Low & Slow Issue 13 1972

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Official booklet series of Self-Soar Association

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13. 2 SELF-SOAR ASSOCIATION REPORT Welcome fledglings! Open your notebook and kccp a chapter on "How TO KEEP Flying 11. Seems as though some have forgotten about this chapter..

We hope Oave 1 s knee bruise gets well soon; Die~ leg bruise: and we hope the broken leading edge

*Frank Colver dynamically soared a few feet in his Colver Sail wing,. ••• off level ground! Its !light from 10 {t. release on level ground(2nd flight) showed evidence of the wings promise.

More soon in L&S on this wing. See past L&S #5.

tubes all get repaired soon. SAVE THE PIECES!

•SAFETY: Watch the: wind spc«i. Over 15 m_ph.

HELP NEEDED: All money was spent on winds ,-hould be avoided unless it is very steady, print shop equipment and addressing system £or your era.ft is very controllable, and further that your coming benefit •••• so please hand the info. you arc very experienced. Take hcir:d and fly mere! shee'::b to interested persons only. H14 will be :«EASTER reverently: He ls Risen.

Peace to you. out in one week and ff 15 in. two more weeks to p..t *Spring is ruffling the feathers of £as terr. brothers .. us close to what is happening. WOW: Skyboa:rd Many good reports will be published about them.

HI is close at hand ••.•• that is. in one of the Contact for professional dealings: Mike Markowski several branches of low .-:ind slo\v flying. we of Man-Flight Systems Engineering• P.O. Box 375 arc fairly sure of corning upon a design that will Marlboro. Mass. 01752. satisfy most all the first year goals of Self-Sco.r. :«OTTO MEETS WILL BE HELD MAY 20-21 at many See issue H14 and then H15 !o:r the Koman Kite:i: places throughout the nation. SEND JN YOUR PLACE Independent of Cronk. Koman zooms ahead to the ~o people local to you might !ly bcsi<le you. Keep th= reaches of sa:ilwing simplicity. These new birds affair safe for the byst,lnder: assure yourself of a. will be greatly evident at the coming: Otto S-S Med:. flight future this way.

II 14 and II 15 will be out soon enough fo:r yo\1 to put CREDITS FOR THIS ISSUE: irnprovements on these birds i! you so choose.

Cover: Bob Lovejoy tandem concept ~nd speedy Plans will be shared for .Kom.an Kite ff I in H14 and self-hunch concept. Tha.nk )OU, Bob. Koman Kite 1'2 in H15.

Share with others by Center-Cold: Photogr.:,,ph by father. Doug, of handing out the Scl!-Soar applic.\tion, plc:i.sc. We son Ken Privett in serious biplane manaim at giving mankind oursdvcs .,s regard super po,vcrcd augmented flight system. available self-soaring personal wings..

"M,1n-Powcrcd :Flight''•• .courtesy of A:rthur Congratulations to Chuck Slus.uc,-.yk !or aidSlotkin !or reprint privilege. editor of ing East~rncrs on matcri."l.ls: 4200 Roy.,lton Rd. A. I. A. A. Student Journal. Thank you.

Brecksville, Ohio 44141..

Dick Henderson for !inc cartoon.

Issue #13: Copyright @ by Joe Faust, 1972

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It may not be the sands of Kittyhawk, S.C., but Self-Soar Assoc. President Joe Faust is still able to test air-foils behind his house at Venice beach. The interna-

tional organization puts its members in the air by foot-launch and brings them back to earth the same way.

(Evening Outlook Pholo by Mo!.,e!. Armslr~mg)

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'Last Flight Frontier'

One Jump Leads To Another

By DICK BETIS Evening Outlook Staff W,iter

In 1960, former Culver City High School track star Joe Faust went to the Olympic Games in .Rome.

Italy, and high-jumped 7 feet. 2 inches.

Twelve years later, Faust is still jumping and. so far, has gone as high as 100 feet.

Of course, nowadays he has a little help.

Faust, of 59 Dudley Ave ..

Venice, is the founderpresident of Self-Soar Association, a group dedicated to conquering "man·s last frontier in flight. ..

Individual Flight ~- We have spaceships going to the moon ... Faust ~aid. "but individual flight 1s yet to be conquered.""

This will be the last chapter in mechanized fli ht.". ftie organization·s 1.100 members - nationwide and from as far away as Australia. England. Ger-

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many and France - build their own air-foils for a cost of anywhere between $30 and $130. There are about 300 members locally.

They launch themselves from gentle slopes.

The aim of the association .is to promote safety consc10usness, share ideas and design plans, and put man mto the air under his own power, Faust said.

The record flight, Faust said, was achieved last year when a club member stayed m the air one hour and four minutes.

Private Pilots "About five per cent of our members have private pilots licenses, but they are unnecessary for our group,.. Faust said. "We don ·t go any higher than 500 feet and stay out of. regulated airspace. :·And we don't identify with human kites or that sort of thing. We use only leg-power and a wing.·· Faust. who also is editor 01 the club's official

JOE FAUST

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CAUTION THIS,AREA SUBJECT TO EXTREME NOISE

ANq JET BLAST

1 Man-Powered Flight' is gi..-en below, written by 1.S.S MPA !:IL"\!! leader Professor John Mc Masters, by permission of Arthur Slotkin of A. l., A. A, Student Journal. lt is .l fund.,mental document for one launching a study of the problem o! m,"ln-powcrcd flight. Coming in future issues of I.&S will be a development o{ man-pO\\'Cred Oight idC,'\S by Dr. Keith Sherv,dn of E:.ngl."lnd who just recently ne,v sorne 30 feet 9'' o!f the level ground in C."llm a.irs.

The centerfold is not a p,nt of the article, although the project by Dougl:i.s and Kenneth Privett must represent the bcg~nning o! :in er,"\ of 'Hang: Loose' ,nan-powered :1.ugmcnted gliding:{Plcasc not<:: tliat the µrivctt ship i!!. 1,,uch modified from the l.."lmbic •H:tng Loose• biplnnc hang-glider.

We arc looking forward to rnan-po,.vcrcU augmented Kom:m Kite 2 systems to be sensed and :revicwccl in I.&cS i/15. ((Please, all ornithoptcr cnthusi.asts. help me get an ornithoptcristt list: Write to S. David Coleman. ZOOS Springbrook Ave., Rockford, Ill, 61107 Colem.:m will org,-inizc the list for Self-Soar Association.))

