DISCLOSURE / FILE
The initial Air Materiel Command report on Project Sign (the U.S. Air Force's 1948 UFO study), tabulating 100 sightings from 1947-1948 plus an appended magazine article, 'The Biology of the Flying Saucer.'
DOW-UAP-D097, Project Sign Progress Report, 1948
The initial Air Materiel Command report on Project Sign (the U.S. Air Force's 1948 UFO study), tabulating 100 sightings from 1947-1948 plus an appended magazine article, 'The Biology of the Flying Saucer.'
Dated April 1948, this Air Materiel Command report to the USAF Director of Intelligence answers a 30 December 1947 directive from General L. C. Craigie and formally opens Project Sign (initially Project MX-304 / HT-304, activated 26 January 1948). It consolidates and tabulates 100 unidentified-flying-object incident reports from 1947-1948, breaking them down by object shape, sound, size, number per sighting, speed, altitude, and observer occupation, with disc or saucer shapes reported 51 times and exhaust trails 23 times. Air Materiel Command consulted General Electric physicist Dr. Irving Langmuir, who was reluctant to treat the flying discs as real, but the Headquarters concluded a low-aspect-ratio aircraft could duplicate many of the reported characteristics. The file's six inclosures include the incident tabulation, photographs of Incident 40, an evaluation, a Horten Parabola comparison, and 'The Biology of the Flying Saucer' from The Aeroplane.
Thie ie an initial report on unidentified flying objecta aa direoted by Rq, USAY letter dated SO Deoember 1947, signed by General L. C. Craigiep.1
Qtarterly reports will be submitted beginning 1 July 1948.p.1
Reported sizes have varied from that of a 26-oent pitoe to 260 feet in diameter, and from the aise or a puraui t plane to tht ePulk of six B-29 airpl.&nea.p.1
Exhaust traile were reported 23 times.p.2
Speed has been eetime.ted throughout the entire range from very alow or hovering to supersonio.p.2
Representatives from tbie Headquartere visited Dr. Ining Langmuir of the P~sea.rch Laboratories.p.2
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Authority: NND927545 • • I HEADQUARTERS AIR KATERI BL COWAND MClA/JCB/amb Wright-Patterson Air Force Base KCIA 2DjytAPH 0 i948 SUBJECT, Projeot "BIOi" • TOs Chief of Staft United Statea ilr Poree Waahington 26, D. Co ATTN s Director ot Int-,lligenoe l. Thie ie an initial report on unidentified flying objecta aa direoted by Rq, USAY letter dated SO Deoember 1947, signed by General L. C. Craigie, subjeot1 •r1~Jng Diaea~. Qtarterly reports will be submitted beginning 1 July 1948. 2. Ae a reeult of thia letter, Pro~ot HT-304 was a.otiTated on 26 January 1948 and Technical Inatruotion 2185, dated 11 Pebruaiy 1948, wns published. Present ti.lea on Projeot •s10~• represent a oonaolida tion ot reports received directly by Hq, AMC and thoee forwa.rded by the Direotor ot Intelligence, USAF. ~. Schedules of activities of lighted night-flying adTertising blimps have been secured a.nd crosa-oheoked at thi.a Headquarters to consider them as a possible souroe ot incident nporta. 4. Inoloaure l represents a tabulation am breakdoWll of all available reports through l February 1948. 5o The following ia a series of interesting observation• that were noted when rev19Wing the many incident 0ase11 a. Rigll rate of olimb, aa well aa the apparent a.bi lity to remain mot1onleu or hover for a oonBiderable length of tiu o bo The objeot was described aa being oval, d1ac or 1auoer- t ehaped ~l times. o. Assooiated sound was preae?It ll tim.H o d. Reported sizes have varied from that of a 26-oent pitoe to 260 feet in diameter, and from the aise or a puraui t plane to tht ePulk of six B-29 airpl.&nea. , NND 927545
Concatenated page-by-page transcript. Born-digital pages came through pdf.js; scanned pages were transcribed by Claude vision OCR. Pages marked unreadable failed multiple OCR retries (heavy redaction, microfilm artifacts, or blank separators) and are kept in place for audit.
Authority: NND927545 • • I HEADQUARTERS AIR KATERI BL COWAND MClA/JCB/amb Wright-Patterson Air Force Base KCIA 2DjytAPH 0 i948 SUBJECT, Projeot "BIOi" • TOs Chief of Staft United Statea ilr Poree Waahington 26, D. Co ATTN s Director ot Int-,lligenoe l. Thie ie an initial report on unidentified flying objecta aa direoted by Rq, USAY letter dated SO Deoember 1947, signed by General L. C. Craigie, subjeot1 •r1~Jng Diaea~. Qtarterly reports will be submitted beginning 1 July 1948. 2. Ae a reeult of thia letter, Pro~ot HT-304 was a.otiTated on 26 January 1948 and Technical Inatruotion 2185, dated 11 Pebruaiy 1948, wns published. Present ti.lea on Projeot •s10~• represent a oonaolida tion ot reports received directly by Hq, AMC and thoee forwa.rded by the Direotor ot Intelligence, USAF. ~. Schedules of activities of lighted night-flying adTertising blimps have been secured a.nd crosa-oheoked at thi.a Headquarters to consider them as a possible souroe ot incident nporta. 4. Inoloaure l represents a tabulation am breakdoWll of all available reports through l February 1948. 5o The following ia a series of interesting observation• that were noted when rev19Wing the many incident 0ase11 a. Rigll rate of olimb, aa well aa the apparent a.bi lity to remain mot1onleu or hover for a oonBiderable length of tiu o bo The objeot was described aa being oval, d1ac or 1auoer- t ehaped ~l times. o. Assooiated sound was preae?It ll tim.H o d. Reported sizes have varied from that of a 26-oent pitoe to 260 feet in diameter, and from the aise or a puraui t plane to tht ePulk of six B-29 airpl.&nea. , NND 927545
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2 3 APir 1948 over 10 9 • .. AMC Subject, Project "SIG!i" e. »umber of objects per aighting, Objects per sighting l 2-6 6-10 Number of eightioga 77 21 8 t. Exhaust traile were reported 23 times. g. Speed has been eetime.ted throughout the entire range from very alow or hovering to supersonio. 6. Incloaures 2 and 5 are anlargementa of photographt taken of Incident f40o Inoloaure 4 1s an evaluation of inolosure 2 by thie Headquarters. Attention 1s iovited to the marked aimilarity between incloaurea 2 ands. and inoloaure 6. Similarity also exiata between inclosures 2 and 3 and oonfigur&tiona illustre.ted in inolosure 6. 7. Representatives from tbie Headquartere visited Dr. Ining Langmuir of the P~sea.rch Laboratories. General Electric Comp&ny. Schenectady, N. Y. to discuss Project "SIGN". It was the opinion of this acienti st that prosent a.vai l!I. ble data does not encompass suffi ci ent information to enable a positive identific~tion to be ma.deo Dr. :.a.n&muir was relucts.nt to consider the so-called "flying discsM as a reality. However, it io be'lieved at this neadquarters that it is possible to oonstruot a low aspeot ratio airoraft that would d~pli oate many of the appearance and performance oharaoteriatics of reported "flyint discs~. Experts have agreed that thie would be possible through the intelligent application of boun:lary layer control. FOR THE COMMANDING GENERAL: ~Me~ 6 Inols H. M. ticC~!1. J l. Tabulation Co lone1. US&F 2. Photo Chief ot Intelli gence 3. Photo 4. Eval of Incl 2 6. Horten Parabola 6. Biology of I'lying Se.ucor 2 ~ NND 927545
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~ ARCH 19, 1948 339 THE AEROPLANE ., ... M. B. Morgan has recently communicated the following 0·3 r-------- ------------- -i~ values for the limit of stability at the stall from this araph : - <=o, 0 Upper llmic of th• Ansl• of Swetp,back (r•lerred to th• l chord) beyond which Hll • •tall can be A,poc, Ratio 11.•qulr•d expected Ocareu 6S 1 S4 2 46 3 38 ' 2S 6 14 •• 8 s It is thus advisable to combine sweep-back with low-aspect ratio w!1en s~fc stallin _g is required. . Consaderataon, of high speed lead to a ,imilar combination. since both feature~ tend to delay the shock stall. We have. 04 as ~ res!lll, the rare ca~ i;,f two quite d ifferent aspects of an o-a 1·0 enginee~ing_ problem pointing to an identical solution . 1 he incv11 able result ha s been the development of arrow s h<;1ped: . more ?r less triangular, . disc wings, termed " Oelta Fig . 23.-lncrease of xero lift profile drag wi th thickness ratio Wang s, _ for lhgh~ at sp~eds which are trespassing into the of symmetrical aerofoil sectldn. The saving In profile drag Is tr~ns• s? nlC velocity rtg1me. An ot her advantage of such one of the advantages of disc wings because of their thinner wings as that when the shock stall occurs. the backward shift of aero~oll section. (Data from Gerber, Zurich Report No . 6). !he centre of pre ss ure is less than with normal wings. Th e induced drag doe, not count quant itatively at tbeg high speeds explain the extr~ordinary ability of the reported •• Flying Development of s uch abnormal aeroplane types began i~ 9e:many during the War_. following the progress accomplished Saucers·• to be able to fly very fast and high, and also to h over, •~ 1et and r~ket propulsion since 1937, which had shown that ascend _a nd de _sceo d with pr actically no forward speed. No flight . at so nic vcla<:IIY wa, a r,ractical proposition. A few ~ther a!rcraft 1s known to do th a t. On the other hand, it is ll!(ODCeavable that whole s quadr ons of such unconventional experimental delta -wing types had been brought to initial fl ying te ~t, when the War came to a close. atreraft could already be observed at air exercises. It is rare . The German ~evclopmcnt had two d istinct aims, resulting for military developments to progress as quickly as all that. 11_1 two separate hn _es of approach. The immediate target neces . For operatao~ with gas turbines a speed range fr om zero satat~d by the Allied bombing raid s. was the creation of very (1.c., hovcrin~ flight) to more than .500 m.p.h. has been claime d fast Jct fighters or fighter-bombers which could surpass in speed for t~e Chance:V~ught-Zi mm crmann helicopter-aeroplane. even the Mc 262. _ Secondly, there was the long-term develop Technically. there 1s httlc reason to doubt th at such an amazing spec<! range can be attained with the combination power plant ~ent of a supersoni c aeroplane capa ble of fl ying over ver y lon11 \ d1sta~e s. such n, from Europe 10 Amer ica and back. and menuoned. Jn cidcntall y, as there is not as yet a standar d term for the dropp11_1g a born~ or two ~n the way. Jt i, perhaps not too fa_ ntas tac to surm1,e that t~•s development had some connection combination of an aeroplane with an heli copter, the name with the research on atomic bombs and bacteriological warfare •• heli co plane •• is tentatively suggested. The. oth~r line of engineer ing approach which has led to instituted by the Hi tler Gang. F or th~ immcdia!e. target, orders for interceptor-fiahters were the da..c-winl! aeroplane of near-saucer appearance derive s from the trend towards very high flying speeds within the sonic placed wath cnterpming firms, notably with the Honen brothers and Messerschm111 (both pets of the Rcichsluftministerium) with range of velocities. an d in pani cu lar 1 at great altitudes. As now the Gotha Work s, ttenschcl, Junkers, Heinke! and Arado (a commonly realized, the compres,ibi ity of the gaseous medium sets a speed limit for conventional aeroplanes. Thi s limit is G?vernment cntcrpra~). etc. In order to facilitate experiment ~ reached when the speed of flight approaches sufficientl y to the ~•th rather unu ~ual aarcraJt ~ypcs and to enable an exchange of veloc11v at which sound is propa&3ted through the air. This idea s.a nd expenences, a special research aerodrome was built at "acoustic velocity" depends solely on the air temperature. and (?ranien~urg ( near Berlin) with all facilit ies for flight testing is, therefore. lower at altitude. Hence. com pressibility effects (in ~anacular , ve_ry l~ng wide runway, and work sh op, for begin to be felt at lower speed s when flying at altitude. repairs and mod1fica11on, were provided). This was placed When the "shock stall," due to the compre~sibility of the under th~ command of a capa~I~ _tec hnician, Lf .-Co l. Kncmeyer . On this aerodrome, all the in111al and development tests with air, ,;cts in, the lift is catastrophically decreased (hence the novel prototypes had to be made. When the Russians collected ju stification for the expression "shock stall "), the dmg ri,cs to enormous values, and the longitudinal ~tability i, grossly the aerodrome, they were agreeably surpri,;ed to d iscove r so me impaired by a rapid backwards shift of the aerodynamic centre of the most progressive aircraft ever co nst ru ct ed . It has since beco!11e cenain that thcr have made intelligent use of this aero a~ well as by fluctuations in the flow pattern at the wing. The nau11cal treasure as wcl a, of the technicians collected then and experience of phenomena of such di s tre ssing nature has given rise to two distinct aims in aeronautical rc ,carc h. One is afterwards. Of the German firms interested in the develop · ment, at least one. the well-known Junkers works at Ocssau has to d elay the ono;et of the phen omena to higher Mach Numbers; the o ther aim i, to find wings which would permit flight within been co mplete!y t!"llnsferred ~o Rus sia, lock, stock and barrel. M ost of the sc1cnt"_ ts and ~e 1snen were urged to volunteer for or throuF,h the tran,-sonic regime. The alternative. " within or thr ough,' is still a neces sary impediment of definition, since developm~nt work 11_1 Ru s~m. Fe~ could afford to refuse. we do not know yet if Mable, s teady flight will be at all According to reh _abl e mrorma11on, amont: the interceptor prot otypes at 9ran1cnburg, at the time of the Occupation. possible within the tran,-sonic regi me (extending from about 0.8 to 1. 