DE C LA S S IFIE D A u tho rity: N N D 927545 M C L A . H EA D Q UA RT ERS A IR M A T ERIEL C OM M A ND M C IA /jC B/amb W right-Patterson A ir F orce Base SUBJEC T ! Project "SIG B" T Oi C hief of Staff United States A ir F orce W ashington 25, D . C . A T T Nt D irector of Intelligence 1. T his ie an initial report on unidentified flying ob jects as directed b y H q, USA F letter dated SO D ecemb er 1947 , signed b y G eneral L . C . C raigie, sub ject! "F lying D iacs'*. Q uarterly reports will b e sub mitted b eginning 1 July 1948. 2. A s a result of thia letter, Project H T -304 was activated on 26 January 1948 and T echnical Instruction 2185, dated 11 Peb ruaiy 1948, was pub lished. Present files on Project "SIG N" represent a consolida­ tion of reports received directly b y Bq, A M C and those forwarded b y the D irector of Intelligence, USA F . , 3. Schedules of activities of lighted night-flying advertising b limps have b een secured and cross-checked at this H eadquarters to consider them as a possib le source of incident reports, 4. Inclosure 1 represents a tab ulation and b reakdown of all availab le reports through 1 F eb ruary 1948. 5, T he following Is a series of interesting ob servations that were noted when reviewing the many incident oases: a. H igh rate of climb , as well as the apparent ab ility to remain motionless or hover for a considerab le length of time, b . T he ob ject was describ ed as b eing oval, disc or saucer­ shaped 31 times. . c. A ssociated sound was present 11 tines, d. Reported si see have varied from that of a 25-cent piece to 250 feet in diameter, and from the site of a pursuit plane to the £ulk of six B-29 airplanes. CWiL£H TIA L N N D 927545 ^ bOkt kitH TIM ^ AM C Subject* Project "SID E " 23 A PR 1948 e. Numb er of ob jects per sightingi Ob jects per sighting 1 2-6 6-10 over 10 Eumb er of sighting! 7 7 21 8 9 f. Exhaust trails were reported 23 times, g. Speed has b een estimated throughout the entire range from very slow or hovering to supersonic. 6, Inclosures 2 and 3 are enlargements of photographs taken of Incident #40. Inclosure 4 is an evaluation of inclosure 2 b y this H eadquarters. A ttention is Invited to the marked similarity b etween inclosures 2 and 5, and inclosure 5. Similarity also exists b etween Inclosures 2 and 3 and configurations Illustrated in inolosuro 6. 7 . Representatives from this H eadquarters visited D r. Irving L angmuir of the Research L ab oratories, G eneral Electric C ompany, Schenectady, N. Y. to discuss Project "SIG M *. It was the opinion of this scientist that prosent availab le data does not encompass suffi­ cient information to enab le a positive identification to b e made. D r. L angmuir was reluctant to consider the so-called "flying discs'* as a reality. H owever, it is b elieved at this H eadquarters that it is possib le to construct a low aspect ratio aircraft that would dupli­ cate many of the appearance and performance characteristics of reported "flying discs". Experts have agreed that this would b o possib le through the intelligent application of b oundary layer control. F OR T H E C OM M A ND ING G ENERA L * 6 Incls ' H . M . M cC OY 1. T ab ulation C olonel, USA F * 2. Photo C hief of Intelligence 3. Photo 4. Eval of Incl 2 6. H orten Parab ola 6. Biology of F lying Saucer ----------— N N D 927545 Incident M o. D ate H our L ocation • M o. Sighted Ob served F rom 1 8 Jul 47 09 30 Vuroc Air F ield, M uroc, C alif. 2 G round la 8 Jul 47 09 30 M uroc,Air F ield, M uroc, C alif. 2 G round lb 8 Jul 47 09 30 M uroc Air ^ield, iiuroc, C alif. 2 G round 1c 8 Jul 47 09 45 M uroc Air F ield, M uroc, C alif. 2 G round Id 8 Jul 47 1000 M uroc Air ^ield, M uroc, C alif. 3 