Man-Powered Flight John H. McMasters, Curtis J. Cole, and David A. Skinner Despite the spectacular advances made in the aerospace sciences during this century, one of man's ageold dreams remains largely unfulfilled-to fly by his own muscle power. Since before the time of the ancient Greeks with their famous legend of Daedelus and Icarus, 1 men have tried to construct devices which would allow them to fly in simulation of the birds. Although almost completely overshadowed since 1900 by the advent or modem powered flight, made possible by the development of sufficiently lightweight and reliable internal combustion engines, the dream of achieving flight by human muscle power alone was kept alive by a few enthusiasts in Europe and the United States. Little real progress was made, however, and with the exception of a few noteworthy projects such as the Gerhart hexaplane' built at McCook Field in Dayton, Ohio, in 1923 and the very interesting "Schwinguin" 3 or~

nithopter designed by Lippisch and successfully flown in J929, almost all man-powered aircraft designed up to that time were based more on whimsy than on sound scientific principles. An excellent historical survey of early attempts. fanciful or not, to achieve man-powered flight (MPA) is contained in the book Flug durch Muske/kraft,• published in Germany in 1936.

The first machine representing what has become the "conventional" approach to man-powered aircraft design was the German Haessler-Villinger "Mufti"• built in 1935. This aircraft, designed to compete for a prize offered by the Polytechnische Gesellschaft at Frankfurt, made many successful flights between 1935 and 1937. The best of these flights occurred on July 4, 1937 when a total distance of 720 meters in a straight line was covered, following a catapult launch. On this flight, 615 m. were flown at a constant height of 3 m. This was an impressive achievement considering the state of aerodynamic and structural technology at that time,

J. H. McMasters and D. A. Skinner are graduate in-

structor and graduate teaching assistant, respectively, at Purdue University. C. J. Cole is an instructor nt Indiana State University.

and the fact that the machine had been designed on the basis of overly optimistic estimates of human power output.

A contemporary project of considerable significance was the Bossi-Bonomi "Pedaliante'''1 built in 1936. Again, many successful flights were made following catapult launches; the longest of these, a flight of 900 m. made in December 1936. The Bossi-Bonomi is generally credited as the first MPA to be fitted with a wheel driven by the pilot, for attempts at maa-powered take-offs. There is still some controversy over whether the "Pedaliante" actually accomplished this feat. Although the BossiBonomi's performance was impressive for its day, it could have beer, even better had not Italian civil air regulatioas forced the aircraft to be designed to a much higher load factor than was necessary, resulting in the machine being considerably oveiweight.

Perhaps the most important contribution to the advancement of man-powered flight made during the l 930's was the research done at the Muskellluglnstitut, established in l 935 at Frankfurt by 0.

Ursinus, the published of Flugsport magazine and well-known aviation entrepreneur. Of particular importance was the very extensive and thorough research done mainly by Gropp' on human power output and methods of power extraction. This informatioa has been one of the basic sources for almost all serious man-powered aircraft design work since its publication in 1936/37.

World War II brought man-powered flight experimentation to a halt. Following the war, a few articles appeared in the popular press describing prewar machines and speculating on future prospects.

Little new work was done, however, except for a few design studies. Notable among these was one done by Raspet8 at Mississippi State University in 1952,. based on part of his work on sailplanes and boundary-layer control.

In the mid-l 950's, Shenstone• and Nonweiler10 in Britain began lecturing on man-powered flight, with the result that a Man-Powered Aircraft Committee was formed at the College of Aeronautics at Cranfield. This committee later became a .Group within the British Royal Aeronautical Society

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crossed at a minimum height of ten feet, there being no altitude limitation for the rest of the course. No stored energy devices or lighter-than-air gases were permitted, and the machine had to be controlled by the crew for the duration of the flight. No limit was set on the number of crew members.

In March of 1967, two important changes were made in the Kremer Competition rules. The prize was doubled to £ 10,000 ($24,000 at the present rate of exchange) and the competition was opened to entrants of any nationality. The other rules remained unchanged. ( See Kremer Competition rules, page 12.) At the same time, an additional competition was established, still limited to Commonwealth citizens, for flights around a simpler "slalom" style course. Prizes of £2,500, £ 1,500 and £1,000 are offered for the first three MPA's

(RAeS). An excellent summary of 'the formation of the committee and its subsequent activities is contained in a paper by Shenstone. 11 The role played by the Man"Powered Aircraft Group in stimulating MPA development during the last decade has been extremely important.

By 1959, sufficient interest had been generated in Britain to encourage the industrialist Henry Kremer to establish the £5,000 Kremer Competition in November of that year. The basic rules for the original competition, which specified that the aircraft had to be designed, built and flown by citizens of the British Commonwealth, required that the aircraft take of] and fly a fi._'llre-eight course, solely by human muscle power, around two pylons placed one-half mile apart on a level field. The rules further stipulated that the starting and finish lines be Table 1.

Characteristics of selected man-powered aircraft*

Southampton Haessler- Bossi- SUMVillinger Bonomi PAC Country First flight Wing span (m.)

Wing area (sq. m.)

Aspect ratio Empty wt. (kg) Wing wt. (kg) Flying wt. (kg) Wing loading (kg/cm 2)

Germany Italy Aug. !935 1936 13.5 17. I 9.65 21.4 18 .8 13.4 36. 7 97.5 24.0 44.8 11! .5 162 11. 5 7.60

Root airfoil

Go 535

Hatfield Puffin I

Puffin II

Linnet II

Linnet III

Britain Britain Nov. Nov. 1961 1961 24.4 25.6 27.9 30.7 21. 3 21.4 58.0 53 .5 36.2 29.5 121 122 4.33 3.94 NASA Wortmann 65,-818 FX-05-191

Britain Aug. 1965 28.4 36.3 22.2 63.5 38.5 131. 5 3.62 Wortmann FX-63137

Japan Feb. 1967 22.3 26.0 19.1 44.7 19.5 102 3.92 NASA 63,-1218

Japan Mar. 1970 25.3 30.2 21.2 50.2 22.0 100--105 3. 59-3. 77 NASA 8418

Ottawa

McAvoy MPA-1

SatoMaeda SM-OX-I

Herts.

Liverpool U. "Toucan" Weybridge "Liverpuffin" Country Date completed Wing span (m.)

Wing area (sq. m.)

Aspect ratio Empty wt. (kg) Wing wt (kg) Flying wt. (kg) Wing loading (kg/m') Root airfoil

Britain 1971 37.5 55.8 25 65.8 36.3 202 3.61 NASA 63,-618

Nihon Univ.

Britain 1971 36.7 45.1 30 58.9 39 127 2.82

Britain !971 19.8 29.6 13.3 56.5 33.0 127.0 4.29 Wortmann

FX 63137

Canada 27.4 41. 7 18.0 95 57 237 5.67

U.S. 1963 16.5 24. 7 11.0 52.0 23 120 4.88 NASA 65-915

Japan Aug. 1970t 22.0 27.D 17 .9 55.0 110 4.07

* Some discrepancies exist between various sources of published data. The most recent published data have been used where the actual designers' estimates were not available. t First flight.

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capable of negotiating a half-mile course around three pylons placed at one-quarter mile intervals.

The aircraft may land at each end of the course, but the total flight through and back must be accom-. plished within a period of one hour. So far, none of lhese prizes has been claimed and if. there are no winners by December 31, 1973, the Royal Aeronautical Society, as trustee of the prizes, will consider revision of the rules and extension of the deadline.