2 Mach Number) while there is certainly that beyond were the following :-O ne Honen taille,, delta -wing, which had been dama_ged d(!rmg tests and ~as undergoing repair: another this tran~-sonic regime. i.1:., within the supersonic regime, ~table. steady fl ifht can be predicted. H onen ta1ll e,, Jct-fighter was J .ust ready for it~ first test,. There was also the latest version of the lippi-;ch-Junke r,,· Tw o \ample mean, have become known which delay the dev~lopmem of . the Mc 16.\-C: another advanced Junker, occurrence of lhe "shoc k stall" until much higher (but sti ll sub,onic) flying spee d, are attained.· One is sweep of the design: an experimental Gotha. an d several re;,e arch gliders. , leading edge of the wing, either a, sweep hack o r a, ,weep Hitler's Last Secret Weapon forward. The o th e~-a Farnborough _ discovery of nearly The G~rman long-term development of an aeroplane capable 30 years ago, when high top ,peed, of a1r<.erew, were investi ~f reac _ hing truly s uperso nic ,peed, discarded the gaHurbine gated -i , the adoption of very thin aerofoil sections. The 1et engine. It wa, based on the ram-jct or aerodynamic pro latter lend,. as we ~ave po inted out already. straight to aerofoils puhivc due~ (" Ath _o dyd ")-the simplc~t en11ine ever' invented of low a,pect ratio when, for rea,on, of structural ,ti ffness 1 ~e. ram-Jet, a widely d1,cu,,ed invention by the genial Rtnci a certain wing thickne,, is required. ' Lorin in 1~1~. had been c~pcrimented with in Germany, notably ln the discu,sion of the "Stalling Characteristics of Toille,s hy the Austrian Cugcn Saenger (for whom a special laboratory Aeroplanes'' (THP AER0PLANr for April 2.5. 1947). it was had been built hy the German authornie~ in 1938), by Otto ,hown that a_t l ow soecd,. i.e., duri _ ng take-off and landing, P abo\t, of Focke-Wulf, _an~ by others. Following a suuestio n swept-back win1t ,s ,u ffer fr om the d1s.1dvanta11e of in,tability m~de by Al~xander L1pp 1sc h (formerly known as an eminent at the ,ta ll. W11h pronou_n~ed sw«:e p-back, & wept-back wing, sa1lplnne de s1(tne r and resc~rch worker on _ tnillc s, aeroplanes). of normal a~pcct rataos exh1b11 the vice of" ,cl f -, ta lling," due to prog~e~, had been made wath the combustion of solid fuel in premature tap stall. It was al'° shown that this vice can be ram-1ets. Such fuel took the form of ~olid blocks of ~pccinlly remedied bv reducing the a,r>ect ratio. and a curve based on r,rcpared coal which lined the walls of the doct. This develop exten,av~ wind-tunnel te,ts CT11c ~ER0P~~c for Jul y t I. 1947, ment ha~ bee~ perfected by the Germ an Research In1titutc p. 47, F111_. 8) proved that there 1, a d as tmct relation between for Soarmg Fhaht. a,r,ect ratio and an11le o f sweep-back in this connection. (To ~ continued.) NND 9275452 3 APir 1948 over 10 9 • .. AMC Subject, Project "SIG!i" e. »umber of objects per aighting, Objects per sighting l 2-6 6-10 Number of eightioga 77 21 8 t. Exhaust traile were reported 23 times. g. Speed has been eetime.ted throughout the entire range from very alow or hovering to supersonio. 6. Incloaures 2 and 5 are anlargementa of photographt taken of Incident f40o Inoloaure 4 1s an evaluation of inolosure 2 by thie Headquarters. Attention 1s iovited to the marked aimilarity between incloaurea 2 ands. and inoloaure 6. Similarity also exiata between inclosures 2 and 3 and oonfigur&tiona illustre.ted in inolosure 6. 7. Representatives from tbie Headquartere visited Dr. Ining Langmuir of the P~sea.rch Laboratories. General Electric Comp&ny. Schenectady, N. Y. to discuss Project "SIGN". It was the opinion of this acienti st that prosent a.vai l!I. ble data does not encompass suffi ci ent information to enable a positive identific~tion to be ma.deo Dr. :.a.n&muir was relucts.nt to consider the so-called "flying discsM as a reality. However, it io be'lieved at this neadquarters that it is possible to oonstruot a low aspeot ratio airoraft that would d~pli oate many of the appearance and performance oharaoteriatics of reported "flyint discs~. Experts have agreed that thie would be possible through the intelligent application of boun:lary layer control. FOR THE COMMANDING GENERAL: ~Me~ 6 Inols H. M. ticC~!1. J l. Tabulation Co lone1. US&F 2. Photo Chief ot Intelli gence 3. Photo 4. Eval of Incl 2 6. Horten Parabola 6. Biology of I'lying Se.ucor 2 ~ NND 927545
/ • CONFIDENTIAL - Incident No. Date 1 g Jul 47 ; la g Jnl 47 lb e Jul 47 le g Jul 47 ld g Jul 47 le g Jul 47 2 g Jnl 47 ~ 7 Jul 47 4 $ Jul 47 5 4 Jul 47 6 4 Jul 47 7 4 Jlll .47 ~ 4 Jul 47 9 4 Jul 47 10 4 Jul 47 ll 4 Jul 47 12 4 Jul 47 1~ 4 Jul 47 14 4 Jul 47 15 4 Jul 47 l.6 4 Jul 47 17 2ll. Jun 47 l!S not stated 20 Oot 47 20 19 20 Oct 47 Hour 0930 0930 0930 09tl9 1000 1000 1200 1010 1150 1305 1305 1305 1305 1305 2004 N<>• Obser,ed Location Sighted P'rom Muroc ilT Field, M'uroc, Calif. Muroc,Air Field, Muroc, Cali£. Muroc Air li'ield, li&uroc, Cali.f. Muroc .lir Field, lluroc, Calif. lmroc Air Field, Muroc, Calif. Uuroc A.Lr Field, itiuroc, Calif. Muroc Air Field, Mu.roe, Call!. Iifuroc Air Field, Vuroc, Calif. Area 113, Rogers Dry Lake, Muroc Air Field, Muroc, Calif. ~ortland, O regon 1llli.lwaukee, Oregon Portland, Oregon Portland, Uregon Portland, Oregon undetermined wt atated Roi se, Idaho 5 Air 2 Ground 2 Ground 2 Ground 2 Ground 3 Ground 3 Ground 1 Ground 1 Ground l Ground 5 Ground 3 Grotmd 1 Ground 3 Ground not stated Seattle, X ashington l r .:.round 1305 Vancouver, Washington 20-30 Ground 1400 Portland, Oregon 4 Ground 16}0 Portland, Oregon 1 Ground 1700 Portland, Oregon 3 Ground ll.00 Mount Jefferson near 4 Ground Redmon, Oregon 1500 14t. Rainier, a.shington 9 11r not stated Toronto, Canada 1 Ground 1320 Dayton, Ohio 2 Ground 1100 Xenia, Onio • l Ground CONFIDENTIAL NND 927545
31 CO~FIDENTIAL e No. Sighted l~ 1 2 l l l l 10 1 l l 1 l 1 1 1 1 1 1 1 1 l , ~ l ,l - I. ~ \ \ \ I Observed From not stated Ground Ground Ground Ground Ground Ground Ground Ground Oroum Ground G round Ground llr Ground Ground . Ground Ground Ground ~ Ground Ground Boat Incident No. Date 21 29 Jun 47 22 21 Jwi 47 23 30 Jun 47 24 12 J\111 47 25 4 Jul 47 26 10 Jul 47 ~ 10 Jul 47 2g 24 Jun 47 29 23 Jun 47 30 7 Jan 4! 30a 7 Jan 4g 30b 7 Jan 4a 30c 7 Jan 4g 1946 32 32 not stated 33c 33d 33e 331' 33g 34 35 7 Jan 41! 7 Jan~ 7 Jan~ 7 Jan 4g 7 Jan 4a 7 Jan 4g 7 Jan~ 7 Jan~ 13 Oct 47 12 Nov 41 dour 1645 about noon 1745 1&5 2345 not stated ~ not stated not stated Location D es M oines, 1owa Spokane, ·1ashingt,on Boise, Idaho W eiser, Idaho Vfest Trenton, t~ . J. Harmon Field, Newfoundland Hamon Field, bewfoundland Idaho Bakersfield., Calif. l~T Lockbourne AB, Co1umbus, Ohio 1925EST Lockbourne,!B, Columbus., Ohio 1915EST Lockbourne AB, Columbus, O hio 1940 Lockbourne il, Columbus, Ohio mid-December early a.m. Northern Arizona after dark Columbus , Ohio 133&.l'T,OO"' Oocbnan Field, Ky. (south of) l4000ST Godman Field, Ky. 1320CS'J.' · 0odman Field, Ky. J..420 CST 2100 from Oodman Field, Ky. J..430-1600 11!54-19()6 05}0 GQ'l.Jr a.m. Gedman Field, Ky. Godman Field, Ky. Godman Field., Ky. lladi.eomi-1.le , Ky. l4 mi1es north of Dauphin, J.lanitoba, Canada ticonderoga at sea (40 miles south of Cape dlanco, 20 miles o£f shore) CONFIDENTIAL NND 927545
vu~FIDENTIAL - . lo. a...nect DIOIDD'f Is, ;w. 12111:. r,ooat1cm SMaatfd rra ,6 Jot Stated lot Stated !oilt, Idaho 1 Ground ,1 12 oot 47 1200 Oa•• Creek, Ar1■ ona 1 Qro\md ,s 10 Jun 47 lot Stated !udape1t, Bung&J"1 1 Ground ,9 9 Jlll 47 2,,0 Onnd Palla, levtoundland 5 OJ"ound 40 7 Jul 47 1600 Phoenix, Ar11ona 1 Oroun<S 1 Qro,md •n 11 JUl 47 lot Stated lltndort J1eld, llatlta 42 12 lUl 47 04,0'L BltndOl't J1eld, Alatll:a 1 Oroun4 I 18 Oro\lDd 43 29 Jun 47 1645 Clll"1on, Ion 28 Jun 47 1~, Roekt1tld, W1■cou1n 7-10 Ground " 7-10 Ql"0\1DC2 28 .Jun 47 Afternoon n11no11 -5 46 22 Jun 47 11,0 Ortent1eld, 1111, 1 Ground 47 6 Jul 47 lot Stated 1a1rt1tld-6uilm Air S.le, 01111. 1 Oround 48 7 Jan 48 1920-1955 V1la1Jllton, Ohio 1 Ground . 48a 7 Jan ,s 1925 111111.ngton, Ob1o 1 Ground _ ,,,.,.• 1 Qrowu1 481> 7 Jan 48 1910&ST V11111ngton, Ohio 4& 7 Jan~ 19,0 Y1la1Dgton, Ob1o 1 Orcnmd -84 7 Jan 48 1920-1950 111.111ngton, Ohio 1 ll'ound ~ 9 Jan 48 2,00-2,15 J>aJffi 11 e , ltntllolq 1 Qroimd One at tb11 Orouad 50 10 Jan Ji8 2200 11lcSVood, In Jei-■r, date, PNT - 1wa17 1 ..oh 27 Deo,, JUI all at 2000 o 1 oloek. 'Sept lf 1215 on.ao, oneon 12-15 Ground 51 52 29 Jul 47 1450 1181111 ton 11eld, Cal1torn1a 2 Oroad 2 Ground ,,. 29 1111 •n Atter 1200 llllilton Jield, ca11tarn1a 53 28 Jan IJ7 1515 Lake Jllead, ore1on 5~ Air 1 Air 16 Jan IJ7 22:50 Jorth Sea (50 ail•• troa 54 tbe Dutch coa,t) l Orolll\d BIJ'llCffl Pield, ltvtoundland 2:, Jul 47 o,45Z 55
-CQ~F~DENT IAL - - IAo1c1ent ?fe, 15a. us. Looat1on lo. simaa Ob1enec! D:99 56 6 Jul 47 2945 1-10 Gi-oan4 57 20 lul 47 0015Z Abou-c! the BUl'aeo (at sea one hr. troa 874ne7, Autft11a) 1 Boat 58 4 Aug 47 BYeJWII Bethel, Alaska 1 Ail" 59 14 Se»t 47 055ae1T Reeter Ialand 1 ill' 60 10 Jul 47 1000 Oor4707, Canac!a 1 OPOUDCS 61 8 Sept 47 22:,0 Salt Lllce Cl tJ, Unb 12 Ground 62 8 Sept 47 22:S0~:S00 Salt Like Cit7, Utah 5 Sl'0'QP8 Ground eaoh oan - ta1D1Dg :S5~0 01:tJecta. 6:s 29 JuJ. 47 1205 can,on 1em, llontana l Ol'om:ad 64 19 Aug 47 2130 Tv1n Jalll, Idaho A.pprox. 55. Ol'oun4 65 2 Jun 47 lot stated Rehoboth Beaoh, Delevan 1 Ground 66 10 Aug 47 2100 811Yer 8pr1.ngt, Ohio l Ol'ound 67 llJ. Aug 47 1600 Placemlle, lalitornia 1 Ground 68 24 Jun 47 Hot 1tattd Cuoa4e lountaiJ:aa, Pwtlan4, 01-egon 6 Ground 69 6 Aug 47 22,0-2245 Ph1l.a4elph1a, Pa. 1 Ol'Ound 70 6 iug 47 1045 Ph1lt4elph1a, Pa. l Ol'oand 71 8 Oot 47 lot 1tatecl Laa Vega■, leYa4a 1 Ol'Ound 72 lot atate4 Jot 1tatec1 Port R1obardl0J1, Alllb 1 Ol"oand 7J 4 Aug 47 1600 Boston (101111e1 n) •••· 2 A1r 74 24 .JW'l 47 App. 1500 •t. A~IU, ftlh!ngton lot stated Ground 75 1, Aug 47 1300 saote Rl•er aaix,on, Idabo l Ground 76 1:5 Aug 47 Jlornlng Salaon Du, Ic!aho 2 Ornnd 77 :S 11117 47 1s,~ South BrookYille, Dine 10 Gl'O\IDl2 78 :,o Jun ~7 0910 JIST Oran4 ClllQ'on, AP1aoaa 2 ill' 79 Apr 47 1100 ES! R1oba0nd, V11"g1n.1a 1, other■ on Grcnmd other ooou1ona
80 85 90 95 100 coNriBcN TIAL lno1dent Jo. °'8tl"Ytd 19, em.. Looat1op SUhtn rrw 1 Ground 81 7 Jul 47 0900 Biokaa Jield, lava11 1 82 171117 47 2030-2100 0klahOllll CitJ, OklahOJII 1 Ground 83 9 hl 47 1217 Bo1 ■t (Between Boise and 1 hr1d1&n) Idaho z, 84 7 Jul 47 l:500•140<Bft Lakeland, Jlorida 5 Cll'ound 1200 Portland, oregon 10 Qromd 86 6 lulJ ~7 lot ■tated Hollywood, Cal1tonia l Qro,md 87 lot ,tated •ot 1tated HabMrbi1hopehiOJ1 {20 mile, 1 Ground zx, r tb ) Gorm.any 88 S J.ug if Atternoon Baokenaaok, a. J. l Ground 89 6 Jul 47 lS45 lanaae City (100 miles west), l Air Ke.neaa 29 Jun 47 1500-15:SO Lae Cruoe ■, !low Mexico l Groun4 91 28 Jun 41 2120-2146 Maxwell Pield, Alabama 1 Ground • 92 lg Jun 47 l2l5-1Sl6 Colorado Springe, Colorado l Grcrund ll Jan 48 l 1650 Harttord, Coumot1cut l Air !O Deo 47 l926PSf Between Great l'alle, Montana l and Pairfield, Ca!1tornia SO Dec 47 l926PSf Rosedale, Oalitornia l A.ir SO Deo 47 1926 Lov•look (30 m1lea weat), leTae1& l Ground 97 30 Dec 47 1926PST Between Medtord and •t. Chaata, l A1r Oregon 98 2 l(oT 47 Daybreak Houston, Texas l Ground ~ Jan 46 lot stated Vasea, 11nland l Ground 5 Jan 46 lot 1tated Pretaraa&rl, F1nla1'ld l Ground• Incident Observer ' s No . 1 la lb le l d le 2 3 4 5 6 7 9 Occupation 1st Lt, UJAF :,/::,gt, 0::i,v' Uninown s/sgt, USAF Pfc, USAF ~fot stated :Uaj, USAF liajor, USAF Capt, USAF Patr olman, ?ortland Police Dept. Sgt, Oregon Police Patr olman, Por tland Police Dept., former Air Force pilot Patrolman, Portland Police Dept. Pri vate pilot Patrolman, Portland Police Dept . ?ri vate pilot Capt., Harbot pilot Jo1aneuvers 1lone - horizontal fl1gnt 1"ot stated t-:et stated Not stated Flying in tight circle Horizontal anrl tipht circles Descended from an intennediate altitude in an oscillating fashion almost to the ground, then started climbing again to a very high altitude and moved off slowly in the distance. Oscillating in a downward twirl - ing movement Falling at three times the rate of a parachute Dippi nP, up and down in oscillat- - ing motion Following each otner Not stated Str aight line formation; last disc fluttered very rapidly in side-way arc Strai~ht line fonnation ; last disc fluttered very rapidly in side-way- are Discs wo'.lld oscillat e and SOl11131-' times a full disc would be vis~ ibl e, then a half-moon shape, t hen nothing at all Heatner IiOt stated .,ot stated l1ot stated ~!ot stated !fot stat'3d !lot stated Not stated Not stated ?!ot stated Not stated Clear with little or no cloud f orma tion Clear with little or no cloud forma tion Clear with little or no cloud for.na tion Clear with little or no cloud forma tion Not stated CUiqfiDE~~TIAL NND 927545
10 15 20 25 30 • Incident ObaerTer' s •oo Ocoupad.on Ka.neunra Weather Capt, United Airlines Straight-away horizontal flight lot stated ll 12 lS 14 16 17 18 19 21 22 23 24 26 27 28 29 30a Coast Guard Deputy Sheriff !lot stated Sot ste.ted Jot stated Mot stated Private pilot llot stated Farmer lot stated lot stated Wot stated !lot stated lot stated Not stated llecba.nic TWA Representative Lt Governor ffest Coe.st Pi lot. 7000 hrs. Ca.pt. USAF. Asst Operations Officer VHF/DJ' Operator Horizontal flight Mot stated Not stated FUppi ng around Not stated Hot stated Straight horizontal flight Horizontal fli ght Straight course - were flying about a city block apart. one behind the other Straight course Single file Flashing Horizontal flight Shooting up and down Hori&ontal flight lot atated llot stated lot stated Bot stated Climbing and descending ver - tioally Hovering, made three 360 0 turns around one place. Moved to another position and circled more. Turns required 30-40 seo. Diaaeter estimated at 2 miles. Kot stated Not stated Bot stated Mot stated Iot stated Mot stated Clear as crystal Clear Cloudless and sunny lot stated Rot stated Bot stated •ot stated Clear Bright moonlight Not stated Clear Kot stated lot stated Solid overcast Overcast. 1000 ft.
