Gateway Newshttp://www.me.wustl.edu/ME/orgs/aiaastl/

American Institute of Aeronautics and Astronautics, St. Louis Section

Gateway NewsGateway Newshttp://www.aiaa.org

NOVEMBER 2001

C ausal observation of twin engine propelleraircraft reveals that most configurations consist

of a forward wing with nacelle-mounted engines oneach side and a single tail empennage. However,about a third of the aircraft are of various engine andairframe arrangements. The purpose of this article isto review the alternative ways in which a twin-engine propeller-driven aircraft can be put together(excluding bi-planes and helicopters.) Interestingly,25 different configurations were identified in thisstudy, and illustrated in Figure 1. Aircraft arearranged in nine categories, as much as possible,with similar configuration traits. Each configurationcategory is identified with a sample aircraft. A fewaircraft do not fit perfectly a single category and thusspan multiple categories. Additional configurationshave been proposed, but all of the ones shown herewere actually built and flown. Baseline twin engineconfigurations have been around for years; however,the design alternatives provide the most interest.

Several of the alternate configurations are mor-phological extensions of the baseline. Lengtheningthe nacelles and shortening the baseline central fuse-lage results in a twin boom configuration. Carrythis further with elimination of the center fuselageand a twin fuselage configuration emerges.Developers have moved engines closer togetherresulting in a reduced spacing configuration. Thefinal movement of the engines to the centerline pro-duces the centerline thrust configurations as a limit-ing condition. Moving the engines (or at least thepropellers) outward results in the wing tip configura-

tions. The engines can be turned around resulting ina conventional pushers configuration. And some-times the engines are located roughly where they areon the baseline, but attached to the fuselage or wingby pylons. Aerodynamic advantages can be obtainedby switching the wing and tail, resulting in a canardconfiguration. Flying wing configurations, on theother hand, dispense with the tail (and sometimesmost of the fuselage) all together. Sketches that arestraddling the regional dividing lines in Figure 1incorporate the features of both groups.

Of the 25 configurations identified, the questionarises as to how popular is a particular configura-tion? A review of 292 aircraft: British, Canadian,French, German, international, Israeli, Italian,Japanese, Russian, and US origin provides the break-down shown in Figure 2. This list is arranged in theorder of decreasing popularity. For each of the iden-tified aircraft, a sample aircraft name is given alongwith the configuration type. For example, theLockheed P-38 is a twin boom arrangement withtractor propellers. (It shares these configurationtraits with the Fairchild C-82, C-119, XC-120, IAIAravia, and others).

Figure 2 also shows that the baseline configura-tion accounts for about 66 percent of all configura-tions, while the P-38 type is second with about 6 per-cent. The other 23 configurations make up theremaining 28 percent. Another interest note, of the25 configurations, 13 did not have a productionrepresentative.

Twin-Engine Propeller-Driven Aircraft Configurationsby John Leonard

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Figure 1. Twin-Engine Propeller Driven Aircraft Configuration

What advantages can be attributed to the alterna-tive twin engine configurations? Speed is certainlyan advantage for the majority. The twin boom P-38was much faster than contemporary WW II twinengine fighters. A twin fuselage configuration, as onthe P-82, increased speed, payload, and range overits single engine predecessor. These benefits weredue in part to reduced frontal area, drag, and morepowerful engines. The centerline thrust arrange-ments deals with a serious twin engine aircraft prob-lems; engine out controllability. With both enginesthrusting on the aircraft centerline, an engine failuredoes not produce a yaw moment, plus the torque of

the two engines cancels each other out. Drag wasalso reduced in these configurations by eliminatingsome of the interference drag between the nacellesand wing. Getting the engine off of the wing natu-rally results in a cleaner, more efficient wing. Thisinspired the Macchi M.C.72, Douglas XB-42, andDornier Do-335 (all centerline thrust engine arrange-ments) to be fast propeller driven aircraft. An aftpusher engine also tends to reduce the fuselage basedrag by pulling the air around the fuselage. TheCessna Skymaster is reported to be faster with thefront engine out than with the rear engine out.