G round le 8 Jul 47 1000 Iiuroc Air F ield, iiuroc, C alif. 3 G round 2 8 Jul 47 1200 M uroc Air F ield, M uroc, C alif. 1 G round 3 7 Jul 47 1010 M uroc Air F ield, M uroc, C alif. 1 G round 4 8 Jul 47 1150 Area # 5, Rogers C ry Lake, M uroc Air F ield, M uroc, C alif. 1 G round 5 4 Jul 47 1305 Portland, Oregon 5 G round 6 4 Jul 47 1305 M ilw aukee, Oregon 3 G round 7 4 Jul 47 1505 Portland, Oregon 1 G round 8 4 Jul 47 1305 Portland, Oregon 3 G round 9 4 Jul 47 1305 Portland, Oregon undeterm ined not stated 10 4 Jul 47 2004 Boise, Idaho 5 Air 11 4 Jul 47 not stated Seattle, W ashington 1 'round 12 4 Jul 47 1305 Vancouver, W ashington 20-30 G round 15 4 Jul 47 1400 Portland, Oregon 4 G round 14 4 Jul 47 1630 Portland, Oregon 1 G round 15 4 Jul 47 17 00 Portland, Oregon 3 G round 16 4 Jul 47 1100 M ount Jefferson near Redm on, Oregon 4 G round 17 34 Jun 47 1500 M t. Rainier, W ashington 9 Air 18 not stated not stated Toronto, C anada 1 G round 19 20 Oct 47 1320 D ayton, Ohio 2 G round 20 20 Oct 47 1100 Xenia, Onio 1 G round CON FIDE N TIA L N N D 927545 -CWifOTiA t- In aidant, N o. D ata • dour Observed F romLocation N o. Sighted 21 29 Jan 117 1645 D es koines, Iow a 18 not stated 22 21 Jon 47 about noon Spokane, flasK inston several G round 25 30 Jun 117 17 45 Boise, Idaho 1 G round 2U 12 Jun 117 1815 W eiser, Idaho 2 G round 25 4 Jul 47 2545 W est Trenton, K , J, 1 G round 26 10 Jul 47 not stated H aroon F ield, N ew foundland 1 G round 27 10 Jul 47 2000Z H arm on F ield, N ew foundland 1 G round 23 24 Jun 47 not stated Idaho 1 G round 29 23 Jun 47 not stated Bakersfield, C alif. 10 G round 50 7 Jan 48 19 25E ST Lockbourne AB, C olum bus, Ohio 1 G round 50a 7 Jan 48 19 258ST Lockbourne,AB, C olum bus, Ohio 1 G round 30b 7 Jan 48 19 158ST Lockbourne AB, C olum bus, Ohio 1 G round 30c 7 Jan 48 19 40 Lockbourne AB, C olum bus, Ohio 1 G round 31 52 m id-D sceraber early a.m . N orthern Arizona 19 46 1 G round 32 not stated after dark C olum bus, Ohio 1 Air 33 7 Jan 48 133017 00’ G odm an F ield, K y. (south of) 1 G round 33« 7 Jan 48 1400C ST G odm an F ield, K y. 1 G round 33b 7 Jan 48 1J20C ST G odm an F ield, K y. 1 G round 33c 7 Jan K g 1420 C ST 210° from G odm an F ield, K y. 1 G round 33d 7 Jan 48 1400 G odm an F ield, K y. 1 G round 33* 7 Jan 48 1430-1600 G odm an F ield, K y. 1 G round 33* 7 Jan 48 1445 H odm an F ield, K y. 1 \ 1 Air 33g 7 Jan 48 1854-19 06 M adisonville, K y. 1 G round 3U 13 Oct 47 0530 14 m iles north of D auphin, M anitoba, C anada G round 35 12 N ov 47 early a.m . Ticonderoga at sea (40 m iles south of C ape Blanco, 20 m iles off shore) 2 Boat 4 CON FIDE N TS N N D 927545 ubiuiDiN TIA t C Ok hDE N iIA L INC ID ENT No. Ob served *9, Pit? H owr lA Ullfll SAAisl 56 Sot Stated Sot Stated Boise, Idaho 1 G round 57 12 Oct 47 1200 C ave C reek, A rleone 1 G round 58 10 Jun 47 M ot Stated Budapest, H ungary 1 G round 39 9 Jul #7 2330 G rand F alls, Newfoundland 5 G round #0 7 Jul 47 1600 Phoenix, A rlxone 1 G round 41 11 Jul #7 «ot Stated Biendorf F ield, A laska 1 G round 42 12 Jul 47 0430Z Biendorf F ield, A laska 1 G round 4? 29 Jun 47 1645 C larion, Iowa 18 G round 44 28 Jun 47 1543 Rockfield, W isconsin 7 -10 G round 45 28 Jun 47 A fternoon Illinois 7 -10 G round 46 22 Jun 47 11J0 G reenfield, Noss. 1 G round 47 6 Jul 47 M ot Stated F airfield-Buisun A ir Base, C alif. 1 G round 48 7 Jan 48 1920-1955 W ilmington, Ohio 1 G round 48a 7 Jan 48 1925 W ilmington, Ohio 1 G round 48b 7 Jan 48 1910EST W ilmington, Ohio 1 G round 48c 7 Jan 48 1930 W ilmington, Ohio 1 G round 48d 7 Jan 48 1920-1950 W ilmington, Ohio 1 G round 49 9 Jan 48 2300-2515 D anville, K entucky 1 G round 30 10 Jan 48 2200 W ildwood, New Jersey One at thia G round date, prev­ iously 1 each 27 D ec,3 Jan all at 2000 o'clock. 