The establishment of the Kremer competitions has stimulated a great deal of effort in MPA design and construction, but in the process the competitions have concentrated work on the development of "conventional" aircraft layouts, to the near exclusion of both helicopters and omirhopters. It appears that man-powered helicopters have little chance at present of attaining the three-meter altitude required by the competition rules." Although showing some promise aerodynamically ( there is considerable controversy concerning the relative efficiency of propellers and flapping "wings" for providing thrust at MPA flight speeds), omithopters must necessarily be rather complex mechanically and in the light of the present state of materials and structural technology, they must be considered a marginal prospect within the time scale of the present Kremer competitions. It is hoped that successful man-powered helicopters and ornithopters will eventually be developed, however.

Since the original Kremer prize was first offered, many design studies of vehicles capable of competing for the prize has been undertaken. Of the resulting aircraft designs, at least nine have been built and seven of these have made successful flights, including unaided man-powered take-offs. In addition, at least four technically sound machines are currently in an advanced stage of construction. The characteristics of a representative selection of these aircraft are presented in Table 1.

Despite the fact that numerous groups, including teams of highly competent professional engineers, have devoted years to the design and construction

Puffin I. (Photo courtesy De Havilland Aircraft.) of very sophisticated machines, the longest flight made to date was one of only 910 m. in a straight line, at an average height of 2 m., by the British "Puffin I" on May 2, 1962. This distance was covered, however, following an unaided man-powered take-off; a significant advance over pre-war flights made with the aid of catapult launches.

The "Puffin I" was designed and built by a group made up largely of engineers and apprentices associated with the then DeHavilland Aircraft Company at Hatfield. The design and construction of this machine was a remarkable achievement, and it shares the honor. with the Southampton MPA, of demonstrating for the first time that unaided manpowered take-offs arc feasible and that very large wing structures of sufficient strength can be built within the very stringent weight limits imposed by the very low values of available power. The "Puffin I" made numerous flights during 1962, but was heavily damaged in a crash on April 24, 1963. The Hatfield group took this opportunity to completely redesign the wing and make many other detailed changes in efforts to reduce drag and improve the

Puffin I in flight. (Photo courtesy De Havilland Aircraft.)

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John Winnipcnny and Puffin I. (Photo courtesy De Havilland Aircraft.) handling characteristics of thl! aircn.1ft. The resulting .. Pullin / I" { pictured on lhc ctn·cr) made ~1 num-

ber of succcs::,;ful tlights. including 180' turns. but had not p,.:rformcd to the k'\·cl required for the Kr1.;mcr competitions by the time it was virtuafly demolished in an accidcnL in 1969. 1:: The Hatfield group decided. for Y~irious rcasons. against n:huil<l-

in!.! the machinc a~ain. and the wrL'Cka~c was !.!ivcn to.. a group of stuJcnts and st<.1fT in the.. Mcch;.(nical

Enginccrin~ D...:partmcnt at Liverpool Unin.·rsity.

This group. u11,1..k-r the leadership of Prof. Keith Sherwin, is presently building. a dr~1stically modi-· ficd Ycrsion of ''Puffin.'' now calkd '"Livcrpullin," retaining only the wing box spar. pilot support

structure and propcJlcr from the origin.ii machine.· The "Livcrrullin" is 1101 intended for competition for the Kn.::m~r prizes. but represents, rather. an attempt to build a fairly sturdy training vehicle capable of making short flights of a few hundred meters, to build up flight experience with an MPA prior to design of a more sophisticated aircraft. The "Livcrpuffin" is due to be completed toward the end of 1971.

Paradoxically, despite the great difficulty of achieving even limited man-powered flight, a relatively inexperienced group can make signi~cant contributions. As an example, the Southampton University "SUMPAC" (Southampton University ManPowered Aircraft Club), made its first flight a week

before the "Puffin I," thus gaining the distinction of being the first MPA to unquestionably take off solely under human muscle power. A good account of the first and subsequent flights is contained in an article" by Derek Piggott, who made most of the early tests. The "SUMPAC" made many flights, the longest of these about 550 m. Following the graduation of the designers, the aircraft was taken to London by one of the group. Modifications were made, particularly to the power transmission system, and the machine was again flown several times.

The "SUMPAC" finally crashed on November 12, 1965 and was not rebuilt for further flights. The machine is now on display in the Shuttleworth museum. The example of the ."SUMPAC" demonstrates that at this stage of MPA development, ing_cnuity is at least as important for success as experience.

The development of both the Southampton and "Puffin" were greatly aided by grants of £1,500 each from the Man-Powered Aircraft Group of the RAeS. This money came from a fund, initially totalling £5,000, which had been collected from various donor~ at about the same time the original Kremer prize was offered. These RAeS grants were available only to British applicants, and this policy was not changed when the Kremer competition rules were modified in 1967. The conditions for the award of these grants have been published by Shenstone. 11 Four other MPA projects, all fixed wing machines, have subsequently been given grants varying from £ 500 to £ 1,500. Of these, the Southend "Mayfly'' two-place MPA was completed but never flown, due to transmission difficulty and plain bad luck." The single place Woodford machine was damaged by fire when about 75% complete, after years of construction work by its designer, S. Hodges-Roper."' The remains of this

Liverpuffin. (Photo courtesy RAeS.)

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SUMPAC. (Photo courtesy British European Airways.) aircraft have hccn given to a group of RAF apprentices who have ratlK'r indefinite plans to rebuild it. The other t,vo aircraft involved arc the Hertfordshire Pcd;d Acronauts' "·1 oucan" .:ind the \Vl~yhridgc MPA. Bt1th of thL''-c ;1ircraft arc pn..·s-

cntly nearing ~0mpktinn.

Both the twn rl:,cc ··Touc;111·· :111d thL' sing.k p!:1co...' \VeyhridgL' machines :rn: nf grL'at IL'chnic:11 interest and ha\'C hL'lk'fitcd frnm the J....·,..,t,ns h:;irncd fr\,m the earlier Sou1hampt(111 and 1L1tlh:!d c!Tnl'I". The "T()UC:111:· 1hc !ar~l':-,! \1P.-\ ~·L'I .... ainu•-.ly pr1,po,.;,nL was dc:-ig.ncd hy a ~rnup made up m;1i11ly or employee'> nf the lfondk·:-Pa~L' C\1rnpany ;ind lead hy Mnnyn PrL'ssncll. It is Jwpcd that lllght te~ts of tht.:: ··Tlrnc:111·· will h,. :lp ,-...·solv1.: annthL·r current enntro-

n~rsy in MPA di.·,ifll phill~,oph:,.-\\·hcthL'r a <'Th:man or l\\'O-rnan <.:rl"\\" is q1pL'rior.