Incident loo SOb 30o 32 33a 33c 33d 3:Sf :S3g 34 35 36 37 38 39 40 - cor~FIDENTIAL Observer's Occupation Maneuvers Traffic Air Controller Bobbing up and down lot a~ated Climbing and de~oending Profe11or and Bead Mone or Aero Kn.gineering Lt, USAP Bone T/Sgt, USAF Jone 1,it.,Lt, USAF Bone PFC lone Capt, USA1 Kay have been turning Capt, Us.Ar None Col, Ky. State Police Kone Capt, USAF (Plight Not stated Leader •a 869) Unknown Mot stated Judge Bone Second Officer.Wavy Mone CAA Official Sot stated Pilot Kone Hungarian Peasants Not stated Constable Not stated Spiraled downward f'rom 5, 000 to 2,000 f't am then went upward at a 450 angle Weather Overcast High overcast Clear Overcast High acattered olouds Visibility unlimited. High scattered lfot stated High overcast with BIS High ecattered, vi ei bi lity unlimited Clear .Not stated Not stated Clear !lot atated Rot stated Clear ..,-.'! !lot stated a.tVU. ~ d Cumulus clouds
(;J~iadJENTIAL 41 e Ine14ent lg, 1'1 Obaenv'• QoogtS,on Colonel. USU •entuur• . lot atated 42 ..jor, USU Jo\ atated 4, Bua Dl'"1"1" lone "4 lot 1tated lone Jot ltated IJ5 lot 1tated lot 1tated Jot atated 46 Wot 1tat.d lone Cloud Nnb. ~7 Captain, usu lolled frOII 11a. to lid• Jot ttate4 48 KaJor, USAJ uoerMlillg 1na deNen41na lot atawd 48a !/Bgt Up and down and 114• w lid• Cold and eleu Wi'll t.. 11attffff 1101141. Cpl. .lao•Ddtnc and 4eaoendbll r.t&bt aoattezaed oloudl 1'11:la bait tOIIU'dl S/1. leeendina and deaoendiag ••'17 np'idl7 Clear nth onr• eut 1Jl S/1. 48d 49 lot stated .. lot stated laoendlng' and deaeendine lone lot lbttd 50 En.1.ttlng deatan.er Approaohil!a llhON traa Ooean then Pile and tall 1lovly. lot stated 51 Jot 1tated lot stated lot 1tawd 52 Capt, USU, ASS'!. Bon.aonal lett to ri&ht, ri&ht to Opentiona ottieu 1•tt lib• cuard 1n an a1Pplane ~ inawuotor Pilot fOl'Mtian. CltlP 52• lit Lt. 1n Air Il•••ne• t01:1Mr B-29 Pilot SSll1lar to a ti&hter aiNNtta aueu.•r• llben ue~ heaT1.eP 1h1p1. lot stated lit Lt, UW, Pilot Boruoul ftJl7 elon tCll'Mtim lot 1tated Moaquito Pilot lot 1tat1d G<JTernaent Bllplo1•• A)rupt 4atl Bieh toattered oond1\1on Tie1\111'7 15 a.ilea. 'rNTel1ng in a detillt't1t are. lot 1tated CONFIDENTIAL NND 927545
- Incident Ol>aeryer's 110. Opomtion IM!¥I 8 £1 Yt•Hitr 57 Bridge Corustruct1on Bot stated Clear and dark. 58 Chiet Pilot- Not atated lfot auted Plying 1er-,1oe 59 Pilot Hone Rot stated 60 Storek:eepel" lot Stated Clear at duak 61 Kot stated lfone Wot stated 62 lot stated Not stated Cloudy 63 Hot stated BOYel"ing and fluttering, 1'1S1ng and deecendtng. Scattered aull olouda, 64 Executive Direct - Hor11onal OnNalt or ot Housing Authority. 65 P1lot lfot stated Not 1tated 66 Lt. Col, QSC Sc1ent1t1c Horizonal Pl1.g?\t lfot 1tated Branch Research Group. 67 Insurance Adjuster None Clear 68 Prospector Banking Cleu 69 Not stated Hot stated Not 1tated 70 Insurance Agent Not stated Clear 71 Capt. AC Reser-,es N ot stated Clear 72 A1!S1 0tf1ce1' Not stated Cloud to1'118t1on 1oattered abOYe 10000 tt. 73 lavigator (Conatellat1on type ail"cNft) Not stated 5/l.O acattered cuaulus vith tops at 10000, Y111b111ty 10 a11H. 74 Prospector Standi.nc on edge and banking 1n the clouda. Mot 1tated 75 Trout Parm Oper. Rode up and dovn oyer the hills and hollow ot the canyon tloor. Mot stated County COlllliaaioner Hot stated Rot stated It NND 927545 76
In.ctdent Ko, 77 78 79 80 81 82 83 ~ 85 86 87 88 89 90 91 92 95 96 97 98 99 10 0 Ob ■erTer'• Qo9upgt109 Astronomer Lt, USI (P80 Pilot Weather r-,o7tff Lt. Col. USAP C1T11 Service bplo,ee P1eld Bngtn,er Pilot Sign Painter Pl'1Tate Pilot Hot 1tated U. S. Army Not stated M ajor, USAF Administrative Asst, Rocket Sonde Section Captain Railroad Employees Capt, USAP L~ Col, Hq, EPlf C-47 orew Bot stated Airplane crew Immigration Service Not stated lfot stated Manemrp N ot stated lot 1t1ted Rot 1t1ted Jot ltated A1oendtng slowly Bot stated Slow roll or barrel Cl1Jlb1ng lot stated 'l'm"ned a corner and seemed to roll. Descended slowly and then dropped in a spiral motion, Not stated dot stated Not at~ted Trave ling in zig-zag course Climbing, diving and reversal of direction whioh happened enry few aeoonds. Shooting toward, the eaat at 45° angle Descending vertically - aeaned to slow down on nearing the earth Not sta.ted Bot stated Not stated Appeared to be spinning in its descent Bot atated ?lot stated I L NND 927545 J!eather lot stated lot ■ tated Clear Scattered clouds Y111b111t7 10-12 ailea. lot stated S<ae clouds Clear ...cattered cloud• lot stated Clear ~ot stated N ot stated Clear Clear Cle ar alld 1unny Not stated •ot 1tated Not stated Not stated tiot &tnted lot stated lot stated Not ata.ted
• Incident llo. l la lb lo ld le 2 s 4 5 6 7 8 Sa 9 10 Color Silnr, - S11Tery Retleoted the •un' • raya Silvery Ahai.num colored 1urface Ye llowiab-llfhite lihi'te aluminum lot 1tated 1'h1ti ah-brown J.lumima White 1'hite Like s hiny ohro aium hub cap .bot 1tated Shape Size Not stated Not stated Saucer shaped lot stated Diac llot stated Diec •ot stated Thin metallic ob - jeot, unconventi on ah11pe al Puraui t eh1p Spherical 5 - 10 t't, dtaaeter Dietinct oftl out- 50 tt. J.1m; ta> projec - tiona on upper sur - face which llight han been thick fine or nob1. Tne,e croaaed each other at intervals, 1ug ge1ting either ro tation or oaci lla• tion ot alow type Round .Not 1tated Diac Jllot atated Di1e Mot determined Dile Out ol light be fore det&iled ob Hrfttion •d• Diec Out of 11 ght be ror• detailed ob aen-at1on made Di,o Mot 1tated Thin a.nd a.ooth Not stated on bottoa, rough appea.rinc on top NND 927545 Sound Mot atated ■om ltot atated None Mot stated lot 1tated .llom Jllom lone !tone Mone !lot stated Jot etated
II~· ,DENTIAL Inoident llo. 11 12 13 lt 15 16 17 18 19 20 21 22 24 25 25 26 27 28 29 50 Color ffbi t e mot atated Resembled •tallic Lin a new di•• Sil•er Not stated ltirror bri t ht Jellow Reflected the 1un brilliantly Silnr Dirty 1'hite Shiny d l nry Bri ght and sil•ery Gli&tened in av.n Luminous lot 1tated Silvery ' Not etated !lot stated White (.light) Shape Saucer Like tlock ot geese llot 1tated Like a nn dime lilot atated Approximately circular. no tail Like ci ga.ra - 11uch longer than wide Round Betwe.n circle nnd on.l - in ••rt•d aa.ucer Slim body Ral t-circle Too far away to dotenune ahe.pe Plying saucer - DO tai l lilot etated Citoular in shape like a wagon whee l ·eomet-11ke Almo1t round dot stated NND 927545 She Jlot stated •ot stated lot 1tated Like .. run, di• lot atated Not stated Diameter equal to di atan ce between outboard enginea of DC 4: llot s t ated Jlot atated About 12 inches in diameter 175-2 50 t't. dia:aeter 12 ft. t hiok Quite large Not atated Too far away to dete nain. ahape lot atated Jiot sta'ted Same apan •• C-54 at 10. 000 rt. Not stated lot stated lot atated Sound ~t stated Low hmmdng aound l ot atated lot etated llot stated lfot auted lot atated Not stated Mom Mone Like electric motor or dy nmo Not stat ed lone lot atated lot atated Wot stated lot stated !lone
vbV~r IDENTIAL lnoident No. Color Sha.pc Size Sound 30& Amber Round or oval C-47 airplane Jliono !Ob Bright white to amber Cone-shaped. blunt on top and taper ing orr toward bottom ' Rnonnou• 30c White lligbt) RoWlld Comparable 'to way light run- Bone 31 White Not stated lot stated ltone 52 Amber Mot stated tiot stated !lone 33 Sun flashes on metal or metallic Roughly circular At the distance and lone altitude the object appeared ~o be the size of a11Ter dollar ffll.1 te or luminous. ·rurnod to be more red aa the aun aet Round teudi og to be conical Unknown - altitude a.na distance too great Iona ~ot auted Cone. red topped with Jot stated lone :53e Si lver with shadow Raindrop Unlcnown - believed to be lar~ lJnJcnoa 53d 1'h1. te Round at time• cone ~haped - Uneert&in because of distance 53e lfhi.te Round l/4: she full moon lone 33.f l(atallio Bot stated Tremendous SSg "lfot stated Cone 100 ft. high. 43 .rt. acrose !lone Redish tinge Round Large gre.pef'rui t Ion• 35 Fire oolor Ball liot stated llot atatecl 36 )lot stated Bot stated Mot at&.ted Bot stated 38 Reddish with blue background.. Black with white baokground SilTer lot stated Ball S ft. from point of view .Not ate.ted lone Mot stated NND 927545
GONfHltJ'TiAL Incident lo, 001or Shape ~ Soupd 39 Phosphoru1 Ba-shaped diaoa lot 1tated lot atate4 ~o Gray El11pt1cal 20-,0 tt. Ho11e like Jet airoratt prior to 1ts appell" - ~ .. No audible sound beai-d 11h11e object va1 1n Yiev. Aluaim"- Round 3 tt. diameter lot atate4 "1 ~2 OH.yilh Balloon 10 tt diaeter lot 1tate4 1'-3 Dirty 1'lite Between a o1.role IJ1d 12 tt thiolc and llectJ"ie Jlotor an oval (ln-.erted 175-250 tt diameter ordynaao sa~er) 44 lfot atat.d Jlyina Saueers Wot 1tated none (not actually des - oribed as being this shape) lJ-5 Hot stated Rot stated Hot stated Bot stated 46 Silvery vh1te Round Small lot stated 47 No detin1te Bo detim.te shape C -51'. airplane lot deterained oolor top due to the noise ai(!e l"etleot- ot airplane. ed 11ght. lf.8 Red PllUli.ng Red cone Wot stated Rot stated IJ.8a Bright light CirculU'-like a •tU' Ve17 lai-ge cOlll)U'ed Hone ohangi.ne to 1n tbe ak7 only luga. to an aeroplane 11,;bt. red then to White OI" J"•llow 48b Red - ldltn Cone Hot detel'llintd Jot 1tated descending Red men IIO"fin8 lot atated Kot 1tated lot ■tated then grean and black to red. lot stated lot 1tated 48d Yellow or tlame Rot 1tated colored. 49 Not atated Pencil shaped ob3eot !lot ■ tated lot stated t
cot~FIDENTIAL Incident 10. color Shape Si•e sound 50 Stated aa queer 11.&ht. Referred to aa aauoer but not stated as being ot thie detinite shape. Kot stated Jfot atated 51 11lver Bomd Not stated •ot •tated 52 llhite. ah1Dy Circular like a ball en the bott011 but not completely round. 15-25 tt Diameter !lot atated 521 ■ilk mite Bot atated •ot stated lone 53 Whit. C1roular 36 inches diameter Rot stated 54 Rot atated Not etated Rot eta,ed Not stated 55 RecUab lot stated Bot atated None 56 Dia glow ot light Round 2 :tt. d1aaeter Hone lfot stated Kot atated 58 Blaok Saucer (not det1n1tel7 1tated •• being tbia shape) Larger than C~4 airplane Not stated 59 Incandescent 11Cht without appreciable blue and no redd1eh tinae. Hot stated Not atated Hot stated 60 Plame oolor Diec shaped (the 11'ter glow •de 1t look like a oone) Barrel Bead, dinner plate am the aise ot a plane tl71,ng hi&h. Wot stated 61 White ancS 111Ullinated Bot stated Sue ot Pigeons lfot 1tated 62 YelloV1ah vhite Bot stated 811811 Mot stated Gleuaed and Shialered D1so (not actuall7 stated aa being ot this shape) , rt. a1aaeter and ot no great th1ok• neaa. lot stated 64 Color 111111ar Kot stated to eiectr1c 11.&ht. lot stated Hot stated 65 lot ltated Bot stated 15 1nohea diaaeter lot stated 66 Bright onnge lot stated lot atated Hot stated 67 Jllutal col01" top 1urtaoe al1ghtly IJ.-6 tt 1n le~h ll'ot stated 57 h1ghl7 po111h- ournd-larger 1n front 4 ed chi-Ollium. than 1n the rear . :~e :O-l 1nchea liOMflDENTIAL NND 927545
• flDENllAL e Incident 68 ColOJ' Hot stated Shape I D1eo - appeare~ a tail. to have UU. 30 tt d1aaeter sounc1 lone 69 White lot 1tated Not stated Bussing sound. 70 Not stated Giant til'e cracker Kot stated Bu11DI aound not aa loud aa a rocket Ship. 71 Rot 1t1ted Hot 1t1ted lot atated Not stated 72 Silver Sphere( nt not like 1auoer or diac. 2·3 tt diameter Rot 1tated Deep Gold 1111pt1oal 15 tt long 2·3 tt 1n length. lot atated 74 Bot stated Tapered lbarpely to a point in the tront end. ,o tt. diaaettr Hone 75 Slq blue Oblong like a broad rill hat with a low crown. 20 tt. lona am 10 t,. thiolr. Kade a av1shiq sound. 76 Not stated Jot 1tated Hot stated Lite the eoho ot • aotor. 77 Light colored Only oonerete evidence 50•100 tt lfide. or tora appeared on the lett tangent ot the group. Loud roar 78 Light gray e1rou1ar 8 tt. diueter Bot ■ tated 79 S1lftl' Bot atated Lu•er than a Pibal balloon When obaened through a theodolite. Not atated 80 Retleoted vh1te light. "Blob 11 SMll ail"plane Hone 81 S11Yer ' Large Balloon With silver Large d11c below it, no attaebing cables vere noticed. lot etated 82 Proat7 ltbite Round and tlat Equal to b\11.k ot 6 eaob, B-29 air· planes td th dia .. •t•r to tluomeas ratio ot 10-1. A 1l1gbt mahing. 83 Black Round 'tVtnt,-.f'ive cent piece. lot atated
, .DENTIAL e Incident 110, 84 color Sb1Jm7 Ship, Road lot ltated lore~ le11 SbJ-111. 85 Bot 1tated Reseabled the D5U•l. Jot 1tated lot 1tated 86 Not 1tated lot atate(! IOt ltated lot stated 87 Jot S1t&ted Bot stated lot ata.ted lot atated 88 lot stated 1lying di ec (not ao tual ly deaoribed aa being ot thi• aha.pe) )lot 1t1.ted lot atated Ro\lDd di,o ahaped object 50-60 rt. diameter bot at&ted Refleote4 light Unitonn with no protu berano•• euoh •• wing• of an airplane Hot atatad Bot 1tt.t1d Light lot atated Not stated looe 92 Silver lot ,tated S-11 lloli ata.ted 94 Bluish center Appeared to be a ·.rl th rod on its edgH !ot atatad lot 1tated di10 Reaembled ~ shooting at~r; however. ob - aervera not oertain Not stated Not etated Not ,tated 95 Not stated Not stated Kot stated Bot stated 96 Not st:i.ted Hot etated Not stated Not atated 91 Flaah of light Kot atat•• Hot stated Hot atated 98 Bright light Ahaoat round or perhaps oval or aauoer-ahaped 2ti-30 miles diametor lot etated 99 Shining Brightly ehining object with long td 1 lot atated Bot atated 100 Wot ,tated lot atated !lot stated NND 927545
-COt~f\DENTlAL: - e - Incident No. Exhaust Trail Heading Altitude Ft. Speed lffect on Cloud• l t:one 320° 1000-sooo rt. ~00 mph lot at&ted la. lb le Not stated liorthwest 7500-8000 ft. ~50-400 mph Hot stated ld f.ot stated northwest 7000-8000 f't. 300-400 mph tlot atatod le tlot stated tiorthwest 6000 rt. 300-400 mph ~ot stated 2 tot stated Not at&ted From very near the ground to vory high Not ste.tod llot atated 3 Not ata.ted frost to east 10000- 12000 rt. 200 - 225 mph )lo-r; stated 4 Not stated North of due east Under 20000 ft . Slower than Hot stated lllAXimUDl speed or P- 80 5 Bot stated Two flying aoutb - S flying ea,t Bo'\ stated.d Great speed lot atated 6 Not stated llorthweater ly Undetermined Terrifie lot stat.d 7 None Southweat 50000 fto Terrific - faster than any object ever seen by him lot stat.cl 8 8a 9 Rone- Jlone Not atated South South S01..-th 40000 tt . 40000 rt. High over Globe Mille Terrific ?errifio Terrific lot atated Not ,tated lot stated 10 !Jone Northwest llot stated Cruised for Not atated 46 min. at oonventional airline apeed (180 mph) then rapidly dis - appeared 11 Not stated OTer north end lot stated ot Lake 1'o.sh - ington llot stated .ttoi; a ta.ted CG."f,DENTIAL NND 927545
Incident Bo. 12 14 15 16 17 18 19 20 21 22 23 • F1DENTIAl E:xhauat Trail Wot atated Bee.ding Hot stated .lltitude Ft. Not atated lot atated 3 west to eaat. l north Did not appear Tery high lot atated lot atated Iot 1te.ted lfot 1tated l beaded s outhea1t. 2 headed north1a1t .lot atated High lot 1tatad lot ete.ted north to IOUth 9500 rt. about 17<i' Trail atreaa- aeenronr Jiot atated 1ng out be- weatend him like of Toronto vapor trail 'beh1m air - plane on misty day Lim alight eat to east One 11.ile high trace ot steam. Disappeared 1m::nediat•ly. Not atated Southwest About 1500 rt. Rot stated ~.N.W. 1200 ft. Bot stated S.W. ot S. 7000 tt. Not stated !lot stated 5000 tt. Cloud-lie 8outheut Very high n.por - re - tained shape a.nd persiated tor onr an hour Spoed Effect on Cloud.a lot •~d Hot at&t.<l Tranlini BO taat they •ere out ot llot ,te.ted eight in eaat in 2-4 aeoonda JloT1ng slowly llot atat.d onr aandy dletr1ct Sot atated lot atat.d !tot atate4 llot atated Not 1tated lot 1tated Not stated Hot stated Very taat Bot stated Faat llot stated About SOO lot atated mph Slower than lot atated two-motored U1lY plane lfot ate.ted lot stated Very tut Mot atat.d \ NND 927545