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Twin engine flying wings have two benefitsinherent to their configuration. First, structuralweight is less because the weight and lift are spreadacross the span so that the local lift supports the localweight (engines, fuel, payload.) Second, without afuselage or empennage, drag and weight of theseitems are eliminated. Wing tip propeller configura-tions allow large propeller diameters for V/STOL air-craft, and large amounts of lift from the availablepower. In these configurations, propellers or enginesare usually shafted together to prevent a catastrophicyaw moment in the event of an engine failure.Canard configurations typically have reduced dragbecause both wing and tail produce lift. Classicalwing and tail configurations have a down load on thetail that must be compensated with additional lift ofthe wing. Each of these alternate configurations hasa particular mission advantage; however, the general

purpose baseline configurationis a compromise that satisfiesmost user requirements.

Twin engine propeller con-figurations were of more interestbefore the days of jet propul-sion. However, turboprop air-craft continue to be designedand produced for private andcommercial use. In fact, Sukhoiis presently building a new tur-boprop light transport (the S-80)of twin boom configuration.Ayres is building theLoadmaster, for FedEx, which isa side-by-side coupled tractorconfiguration. The Bell/Boeingteam is just starting production

of the V-22 with wingtip mounted engines and pro-pellers. Adams Aircraft is starting certification ontheir M-309 centerline thrust general aviation twin.The Rutan Defiant canard tractor/pusher and theEmbraer/FMA CBA-123 fuselage pylon mountedpusher are recent designs. In the future twin enginepropeller configurations will continue to be devel-oped along with the more common baseline configu-ration. However, special missions may require inno-vative solutions.

SUKHOI S-80

ADAM M-309

AYRES LOADMASTER

Figure 2.

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American Institute of Aeronautics and AstronauticsSt. Louis Section 2001 - 2002 Council Roster

Office Incumbent Address Telephone Fax E-MailChairman Margaret A.R. (Peggy) Holly MC S276-1009** 234-3513 234-5010 margaret.a.holly@boeing.comVice Chairman Andy Hesketh MC S270-3800** 232-2584 andrew.a.hesketh@boeing.comSecretary Bob Dowgwillo MC S106-7126** 234-1013 robert.m.dowgwillo@boeing.comTreasurer Karen Copper MC S001-2700** 234-5742 234-2369 karen.k.copper@boeing.comAdvisors Dianne Chong MC S001-2700** 232-9719 234-2369 dianne.chong@boeing.com

John L. Mohr 11638 Summerhaven Dr. 567-3398 JLMohr@aol.comSt. Louis, MO63146

Rudy Yurkovich MC S106-7126** 233-2563 777-1328 rudolph.n.yurkovich@boeing.comRegion V Rep Larry Brase MC S064-1092** 777-5586 777-5161 lawrence.o.brase-jr@boeing.com

Committee Chair Address Telephone Fax E-MailArrangements Walt Reschke MC S064-3449** 777-4038 walter.j.reschke-jr@boeing.comAttendance Andrew Cary MC S106-7126** 234-1830 andrew.w.cary@boeing.comCareer Enhancement Steve D'Urso MC S064-2809** 233-5441 steven.j.durso@boeing.comEducation Marty Ferman 1452 Old Farm Dr. 542-0703 997-8437 fermanma@slu.edu

St. Louis, MO 63146EducationHistorian Fred Roos MC S102-1431** 234-9935 233-2918 frederick.w.roos@boeing.comHonors & Awards Ray Cosner MC S106-7126** 232-6481 raymond.r.cosner@boeing.comMembership Joe Stemler MC S107-7250** 232-3362 232-3722 joseph.n.stemler@boeing.comNewsletter Dave Morgan MC S106-7250** 234-1919 232-3722 david.e.morgan@boeing.comPilot Education Jeff Larrick MC S102-2272** 232-3455 jeffrey.c.larrick@boeing.comPre-College OutreachPrograms Bill LaManna MC S276-1007** 234-3526 william.j.lamanna@boeing.comPublic Policy Dick Pinckert MC S034-1126** 234-0623 richard.e.pinckert@boeing.comPublicity-Internal Bruce Scheidhauer MC S270-4360 233-0759 234-0241 bruce.r.scheidhauer@boeing.comService Projects Gary WhiteTech. Specialist Mtg.Webmaster John Donigan MC S064-1426** 234-4103 777-1139 jdonigan@swbell.netYoung Members Jeff Gray MC S270-3200** 233-6912 jeffrey.c.gray@boeing.comYoung Professional Ron Smith MC S106-2103** 232-4671 232-1454 ronald.e.smith@boeing.comAwardsStrategic Planning Larry Brase MC S064-2355** 777-5586 lawrence.o.brase-jr@boeing.com