The \Vc,·hridf!C m:u.:hinc is being built hy a group hc.idcd h:v P. K. Green. M:iny rnemhcrs of this group :iri.' l'lllj')h)_yL'd hy thL' British Aircraft Corporation. The \VL·yhridgL" design relics on a wing of extreme aspl."ct ratio ( and apparently ennsiderahlc bending flexibility) h) reduce induced drag. The

\Vcyhridgc group h:1s so far received a total of C 1.500 from the RAcS. which has been suf!icienl, it is claimed. to cover the cost of materials for the

c~mstruction.

There is reputed to be quite a lot of other manpowered night activity in Britain. but only those projects given financial assistance by the RAcS have received much publicity. One very interesting Briti,h project. \Vhich has received little attcnticm. and .ihnut which few detail:-. arc avaikihlc. is the carnard nrnithoptcr c.ksigned hy John Elliott of the Farnborough M-P Groups. 1 :; Some very imprl..'ssivc work on MPA development has hecn c.lnni.:: outside Britain during the past dc<.:,tdi.::. mainly in J,1p;111 and Canada. The most import.in\ C.inac.lian pn)jl."ct is the Ottawa MPA, 1 i: dc:,.,ignl·d by a group lead hy W. Czerwinski. This two pl:il'l' ni:1chinc has been under construction for scvL'ral year,.;. hut a completion <late is indefinite because nf fin;rncial limitations. Czerwinski has puhlishcd several papers on man-powered flight, rn 1R with particular emphasis on structural aspects of MPA design. A major fcatt1rc of the Ottawa ma-

Weybridge MPA. (Photo courtesy British Aircraft Corp.)

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chine is the extensive use in its construction of very thin-walled light alloy tubing, a very significant departure from the customary balsa and spruce structures of most contemporary MPA's .

There are reported to be at least three groups working on MPA projects in Japan and descriptions of the work of two of these groups have so far been published. The best known Japanese MPA project is the superb "Linnet" series designed by Prof. H. Kimura and his students at Nihon University. The "Linnet I," first flown in February, 1966, had the pilot sitting in a semi-reclined position, which apparently caused some center-of-gravity position problems. The design was consequently reworked, with the pilot now placed in a conventional cycling posi-

Linnctt I. (Photo courtesy Prof. Kimura.)

tion, as "Linnet II," which flew for the first time in February, 1967. The longest flights to date were 40 m. and 91 m. by "Linnet I'' and "Linnet 11," respectively. A highly refined version, "Linnet III," began flying in March, 1970. An improved version of "Linnet III," to be called "Linnet IV," is presently under construction. No details of this latest development are available, however.

The ()ther Japanese project, for which details arc available, is the Sato-Maeda SM-OX-I. This machine was designed by H. Sato, Dean of Kurume Technical College and K. Maeda, a pioneer of gliding in Japan. The first flight, at the end of August, 1969, covered a distance of about 20 m. at a height of about 1.5 m. The second flight at the end of March, 1970, extended the distance to 30 miles. No other flights have been reported.

The United States, with the largest, most advanced aerospace industry in the world has so far produced relatively little MPA hardware. Only two recent projects have received any publicity, the first of these being the McAvoy MPA-1. The MPA-1 was designed and built by James McAvoy of Atlanta, Ga. as a thesis project for his Master's degree at Georgia Tech. The machine was completed in 1963 but was never flown, first because of minor

structural failure in one of the wing spars, and second because of a ground handling accident which resulted in extensive damage to the machine, yet to be repaired.

The other U.S. project of note was an MPA resembling the "Liverpuffin," designed by Alexander Lippisch" in 1964. Dr. Lippisch was then Research Director at Collins Radio Corp. in Cedar Rapids, Iowa. The project appeared quite promising, but had to be given up m the summer of 1964 before any major components had been built, because of Dr. Lippisch's ill health.

Man-Powered Airplane Design The preceding discussion indicates the general trend in MP A design since the establishment of the Kremer Competition. Good. introductions to the technical aspects of MPA design are contained in papers by Spillman'" and Nonweiler,' 0 and in the book by Sherwin. 20 Some of the major technical considerations in Kremer Competition MPA design may be briefly summarized as follows: I ) The principal fixed parameter in the design problem is the power available. Theoretical and experimental studies7 · " have shown that the steadystate power available from a champion athlete, using his leg muscles alone, is on the order of 0.4 to 0.5 brake horsepower for periods from 5 to 150 minutes can be produced by going into "oxygen debt."

An ordinary healthy individual should be capable of producing 70 to 80% of the values. The most efficient means of extracting this power appears to be pedaling while seated in a semi-reclined position. 7 2) The power required by an aircraft in level flight can be expressed as a function of the weight, flight speed, propulsive efficiency and aerodynamic efficiency (lift-to-drag ratio). In order to keep the power required by an MPA consistent wilb the very low values of power available, the weight and flight speed must be very low, and the propeller/ transmission and aerodynamic efficiencies must be as high as possible.

3) If the Kremer Competition courses are to be flown in the conventionally conceived manner (i.e., as close to the ground as possible within the height limits specified in the competition rules),• the air• There is considerable merit~ particularly from the point of view of post-Kremer Competition development, in simply optimizing the aircraft such that the power required is less than the power available at aU heights below a given teveJ. An aircraft. with sufficient structural strength. then has the potential of climbing to a height (greater than about 6· to 10 m.) where conventional soaring techniques based on suitable atmospheric conditions could be used. In this case the 3;m. height limitation of the Kremer Compe~ titions becomes irrelevant.

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Linnett ll. (Photos courtesy Prof. Kimura.) craft must be designed for almost continuous flight in a banked turn. This condition places additional demands on aerodynamic efficiency and aircraft handling characteristics.

4) Much of the basic design problem revolves around the interaction between acrodynarnic and

structural factors in the design of the wing. The conventional approach to wing design is to find an optimuzn balance hctwccn the conflicting require-

ments of: a) a high aspect ratio wing to minimize induced drag ( drag due to lift); h) a large wing area co yield very low values of wing lo.1ding; c) a long span wing to minimize the beneficial reduction in induced drag through ground effect:"" d) a short wing span to reduce wing. weight: c) a short wing span to minimize adverse roll and yaw moments produced during turning flight; and f) a small wing

to reduce the aircrnf!'s response to gusts.

Most of the major MPA designs proposed or built to date arc listed in Table I. All of these machines may be considered re;isonably "conventional" in concept and in some cases quite conservative. given the nature of the design problem. It is startling to realize, however. that most or these aircraft arc at

least 50% larger than and weigh only about one third as much as conventional Open Class sailplanes. The average cruising speed of the MPAs listed is on the order of 5 to 6 m./sec., considerably below the stall speed of even most STOL aircraft.