• CONFIDENTIAL e Incident Ho. 25 26 27 28 29 30 .. ' S0b 300 SI 32 33 33a B.xhaust Trail Heading Altitude Ft. Wot stated Bast High Bluish-black Not sta.ted Bot stated Bluish-black Not stated 10000 ft. 15 mi. long Not stated Not stated Not stated Not stated 10 flying High north; on reverse course there were only 7 None (ap- West 3000 peared to ha.ve bluish streaks out t'rom aides Five times 1200 Prom .,ery near length ot g?'Ound to 1000 object Small streak 8.8.Wo trailing object Wot stated Kot atated di!teNn.~ al• titudea ; White., heavy West to eut 20000-50000 ft. lone Stationary 3000 tt. lone lone visible Unknolm Jfone 210° from Extremely high Godman Field None Not stated Not stated Speed Effect on Clouds Fast Not stated llot stated Cut a clear path throup cloud• Fast Seemed to out 0loud1 open Did not moveo Seemed to go below horizon Bot stated with rotation of earth 300-400 mph Bot ate.ted Slow Bot stated 500 mph Jlot stated rt. a,tter 1 t atartecl to le&"ff n.e1n1ty bceeding Bot ate.ted. 600 aph Jfotionlesa lot stated ~-~----- - 600-~00 mph Bot 1ta1;ecl • • Stat1anary "lone nom n.aible Ione Stationary !lone Not stated Bot sta:t;ed NND 927545
COhFIDENTIAL - . . Ino14ent Ezhautt Jo. Trf1l lta4w uutud• rt, Sptfd lf(n\ op Cln4f )lot • ••n Apptlll'ed to be Very h11b. Appeued lont ■ tat1onaJ7 . to 1M ''° 1tat1ozw-y. ?lont 210• t'Poa Uncei-tain- Stationary.Could be seen ''d GodMn Jld. ••PJ higb. throuab oi.ffU ,,. lone 210• t'Poa 25000 tt. Stationary.lone Oodllan Pld . ,,r lot atated Approx. 210• 15000 tt. 500 IIPh lot atate4 frt• Oodllan Jld. ,,s Not ■tated Southw■ t ~ aile• lOJll)h lot atated ,4 llcmo , Vest to nat lot stated Speed ot a lcmt aeteor ar tallinC atar. IOJ"tbwaterl7 Rot atated 700-900 IIPh lot atated ,5 81.N• ot tire. lortbeaat lot atated Jot atated ,6 lot atated Jot atated ,1 lot 1tated lortheut aooo-10000 tt. 350111'h lot ■ tated JIOt stated lot ■ tated lot 1t1t.d ,e lot 1tated lfa,t stated Ion• Bait ,0000 tt. V0'7 ta1t lot 1tated 39 40 Kot 1tated Appeared troa 5000 tt. ~0-600 aph lot 1tated nOJ'tbeaat. 41 Jot atated South lot 1tated Great lot 1tated lOOaph lot 1tated 42 lot ,tated Borihweat 1500 4, lot 1tated 11rat group 1200 ,oo mph Jot 1tat14 S S/£, 8HOnd group 1/V. lot 1tated South lot 1tat1d hat lot 1tate4 44 lot atat•d lot 1tatecS Jot stated lot stated lot stat•d 45 , ••tel" lot 1tated Jot stated lortbwtatff1,1 1000 46 than an air• plane. 10000 J'uter 11ml lot 1tate4 Jot etated 80'1thfllterl7 IJ7 •ftT aiNratt h• ba4 rnr •••n. Gained an~ lot stated Ga1eous green 5/V llhtn 1t Mot stated 101t alt1t• a11t. lett the 'f'101D.1t7 • NND 927545 udt at a te1"1"1t1o nte. 60111 1uENTIAL
n u N T IAL ?no1dent 10, Exhauat n:,11 leaflN Att1\Jde Pt. Spefd Btteot on ClOlldl 4aa ver, tatnt S/1 llhen 1t lett emaut trail the Y1t1n1tJ. llben 1IO'fing. lot 1tate4 Lett Jfot stated T10in1t)' at nr, h1gb 1peed. Gl'eenlah 111st 1hen deaoending. S/W ldlen it lttt the TlO 1n1ty. lot 1tated lot stated Not stated lot 1tatect 210 degree, lllben 1 t lett the Tic - 1.nity. 15000-20000 lot stated Hot stated ~d lone Approxblately 1l'011 4000 to due nat lalen 1t Ter1 hi&b. lett the T1o1n1ty. Slow Not stated 49 Lon, trail ot Doke. Vest Very hi&h lot atated lot stated 50 Kot stated Shor•wrd Rot atated but •aid to be quite close. Slov until Bot stated OTer land then higher speed lfbile leaving. 51 Hot atated lot 1tated High Hot stated l ot stated 52 Bone Soutbnrd ; 8000-10000 JCade a P-80 Hot stated look llke 1t wu motion - leH 1n the air. 52& Wot stated 120• 6000 Approxiaate- Not stated lT 150 aph. 53 Bot stated 120• 6000 285 aph. Not stated 5~ Bot 1tatecS Borth Sea to lortolk 22000 Equal to Not stated or greater than • Brit - 1ab Mosquito . 55 lot 1tated DE 10000 Rip yel• Not ■ tated oc1t7• 1tated to be taster than conyent - 1onal airplane. 56 •ot lt&ted Soutb saat 2000 tt 500-600 mph.Mot atated CONF 1 DENTIAL NND 927545
»ioldent lo, 57 58 59 60 61 62 64 65 66 67 68 69 70 71 rlDENTI AL • CO~ Bxbauat m11 lltfflPI il\1'1\4• ,t. lo\ 1tated DZ <,o• I ot ,o• ott the true IOJ'th on llor1son at bor1.Sonal plane. an ••t1111ted 1,A 1111• rap. lot 1tattd 1/W 1000 9500-10000 lot attted ,50- later ohaJll•d to 1or. Liabt tlae JPrca 1/1 bead- 6000 oolor. 1DI Eutwrd. 2000-,000 lot 1tated lorthern &e-nral Jot atattd lot atated thOUlud tt. lot 1tattd lortheaaterly 3000 Jot 1tated lortbeaaterly lot atated 1000 lot atattd Weit to la1t Low Lone atl'a - lorth to South tsht '4\itt 1treak 11.ll - ilar to th• 1treak left by• traoer bullet. 500-1000 White bail lot 1tattd of l■Okt. 6000 Wot 1tated Southea1terl1 lot 1tateO Thin 1treaJc South of gl"e7ill\ color. 1000-,000 Bitber 1aokt 1B to SV or conden - eat1on laat- SAI 2 1eoonda. Jilt)' hav• Southeaat then wot atated been IIIOkt t\ll"Jled and vnt or npor net. tr• 1nttnae NND 927545 ltt1s\ on 212'94• Jli,tl .el.. lot 1tated 001t7, 1ta - wd toM taatu t:bUl • tnoer \,ullet. 510 apb. lot 1tattd 1000 lmota lot atat.4 raster than 1'0t 1tated ,ua,. Jl1&b rate lot 1tated of 1peed. TrandOUI Jot stated Speed. terr1tlo Jot 1tattc1 1000•120011>h lot stated Required ,-4 lot 1tattd 1econd1 to tnffl 70• an. Tnr1tlo lot 1tated lot 1tated lot 1tattd Vff"f t11t. lot stated a.oo,oo 1ot 1tated 7ooteoo lot stated ■i,eed WI aiaoet wit•.
Incident lo. llxhauat ffiil - Bgd1ng ~hr r~eE ·~flAl: iiUuii i i 41t1t1»4e Pt, • Sp••4 Vtftt op Qlouf• 72 Iona South Below 10000 'flteaendou Jot 1tated 1, lone Ba1terl7 approxillatel1 110• -,netio. 7000 175 IIPh Rot 1tated lot stated •ot 1tated Jlot ■ tated Oreata thd&ft7• thm, n•r Witneaaed. 75 lone Baat to wet 75 lot ,tated loi atated 76 lot stated Bot 1tated 4000-6000 lot atated Jot stated 77 lot stated Jfortihwat(Trut) •ot stated 600-1200 lot •ta'-4 78 lot stated 8va1&ht down. Deorna1Jlg tr• approi111atelJ 25000. Inaono~nblt lot stated 79 Jot atated Batt to lfe1t LIii t.ban 15000 Jot atated Kot 1tated 80 Jone southeast Lesa than 500 CCIIIPUttd at ·1:550 IIPh, hOWffJI IP• pelNd to aOTe "1th tbt speed ot • Jet 11.Jlcntt. lot atawd 81 lot stated • ortlnreat 6000 lot stated Bot stated 82 lone ,5t• 10000-18000 Tbree t1M1 lot 1tated that ot a Jet atrontt. 8:5 lot 1tated lot atated 11000 lot stated lot atated 84 lot atate4 lortbeaat 7500 lot atahd lot 1tated 85 Bot atated Borth 8500 35011Ph lot atated 86 Jfot etated IOJ1thard lot stated lot 1tated Rot atated 87 lot stated Not etated trom 6000 lot stated lot atated 88 lot stated lot 1tated 200 yards 110vhig ra, - ?idly liot stated 89 llot etated Eaet 11000 210 mph JIJot stated NND 927545 CONFID ENTI AL
11JcnTIAl Incident Bxh&uat lo. Trail Beading lltitude Ft. Speed Ureot on Cloud• 90 One w1 tneH lor'therly 8000-10000 lot atated lot atated thought be eaw Tapor traile 91 lot stated Diaappeared Great height High rate lot atated in the aoutb- ot apeed weat Jlot stated W.at Abon 1000 Orea t a pffd lot • ta ted Dropped troa Iot atated Ver, high lot atatecl sight on north Telooity aide of •t. Tom near Holyoke. MaH. Green and Deaoending Ter- Prom lSOOO 'fery high liot atated blue tleaea tioally rate ot apeed 95 Se..-eral color• Saatwa.rd Very high Jlot atated ot r1 ..... - rate or red and green apeed predominating 96 lot stated Bot stated 1200-1500 lot atated Hot atatecl 97 Wot stated 1'ot atated Mot stated !lot etated Mot atated 98 lot s tated Jlot atated lot at&ted lot a ta ted lot stated 99 Mot atated lreat to eaat tilot stated lot stated llot atated 100 Grey streaks Borth to aouth lot atated .llot stated lot atated were left in eky .. NND 927545
lfOtE: Inc1dent f 18 It has now been d•tinit•ly determined that both tho photograph and story were t. hou:, perpetrated tor publioity e.nd aooey. Incident #8• The peraon malting t he report on thil 1nc1deat was detsrainod to be & n excitable person, ••r/ talkt.tive, and poaseaaing a.n ex a ggerated.. iugination and 1nol1ned to iJlpreaa people with his continuous uhatter. NND 927545
CONFIDEN T IAL REPORTED DIRECTIOIS OF PLIGHT D 5 I Circling 16 Straight down 5 Directi on Indefinite 64 Direction lot Stated 61 2Z 34 s • 1'he re an undetermined number ot ob jecta ware reported the minimum number of object& are pl ottedo Same object reported by di !'terent p,ople only shown oncto NND 927545 CONFIDEN TIA L
. rea > s 4 POs Aa NND 927545
; ‘ «3
e CONFIDENTIAL • Identit1c&tlon ot Subjeot llatter (a, per ••Pl•) IIOU 11CIT 19 Feb 48 l l. Reterenoe 1a ade to th• £11&1 tann b7 llr. Rhoad•• (In.oident f,40) which ••re tonrarded tor exuination. Tb• tollcnriq data ••r• dtri·Hd. froa a atucly ot the 1peciaen1 a. It ia oonoludecl that th• me• ii of tne pbotogn.phio m.ture, and 1• not due to 1~rteotion1 in th• nul.S.011. or lack o1 deTel opaent in the ■ to tion in quHtion. Th• im.c• •xhibit1 a "tt.11" indicating th• pn,per t)'~ ot di1to·rtion due to the tne ot 1hutter u1ed, tht apt.cl of the o'bj•ot and tht fixed •peed. of the abutter. Thll trailing ott oontona, to th• g.ntral intor•• tS.oD gi T~ 1n th• report. l>. Th• nport 1tatH th• objeot na •••n a.1- approxiat•ly 2000 t••t at tho ti• ot expoaure. !he obaerHl" allO report, bein& abl• to Ht oltarl1 t. oanow of •nolo1v•. !h• Tiaual aoui ty ot an aTerag• perao!lf'woulcl allow tor thi• peroeptioa, bu't oH•te:l Illy not auoh t'\ll'ther •• 'the 1ubjeot Md low fl nal ooutraat, being cn.y againat a C!'&T •~• It•• ou e1tabl1ah the 41,teoe troe o&aora ~o 1ubjeot, •• Will h&Te quntlty ,fl. !he report 1tate1 tha.t a 820 oaatrt. n.1 u,.ct, in4ioat1ng Hnn.l po111Mlli1••• ti.not tht 620 ia ooa111cle.tur• for the •pe>oli~ a.114 width ot the til.a •• aay h&Ye mptiT•I 2t' X 2t", 2f X ~ a.n4 2-t x 4f'. The aaapl• aubaitte4 ha.cl been out and it wa1 not po11ible to Ht&blilh the 1xaot traat dse. !be 2t x 2f' Iii• waa rul•d out, 1-anrc 2¼ x st" a.nd i¼ x ~. It 1 t ftre th• ro,...r, them. the tooal leqtii ot the 101 would be ••• an4 uelisg 2000 teet ... the approid.u.te aubj•ot diatanoe and the lagt dH at 1 /M•, .. ban an app,onaat• ••se ot '4 t••• a, the cllagonal of the objeot. low 1t wa ohoo ■• the latter n.lue ot a• tor t.,eal length, •• h&Te an approxi• •te T&lue ot' &&• tor th• cliagon&l. Poln-t:1 ot meaauNaent are 1ndioated troa . x to x on lxhibit •••• CONFIDENTIAL NND 927545
» é ag Da} , ‘ee! 4 kad” ie ale. 7 coy See SEM | an a? er. “y Pee het bp ne eee F ye ee ; SD 5 ii Pate Te ne + y s pane Pe a es, de F a 4 #73°3 © Sf ee f ie pth ee Spe fee a 2 . mt ee ER he 7 Z re 4 ; OF Fea tyes AAS PO GAL pei 4 °* ; ‘a <i oe , “ Pe er * 0 Se a “ . is ‘ , ars ; : at ss ois : ¥ Pe a —. wy ae) Prenat v : ~ yr : . * , 3 AS J x * ‘ * 5 iF y : © 0 é “a ale. 14 NND 927545
j ‘|| i | | 4 ' = ae. ? -@ me : / _- o a =. 7 ° tS _ tS “~ oo ; oe ~~ : a Dag ae te ee a i » Ps Fe —. : . art a NND 927545
THE AEROPLAtlE 18S I FEBRUARY 13, 194& # The Biolo! of the Flying Sa f cer - I The Story of Low Aspect Ratio Aircraft By A. R. Weyl, A.F.R.Ae.S. o t her hand. the U.S. Air Force co nsidered the matter seriQU\ S E VERAL MONTHS AGO pe o ple o n both side .. of the enough to warrant inve .. tigations into the incidenis which had Atlantic rushed into print wn h cl aim s of havi ng ob~e rved queer saucer-shaped aircraft wh ich new very fast . Some main bee n reported . ta ined, indeed . th a t they had s een ,qua dron \ of , uch mysterious In the meantime. the occur rence of Flying Saucer\ ha .. ceased ob{ " ccts; others described vividly ho w these celestial saucers v.ere to be n ew\. P resuma bly. the~ have all landed. [A new cr op ab e 10 descend vertically. All agreed on the \aucer-hl.e , hapc . w a<; reported in Tu r AER0PLANF for J anuary 16 la~t under the heading •• Tuppence Coloured."-Eo.] Sceptics considered that, for n on-aero nautical people ltv1ng far from the form er playar oun d s o f V . I. V.2 , a nd all the re st Aerooaudc-al Aotlquities and lniquiti tt of H itler's "civi lizatory • practices. fl ying sa ucer<; might indeed As a matter of fact. saucer-\haped aeropla ne .. are not quite constitute phenomena of threatening aspect, from their experi Quite ence of domestic di sag reement s. Doctors, however. hastened to as new as some people have tried to ma l. e ou t. (Fig. I.) assure the World that sa ucer -s haped or lent ic ula r objects could a number of a1rernft have been constructed and nown with well be nothing more than specks in the lenses of the eyes of the wi11gs o f the ring or disc type which coul d well hav e bee n mi s observers- the so-called m11sae 1·0/ames associated with high ta ken for saucers. hat-brims. ~pa de s, doughnut~. diamonds. blood pressure. Teetotallers blamed the sorry consequence.. o f Greek letter,. pancal.e\, nat fhh. geometrical symbols. d inner imbibi ng intoxicating liqu ors for the observations. On the plates, and ot her entirely no n-a eronautical commodities. Moreover. it is qu ite true. .a nd n ot even a minor secret, that, at present. aero nautical engineers are paying increased a ttention to s uch queer wing shapes: disc wings. for instance. permit ceriain disadvantages of conventional wing\ to be overco me. It 1s even thought that such shares have been neglected too long 1 he blame for rheir neglect can be ascribed to the doctrine o f the induced drng. When the Lanche .. ter-Pranc.ltJ ae rofoil theory became recoi,1nized nearly 30 }ears ago, and \\hen the !>a1lplane movement proved that slender wings were a necessity fo r soaring. designer, began striving a fter .. good .. aspect ratios. The theory blinded their eye~ agains, the poss1bili11es of other than convenrional wings. T hi~. h O\\Cve r. was not the fault C"f the theory.,\\ Prandtl soon sho\\ ed its restrict io ns . We have now come 10 reconsider the matter of wing sh ape in an objective way. as it is quite possible that aircraft d esign is approaching a cul-de-sac ~o long as it retains it~ bias in --6---- ~ Apttro.l 1 L - I ._ ' _ °' , -r.:--i, I c 6) - ___ __ ,_ _ '°' _1 ___ ___, ==~ (b OCl5S • stCTIO!'I \ ,pa" C chor4 t \ )(•-,lod a,u Fig . 1 .-" Turbine flying mach ine" (proj ect ) of the Munich engineer Gustave Koch, 18931 1894. Tailless monoplane of SquHC' low aspe ct ratio. propelled by a ducted fan. A SO h.p. ...~ , steim engine wu deemed sufficient for th is flying mo to r car. The design of the duct shows intelligent anticipation. L ...._______. AR • 0-1 I- b , __j l t t Fig . 2 (Right).- Definitlon of the aspect ratio of an aerofoil. The arrows signify the direction of the air flow against the t t t wing. The terms pteroid (feather-like) and apterold have been introduced by F. W . Lanchester. NND 927545\ I THE AEROPLANE 186 FEBRUARY 13, 1948 C..HlUr of the "well-tried " co nvention, .. normal " wings. For the c reasons. a study of. the hi\lory of the u'IC of low asp,.-ct. rat,o) m wing de:.11n will be of interest. Sp1ruually, the fathers of uch acronauucal exhibits were Ens!"hmen . 