51 3 Sept 42 1215 Oswego, Oregon 12-15 G round 52 29 Jul 47 1450 H ani1 ton F ield, C alifornia 2 G roimd 52a 29 Jul 47 A fter 1200 H amilton F ield, C alifornia 2 G round 53 28 Jun 47 1515 L ake M ead, Oregon 5-6 A ir 54 16 Jan 47 2230 North Sea (50 miles from the D utch C oast) 1 A ir 55 23 Jul 47 0345Z H amon F ield, Newfoundland 1 G round Incident No, D »U H o u r Location No, Slated Ob served -fta 56 6 Jul 47 2045 Blr®lngha®, A lab aaa 7 -10 G round 57 20 Jul 4? 00152 A b oard the Burgee (at Sea 1 one hr. fro® Sydney, A ustralia) Boat 58 4 A ug 47 Evening Bethel, A laska 1 A ir 59 14 Sept 47 O558C C T Necker Island 1 A ir 60 10 Jul 47 1000 C ordroy, C anada 1 G round 61 8 Sept 47 2230 Salt L ake C ity, Utah 12 G round 62 8 Sept 47 2230-2500 Salt L ake C ity, Utah 5 groups each con­ taining 55-60 ob jects, G round 65 29 Jul 47 1205 C anyon F erry, M ontana 1 G round 64 19 A ug 47 2130 T win F alls, Idaho A pprox. 55. G round 65 2 Jun 47 Not stated Rehob eth Beach, D eleware 1 G round 66 10 A ug 47 2100 Silver Springs, Ohio 1 G round 67 14 A ug 47 1600 Placerville, C alifornia 1 G round 68 24 Jun 47 Not stated C ascade M ountains, Portland, Oregon 6 G round 69 6 A ug 47 2230-2245 Philadelphia, Pa. 1 G round 7 0 6 A ug 47 1045 Philadelphia, Pa. 1 G round 7 1 8 Oct 47 Not stated L as V egas, Nevada 1 G round 7 2 Not stated Not stated F ort Richardson, A laska 1 G round 7 5 4 A ug 47 1600 Boston (10 K iles NV ) M ass, 2 A ir 7 * 24 Jun 47 A pp. 1500 M t. A dans, W ashington Not Stated G round 7 5 15 A ug 47 1300 Smoke River C anyon, Idaho 1 G round 7 6 15 A ug 47 M orning SalM on D an, Idaho 2 G round 7 7 5 July 47 1830Z South Brookville, M aine 10 G round 7 8 30 Jun 47 0910 M ST G rand C anyon, A risons 2 A ir 7 9 A pr 47 1100 EST ----- - Richnond, V irginia N N D 927545 1, others on G round other occasions '111 1UL11 iiM L -eeioOH A t Incident JL _ 80 81 82 83 I 84 85 86 87 88 89 90 91 ’ 92 93 94 95 96 97 98 99 100 ggte L £££tlon Bo. SA Otgl Ob served — EM U. 7 Jul 4? 2230-2300ED T A rlington, V irginia 1 around 7 Jul 47 0900 Biola* F ield, K ewell 1 G round 17 M ay 47 2OJO-21O0 Oklahoma C ity, Oklahoma 1 G round 9 Jul 47 1217 Boise (Between Boise and M eridian) Idaho 1 A ir ■ 7 Jul 47 1300-140C EST L akeland, F lorida 5 G round 14 Jun 47 1200 Portland, Oregon 10 G round 6 July 47 Rot stated H ollywood, C alifornia 1 G round lot stated Rot stated H ab b erb ishopahiea (20 miles north ) G ermany 1 G round 3 lug 47 A fternoon H ackensack, 1* J. 1 G round 6 Jul 47 1345 K ansas C ity (100 miles west), K ansas 1 A ir 29 Jun 47 1300-1330 L as C ruces, M ew M exico 1 G round 28 Jun 47 2120-2145 M axwell F ield, A lab ama 1 G round 19 Jun 47 1215-1315 C olorado Springs, C olorado 1 G round 11 Jen 48 1 1630 H artford, C onnecticut 1 A ir 30 D eo 47 1926PST Between G reat F alls, M ontana and F airfield, C alifornia 1 A ir 30 D eo 47 1925PST Rosedale, C alifornia 1 A ir 30 D eo 47 1926 L ovelock (30 miles west), Nevada 1 G round 30 D ec 47 1925P8T Between M edford and M t. C hasta, Oregon 1 A ir 2 M ov 47 D ayb reak H ouston, T exas 1 G round 3 Jan 46 lot stated V assa, F inland 1 G round 6 Jan 46 Not stated Pretarsasri, F inland 1 G round ^n jL^-^ N N D 927545 tutu ibLft H A L Incident N o. Observer's m aneuvers gaatngrOccupation 1 1st Lt, USAF sone - norizontaj. fllgnt w ot stated La b/bgt, UbAF w ot stated .»ot stated lb Unknow n Lot stated liot stated 1c S/Sgt, USAF N ot stated M ot stated Id Pfc, USAF F lying in tight circle ’lot stated le K ot stated H orizontal and tight circles N ot stated 2 M aj, USAF D escended from an interm ediate altitude in an oscillating fashion alm ost to the ground, then