In spite of the remarkable structural and aerodyn.:unic ctticicncics achieved in past MPA designs. the

Kremer prizes have not been won, and the difference between required and achieved performance has in most cases been large. One may speculate that any one or a combination of the following factors have lead to the failure of recent designs to achieve theoretically predicted performance levels. l) A major problem in MPA work has always been to find a first-rate pilot who also happens to be a champion athlete (preferably a cyclist). For reasons that are not clear, the desired combination has only rarely been found. Because of the very

difficult handling characteristics of the machines built so far, reliance in sekcting a pilot has tended to favor his flying ability over his potential power output. This sort of consideration lead the Southampton group to select Derck Piggott. a well-known glider pilot. as test pilot for their machine; a wise choice in retrospect.

2) It seems probable that the pilot of any MPA must have his potential power out-put degraded to some extent by the demands of flying the airplane.

An obvious solution to the problem is to design a multi-place machine, and select the pilot primarily for his flying ability and to "slaves" for their potential power output. It is to be hoped that flight tests of the two place 'Toucan" .ind "Ottawa" machines will demonstrate the validity of this approach.

3) It can be simply demonstrated that the power required by an aircraft like the "Puffin" to establish even a small rate of climb ( on the order of 0.1 m./ sec.) is 50 to I 00% greater than the power required for level flight. A typical flight path around the Figurc-8 Kremer course would have the pilot "zoom" the aircraft to the required 3-m. height across the starting line and then gradually descend to a lower height to fly the course with the maximum benefit from ground effect. This path would require a final climb to 3 m. when crossing the finish line.

In spite of the ability of the "Puffin II" to make the required, 180° turns. the inability of the pilot to muster the strength necessary to make the final climb to the finish line was apparently one· of the factors that dissuaded the Hatfield group from making an official attempt at the Kremer prize.

4) It appears that the single most important factor in past failures has been the very large size, particularly the span, of the wings of the aircraft involved. In retrospect, it appears that the benefits in drag reduction of large span wings operating in ground effect have been largely cancelled by the structural and handling problems which such spans have introduced. It is interesting to note that the handling characteristics of "Puffin" aircraft suffered

13.14

ROYAL AERONAUTICAL socmTY

MAN POWERED FLIGHT A prize of £ J0,000 is offered by Mr. Henry Kremer for a successful controlled flight of a Man Powered Aircraft under conditions laid down by the Man Powered Aircraft Group of the Royal Aeronautical Society. The official observers will be selected from a body approved by the Royal Aeronautical Society and the Royal Aero Club. The Regulations and Conditions governing the award, which is to be known as the £ I 0,000 Kremer Competition, have now been laid down by the Royal Aeronautical Society and are as follows:

REGULATIONS

I. GENERAL

The prize will be awarded to the entrant who first fulfills the conditions.

2. PRIZE The prize is £ l 0,000 sterling.

3. ELIGIBILITY The competition is international and is open to individuals or teams from any part of the world.

Rights of appeal will be governed by the Com1 , petition Rules of the Royal Aero Club and the Sporting Code of the Federation Aeronautique Internationale.

4. CONDITIONS OF ENTRY 4.1 Aircrait 4.1.1 The machine shall be a hcavier-thanair machine:.

4.1.2 The use of lighter-than-air gases shall be prohibited.

4.1.3 The machine shall be powered and controlled by the crew of the machine over the entire flight.

4.1.4 No devices for storing energy either for take-off or for use in flight shall be permitted.

4.1 .5 No part of the machine shall be jettisoned during any part of the flight including take-off.

4.2 Crew 4.2.1 The crew shall be those persons in the machine during take-off and flight, and there shall be no limit set to their number.

4.2.2 No member of the crew shall be permitted to leave the aircraft at any time during take-off or flight.

4.2.3 One handler or ground crew shall be permitted to assist in stabilizing the machine at the wing tip during takeoff.

4.3 Ground Conditions 4.3.1 All attempts, which shall include the take-off run, shall be made over approximately level ground and on a course to be approved by the Royal Aero Club or in conjunction with its authorized representatives.

4.3.2 All attempts shall be made in still air, which shall be defined as a wind not exceeding a mean speed of approximately IO knots, over the period of the flight.

4.4 Course 4.4. l The course shall be a figure of eight, embracing two turning points, which shall be not less than half a mile apart.

4.4.2 The machine shall be. flown clear of and outside each turning point.

4.4.3 The starting line, which shall also be the finishing line. shall be between the turning points and shall be approximately at right angles to the line joining the turning points.

4.4.4 The height.* both at the start and the finish, shall be not less than ten feet above the ground; otherwise there shall be no restriction in height.

4.4.5 The machine shall be in continuous flight over the entire course.

4.5 Observation Every attempt shall be observed by the Royal Aero Club or by any body or persons authorized by the Royal Aero Club to act as observers.

5. REVISION OF REGULATIONS These regulations shall remain in force until 31st December 1973. After this time, the Royal Aeronautical Society reserves the right to review and amend these Regulations if the prize has not been won.

•By "'height" is meant ground clearance, everywhere: in these rules.

13. 15

Linnell III. (Photo courtesy Prof. Kimura.) a marked deterioration when the span was increased fom 25.6 to 28.4 m.

5) A second dilliculty encountered in the use of wry high aspect ratio. very lightly loaded wings, is the sensitivity of the aircraft tu wind and particularly gusts. This problem was so severe in the case of "Puflin II" that flights were limited to times of almost dead calm. In Britain this allowed only about twenty nights to be made each year: hardly sutlicicnt to build up any confidence in or to thor1..)ughly test thi.,:, ~iircraft.

6) Acroclastic <.kformati\ms of the structure may 1\:-sult in less than optinwm aerodynamic performance. This dilliculty is again atrributahk to the \·cry large size. very low \Vcight and very low load factors of 1nost M PA tksigns.

Man-Powered Flight Research When the HcrtforJshin.: and WcyhriJgc machines arc completed. hopefully this spring. it is probable that thi: upper limit on practical \Ving size will have hl2'L'rl rcachi.:d. If neithi..:r of thes1.: two aircraft is successful in attempts 10 \vin the- Kremer prize, it is clear tlial convi.:ntional ll.:chni4ui.:s in a(:rodynamic design (L'.g., increased aspect ratio an<l long span

wings in ground effect to reduce drag) will be nearly exhausted. In addition, the limit has probably been reached in achieving ultra-light weight by means of conventional structural techniques using spruce and balsa as the primary construction material. Where docs one go from here?

A great deal of research in almost all aspects of man-powered flight needs to be done. This is particularly true if one takes man-powered flight in its broad sense. wherein winning the Kremer prizes with a "convcntionar· aircraft is only one limited goal.

The following arc some of the major areas requiring further research.

I) Analysis of man as an aircraft engine: a) What is the optimum (if one exists) power to weight ,·,nio of man (average, trained athlete)? b) What is the optimum means ( pedaling, rowing, etc.) of extracting useablc power? c) What is the optimum position ( siuing. reclining, etc.) for the man while both producing power and flying the aircraft? d) What training might possibly maximize a given man's power output? e) Can a man produce his full potential power output while supported several feet in the air in a flimsy, flexible, vibrating structure? f) How much is his power output degraded

.»:--;·-~···

:~~J2!t;~;;J t~ Linnell III. (Photo courtesy Prof. Kimura.)