1 hey were people of good reputation ttnd by no _me.ins suspect o( aerodynamic perversion. F. W. Lanchcstcr was undoubtedlf the first acrodynamici,t to g,~e thought to aeroplane winis ot circular or squ.irc ,hapc. lo ht) bool.. publl\hcd m 1907, he referred c'<prcssivcly 10 ~uch "aptcrold" wmii hnpc~ {F1a. 2) i,nd advanced the view th a t Nc11.ton's law wa, valid for these. 1he correctncs; of th i~ Fig . 3. -A simple experiment In annular .ierofolls. vie\\ wa~ c~pcrimentally proved 30 ~cars later. In a prev1ou\ article on " Stalling Characteristics of Taille-.s Aeropl.rne~ •• ( lttE AFROl'LANI:. for August I S. 1947), tl,e early mtcrc-.t tal..cn by F. <i:iow Sir Frederick) Handley Pa~e m the stalling quahucs of wmgs of low aspect rauo was mentioned. He showed, 10 a pap~r read an April. 1911. that marginal vortices and press urc-equalmng flow a r ound the tips were respon~iblc for the delay of flow separation which h.id been obmv ed at high incidence). He stated. in this connection :-• · . .. With planes of high aspect ratio _(I. e.. with slen der wings of normal span chord rnllo), \here " not the same facility for the " feedmg m " of f_rcsh air at the plane sides (i.e .. nt the wing tips) 10 act as a l~nk between the plane and the live stream. and therefore the live stream leaves the plane's b11ck at .in earlier st11i;e than in the ca,e of the plane of lower aspect ratio .... " He then sho11.,ed _ some experimental evidence for the delay of flow separauon with decrease of the aspect ratio and for the greater Fig. 4.-Prlnclple or th• Huth annular-biplane system. maximum lift of such wing~. . When Lanches. tcr published his bool.., man was ju~t begin main wing. the tailless aeroplane is created. For all th ese nma to _ spre~d his wmgs. and in order 10 fly with a minimum arrangements. th e condition is that, in the case of a wina com ellpend1ture m power, wini:s of fair aspect ratio were a neccs s11y . N everthele\s, there were a few early aeroplanes. notably pmed of n orma l (unstable) ae rofoil ~lions. the stabi lizin& aerofoil exens a certain leverage in relation to the centre of the little :· Demo1~lle •• monoplane o f Santos Dumont (1909 - gravity of the aircraft. 19 !0l, which had an aspect ratio of only 2 and proved to be qu Ile \Ucces,ful. Another possibility is to combine two lifting winas so that they will stabilize and balance each other. For th is pu rp ose, all One o( the earlie~t attempts at a genuine •· apteroid" 11cro pl ane was an experiment by a German architect, Flick-Remig that is required is th at th e front wi ng shall possess, at all inci d ence, of .flight, a greater effective incidence than the rear wiog. ( 1910). It had a span of 7 j ft .. and performed in hops only. In other words. the cent re of gravity must be nearer to the le.iding wing than to the traili9g wing, and the whole arrange Annular Aerodynamks ment must be ba lanced accordmgly. In this way, we arrive at A ,1mple experime nt with ~ome paper and a pair of sci,sor; the conception of a stable tandem aeroplane. s how s that the ~i nl.. ing speed of a circular disc loaded with a If we now take such a tandem arrangement and sweep the paper clip is decreased when a hole of suff1e1ent d iameter is cut leading wing back and the trailing wina correspondingly forward out in the centre (Fig. 3). Thi s justifies the development from so that the tips of both wings merge into each other, we obtain the circula r d1-.c wmt; to the annular aerofoil. The the ory of an annular or ring-shaped wing system. Aerodynamically, it is the phenomenon i~ still somewhat obscure. of minor importance if the s hape is ac tu ally circular or oval, (Having tried thl\ experime01 . we can confirm that the char or 1f triangul ar or quadrangular shapes con,titute the wing. For acteristics of an annular aerofoil are certainly very d iffere nt ,implicity's ..ake , in all such cases considered here, the term from th ose of the plain d1 -.c aerofoil. Our own experiment, .. an nular" 1, appl ied. 11.cre admittedly somewhat lim1ted in scope a nd we were unable As mentioned, the aerodynamics of such shapes cannot yet !O form more than an imprc~10n of the relauve sinking ,peed, : be considered as fully established. But it i, proved that longi II did, howev~r. arpcar to be le,~ with the annular aerofoil. Our tudinally stable wing systems can be obtnined with such shapes. mam conclu\lon, w•!re that cutting a 2.25-in. diameter hole in Some type~ relying on such wings have shown quite remarkable a .5 37S-in. diameter disc. resulted in a much flatt. er glide; the llying qualiue~. It is also p os,ib le that, with annular wings. the ,tall 11. , 1, not ,o abrupt. and the stability in the glide wa, induced drai; i, less than with conventional wings of equiva 1mpm,cd. We were so fascinated with the e>tperiment th.it we lent aspect rat io. hope to repeat u ,U a later date on a more ..c:1ent ific levcl.- Eo.) In common with circular wing,. annular wings have the fh e conven11onal aeroplJne " constituted of two ba\ic aero remarl..able property th at the lift force ,teadily increases with frnh : a "ing (,, h1ch ,upp l 1e~ the lift) and ri tail (,, hich balances incidence up to fairly high values without a stall. For all and ~tabilize~ the wing). We I.now that \Uch a n arrangement I.n o" n arrangements the maximum lift seem, 10 occ ur at o.f the 111.0 aerofoil compnnenh i, by no mean, the only pos incidences exceeding 30 deg ree,. A, ,uch h ig h angle~ of \tblc one. The balancing .ind st11b1lmng aerofoil (tailplane) incidence are not likely 10 be reached an fl ight unintentionally. need not to be aft of the lifting w ing a, a tail. It can be It 1s obv1ou, "hy annular wings have become renowned for arrange d a nywhe re 1n relation to the wing. e.g .. above It, belo11. their good-natured flying charac1eri,1il:,. it. o r in front of it. Another property of annular wi ngs (first establi,hed by If the balancing aerofoi l i, in front o f the main win~. the aero Tilghman Richard,) i, that the centre of pre,sure of ,uch wing plane i~ of the tail-first type. an d if it i, attached to the ,y,tcm, i, nearly stationary in flight , or that a travel o f the centre of pre,wre can be obtained which i, po,itively stable unul incidences o f the order of 18 degree are reached. In fact. no case of longitudmal in,tabihty ha, ever been reponcd w11h an annular wing. although the centre of gravity has often been located d:ingerou,ly far back. The fi~t annular-wing aeroplane dates bacl.. 10 1908. It h,1d little succe\\. Two type, 11.ere co n~tructed m ,ucces\ion tu the de,1gns of a capable German aeronautical engineer, Fri tz Huth . who "as by profe\\1on a teacher at a technical ,;chool ( f-tg,. 4 and 61. The ,econd type. which had a less elaborate a1r,crcw drive. fl ew in May. 1910: it wa,. however. ,o devoid of performance. in spite of a SO b.h.p. engine. that it was soon ,1f1e rv.ards d1..carded as a hopeless proposition. Britain'~ Fir..1 Doughnut The Br i11,h concepuon of the idea has been for more ,ucccs,ful. A, it i, cun,1i1u1ed, until now. the best tried reprc,cntativc. it~ hi,1ory may be given somewhat more c,1cn,1vcly. I he ori~mal idea for an annular-wing aeroplane came from (, . A K itchen. m about 1910; he con,tructed a b1pl.1ne with Fig . S. Kitchen's doughnut of 1911 . rini:-,haped wmg,, but made no progrcs, "ith it. The stable NND 927545FEBRUARY 13, 1948 187 THE AEROPLANE flight of Kitchen's models. however. convinced Cedric Lee that an aeroplane of such de~ign would be - a succes,. 11nd late in 1910 he acquired the patents. At the same time, G. Tilghman Richards, who was a qualifii:d aeron:iutical engineer, became , ~uffic1ently interested in the mailer to give up a budding engineering bureau in order to join Cedric Lee and 10 devote ·JUI· tl?, !i m hib energy 10 tbe idea of a ·• safety " aeroplane. Tilghman Richards began with systemat ic experiment, on __ .._ models and on large gJiders. Later, careful wind-tunnel test~ (including the o bservation of the pressure distribution) were made by him in a :!-ft. tunnel he had constructed at East London College and al~o in tunnels-of tile National Physical Laboratory. The preparation of the design was, therefore, uncommonly ~-ardul for this early period of 1911 - 1914. In o rder to ap(>reciate the intention~ for the development, the following quota11on from a paper read by Tilghman Richards in about 1912 is illuminating: - ... . . 1 he ve ry fnct of high lift occurring at small angles rreans the provision of large area for l•nding speed resulting in an inefficient altitude of the plane at high speed: and the inherent instability of curved aerofoils means a continual dependence on extraneou, controls carried at some distance f_rom the wing by heavy and redundant Structure. . . . High lift at small angles il> u~eles~. likewise high lift/ drag ratio at ,mall an,les, and what is required is the reversal of the normal type of hft c urve i:iving little lift •lit small angles with low value of the lift/ drag ratio for landini. . . ." Seen from our pre.sent state of knowledge and development, a nd facing the burning problems of personal aircraft for the man in the street. it wo uld seem that this opinion is a very i;o~ argument for further experimentation along the lines indicated. _ The. experience with _powered aeroplanes was at first beset with disappointment~. Famine P_oint, Heysham, was apparently no t a spot from which aeronauucal experimenters could derive any comfort. The original Kitchen biplane with a 50 b.h.p. rotary engine was wrecked by a gale, during I 9 I I. before flight tests could b~ m~de. After recort~truction some flight~ were performed wtth 11 at Sho!eham <!~ring 1911- 12: yet it never gave any pr~~f of superior q~ah11es. The biplane had ailerons o f the or1gmal Farman variety between the wings. Very soon the biplane arrangement w!1s given up in favour of the monoplane. A subs~quent experimental monoplane was nicknamed the " Sccret-C1rct1: Plane ". ~r "Doughnut,'' the experiments being shrouded agamst pubhclly (much against the interests of the dev~lopmen!), This annular-wing aeroplane (Fig. 7) was equipped with an 80 b.h.p. rotary and test-flown by Gordon England on November 23, 1912. at Shoreham. The flight was _remarkable and luck>; for the pilot, but. unlucky for the precious craft. After havmg flown a large circuit on the first attempt. the pilot noticed, when coming in to land that the aeroplane was exceedingly tail-heavy and getting out ~f control the elevator. bei!Jg insufficient. At about 150 ft. above th~ ground the inevttable stall took place: but the pilot managed ~~mehow to drop his mount upside down on to telegraph wire~ and escaped without personal injury. Wtth the reconstructed and improved monoplane many s\iccessful flights were made by G o rdon England, N. S. Percival -:'x: - -' - Fig. 6.-Huth annular biplane of 1909. and Gordon Bell. Finally it came to i;ricf when flown by Cedric Lee himself without previous training. After a good fliaht he managed to put it into a river. Another incident happened with a subsequent annular monoplane: the elevator jammed anct broke in flight. The aeroplane merely pancaked to the ground, again preserving the health of i~ pilot, E. C. Gordon England. These types in their final form had lateral control effected by differential deflection of the elevators. It was realized that this elevon control was not very effective for lateral manceuvres. yet the lateral stability of the wing proved so great that the provision of ailerons seemed superfluo us. The loneitudinal stability was always satisfactory, once the centre of gravity was properly located. Because of the great inherent · fore-and-aft stability, a separate elevator was, at o ne time, located on top of the vertical fin and permitted the fitting of special ailerons. For directional control a vertical rudder was attached to the stern of the fuselage at the trailing edge of the wing. A form of tricycle undercarriage was employed. - In respect of perfo rmance, the wind-tunnel tests indicated that a better lift/ drag' ratio could be expected than with a comparable conventionaf aeroplane., However, no co nclusive evidence for this has, as,yet, been presented. The third British monoplane of this type also had an 80 b.h.p. rotary engine. but this time it was located aft and. further, drove the airscrew by means of an extension shaft. Unlike its pre d~cssors, ~~ dihedral was provided. and because of this the flying qualities were found to have been greatly improved. From early in 1914 until the outbreak of the 1914-18 War this unco nventional aeroplane was frequently flown (mostly by Gordon Bell): it was demonstrated before Winston Churchill in the hope of securing orders from the Admiralty. Altogether, 11,000 miles were flown in about 128 hours, a nd eve~ people not previously trained as pilots were able to fly 11. In Ma y, 1914. two such aeroplanes were being designed for parlicipation in the Gordon-Bennett Race of 1915. When the 1914-19 18 War terminated the work. it had clearly grown far beyond the stage of an untried project and could have well been termed a successful experiment with every prospect of becoming a practical proposition. In l?l~-10 Tilghman Richards succeeded in persuading the Air Mm1stry 10 place a n order for a further experiRlental aeroplane. But a week after communica1ing this decision Major-General Bagnall-Wild, the promoter of the idea, retired, and red tape killed an intelligent intention. It is only fair to record that aeronautical progress has suffered fr~m the failure to have this develop'ment continued. As Tilghman Richards stated many years ago: - .. There i~ no!hing myMerious about th~ annular plane. It affords high ltft at large angles, ha~ no >urble point and has ~ good lift/ drag . rati_ o for wings with a body. ' The !Tiachm~ was very fast in p,ght. for its day, and extremely slow m lan~mg: and there bei!)g three dislinct regions of lift, one a ptero1d and two pterygo1d on each half-wing. the movement of the centre of pressure was a resultant of three distinct regional movements; ,tnd with slight modifications could be made 10 move in any desired manner witho ut affecting the general efficiency of 1he plane." As _mentio ned. th«: c!rcular shape for the wing is not in itself ~ dec1s1ve cha".\c1enst1c. ?reviously. in 1908, A. H. Edwards invented the ring-type wing with rhomboidal or triangular shape_ (Brit. Pat. Spec. No. 4519 of February, 1908). An experimental aeroplane of this type, "The Rhomboidal,'' was constructed and tested at Brooklands. It wa~ not s uccessful. (To ~ conlit1u~d.) Fig 7.-Cedric Lee Monoplane No. 1 of TIighman Richards, 1912. NND 927545
