

Maximum 600-Velocity-mph _—

400-

300-

200-

100-

0 1000 2000 3000 4000 5000 6000 7000Horsepower

Figure 1 - Speed Limit of Propeller Driven Aircraft

supersonic sections of the propeller bladencrease the local drag and reduce efficiency.

Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate more efficiently at super-sonic speeds. These propellers were character-.zed by: (1) thin blade sections and (2) highrotational speeds. Supersonic propellers;ypically have a rotational Mach number of 1.0at the hub and 1.7 at the tip. Thin bladesections are a requirement for supersonicoperation; however, high rotational speedsinduce large centrifugal stresses. Conse-quently, supersonic propellers require bladesconstructed of high strength steel. Efficiencyifthese supersonic propellers designs vs.traditional World War II fighters can be seenin figure 2.

PropellerEfficiency

100 <

80-

60-

40-

20-

SupersonicPropeller

World WarHPropeller

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

Mach Number

Figure 2 - Comparison of Propeller Efficiency

Two research aircraft, XF-88B and XF-84H,were developed to investigate the validity ofsupersonic propeller concepts. The McDonnellXF-88, predecessor to the F-101 Voodoo, wasthe prime testbed for NACA development. AirForce investigations used the prolific F-84airframe, with engines provided by the U.S.Navy. Characteristics of these two unique testaircraft are summarized in Table 1 and illus-trated in Figures 3 and 4.

The XF-88 was modified by McDonnell toincorporate an Allison XT-38 turboprop en-gine, while retaining the two main turbojetengines. An offset nose landing gear wasrequired to provide necessary turboprop room.An engine inlet was added on the left and asmaller oil cooler inlet on the right side of thenose. Gearbox ratios could be altered to pro-vide 1700, 3600, and 6000 propeller rpm's.Propeller flight characteristics were gatheredby blade strain gages, a nose mounted pres-sure rake, and fuselage microphones (Figure5). To accommodate the instrumentation, onefuel cell was removed.

Table 1 - Aircraft with Supersonic Propellers

Parent AirframeNumber Suit/ FlownLength /Span -FtWing Sweep Q C/4 - degEngine for PropellerEngine HorsepowerNumber of BladesProp Diameter - ftPropeller RPMAuxiliary EnginesTest OrganizationFirst Flight Date

Last FlightNumber of Flights

Number of Flight Hours

Max Speed Achieved

XF-88BMcDonnell XF-68A1/158.0/39.6735Allison XT-38- A- 526504or310.0, 7.2, and 6.851700 or 35002xJ-34'swithA/BNACAJets only -April 14, 1953Prop also- April 24, 1953195616 (8 with prop turning)by McDonnell. T? byNACA9.25 (2.07 with propturning) by McDonnell. 77by NACAM=0.94(Q,97 with propfeathered) by McDonnell,M=1.1inadivebyNACA

XF-64HRepublic RF-84F2/151.5/33.540Allison XT-40-A-15850312.03000noneUSAFJuly 22. 1955

FTotetty 195511

7.5

about 600 mph

2

Page 3: Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate

Figure 3 -NACAXF-88B Figure 4 - USAF XF-84H

RootRoof 6tade~o'«j!«

recorderS*ot«c ere Mure erYO* aT9-« pfoces

Figure 5 - XF-88B Instrumentation

When the XF-88, S/N 1, returned to St.Louis for modification it had flown 126 hoursand 49 minutes. After modification,McDonnell performed acceptance flight evalu-ations to check its suitability as a high speedturboprop research aircraft. Each of the 16flights lasted between 23 and 48 minutes, dueto reduced fuel tankage. Inflight turbopropoperation took place on 8 flights, with 24minutes being the longest inflight operation ofthe propeller. The XF-88 sister aircraft, S/N 2,became the NACA parts support vehicle forthe research program.