13. 16

by having his attention diverted by the requirements of flying the aircraft?

2) Aerodynamics: a) Suitable laminar flow airfoil sections, with optimum characteristics at the desired cruise condition must be found. Very little data on airfoil characteristics in the Reynolds number range of interest ( !00,000 to one million) has been published. b) Jn turning flight it is desirable to keep the wing span as small as possible, but for a given wing area, the effective aspect ratio must be as large as possible to minimize induced drag. Unconventional approaches to the problem of maximizing effective aspect ratio need to be investigated.

One fruitful area of investigation might be the

mcch;mism by which large land soaring birds ( vul.tur..::s, eagles. etc.) app"rcntly achieve span efficiency factors considerably greater than unity. 2 :i Another rromising possihility is to investigarc a biplane ( or even multi-pl,rnc) arrangement. Both the hird wing ;rnd bi-plane have been discussed by Mitrovich.:: 1 An interesting slotted wing tip arrangement. which holds some promise for increasing effective aspect ratio. has been under study in France."' c) The possibility of using limited boundary-foyer c<>ntrnl. as originally suggested by Cornish and Wclls.:.: 1: to reduce parasite drag or to

delay stall deserves further study.

3) Materials and Structures: Structural weight is probably the single most critical design parameter in a man-powered aircraft.

The structures must be

extremely light and yet sufficiently strong and rigid cnpugh to resist any ::idvcrsc acroclastic deformation.

Optimum materials must he selected and work needs to be done on methods of joining these nrnterials with a minimum weight penalty. Very little information cxisrs on optimum structural techniques in the density r:rngc of interest for man-powered aircraft.

A quick look at several structural materials characterized by representative values of stress reveals that if the ultimate or the yield strength per unit weight were the criterion for judging the stability of materials for MPA, then the spruce/balsa wood technique falls near the bottom of the list. If thinwalled, pressure stabilized, filament wound, fiberglass cylinders were utilized as structural members, perhaps several important pounds could be trimmed from the craft's weight. rn Interestingly enough, McDaniel built several gliders in the late 30's using inflatable tubes, but the idea never seemed to catch on.::? 7 A review of this construction technique ( as well as that of biplanes), in light of new materials, could prove very beneficial.

MPA:

An Excellent Student Project

Aside from the current Kremer prizes, there is almost no prospect for financial gain from manpowered flight work in the near future. There arc, however, other reasons for making substantial efforts to achieve man-powered flight. Aside from the simple desire to solve the problem, man-powered flight inspired research into low speed aerodynamics, ultra-low density structures, and advanced materials and fabrication techniques has clear applications to other types of aircraft ( e.g., powered and unpowcrcd sailplanes, General Aviation aircraft with STOL capabilities). In addition, it is to be hoped that man-powered flight may eventually develop into a viable sport, along much the same lines as soaring.

Because of the lack of any real prospect for direct commercial gain, it is probable that most work (both research and construction) on man-powered flight will continue to be done in universities and by individuals and groups in the aerospace industry on an avocational basis. The design of a man-powered aircraft makes a particularly excellent student proj-

Table 2. Materials in tension (typical values)

======· Material

Specific gravity

F+,.n psi

F+ 11 • psi

X 10"

X 10'

0.43 7. 83 2.80 I. 75 4.51 1.80

5.6 200 70 43 140 75

150 58 33 130

2.22

200

--------·------·-

Sitka spruce Alloy steel Aluminum (tubing) Magnesium Titanium

Fiberglass (general purpose epoxy) Fiberglass (filament wound epoxy)

E, psi X 10·,

F.,,/s.g., psi X 10"

l . .195 29 I0.5 6.5 16 3.7

25.55 24.95 24.58 31.05 4l.6

7.5

90.1

----·----- -----·

F.,/s.g., E/s.g., psi psi X 10' X IO'· 13.02 19.15 20.67 18.86 28.84

3 .25 3. 71 3. 76 3.72 3.55 2.05

3.38

13. 17

ect for the following reasons. 1) Based on the relative level of experience of the designers, it is of about the same order of complexity as present aerospace industry projects. 2) A very sophisticated level may be reached in the theoretical design, but experimental verification of theoretical predictions, including the actual construction of the full-scale machine, can be done by students with the tools and test facilities available in most good mechanical or aeronautical engineering departments. 3) There is. as yet. no "standard solution" to the problem of man-powcrcJ ain.::raft design.

Conscqui..:ntly, stu-

Jcnts must ...:xcrcisc their ingenuity to the fullest, and worthwhile contributions can be made by rdativcly inexperienced individuals.

Although much of the previous discw,sion on prospects for winning the Kremer prizes has been

pcssimistic. it is the authurs' opinion that machines can eventually be built which will attain the required kvd:-. of performance. within thc limits of the present rules. The ma.i,x question is. simply one of the time scak i1woln::<l. Several good qualit;:ith·c discussions of ma11-p,..1wcred flight have appi...·arcd recently in both the popular press and profcssion~il journals. 1 :;.::1.::~ but rclativdy few new con:-.lruction projects ha\'\..~ bi...·1..·11 start1..·d. The authors bclii...'\'C that th1..·rc Jws nnw hL'L'll cnough ilrm \vaving un the "'uhj1..'(I ( this ;irti..·k inclulkd). at least in the Unill..'d States. and that it is time tl) ~i.:t dtm:n to the sl.'.'rious

business nf i..:xp1..'iimcntation h:irdwarL'.

\'-:itll

aci.u~il

References 1 Ayrton, !\I., Th<' Tc'.\'(<Un,·111 of D1h·ddux, LonJon. Methuen. 1962. ~ Editor~ of Y<·ar: Plight, Simon :1nJ S1..·hu~tt:r, New York, 1953. p. 117.

J Lippbch. A. !\1.. ""fl.l:tn-Pow!.!ri.:J F!ighl in 1929." lour~ nal of r!ic Royal A,•r01w11rical Socit'ty, Vol. (J4, No. 5Y5.

Joly 196l), pp. 395-398; .1ho ~on.rncnh in JR,frS. Vol. 65, Jan. 1961. p. 60.

'Schultze. H. G. anJ St.lisny. \V .. Fl11t d111d1 ,\/11.d;t'/J.:.r11fr. N:1wrk11ndc 11nd Tl..'chnik. Vi:r!:tg Fri1z Knapp, Frankfurt :1.i\L 1936. ·, H:1e..,~Icr. H., "Man-Powcn:;J Flight in 1935-1937 and Today." ("ww,/iw1 A('rorwr1tical }ounw/, l\1:trch !961, pp.

89-104.