.. ,. MARCH S, 1948 279 - THE AEROPLANE - .. The Biology of the Flying Saucer- II By A. R. Weyl, A.F.R.Ae.S. In this series of articles the history of low-aspect-ratio aircraft is recounted and technical aspects of their design discussed. leading up to their use for supersonic flight. T (Continued from J>Olt 185, February 13 /rut.) HE SECR ET-CIRCLE "CONSPIRACY;• mentioned pre viously in connection with circu)ar-aerofoil aeroplanes. did not lack congenially inventive spirits. Early in 1913 an engineer in D ijon. M. Bou rgoin. made experiments with an annular wing aeroplane. The tests were unsatisfactory. One feature of this design was the provision made for varying the wing incidence in flight. More recently, a similar idea was suggested by N. H. Warren and Th. R. Young (Fig. 8). In 1937 they secured a p atent ( Brit. Pat. Spec. No. 508,022 of December, 1937) for a non stallable monoplane of rhomboidal shape (i.e., leading wing swept back and trailing wing swept forwards with the wing lips merged together). This was provided with a conventional tail at 1he stern of a long fuselage and a number o f advantage~ Fis. 8.-Project by W arren and Young for a liJht twln en1lned two-seater of 90 h.p. (1937). The elevator is fitted between fin and fuselage. There Is no tailplane. were claimed. lo 1943 a model for a two-seater fighter with tail turret show~ the separate tail omitt~d; special emphasis was laid oo the triangular shape o f each wing and the effect of sweep was relied upon. Nothing more bas become_ known since however b ut it is worth noting that the proJect had been'based oa ;ound aerodynamic considerations. lo 1933 the annular wing of the German sculptor Antes created a mild s~nsation bc<:ause ?f the good performance oC models made to th is coocepuon (Fig. 9). Some.what pecul iar was the aerodynamic ~onceP.tion of the rhomboidal annular aerop lane of P. Nesbitt W11loughby, a = Fis, 9.--Model of the "annular wing " ~f Ant es. 1933. qualified aeronautical engineer (Fig. 10). The Willoughb} Delta Co. of London had taken up the development of th,., idea in 1931 and sufficient means were available to make rather extensive tests. The principle is best described as a tandem monoplane with two aerofoil-shaped parts connecting the leading wing with the trailing wing near the tips. The "side wings" had aerofoil shape not only in their longitud inal cross-section (i.e., in the direction of flight). but also laterally. This was considered a characteristic feature and subject to patents. It was claimed tha t the vortex distribu1ion induced by such shape gave an unusually h igh aerodynamic efficiency in spite of the small span of the aeroplane. In addition. it was pointed out that the maximum lift was shifted to very high incidences. Moreover. the "side wings" should reduce the drag of engine nacelle, filled underneath them. All this was said to be proved by extensive wind-tunnel experimentation here and abroad. Designs of passenger trans po n aircraft reaching weights o f 40,000 lb. were prepared on the basis of model tests made at the National Physical Laboratory a nd elsewhere. T he results must have been so encouraging that a n experimental monoplane with two 125 b.h.p. Menasco e ngines and weighing 2,540 lb. was constructed late in 1938 (Fig. 11). This aeroplane flew indeed and was even publicl~ demonstraled (including one-engine flight) a1 a Garden Party in May, 1939. Shortly afterwards the experimenter was killed in an uneitplained c rash during a flight test. From pressure plots over the "side planes" which have been published, apparently trim changes could be eitpected at various aocidences. These components were thus capable of producing longitudinal inslability a nd it is not improbable that this and poor control efficiency may have contributed to the accident. There was a lso evidence of a stall at normal incidences. although of a very mild character and with little apparent decrease in the lift c~fficient (which. however, would not exclude the presence of fl uctuating lift forces). 1 1 Fig. 10.-frinciple or the W illoughby Delta design. Another suggestion for an annular wing was made by L. Peel, in 1944. This. however. was concerned less with the aerodynamic p roperties of such wing systems than with the arrangement of two engines facing each other with their air screws. in order to overcome the torque reacuon. A phenomenon of which aerodynamic experimenters were alwa)ls well aware. but which aircraft designers failed 10 u1ilizc, was that wind-tunnel tests clearly proved good-natured stalling p_ roperties of wings having very small aspect ratios. Yet even m the very e_arly days when centres of gravity were far too far back on the old box-kites, the square shape of tailplanes. then unaccountably in vogue, ma y have saved the pilot's bacon more than once by its refusal to stall under eittreme provocation. Later on science came and proved that a tailplane of "good" aspect ratio was more eflkient. It was, but it made the stall worse when the centre of gravity happened to be rather aft. The interesting thing is that aerofoils of circular or square shape were tested in the early days at incidences up to 90 degrees, while o n normal aerofoils tests were restricted to rather small incidences onl y. generally ucluding the range o f stall. NND 927545
e MARCH S, 1948 THE AEROPLANE 280 c > \ I \ I I I I I I I \,' I I \,' Fig. 11.-Willoughby's "Delta 8" experimental monoplane of 1938. Thus, an observant student of laboratory tests could have noticed the extraordinary capacity of circular or square shapes 10 give a very gradual, innocent stall, an~ that at v!!rY high incidences. Yet, a part from a few broad-minded experimenters, no designer drew the conclusion that wmgs of such shapes promised safety in flight, t~oug_ h it w~s known f~om ..~rly practical experience that fly1Dg 10 the second regime, 1.e., at the stall, was positively dangerous. It is true that spinning- Pa rker's "Spiral D ive "-was attributed. in those days, to high i~cideoces, and that most _of the lightly loaded rectangular wmgs used at that period rendered the stall relatively. innocuo us. Howeve_r, :iccidental ~tailing was then, as now. the cause of the maJonty of all crashes. And the nose dive following inadvertent stalls was well known to be o f the most serious consequences. . Eiffel, Riabouchinsky, D ines, . Prandtl, etc., began the_1r laboratory experiments on aerofoils of very small aspect rauo and the results were generously published (how closely secret they would be kept to-day!). Eiffe l showed that the ratio of the resultant forces reached maxima for small aspect ratios _an~ that slender wings gave the greatest drag at ~ degrees 10c1 - . <lence, whilst disc wings had then t_ he leas) res\stanc_e of _all. Riabouchinsky proved that the maximum 11ft with d 15:C Wl1'!8S wa~ reached at incidences of the order of 40 degrees. whilst with normal aspect ratios (exceed ing a value of 4) the maximum lift took place at incidences of 12 to 14 degrees only. Beyond their critical incidence disc wings gave a gradual decrease of the lift force whereas wings o f normal aspect ratio gave a very abrupt ; nd unsteady one. 1 he tests by Dines on flat plates in natural wind confirmed this info_ rmauon and that the observation applied 10 cambered aerofoils as well was also proved (by Riabouchiosky). 0. Foeppl s_howed frof!l system atic wind-tunnel tests that a square aerofoil behaves, ID respect of its lift curve in a remarkably d ifferent manner from one having an aspec't ratio of 1.5, although wall interference and Reynolds Number may have somewhat affected the results of the tests. . Later, Pra ndtl was eager to point o~t that his aer~fo1l theory did not hold for very small aspect ratios, and that, ID fact, the induced drag of disc wings was less than the theory suggested. In sP.ite of this, however, nobody seems to have he~ded the possibilities implied and the " ~attle of the Aspect Ratios" was decided in favour of slende r wings. . To be fair, it must be pointed out that there was one senou~ I Fig. 12.-Experimental Hayden glider, 1925. Span, 19.7 rt. : length, 13·85 rt.; wing area, 173 sq. rt. All-up_ weight, 310 lb. No lateral control. argument against disc wings. The best aerofoil sections in use prior 10 about 1925 had a plain camber which implies travel of the centre of pressure when the incidence varies; the length of such travel is linked up with the wing chord. Hence the change in trim o r stabiluy is. with such aerofoil sections, greater with large-chord wings. On this consideration of fore-and-aft stability and control, designers bad some justification for thcir deci sion against experimenting with disc wings. Yet quite useful aerofoil secuons had a lready been used in flight which had practically no travel of the centre of pressure and hence d id not suffer from thi~ disadvantage of the disc wing. The whole argument, however, lost its importance imme diately M. M. Munk proved that very efficient aerofoil sections could be designed with a completely (or nearly so) stationary centre of pressure. It is. therefore, right to say that from that time all conditions existed for a practical evolution of d isc-wing aeroplanes. F. Handley Page converted an aerofoil, leaving an aspect ratio of 6.25, into six square-aerofoil po rtions by five slots. each parallel to the chord of the wing. By so doing he hoped to have the low drag of a oormal wing combined with the high stalling angle of the d isc-type wmg. Although a very slight improvement was claim~d, the principle was that of eating the cake and having it too: the induced drag is respon sible for the stalling properties of the d isc wing and you cannot have the benefits of the high drag without suffering its disad vantages. Moreover, in o rder to have the effect of the disc wing, the provision of mere slots is insufficient. Marginal vortices need room to deploy. On the whole, however, the idea proves that at least one practical aircraft designer had realized that there was some thing in wings of abnormally small aspect ratio. There were other. although not quue as well thought out, antecedents of the disc-wing aeroplane. In the tint soaring flight competitio n on the Rhocn ( 1920), Friedrich Richter, a burly naval pilot o f 20 stone or so, performed on a triplane glider with wings having an individual aspect ratio of far kss than three. H. Hayden secured, in 1922, a patent for a rhom boidal wing with an aspect ratio of nearly unity, claiming for such a shape high lift and good flying qualities. In 192S he constructed a glider with a win, having an aspect ratio of only 2.25. The wing was nearly tnangular in shape, with its apex leading, and a pronounced wash-out towards the tips (Fig. 12); no lateral controls were fitted. The tailplane with the elevator was fitted underneath the trailing edge at the c ==---=- - Fig. 13.-A French project of G. Abrial, 1929. stern of a f11selage. Flyinf experiments in Styria were said 10 have proved satisfactory flying qualities. Some early tailless aero planes, such as certain experimental types of Rene Arnoux, had rather stub wings a nd heavily reflexed (i.e., positively stable) aerofoil sections. A 19?9 design of G . Ab rial showed an aspect ratio of 2.88, with, however, substantial tip discs (which have the effect of increasing the aerodynamic aspect ratio) a nd wind-tunnel experiments indi cated a creditable performance (Fig. 13). Russian attempts, in particular the parabola type of Tscheranowsky, too, were experiments with aspect ratios of three and even less (Figs. 14 a nd IS). Their resemblance in shape to the latest designs of super-sonic aeroplanes is remarkable. . A Modttn Pioneer Further intcre~t in the aerodynamics o f disc wings was displayed by research workers with th.e arrival of Juan de la Cicrv:i's Autogiro. This was indeed s<>mcthing like a circular wing, a nd performance estimates were based on the properties of such wings. Yet the question of stalling stability did not a rise, bccau~e of the rotor properties. The real pioneer of the disc wing was a very able American research engineer of the National Advisory Committee for Aeronautics (N.A.C.A.), who proved capable of following independent lines of development. In about 1930 Charles H. Zimmermann subjected the properties of disc wings to NND 927545
M AR CH S, 19 48 28 1 THE AEROPLANf e wi ng , tru ctu res as well as for the pos\lbility of housing every· thing w11hm a wing. Hence 1hc 1e a re very real design reasons for the preference of disc wings, quite a p an from the ea~cd accommoda11on of shor t-s pan ae r opla nes. So me R ernurkable R esu l ts Zimmerma nn establ.shed that the optimum a~pcct rauo "'"~ fo und bet,..een the values o f 0 .75 and 1.5. l he,c value, in clude both ,quare an d ctrcubr wmg ,hapes. F or a g1Hn wing sccu on (Clark Y) the latter gave the h1gh~t hft coefficient. 1. 85 at 45 degrees incid en ce, compared "uh a value of t.:!4 at 14 degr ee, mc1dencc for an aspect ratio o f six. Funhcr more. an important result "'•'\ evidence that at ~,n a,pect ra110 of unity hquare or elhpllcal .... ,ng,), and :11 an a,pec t rauo of 0.9 (" mg "11h faired ups), no tendcnc)' 111 autorotauon could be found. A circular " mg (:1,ix-ct raw, ... / - -- of 1.27) ind c.llcd the po\\1hili1y of ~1urnrntation (1.e ., ,rinningl at incidence\ below that of maximum l if1. 1 he 1nm1biht)' of ,pinning before the actual ,tall is reached is. indeed, e,tra · ordinary. All these rcwh, r.:fer to te,t• "ith the ( lar~ , Fig . _14.-A Russian • puabola' glider of 1924. aerofoil section. Less establi,hed "a s the contenuon th:11 d1..c wing would 11ive improved la11:ral and longuudmal ,1.1h1htv at l ow incidence, extensive wind-tunnel investigation and the publbh ed reports 1 hi, ..ecm, ,11II 10 be a moot point of the Flyin!l Saucer. \till form the ba,is of prc~ent development. In places. In Fig. 16, Fig. 17. and Fig. 18 some charactcri,tic result, ,,f the re,ults confirm, qual1tat1vel)', the experiments made '.!O year~ before. But, as mentioned earlier, these experiments had been praet1C111ly forgotten. Zimmermann's target has been the development of a really 7 fool-proof aeroplane for amateur pilots. It is no u<,c hiding the fact that in n.:arly all accidents in which blame is attrib uted to an .. error of /'udgment" on the part of the p1l o1, th.: aeroplane is :ietual y at fault. The moq common causes arc the consequences of inadvertent ~taili ng . Once this 1~ completely remedie d, the overwhe lm i ng ma jority of accident will become mere incidents or just fun , an d instead of coroners and ho spitals. aircr.1ft manufacturer) and repair sh op) will I! have the be n efit I I On such very sound lines (which se em to be generally acknowled$ed, but still far too o ften ignored), Zimrrcrmann I I directed his main attention to the stalli ng problem. He :; ., ;>roved that small variations in the aspect ratio made pr ofound 't differences and that the shape of the wing tips also had a great 0-, influence. ... ~. ~ At the same time he confirmed that the induced drag of circular or square wings is by no mean s as proh1b111ve as the simple theory of the " horseshoe " vo rtex line would indica te. He also proved that it was simply the induced drag du e to the predominant in fl uence of the marginal vortices which brou~ht •• about the behaviour at high incidence~: the idea th at the provision of oblique slots might help in this connection proved, h owever, abortive. An advantaae which Z1mmermann's research brought to liaht was that disc wings gave less profile drag at small CIA°', IIC,,O,. incidences (high-speed flight). because of the reduction of the -1.... ___ _... _ .,,. JO' -: relative thic kn ess of the aer ofoil sections. 