started clim bing again to a very high altitude and m oved off slow ly in the distance. N ot stated 3 M ajor, USAF Oscillating in a dow nw ard tw irl­ ing m ovem ent H ot stated h C apt, USAF F alling at three tim es the rate of a parachute K ot stated 5 Patrolm an, Portland Police D ept. D ipping up and dow n in oscillat­ ing m otion K ot stated 6 Sgt, Oregon Police F ollow ing each otner C lear w ith little or no cloud form a­ tion 7 Patrolm an, Portland Police D ept., form er Air F orce pilot N ot stated C lear w ith little or no cloud form a­ tion 5 Patrolm an, Portland Straight line form ation; last C lear w ith little Police D ept. Pri- disc fluttered vary rapidly in or no cloud form a- vate pilot side— w ay arc tion Sa Patrolm an, Portland Police D ept. Pri­ vate pilot Straight line form ation; last disc fluttered very rapidly in side-w ay arc C lear or no tion w ith little cloud form a- 9 C apt., H arbor pilot D iscs w ould oscillate and som e­ tim es a full disc w ould be vis­ ible, then a half-m oon shape, then nothing at all N ot stated — --------------------------------- N N D 927545 * CON FiDE H TlA L * Incident No. Ob server's Occupation M aneuvers W eather 10 C apt, United A irlinesStraight-M ay horizontal flight lot stated 11 C oast G uard H orizontal flight Not stated 12 D eputy Sheriff Not stated Not stated 15 Not stated Not stated Not stated 14 Not stated F lipping around Not stated 15 Not stated Not stated Not stated 16 Not stated Not stated Not stated 17 Private pilot Straight horizontal flight C lear as crystal 18 Not stated H orizontal flight C lear 19 F armer Straight course - were flying ab out a city b lock apart, one b ehind the other C loudless and sunny 20 Not stated Straight course Not stated 21 Not stated Single file Not stated 22 K ot stated F lashing Not stated 23 Not stated H orizontal flight Not stated 24 Not stated Shooting up and down C lear 25 Not stated H orizontal flight Bright moonlight 26 M echanic Not stated Not stated 27 T W A Representative Not stated C lear 28 L t G overnor Not stated Not stated 29 W est C oast Pilot, 7 000 hrs. Not stated Not stated 30 C apt, USA F , A sst Operations Officer C limb ing and descending ver­ tically Solid overcast 30a VH F /d F Operator o H overing, made three 360 turns around one place. M oved to another position and circled more. T urns required 30-40 seo. D iameter estimated at 2 miles. Overcast, 1000 ft N N D 927545 gWOTA b n Incident BOo Ob server’s Occupation M aneuvers W eather 1 30b T raffic A ir C ontroller Bob b ing up and down Overcast 30c Not stated C limb ing and descending H igh overcast J 51 Professor and Bead of A ero Engineering None C lear 32 L t, USA ? None Overcast 53 T /Sgt, USA F None H igh scattered clouds V isib ility unlimited. 33a 1st L t, USA F None H igh scattered 53b . PF C None Not stated 33c C apt, USA F M ay have b een turning H igh overcast with BK S 33d C apt, USA F None H igh scattered, visib ility unlimited 3Se C ol, K y. State PoliceNone C lear 33f C apt, USA F (F light L eader NG 869) Not stated Not stated 33g Unknown Not stated Not stated 34 Judge None C lear 35 Second Officer,Navy None Not stated 36 C A A Official Not stated Not stated 37 Pilot None C lear ^ ' t 38 H ungarian Peasants Not stated K ot stated 39 C onstab le None G A V U:t-; e 40 Not stated Spiraled downward from 5,300 C umulus clouds to 2,000 ft and then went upward at a 45° angle — N N D 927545 gWttOlt- 4 Incident -H £L -___ 41 42 4? 44 45 46 47 48 48a 48b 48c M d 49 50 51 52 52a 55. 