1 • ilo~si, E .. '"A M~1n l-fas Flown by His Own Powt!r in 1937," Cwwdicm Aero1wuricaf Joum/11, Di.:c. 1960. ~ Ur::.inm,, 0., "J\.. liLtcilungcn 1.ks r-.foskcltlug-Instituts l-6," report::. on th!.! Mmcubr-Powcrcd Flight Institute, Flugsport, 1936-37.

"Raspct. A., "Human l\.Iusdc-powi.:rcJ Flight.'' Suaring, May-June 1952.

"Shcmtonc. B. S., "Tht.! Problem of 1hc Very lightWcight, Highly-Etlicicnt Aeroplane," Canwlian Acromwrical Journal. March 1956. '" Nonwc:ilcr, T. R. F., ..The Man-Powcre<l Aircr,Lft-A Dcsi,t!n Study." Joumal of tlu.' Royal At'romwlical Society, Vol. 62, No. 574. Oct. 1958. pp. 723-734. n Shenstonc, B. S., ""Man-Powered Aircraft," OSTIV Publication VIII, 1966.

1= Graves.

R .., "Problems of Man-Powered Rotocraft,'' Joumal of the Royal Aermwwirnl Soci.::ty, Vol. 66 1 Nov. 1962. pp. 707-712.

JJ Shepherd, E. C., ··wh~it Happened to Manpowcred FlighL," Nt·n> S<:it'ntist, Nov. 1969, pp. 464-465. a Piggott, D., "Pedal Extremities," Flight lnta,w.tional,

Dec. 1961.

1• Moulton, R., "Man-Powered Flight." American Aircroft Modl'ia Annual, 1968. pp. IS-29+.

111 Czerwinski, W., '"Structural Trcn<ls in the Development of Man-Powered Aircraft," Journal of the Roy,ll Aero,umrind Soch-1y, Vol. 71, No. 673, Jan. 1967. pp. 9-13. i ; Czerwinski, W .. "'M;m-Powen:J Flight-A Myth or Reality'!" Carwdhm Aa01wwical Jou.ma/, Vol. 7, No. 3, March 1961, pp. 171-182. h Czerwinski, W., "'Manpoweri.:J Flight, Its Purpose an<l Future," AIAA Paper 70-879. July 1970. ,:, Spillman. J. J., ··oe~ign Philosophy of the M:.in Powered Aircr;1ft,'' Jomm1/ of thl' Royal Acronautinil Society, Vol. 66, No. 623, Nov. 1962, pp. 699-712.

-'· Sherwin, K., M,m-Pu11'Ncd Flighr. Mo<ld and Allit!<l Publications LtJ., 1-kmd & Hempstc:ul, Hens., to be pubJi..,hcd Spring 1971. ~·· Wil!...ic:, D. R., '"!\fan ;1.., an Aero Engine," Journal vf tlw Rorn/ Acwnaurirnl Sucicn·, Vol. 64, No. 596, Aug. 1966. p·p. 477-481. . ~:Wetmore. J. W. and Turner, L. L, '"Determination of GrounJ Effect from Tc:-.ts of~, Glider in Towed Flight," TR 695, 1940. NACA. 1 -·· Cone. C. D .. .Ir. "'Theory of Induced Lift and Dr;\g: of Nonpbnar I.iring Sy:,.1ems." TR-139. 1962, NASA.

;·, i\1itrovich, M .. ··Man-Powered Flight:

Achievements

10 D;Ltc ,,..ith ;;\ New Suggestion," Journal of Aircraft, Vol.

7. No. J. May-June 1970, pp. 246-251.

.:. l.imbach. G .. '"Reducing fnduced Dr.ig-A Frt:nch Ap~ rrn:u.:h."" Spon An"atio,1, Aug. 1968; also EAA Aircraft

Do'ig11. Vol.

Ill. Experimental Aircraft Society, Hales Corn!.!r. Wisc .. 1970. ·'' Corni:-.h. J. J. ;ind Wells. W. G., "Boundary Layer Control t\ppiic;1tions to M:rn-?owercJ Fiighl," Ca11adiw1 At'ro1w11tics ami Span.· }minw/, Vol. 9, Feb. 1963, pp. 55-61. .·: ,\lilk·r, R.. Wirhom Visihlr: J\frar1s of Support, Parker :rnd S,.>n. l.o:-. Angeles, 1967, pp. 37-42. :r, \V:thl. P .. "M;1n-Pow!.!rcd Flight," Popular Scicnc(', fan.

1971. pp. 43--l5+.

Man-Powered Flight Bibliography Tiu: Aeroplant!, "Aviating by Muscle Power,'' NQvcmbcr 18, 1955, p. 777.

Bikle. Paul. "Polars of Eight." So"ri11g. June 1970.

Bikk, Paul, "Flight Tl!sting Sailpbncs," Soaring, July 1970 Bikk. Paul, "The T-6 Sailplane," So"ri11g, Aug. 1970.

E.R.B. (Bossi?). "II Podaliantc Vola," L'Ala ,/"lwlia, May 1937, pp. 61-62.

Campbell, D., 'The Hartmann Ornithopter," Sailpla11e a11d Gliding, Dec. 1959.

Charrnichacl. Bruce, "Possibility for a One Foot per Second Sinking Speed," Soaring, Jan. 1962.

Cole, William D .. "To Fly Like Birds,'' Argosy, Aug. 1964.

Cone, Clarence D., Jr., 'The Soaring Flight of Birds,'' Sciemific American, Vol. 206, No. 4 (April 1962), pp. 130-140.

Cone, Clarence D., Jr., "The Design of Sailplanes of Wings with Cambered Span Having Minimum Induced Drag," TR R-152, 1963, NASA. Cone, Clarence D., Jr., "The Design of Sailplanes for Optimum Soaring Performance," TN D-2052, Jan. 1964, NASA. Czerwinski, W., "Dominant Factors in Light Weight Design," Canadian Aeronautics and Space Journal, Vol. 13 (Jan. J 967), p. 9.

Ditre, Wilding J., "Bird Flight and the Aeroplane," Journal of the Royal Aeronautical Society, Vol. 66 (Dec. 1962), pp. 698-721.

Dufaux, H., "Resumcdes Etudes et Experiences Pour la Realisation du Vol Musculaire," Swiss Aero Review, June 1960.

Esquire, '"These Two Men Think They Can Fly Like Birds," March 1968.

Farrar, D. F .. "A Low Speed Sailplane for Research," paper delivered to XII OSTIV Congress. Alpine, Texas, July 1970; should be forthcoming in Swiss Aero Review and OSTIV Publications.

Farrar, D. F., "One for the Birds," Soaring. April, 1966, pp. 16-17.

Flight International. "Big Day for Birdmen," Nov. 16, 1961,p. 6.52.

Flight lnternational, "Man-powered Round-up,'" May 31. 1962. p. 861.

Flight Internatim111/, "Up to Date with Puffin 2," Nov. 3, 1966,pp. 757-760.