Low speed testing, with the XT-38 turbo-

prop running, required about 3/4 rudder andsome aileron to counteract the engine torque.Flight tests conducted in St. Louis discoveredthat the modification had reduced the longitu-dinal and directional stability. Thus, it wasconcluded that the turboprop should not beoperated during takeoff. Typical takeoffs andlandings were made with the propeller feath-ered and clocked in the X position to providethe maximum propeller blade ground clear-ance. This unique configuration was one dayreported to the Lambert tower: saying anaircraft had taken off without the enginerunning. Since fuel tank volume was reduced

Page 4: Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate

for instrumentation and test time limited; theXT-38 was used to climb to the test altitude.Flight tests noted that aileron control wasmarginal during cross wind landings andtakeoff distances long in warm weather. Firstgeneration afterburners frequently quit work-ing during the takeoff run.

NACA was aware of the unacceptable noisecreated by the propeller from USAF investiga-tions with the XF-84H. Accordingly the firsttest NACA performed with the XF-88B cen-tered on static noise evaluation. In addition topropellers, NACA tested various spinnershapes, advance ratios, and gearbox driveratios. Two of the test propellers and spinnersare illustrated in Figures 6 and 7. It is inter-esting to note that of the three 3-bladed pro-pellers tested by NACA each had a lower tipMach number than the one previously tested.This must have been an attempt to deal withthe noise problem.

NACA intended to test a family of super-sonic propellers. Five different propellers wereconstructed, of which four were flown(seeTable 2).

Figure 7 - XF-88B With 60° Conical Spinner

Table 2 - XF-88B Test Propellers

No ofBlades

43334

Diameter-R

10.07.2

10.06.854.0

PropellerRPM

16753500170017006000

StaticTip

MachNo.*0.881.330.890.611.26

Max.Mo

Reported

0.941.010.950.96not

flown

Max.Tip

MachNo.'1.291.671.301.14

III GP69AO€Q05

Figure 6 - XF-88B With 60° Spherical Spinner

* Mach numbers are affected by the air temperature.Exact flight test are not known, so these numbers arecomputed for a typical flight condition of 30,000 ft,standard day.

Air Force supersonic propeller flight testswere carried out with the Republic XF-84H.This F-84 conversion was created by replacingthe single J-65 turbojet, 7,800 Ib. thrust, withan Allison XT-40. This turboprop engineproduced 5,850 shaft horsepower along with1000 Ib. of residual jet thrust. Other XT-40engine installations turned a 6-bladed counterrotating propeller (Douglas XB2D Skyshark,Convair XFY, & Lockheed XFV VTOL re-search aircraft); however, this version turnedonly a three bladed single disk propeller. Thisengine conversion made the XF-84H the mostpowerful single disk propeller driven aircraftin the world. The next most powerful wouldbe the Goodyear F2G Corsair or Martin AM-1Mauler at 3000 hp. Propeller torque was sohigh that Republic added an anti-torque fin to

Page 5: Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate

the upper fuselage just behind the cockpit. Araised horizontal tail was incorporated topresumably keep the control surfaces out ofthe prop wash. Takeoff with high propellertorque required gradual throttle input, asspeed and rudder power increased.

The XT-40 turboprop consisted of two T-38turbine units connected to the propellerthrough a gearbox. Typically a 3 or 4 footextension shaft connected the turbine unitsand the gearbox. On the XF-84H the T-38power units were located behind the wingleading edge connected to wing root inlets.This midship installation necessitated longextension shafts to the nose mounted gearbox/combiner.

Two XF-84rFs were built; however, only oneactually flew. Continual problems with thehydraulic system, engine, and power transmis-sion, resulted in 11 emergency landings.Noise generated by the propeller causedground crew members within several hundredfeet to experience acute nausea. Ground crewsunofficially nicknamed the aircraftThunderscreech." Currently this aircraft is

located on a pedestal at Meadow's Field,Bakersfield, California.

Although the theory for supersonic propel-lers indicated improved high speed perfor-mance, operational considerations made themimpractical. Also, about this time turbojetengines began replacing propellers for all highperformance applications.

References in Article1. Journal of Aircraft, July-Aug 1970,

page 2972. NACA Misc. Report L57C14-153. NACARML55I214. NACARML56D20a5. NACARML57E206. NACA TN 34227. NACA TN 35358. NACA TN 40599. NACA TN 4172

10 NACA TN 438911 NASA Memorandum 4-18-59L12. NASA Memorandum 4-19-59L13. Air Enthusiast 48 dated Dec 1992 to

Feb 199314. X-Fighters, USAF Experimental and Proto-

type Fighters, XP-59 to YF-23

Creve Coeur Airport Rises AgainBy Dr. Marty Ferman and Albert Stix

Several years ago the Great Midwest Floodsof 1993-1995 damaged Creve Coeur Airport.Since then the airport has been rebuiltthrough much hard work. Creve Coeur Air-port is located on the Missouri River floodplain, west of Lambert St. Louis InternationalAirport. This classic general aviation field wasonce part of the Dauster Farm which stillajoins the airport.