** Boeing Address: The Boeing Company, P.O. Box 516, St. Louis, MO 63166

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Saturday, 21 July 2001 marked the 40th anniversary of Gus Grissom’s infamous suborbital flightand the accidental sinking of the Liberty Bell 7 spacecraft. The St. Louis Section of AIAA along

with the Boeing St. Louis Leadership Association and INCOSE co-sponsored a commemorative event.The recovered and restored Liberty Bell 7 spacecraft was on display for the summer at the St. Louis

Science Center during its’ national tour.

The spacecraft was actually “home” for the anniversary! The Mercuryspace capsule was designed and manufactured in St. Louis at McDonnellAircraft Company. Many of the folks who had worked on the projectattended the event. In addition to the touring display, Boeing’s Historian,Larry Merritt provided many photographs and memorabilia items from hispersonal collection and the McDonnell archives. It was a truly unique andspecial display for those involved in aerospace in St. Louis.

One hundred-thirteen folks came out to view the display. GeorgeBaldwin, a retired McDonnell pad foreman at Cape Canaveral brought hiscollection of Mercury and Gemini memorabilia to share. Some grandchil-dren attended and learned not only about the early days of space explo-ration but also of their grand-parent’s part in history. It wasa wonderful night to reminisceand reacquaint with our ownhistory.

Liberty Bell 7 at the Science Centerby Karen Copper

OLDNEW

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The second Family Fun Day Paper Airplane Contest was held on Saturday, 5 May at the LadueMiddle School. Fifty-seven people attended and their enthusiastic feedback indicated a desire for

this to be an annual event! Participation was as follows:

A huge “Thank You” goes to:

Ken Blackburn for speaking, providing design guidance, demonstrating and judging the events. Kendonated copies of his latest paper airplane publications as attendance prizes.

Martin Long for arranging our use of the Ladue Middle School’s gym and cafeteria.

Andrew and Zachary Cary for helping to enter the contest results and prepare lunch.

Age Category Participants Time Aloft Winner Distance Winner 2 - 4 8 Zachary Zuckerman 2.6 sec Peter Jone 27.6 ft 5 - 7 3 Alexander David 5.4 sec Sam Zuckerman 63.3 ft 8 - 11 13 Daniel Nixon 5 sec Mitchell Kramer 57.2 ft 12 - 15 6 Tom Kovacs 6.7 sec Christopher Peters 76.5 ft Adults 13 Gene David 9.9 sec Mark Bierenbaum 83+ ft

Second Family Fun Day Paper Airplane Contest

OLDNEW

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ChairpersonPeggy Holly

Vice ChairpersonAndy Hesketh

SecretaryBob Dowgwillo

TreasurerKaren Copper

AdvisorsDianne ChongJohn L. MohrRudy Yurkovich

Non-ProfitOrganizationStandard A

U. S. POSTAGEPAID

Florissant, MOPermit No. 121

NOVEMBER 2001

2001 – 2002 St. Louis Section Officers and Council Members

Monday, 7 January 2002,5pm - 7pm, in Boeing Building100, Conference Room 2A(behind the main auditorium) General

AviationSafetySeminarSaturday, 19 January 2002, 0730 to 1400Parks College of Aviation,St. Louis UniversityAnheuser Busch Auditorium,John Cook Hall

January Dinner Meeting“Strategic Thinking with Scenarios”presented by Solutia Inc.Tuesday, 15 January 2002Boeing Bldg 100 Prologue RoomAdvanced Reservations Required ofnon-Boeing Employees.