F/11gsport, "Kraftspeichcr fur Muskclfiug," Feb. 19, 1936.

Fl11g.1port. "Muskclkraft Flugzeug Bossi-Bonomi," April 28, 1937 ..

Fl11gspor1. ''Das Hacssler-Villinger Muskclkraft Flugzeug," April 28. 1937.

Flugsport, "Mittcilungen des Muskelflug-Institutc," Nos. 1-6, 1936-37.

Gaubert, L., "Causerie sur le Vol Humain," La Vie Aerienne, Aug. .1920, pp. 61-63.

Gropp, "Muskelflugkraft-hubschrauber," Flugsport, Vol. 29. No. 19, 1937.

Haessler, Helmut, "Muskelkraftflug," Sport/lieger, Feb. 1937.

Haessler, H., "Firsts in Man-Powered Flight," Flight International, Feb. 1962, p. 256.

Klemin, A., "True Human Flight; Bossi Bicycle Glider," Scientific American, Vol. 157 (July 1937), p. 52.

Low, Bill, Letter to editor of Sailplane and Gliding re: Campbell's article on "Hartmann Omithopter" and Nyborg's letter on same.

Machine Design, "Muscle-Powered Flight," Vol. 34 (Aug. 2, 1962), pp. 86-90.

13. 18

May, Daryl, "Man-Powered Flight," Flying, Vol. 72, No. 6 (June 1964 ), pp. 36-37 Morrelli, Piero, "On the Weight of Sailplanes as a Function of their Main Geometric Parameters," Swiss Aero Revue, Aug. 1959.

McDougall, Harry and Best-Devereux, Harold, "Man's Flight to Fly by Muscle Power Alone," Air Progress Homebuilt Aircraft Annual, Summer 1968, pp. 44-47+.

McMasters, J. H. and Cole, C. J., "The Prospects for Man-Powered Flight, (The Future of an Illusion)," paper delivered at Xll OSTIV Congress, Alpine, Texas, July 1970; forthcoming in Swiss Aero Revue.

Moulton, R. G., "Muscle-Power," Aeromodeler Annual, 1964-65, pp. 58-63+.

Nonweiler, T., "A Realistic Aim for Man-Powered Flight," Swiss Aero Revue, Jan. 1959; also in OST!V Publication V-"Summary of the Lectures held during the VIII Congress," Poland, 1958.

Nonwciler. T. R. F., "The Man-Powered Aircraft -A Preliminary Assessment," CoA Note No. 45. 1956.

Nonwcilcr, T. R. F., "The Air Resistance of Racing Cyclists,'' CoA Note No. 106, 1956.

Nonwciler. T. R. F., "The Man-Powered Aircraft," Journal of the Royal Aeronautical Society, Vol. 63 (Oct. 1959).

+.

Poyser, Ted, "The Flaps and Follies of ManPowered Flight." Threadbare, Voi-Shan, a division of VS! Corp., Culver City, Calif.

1969.

RIL~pet. August, "Performance Measurements of a Soaring Bird," Aeronautical Engineering Review, Vol. 9, No. 12 (Dec. 1950), pp. 1417.

Raspet, August, "Boundary Layer Studies on a Sailplane," Aeronautical Engineering Review, June 1952, pp. 52-60.

Richard, G. C., "La Recuperation de l'Energie Tourbillonaire, Libres Propos Aeronautiques," Les Ailes, No. 1786 (July 1960), p. 10.

Richmond, S., "Man-Powered Flight-A New Approach to an Old Dream," Journal of the Royal Aeronautical Society, Vol. 73, No. 03 (July, 1969), pp. 615-619.

The Royal Aeronautical Society, "Man-Powered Flight-Regulations and Conditions for the £10,000 Kremer Competition," March I, 1967.

Shenstone, B., "Le Vol a Propulsion Museulaire Humaine," Swiss Aero Revue, June 1960.

13.19

Shenstone, B. S., "Man-Powered Aircraft Prototypes," The Aeroplane, Oct. 30, 1959.

Shenstone, B. S., "Engineering Aspects in Man Powered Flight," Journal of the Royal Aeronautical Society, Vol. 64, No. 596 (Aug. 1960), pp. 471-476.

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Shenstone, B. S., "Man-Powered Flight in 1936?"

The Aeroplane and Astronautics, Aug. 14, 1960.

Shenstone, B. S., "Man-Powered Aircraft," Sport Aviation, Vol. 15, No. 2 (Feb. 1966), pp.

15-16+ (originally in Shell Aviation News).

Silva, C., "The Study of Muscle Flight in Italy," Mitteilungsblutt 7 der Internationalen Studienkommission fur den Motorlosen Flug, 1938.

Smith, L. W., "Man-Powered Flight in Japan," Sport Aviation, Dec. 1967, pp. 24-25.

Ursinus, Otto, "Vcrsuche mit Energie-speichen (Research on Energy Storage)." F/ugsport.

1937, pp. 33--40.

Welch, Lome, "Gliding and ManPowcrcd Flight," Journal of the Royal Aem11au1ica/ Society, Vol. 66, No. 624 (Dec. 1962), pp. 807814.

Wickens, R. H., "Aspects of Efficient Propeller Selection with Particular Reference to ManPowered Aircraft," Canadian Aeronautical

· Sf/IL WING

Journal, Vol. 7, No. 9 (Nov. 1961), pp.

319-330.

Wilkinson, K. G., "The Design of Sailplanes for High Performance," Aircraft Engineering, Sept. 1951, pp. 263-271,.

Wieselsberger, C., "Wing Resistance Near the Ground," TM 77, 1922, NACA. Williams, David, Marsden, Anne, and Lassiere, Alan, "Southampton's Man-powered Aircraft," Flight International. Nov. 23, 1961, pp. 787-788.

Williams, John and Butler, Sidney F. J., "Aerodynamic Aspects of Boundary Layer Control for High Lift at Low Speeds," Journal of the Royal Aeronautical Society, Vol. 67, No. 628 (April 1963), pp. 201-223.

Worley, Brian, "Can Man Fly?" Aeronautics, Feb. 1949.

Wortmann, F.. X., "Some Laminar Profiles for Sailplanes," OSTIV Publication VII; Swiss Aero Revue, Sept. 1963; also Soaring, Jan. 1964, pp. 6-14.

Wortmann, F. X., "Drag Reduction in Sailplanes," OSTIV Publication VIII, 1966; also Sailplane and Gliding and Soaring, June 1966, and July I 966.

Wortmann, F. X .. "On the Optimization of Airfoils with Flaps," Soaring. May 1970.

Wortmann. Ing. F. X., "Airfoils for the Variable Geometry Concept," paper delivered to XII OST!V Congress, Alpine, Texas, July 1970; should be forthcoming in Swiss Aero Revue.

Zacher, Hans. "Flight Measurements with Standard Class Sailplanes." Soaring, Dec. 1968, pp.

22-27.

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