1 h is drag reduction has indeed beco me one of the rr.ain rea so ns for di.c wings being adop t ed for aer o plane s capable of flying at ~ reed s at which the compressibility of the air needs to be co nsid ere d . Fl& , 16 .- N .A .C. A. te sts b y C. H . Z immer mann which prove the extraordinuy sull1ng qual1t1es of disc wines, Fo r supersonic flight disc wings seem, at P.rcscnt, to be a necessity. Alternatively, for a given aerofoil thickness ratio, !he height avail _a ble f <? r st,:ucture _a nd stora1te (J?O wer plant _sl Zimmem1ann·~ _ wind-tunnel expe rime nt s of 1932 are given. It 1s greatest within a disc wmg ; this ma.,es for light and s utr 1~ seen from F,,. 18 that the difference between the mc1deoce of ma,umum hft and the gliding angle at m:i 1t1mum hft ( "ma '< •a ma'<) rem:im'I fairly independent o f aspect ratt,,, and of the o r der of 9 to 13 degree,. 1 h1~ would me:in th .11 th e attitude of the . disc-type aero plane, when flattening out, w ou ld n ot greatly d iffer from t ha t of convcnuonal aeroplane, In particular, there "'ould be no need 10 provide h1g_h under· cama;ies for disc aeroplane, a .. their gliding path 1s steer Thi, 1s an important di ff erence fr om "''"IJS w11h lead1ng-cd~~ ,lots . . In P !'3C tice, however: the la nd ing of disc-wing aeroplane, ~•vcs rise to undercarriage problem,. As th e induced dr a~ mcrcascs rapidly "ith the reduction of !tying ~recd, when the aerop la ne fl attens o ut prior to touchina·d o" n, the ihdt n ti angle .iecpens abrup tly. Th is 1s particularly true of ta1llc..s de"gn, . a nd the result •~ . a stro ng tendency to pancake 10 the ground a, so ~n as the p1lo_t fl : \lt cn, out. Thu ~ to avoid the nccc\,il) of litt1!)2 _ undercamal\cs able to sta nd the strain of abno rmally high sink mg ~ pe cds, 1t h as been found practical to land "Jtll pow e r on. For a ta11le~s a er op la ne " ith an aspect ratio of three, M . B. Mor gan found that. with out fl aps, the tr immed l\liding angle at 160 m.p.h. was th ree degree ,: it increased to 17 degree, at 126 m.p.h .. while the \tailing speed w as I IS m.p.h. Thi, pronounced , teepcning of the g)idintt anttle makes a mer ~er hct""ce~. the aeroplane and the helicopter an attrac11ve , pr opos111on. . Another occulia_rity o f . !he d i~ wing cstahlished b~ Fie , 15 . -A ' puabo la ' ai rcraf t by B . I . Tsch e nnowsky NND 927545 . Zimmermann wns us scns 111v11 y to the , hape of the wing •ur, ,-- 10 282 ' THE AEROPLANE and _pseudo-circular and pseudo-square wings thus exhibit ~ignificam d.fferences... 1 his also applies to the ground eff.:ct, 1.e., tbe tand.ng <juahues. 1 he prov1s.on 01 ob11que nozzle shaped slots at the lips yielded no useful r.:sults. In any case, squo1re-cut tips Vvere found to be a disadvantage, w11h respect to drag, as well as to other qualities. Later N.A.C.A. research by F. E. Weick and Robert Saundefs referred to aspect ratios of the order of 3 1n conncct,on w11h slotted auxiliary Vevions flaps for the trim of tailless aeroplanes. This constituted the first investigation o f what has b.x:ome known to-day as the .. Delta Wing.'' i.e., the combination of sweep-back with low aspect ratio. Such shapes are of special interest for aeroplanes capable of flying through the trans-sonic region. • Pancakes Ii la Zimmermann The results of Zimmermann's research were so ~onvincing that a number of otherwise quite respectable designers were tempted into experimentation with disc-wing aeroplanes. In accordance with Zimmermann's views, all these designs were intended to be of the safety-first type of privately owned aircraft. This distinguishes the early phase from the more recent interest in Flying Saucers. In '1934 Farman was stimulated into experimenting with a wing with an aspect ratio of only 1.9. 1 his was seen in his F-1020 monoplane which otherwise had a long fuselage with a conventional tail. It was said to have proved very stable in flight. but was noc further heard of. An experimental parasol monoplane with a completely circular win$, a camber flap in the trailing edge and severely skewed ailerons Wl?.$ tested in the U.S.A. (in 1934), with indifferent results. It was shown in flight in news reels. At about the same time Raoul J. Hoffmann. of St. Peters· burgh, Florida, an eminent aeronautical engineer of Austrian origin (known as the first to prove-in 1913-that the r:itio C '/C 9 governs optimum climb and glide with minimum L D sinking speed, took up development of the disc-wing aeroplane. H offmann's Flying Saucer was a tailless aircraft with an aspect ratio of slightly over 2. The fi rst type was an ultra· li$ht single-seater with 36 b.h.p. Later a side-by-side two-seater with an 85 b.h.p. Cirrus engine was constructed and flew well; the wing tips served as ailerons and the elevators formed part of the trailing edre. The aerofoil sectir,ns employed were N.A.C.A. M.6 basically. with N.A.C.A. M.1 at the tips. Both are sections designed by. M. M. Munk. The former is a reflexed camber section with a practically stationarY, centre of pressure; the latter is symmetrical The central structure of the wing, the fuselage and the fin was of welded-steel tube; the wing had three spars. This little two-seater }"as stated to fly well and to exhibit ve_ry go(!d stability. It seems, however. that the controllab1hty, m particular directionally, was not satisf~ctory. 1 he visi(?n fr(?m the cockpit must have been very restncted--a moot point wllh • all these designs. A speed range from 28 m.p.h. to 13S m.p.h. was claimed. The empty weight was given as 900 lb •• and the wing loading was 5.5 lb. / sq. ft. One remarkable characteristic observed during the flying tests of Hotrmann's aircraft was that, when comin(! in to land. the approach was steep: yet prior to the fl lltening out and just before touching down, the glide flattened. 1 his would l MA J( C j c C l MA.( 0 MIN r - 0 MIN ,001----.U---4---1---4----4-----+---~ CI..Akl( T AUl,OfOtL SfCTl()N C,.ACA • IP No u,) z ;• f .., .,,. ~ 60 ~ J ::,., l5 r " • " < .. " fl" It . !i "' z J ~ •> • It ~ " It ti 0 11f 2 10 z c!, " ~ 6 t i; AA o· • ASP(C f U flO ( •' 1J Fig. 1 17.-These resulu from Zlmmermann's wind-tunnel tests on disc; wings (1932) clearly show the character!stits of low aspect ratio aerofoils. • MARCH 5, 1948 c:,_ i g : 0 10 " < Cl ARK I AEAO FOtl SECTION "' 0 (i-v-CA ZIMME~MANN, .. ~l P No ()1) :; o'----~---L---JL_.__ ..L.__ ...L._......:~, ASPEC T AATIO ., ., 18.-Furthcr results from Zimmermann's tesu shown here also indicate the advantages to be gained from disc wings. seem to. contradict the experience referred to above and it w~s aunbuted. to. a ground effect arising from the rak~ of the wing-tips. It 1s indeed rea:.onable to e)(pcct that the presence of t_ he ground would affect the formation of the marginal vort1c~s to an ex\ent which may markedly influence the beh~v1our of disc wings during take-off and landing. Hoffmann proJected a ousher and a twin-engined version but these types did not materialize. • A further development was the Arup monoplane of R: J. Hoffmann and C._L: Snyder at South Bend, Indiana. The w!ng _ shape ~as v~ry s1m1lar. I~ resembled a semi-circle flying w11h 11s straight side a_s the_leading edge; to this wing, ailerons were added as special ups. 1 he aspect ratio practically corres~onded to. that of the previous Hoffmann types. Again, aerofoils wtth little centre-of-pressure travel were used. 1 he latest type ~ad it~ _ tailplane and elevator separately locate~ over the wing tr:11lmg edge (similar to the .. Elytro· plane o f De Rouge!). It seems that the longitudinal control at certain incidences was not satisfactory. 1 he ailerons which formed part of the wing shape and reduced the aspecl ratio to a value ~f I: 15 had a triangular shape and were greatly s_ kewed (taking_ into account the obliqui: flow over the wing tips). The engine was a 70 b.h.p. Le Blond radial; a tricycle undercarriage was fitted. With the oilot alone, a gliding speed of 23.S m.p.h. was r~o_rded (lhe wing loading was about 3.3 lb./sq. ft.) and a gliding angle of 21 degrees was mea~ured, with a sinking speed of 12.3 ft. ocr si:cond. wh.ch ~an be accommopated by a sturdy undercarriage witho ut nattening out of the glide. 1 he maxi· mum speed was 86 m.p.h .. and the take-off was stated to require S secs. in zero wind. Several more Arup types seem to have been constructed an_ d _flown during 1935. 1 h~ flying qualities were pr.iised ghding angle~ or I : 2.6 bemg quoted- and the published performance figures sounded extremely good. Yet, for reasons never disclosed, the production stage was not reached and the development ceased abruplly. It is worth noting that Charles Zimmermann himself has taken no part in this development, b1;11 he was an interested spectator at demonstration flights wnh an Arup monoplane at Langley Field. An Italian "Tortelllno " At the time .of the Arup development (1934). F. Piana Canova. an Italian, began to embark on a development for a tajlless aeroplane with a low aspect ratio. In May, 1935, he secured patents for a rhomboidal wing, one diagonal of which coincided with the direction of flight. 1 he ailerons were to be located at the lateral apices. elevator and rudder at the rear apex. while the airscrew was in front of the leading apex. Another patent related to bi-convex aerofoils with ducts and control valve~ for the pilot, enabling the latter to neutralize the negative oressure on the forward ventral surface when at negative incidences. The latter patent was, apparently, never submitted to flight experiments. NND 927545 (To ~ confin~d.)
, MARCH 19, 1948 337 THE AEROPLANE The Biology of the Flying Saucer- III By A. R. Wcyl, A.F.R.Ac.S. Previous articles In this series appeared In " The Aeroplane" for February 13 and Morch 5 W I 0 -·1 UN l· L I F-••n S w.:rc made in I unn and at Rnme of five C:anovo1 project\ {de-.cnbcd m the prcvtom tn\1,11 - "'!Cnl of 1h1, ar1de). It " in1erc,11ng 10 note that 1he Canov.1 d1-.c-wmg lype, d id not mal.e u,e of rellc'<ed~ambcr aerofoil,. S1abili1y ,ind mm could . 1hercforc. be -..:cured only by an upward, dcllec1iu11 of enlarged eleva1or,. F.arly in 1935. :in ·open ghdl!r of 1he " Zoegling" t} pc wo1~ con,1ructed by a ,~ilan firm and M. A. Garbell made fairly ~ucce,,ful l11ghh w11h 11. He reported that the longitudinal stability (w11h the enlarged eleva1or) wa~ good and 1hat par.i.chute-lil.e landing, could be performed. rhc lateral stability ch.i.racteri\lic. however, proved deficient. ~ince a •• Dutch-roll " motion was experienced: turn, were of quc,tion· able steadine,,. In this rc,pcct, in~uffidcnt damping 1n foll and yaw a_re mentionr.d. Wi1h winch-launching, thi~ glider reached altitude~ of 600 fl. On 1he ba"' of thi, dc,ign, a ligh1 aeroplane wa\ developed and the Italian Government financed the conMruction of two l~~gcr e,-perimental aeroplane~. includmg one with 130 b.h.p. Gip,y engine. A faial accident de~ribcd as "not necessarily retlccti~f? on 1he 1echnical _merit5 of the design," cau,cd the Fig. 19.-An American "Flying Flapjack" w ith two engines. authorities to change 1hc1r minds and 10 terminate this It crashed while under test (1938). development. 1 A Return to Child ish Things Aeroplane, with a long, deep tail affi'<Cd to a smalhpan A third de,ign tin 1938) 1hc "Flcchair" \tngle-,cat fil!hlcr wing form a development of lhe low•tl'pect wing in another rroiect. therefore. incorporalcd two co.1xial coun1cr•rot.11mg direclion. Although the overall a~pect ratio is low wi1h such ~tf'>Crcws driven by two 100 b.h.p. engines mounted in 1andem a n arr.rngemcnt. the wing system i, not tha1 of a di-.c. It is m the long fuselage. 1 he pilot's cockpit was located at the more akin to primitive kites or. belier, to the paper dart of root of lhe fin, and a single·lrack undercarriage w.is adopted. our school day~ which. a, we may be able to remember wi1h 1 here were. however, far too m.iny untried feature in th" some mental effort, exhibited quite remarkable nying quali1ie, unusual design 10 make ii a ~rious proposi1ion. Nothing more has been heard of Payen's cffoA~. and made better use <>four schoolbooh than we ever expt-ctcd. A rcpresent:11ive of 1his aboriginal 1ype is shown in Fig. 19. l he ll)Odern ph:ll!e of .1he Flying Saucer aeroplane i, It crashed during the first tests (which would not seem very charactcn1ed by two d1,ttncl development~. One is the surprising in view of the; arrangement of engine, and air;crew,). hclicop1er-aeroplane, 1he other is the tranb•\onic or buper,on1c Ano1her Je,s eccentric arrangement was the French Payen aeroplane. Hoth have bccome:-unforiunately--cs<;entially single-seat racer of 1935. This was a daring experimental military dcvcl_opment~; the proJ_!re~~ is ~cnce bhroudcd in the type with a 400 b.h.p. radia l engine. A n improved type, this u~ua I pretcnuou~ \ecrccy Iwhich implies that the potential time more reasonable--a 70 b.h.p. light aeroplane- was enemy knows everything) v. hile the work is gravely hampered constructed in 1936. To a very small. conventionally tapered by elabora1c securi1y precautions. wing, a large triangu lar tail was fitted: the wing alone had The helicopter-aeroplane is not a novel idea. Many }Cars d ihed ral. and the overall aspect ra1io was about 1.76. No ago, for in,iance, Nicola T e~la (famous for his elccirical flights have bc.:n reported of one of these Payen aeroplanes. experiment~ wi1h high-frequency phenomena) bccured a pa1en1 but take-off attempts with the ~econd type seem to have for a taille,~ aeroplane equipped with a large lifting air~rcw sugges1cd that with 1he small span the 1orque reaction of the pcrmi11ing a vertical ascent. air,;crcw cannot be adequa1ely dealt with. In 1921 Claud Dornier ~ecured a pa1ent for a eonvcnlmnal - - ·-~ 1/lO C 1110 C L Fig. 20.-Llft and .__ ._ GI drag of wings of lL: different aspect f 120 c• t • 0 ratio. (Left) W ind- \ ~ . : tunnel results I '--- 100 ,_ obtained at Goettingen , in ~j 192 0; Goettingen - 389 aerofoil with n ... ~~ 80 10 per cent. t hick - ~ eo t--t--;illt":!'-~ -+7"lr--+--+..-t---c¥~--+~ 19" ASPECT RATIO ness and square ~ .» 0 1 SQUARE v, ING wing tips. (Right) " ... 2 A reduction of the 1 0 ...a:; ~60 + r esults to an A 3 ~ ~( aspect ratio of ... h ' w 0 (t f i v e. by t he • 1· ._u ,o 0 5 Prandtl Aerofoil Theory of t h e 6 :::; t 4l Ind uced d ra g , () 7 s h o w s t hat a ~ w s quar e aerofoil (aspect ratio of .t one) does not oQ-"11~t---t--t--:,~ o- r-+ ---l- +-~ 20 -+--+--I I D follow the theory. - i--c I - I- 0 i€ I Its induced drag is ORAG C0EfFICIENT 100) 10 20 less than pre I ~ I I dicted by t he DRAG COEFFICIENT < 100) "h orse-s h o e '-- 20 vortex " assump - 0. : I t ion. NND 927545THE AEROPLANE . 338 MARCH 19, 1948 • t L l 100 C AR 1 LA> - . ...l' 1IO ~ --;? ~ :a-: L-/ L,CI" ,_,... f i\ ~ ~ / ~ 100 I - , AR~ ... :z ~Vv V ~ ~ 80 ~ ~ ~" Lu V V ,.I. 00 ,, ' t: 't .. ::; / J v v l,o' '° 1,,1" fif (r l.,o' ~ v .