Currently, the airport is home to 60-80flyable antique aircraft. There are some 180aircraft in current residence now at CreveCoeur Airport. Expansion plans are underwayto accommidate 220 aircraft in the next few

years. More hangars and an expanded "ShadePort" open side storage area will accommodatenew aircraft.

The St. Louis Historical Aircraft Restora-tion Museum hangar was heavily damaged bythe raging flood waters (figure 1). The re-paired museum building is now open andconstruction is underway to double the displayarea.

An example of a refurbished aircraft, aRussian Shavrov (Sh-2), is shown in figure 2.This aircraft is on display at the Museumalong with 75 other vintage aircraft of inter-est.

Page 6: Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate

Figure 1 - Antique Aircraft Museum After the Flood and After Reconstruction

Figure 2 - Rehabbed Antique Russian Seaplane

Other airport activities include assembly ofRussian YAK 55 acrobatic aircraft. Figure 3shows some of these aircraft in various stagesof assembly. Major subassemblies arrive fromRussia with final assembly here. This aircraftis in high demand by acrobatic groups becausethe design can withstand flight maneuveringloads of 9-G's.

Creve Coeur Airport has become increas-ingly more important to local aviation with theclosing of Weiss Airport. Recognizing theseconstraints on local aviation, the FAA hasrecently designated Creve Coeur Airport as a6

Figure 3 - Russian YAK 55's inVarious Assembly Stages

feeder Airport for the St. Louis area.A visit to this quaint general aviation air-

port will be well worth while. It is locatedwest of Lambert St. Louis Airport, at the bendin Creve Coeur Mill road just south and westof 1-70 and the Earth City interchange. Forthose wishing to accomplish two things atonce, the December AIAA dinner meeting willtake place at the Restoration Museum. Acasual pizza dinner is planned before a guidedtour of the museum and workshop area. At-tendance is limited, so call early! •

Page 7: Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate

Awards

Bob Krieger presents the '95 - '96 AIAA Technical ManagementAward to Charlie Dillow for his JDAM Program Leadership

Congratulations to the following Section Vmembers promoted to associate fellow:

Richard M. AndresMark D. BassKevin D. CitursJohn F. DonovanEdward A. EiswirthWayne L. Ely

Kakkattukuzhy M. IsaacSwami KarunamoorthyLeslie R. KovalLinda D. KraiFrank LaackeMartin J. MorrisGary P. White

Web Sites of Interest

International Plastic Modellershttp://ssnet.com/~hpyralph/ipmsusa.html

Aircraft Design Information Sourceshttp://www.aoe.vt.edu/Mason/ACinfoTOC.html

300° Below Cryogenic Temperinghttp://www.tecsolv.com/cryo/

Have some interesting Web Sites of your own??Share them with the membership. Send yourinputs to:

Dave Morgan,MDA m/s S064-2904,e-mail: [email protected] 314/234.1919 or fax 314/233.9997.

St. Louis Branch of International Plastic Modellers,December MeetingBrighton Trails County Library, McKelvy Rd.Tues, Dec. 10 @ 7:30 p.m.

Send us your e-mail address - Save A Tree

Address to:

[email protected]

Page 8: Supersonic Propellers - American Institute of … · Supersonic Propellers ... Studies conducted by NACA and U.S. pro-peller companies identified propeller designs;hat could operate

Non-ProfitOrganization

Bulk RateU.S. POSTAGE

PAIDFlorissant, MOPermit No. 121

Future AIAA Events

St Louis Aircraft RestorationMuseum at Creve Coeur Airport

Thursday, 5 December5:30 pmPizza DinnerLimited Capacity

AIAA CouncU MeetingMonday, 2 December5:00 pm - 7:00 pmMDA HQ, Level 2SConference Room