#J ~ cf 1- ► (l 10 ° 10 o· I . , . - 0 ' •NGt[ or INCll)[NC( ( O!GRCES i 10 ... ~ aeroplane with take·off as helicopter {Brit. Pat. Spec. No.161,948). Earlier still (in 1916), the German, F. Bendemann, a noted fesearcb worker on a1rscrews, conducted a secret development o f an aeroplane with a large tilting airscrew capable of rising and descending as a helicopter. The development of this air observation post was later discon• tinued in view ot the Austrian helicopter experiments by Th. v. Karman and Petroczy. From his early experiments with lifting airscrews, F. Bendemann found that hoverihg without forward movement could be achieved- when the power loading of the aircraft was less than a bout 9 11,../ b.b-.p. With fighter aeroplanes, such low power loadings were already then being approached and 1 operat ional experience bad indeed shown that certain single· sealers could. under favourable conditions, be held in attitudes a pproaching that of hov.ering (later the Fokker D.Vll biplane, with a large airscrew, became renowned for this trick 10 air combat on the Western Front). Attempts to revive the project ~ta la ter date failed. and with the suicide of its promoter (who had gone into the Civil Service), all interest lo the development ceased. • Charles W. Zimmermann, mentioned earlier as stimulator of the disc wing, approached the conception of the helicopter Aeroplane on the basis of his results with low aspect ratio wings. He secured basic patents and constructed during 1934·35, in the cellar of his home, a man-carrying aircraft of bis design. This had a wing of only 7-ft. span, with two airscrews driven by two 25 b.h.p. engines. Due to persistent engine trouble, no flights were made; the Little aircraft showed, however. all the C$SCOtial features of the present types. In 1937 he granted a licence for his patents to the Chance• Vo ught Aircraft Division of the Unik:d Aircraft Corporation in Strntfort, Connecticut, and /'oined this firm for the further development of his ideas. t is possible that the public conception of the mysterious "Flying Saucers" has origmated from this develo,,ment. Zimmermann's intention may have been the development o f a safety-first aeroplaoe for the private owner. The U.S. Navy, however, took an interest in the possibilities of the helicopter• aeroplane, and the work done at present is purely for military purposes. In 1942 a low-powered piloted scale model type V-173 was constructed. This wooden aircraft made many flights and proved that the ideas underlying the design were practical. The principle is that, at high speed and when cruising, the aircraft shall fty as an aeroplane, while for slow speed and hovering it flies as a helicopter. Hence the airscrews are at the same time rotors and must have a rarher large diameter. With the V-173 the problem of the prone position for the pilot was studied. and there is reason to believe that the latest types have adopted this feature. A further step towards the realization of a naval gun-spotter and a fia),ter for use from aircraft carriers bas been the Chance· Vouaht XF5U·l single-seater (1946), for which a speed range from 40 m.p.h. landing speed to over 425 m.p.h. has been claimed; in general, it follows the V-173 model. (See p. 185, February 13.) The aspect ratio of the wing is lesa than unity. Strictly speaking, however, it is not a genuine tailless aeroplane because of the attachment of a trimmmg elevator to both sides ot the wina. The reason for such excrescences is the need to locate I I Fig. 21 . - LI ft 100 Cl curves of aerofoils t 1,10 -- of different aspect ratios. (Left) ~· O+ Wind -tunnel -l . o,."' .. C results obtained, ~- 100 - in 1920, at Goet• o"'f3. I tlngcn, w ith I A . Goettlngen 389 eo ~ ASPIC.T RATIO aero fo i l and ~ a 1 Aou,hf square t ips. The 0 ? WING absence of stall at t V 00 + ,__,__ .0. J normal Incidence ::; Is In evidence, for b • • aspect ratios up .o I ,__ to a value of two. I - t: '° t I+ .. ro ~ (Right) Reducing () ,· the values. by the Prandtl theory.to ,,. an aspect ratio of five, shows t hat wings of very 10 • 10 small aspect rat io - - < I AN(;l[ Of tNCIO(N(( t OIGRH\ I do not follow the IO theory in respect of the induced Incidence correc• tlon. control organs directly in the slipstream of tht: paddle-like airscrew rotor... T he twin rudders, too. are in the slipslfeam. Unlike the V-173 type, the XF-SU· l has an all-moving tail surface and the undercarriage is retractable. This interesting hybrid has a modern metal structure. Two Pratt and Whilney R-2000-2 engines Qf 1,350 b.h.p. each (at 2,700 r.p.m.) are mounted within the wing, entirely buried and cooled by forced draught. Water injection for temporarily boosting the oower is one of the engine features. A special oroblem was the design of a transmission ~ear which a llows both rotors to be driven from either of the eogmes - this is a necessity in case of an engine failure. The four· bladed rotors are contra-rotating so that there is no residual torque and are ,eared down to about one-fifth of the engine speed, hence their substanlial diameter. The wing loading is rather high. reaching the order of 40 lb./sq. ft. The Real Flying Saucer ? Since this experimental t ype was produced, further progress has been made in the development. IL seems that axial-flow gas turbines have been installed, and it is quite possible that a combined oropulsion with thermal jet and airscrew rotor is alt:eadv under test. Wilh this, for slow flight (take-off, climb and landing) the rotors a re driven by the gas turbines, while at high speed the rotors are declutched a nd feathered and pure jet propulsion is used. This would, incidentally, ( ~01! 1---1---1------.1---1----1----1 ; 0 ~ - ,. < i Q ::: ... - NACA 14 SEC11C)N:~ iS V .., 0-00, ._N• '1·1 , 10' ~ 0 0.~L T!HI i ,. ~ ... I ~ T{C ~ - ~01 0-ll 0-16 ~IO 0 •1' AU,0r0tL TMICKN ESS A.ATIO Fie. 22.-lncrease of profile drq with section thickness, at :zero 11ft. The lfnporunce of the tip shape Is obvious. The data refer to an aspect ratio of flve (From D.V.L. wind- tunnel tesu at low turbulence). NND 927545~ ARCH 19, 1948 339 THE AEROPLANE ., ... M. B. Morgan has recently communicated the following 0·3 r-------- ------------- -i~ values for the limit of stability at the stall from this araph : - <=o, 0 Upper llmic of th• Ansl• of Swetp,back (r•lerred to th• l chord) beyond which Hll • •tall can be A,poc, Ratio 11.•qulr•d expected Ocareu 6S 1 S4 2 46 3 38 ' 2S 6 14 •• 8 s It is thus advisable to combine sweep-back with low-aspect ratio w!1en s~fc stallin _g is required. . Consaderataon, of high speed lead to a ,imilar combination. since both feature~ tend to delay the shock stall. We have. 04 as ~ res!lll, the rare ca~ i;,f two quite d ifferent aspects of an o-a 1·0 enginee~ing_ problem pointing to an identical solution . 1 he incv11 able result ha s been the development of arrow s h<;1ped: . more ?r less triangular, . disc wings, termed " Oelta Fig . 23.-lncrease of xero lift profile drag wi th thickness ratio Wang s, _ for lhgh~ at sp~eds which are trespassing into the of symmetrical aerofoil sectldn. The saving In profile drag Is tr~ns• s? nlC velocity rtg1me. An ot her advantage of such one of the advantages of disc wings because of their thinner wings as that when the shock stall occurs. the backward shift of aero~oll section. (Data from Gerber, Zurich Report No . 6). !he centre of pre ss ure is less than with normal wings. Th e induced drag doe, not count quant itatively at tbeg high speeds explain the extr~ordinary ability of the reported •• Flying Development of s uch abnormal aeroplane types began i~ 9e:many during the War_. following the progress accomplished Saucers·• to be able to fly very fast and high, and also to h over, •~ 1et and r~ket propulsion since 1937, which had shown that ascend _a nd de _sceo d with pr actically no forward speed. No flight . at so nic vcla<:IIY wa, a r,ractical proposition. A few ~ther a!rcraft 1s known to do th a t. On the other hand, it is ll!(ODCeavable that whole s quadr ons of such unconventional experimental delta -wing types had been brought to initial fl ying te ~t, when the War came to a close. atreraft could already be observed at air exercises. It is rare . The German ~evclopmcnt had two d istinct aims, resulting for military developments to progress as quickly as all that. 11_1 two separate hn _es of approach. The immediate target neces . For operatao~ with gas turbines a speed range fr om zero satat~d by the Allied bombing raid s. was the creation of very (1.c., hovcrin~ flight) to more than .500 m.p.h. has been claime d fast Jct fighters or fighter-bombers which could surpass in speed for t~e Chance:V~ught-Zi mm crmann helicopter-aeroplane. even the Mc 262. _ Secondly, there was the long-term develop Technically. there 1s httlc reason to doubt th at such an amazing spec<! range can be attained with the combination power plant ~ent of a supersoni c aeroplane capa ble of fl ying over ver y lon11 \ d1sta~e s. such n, from Europe 10 Amer ica and back. and menuoned. Jn cidcntall y, as there is not as yet a standar d term for the dropp11_1g a born~ or two ~n the way. Jt i, perhaps not too fa_ ntas tac to surm1,e that t~•s development had some connection combination of an aeroplane with an heli copter, the name with the research on atomic bombs and bacteriological warfare •• heli co plane •• is tentatively suggested. The. oth~r line of engineer ing approach which has led to instituted by the Hi tler Gang. F or th~ immcdia!e. target, orders for interceptor-fiahters were the da..c-winl! aeroplane of near-saucer appearance derive s from the trend towards very high flying speeds within the sonic placed wath cnterpming firms, notably with the Honen brothers and Messerschm111 (both pets of the Rcichsluftministerium) with range of velocities. an d in pani cu lar 1 at great altitudes. As now the Gotha Work s, ttenschcl, Junkers, Heinke! and Arado (a commonly realized, the compres,ibi ity of the gaseous medium sets a speed limit for conventional aeroplanes. Thi s limit is G?vernment cntcrpra~). etc. In order to facilitate experiment ~ reached when the speed of flight approaches sufficientl y to the ~•th rather unu ~ual aarcraJt ~ypcs and to enable an exchange of veloc11v at which sound is propa&3ted through the air. This idea s.a nd expenences, a special research aerodrome was built at "acoustic velocity" depends solely on the air temperature. and (?ranien~urg ( near Berlin) with all facilit ies for flight testing is, therefore. lower at altitude. Hence. com pressibility effects (in ~anacular , ve_ry l~ng wide runway, and work sh op, for begin to be felt at lower speed s when flying at altitude. repairs and mod1fica11on, were provided). This was placed When the "shock stall," due to the compre~sibility of the under th~ command of a capa~I~ _tec hnician, Lf .-Co l. Kncmeyer . On this aerodrome, all the in111al and development tests with air, ,;cts in, the lift is catastrophically decreased (hence the novel prototypes had to be made. When the Russians collected ju stification for the expression "shock stall "), the dmg ri,cs to enormous values, and the longitudinal ~tability i, grossly the aerodrome, they were agreeably surpri,;ed to d iscove r so me impaired by a rapid backwards shift of the aerodynamic centre of the most progressive aircraft ever co nst ru ct ed . It has since beco!11e cenain that thcr have made intelligent use of this aero a~ well as by fluctuations in the flow pattern at the wing. The nau11cal treasure as wcl a, of the technicians collected then and experience of phenomena of such di s tre ssing nature has given rise to two distinct aims in aeronautical rc ,carc h. One is afterwards. Of the German firms interested in the develop · ment, at least one. the well-known Junkers works at Ocssau has to d elay the ono;et of the phen omena to higher Mach Numbers; the o ther aim i, to find wings which would permit flight within been co mplete!y t!"llnsferred ~o Rus sia, lock, stock and barrel. M ost of the sc1cnt"_ ts and ~e 1snen were urged to volunteer for or throuF,h the tran,-sonic regime. The alternative. " within or thr ough,' is still a neces sary impediment of definition, since developm~nt work 11_1 Ru s~m. Fe~ could afford to refuse. we do not know yet if Mable, s teady flight will be at all According to reh _abl e mrorma11on, amont: the interceptor prot otypes at 9ran1cnburg, at the time of the Occupation. possible within the tran,-sonic regi me (extending from about 0.8 to 1. 2 Mach Number) while there is certainly that beyond were the following :-O ne Honen taille,, delta -wing, which had been dama_ged d(!rmg tests and ~as undergoing repair: another this tran~-sonic regime. i.1:., within the supersonic regime, ~table. steady fl ifht can be predicted. H onen ta1ll e,, Jct-fighter was J .ust ready for it~ first test,. There was also the latest version of the lippi-;ch-Junke r,,· Tw o \ample mean, have become known which delay the dev~lopmem of . the Mc 16.\-C: another advanced Junker, occurrence of lhe "shoc k stall" until much higher (but sti ll sub,onic) flying spee d, are attained.· One is sweep of the design: an experimental Gotha. an d several re;,e arch gliders. , leading edge of the wing, either a, sweep hack o r a, ,weep Hitler's Last Secret Weapon forward. The o th e~-a Farnborough _ discovery of nearly The G~rman long-term development of an aeroplane capable 30 years ago, when high top ,peed, of a1r<.erew, were investi ~f reac _ hing truly s uperso nic ,peed, discarded the gaHurbine gated -i , the adoption of very thin aerofoil sections. The 1et engine. It wa, based on the ram-jct or aerodynamic pro latter lend,. as we ~ave po inted out already. straight to aerofoils puhivc due~ (" Ath _o dyd ")-the simplc~t en11ine ever' invented of low a,pect ratio when, for rea,on, of structural ,ti ffness 1 ~e. ram-Jet, a widely d1,cu,,ed invention by the genial Rtnci a certain wing thickne,, is required. ' Lorin in 1~1~. had been c~pcrimented with in Germany, notably ln the discu,sion of the "Stalling Characteristics of Toille,s hy the Austrian Cugcn Saenger (for whom a special laboratory Aeroplanes'' (THP AER0PLANr for April 2.5. 1947). it was had been built hy the German authornie~ in 1938), by Otto ,hown that a_t l ow soecd,. i.e., duri _ ng take-off and landing, P abo\t, of Focke-Wulf, _an~ by others. Following a suuestio n swept-back win1t ,s ,u ffer fr om the d1s.1dvanta11e of in,tability m~de by Al~xander L1pp 1sc h (formerly known as an eminent at the ,ta ll. W11h pronou_n~ed sw«:e p-back, & wept-back wing, sa1lplnne de s1(tne r and resc~rch worker on _ tnillc s, aeroplanes). of normal a~pcct rataos exh1b11 the vice of" ,cl f -, ta lling," due to prog~e~, had been made wath the combustion of solid fuel in premature tap stall. It was al'° shown that this vice can be ram-1ets. Such fuel took the form of ~olid blocks of ~pccinlly remedied bv reducing the a,r>ect ratio. and a curve based on r,rcpared coal which lined the walls of the doct. This develop exten,av~ wind-tunnel te,ts CT11c ~ER0P~~c for Jul y t I. 1947, ment ha~ bee~ perfected by the Germ an Research In1titutc p. 47, F111_. 8) proved that there 1, a d as tmct relation between for Soarmg Fhaht. a,r,ect ratio and an11le o f sweep-back in this connection. (To ~ continued.) NND 927545