54 55 56 Ob server*! C olonel, USA F M ajor, USA P Bus D river H ot stated Not stated H ot stated C aptain, USA F M ajor, USA F T /3gt C pl. M aneuvers H ot stated lot stated H one H one H ot stated H one Polled froa side to tide A scending and descending Up and down and side to H ide A scending and descending S/Sgt A scending and descending very • rapidly H ot stated A scending' and descending H ot stated None K nitting designer A pproaching shore from Ocean then rise and fall slowly. H ot stated Not stated C apt, USA P, A SST . H or laone1 left to right, right to Operations Officer loft like a guard In an airplane and instructor Pilot formtian. lot L t. in A ir Stall ar to a fighter aircrafts Reserves foraer naneuvors when aecoapanylng B-29 Pilot heavier ships. 1st L t, USA F , Pilot H orlsonal very close farmtIon M osquito Pilot Efficient controlled evasive action G overnment Employee A b rupt darts 3/Bgt, USA F T raveling in a definite are. H ot stated H ot stated H ot stated H ot Stated H ot stated C loud b anks. H ot stated H ot stated C old and clear with few scattered clouds L ight scattered clouds with hate towards SA « C lear with over­ cast In SA . C lear to M attered. H ot stated H ot stated H ot stated C lear Net stated Not stated Not stated H igh M attered condition risib ility 15 alles. Not stated fcON H B E N TIA t tWWIA Lg Incident M o, Ob server’s Occupation termers. & £& ££ 57 Bridge C onstruction Not stated C lear and dark. 58 C hief Pilot- F lying service Not stated Not stated 59 Pilot None Not stated 60 Storekeeper Not Stated C lear at dusk 61 Not stated None Not stated 62 Not stated Not stated C loudy 63 Not stated H overing and fluttering, rising and descending. Scattered small clouds. 64 Executive D irect­ or of H ousing A uthority. H orlzonal Overcast 65 Pilot Not stated Not stated 66 L t. C ol, C SC Scientific Branch Research G roup. H orlzonal F light Not stated 67 Insurance A djuster None C lear 68 Prospector Banking C lear 69 Not stated Not stated Not stated 7 0 Insurance A gent Not stated C lear 7 1 C apt. A C Reserves Not stated C lear 7 2 A my Officer Not stated C loud formation scattered ab ove 10000 ft. 7 3 Navigator (C onstellation type aircraft) Not stated 5/10 scattered cumulus with tops at 10000, visib ility 10 miles. 7 4 Prospector Standing on edge and b anking in the clouds. Not stated 7 5 T rout F arm Oper. Rode up and down over the hills and hollows of the canyon floor. Not stated 7 6 C ounty C ommissioner Not stated Not stated — N N D 927545 -----• CON H iOmL N N D 927545 Incident -iu^ Ob server’s Occupation M £neuxe££. W gather 7 7 A stronomer Not stated Not stated 7 8 L t, USS (P80 Pilot Not stated Not stated 7 9 W eather reporter Not stated C lear 80 L t. C ol, USA F Not stated Scattered clouds visib ility 10-12 miles 81 C ivil Service Employee A scending slowly C loudy 82 F ield Engineer Not stated Not stated 83 Pilot Slow roll or b arrel Some clouds m Sign Painter C limb ing C lear-scattered clouds 85 Private Pilot Not stated Not stated 86 Not stated T urned a corner and seemed to roll. C lear 87 U, S. A nny D escended slowly and then dropped in a spiral motion. Not stated 88 Not stated Not stated Not stated 89 M ajor, USA F Not stated C A W 90 A dministrative A sst, Rocket Sonde Section Not stated C lear 91 C aptain T raveling in zig-tag course C lear 92 Railroad Employees C limb ing, diving and reversal of direction which happened every few seconds. C lear and sunny 395 C apt, USA F Shooting towards the east at 46° angle Not stated 94 L t C ol, H q, EPW ©ascending vertically - seemed to slow down on nearing the earth Sot stated 95 C -47 crew Not stated Not stated 96 Not stated Not stated Not stated 97 A irplane crew Not stated Not stated 98 Immigration Service A ppeared to b e spinning in its descent Not stated 99 Not stated Not stated Not stated 100 Not stated Not stated Not stated Incident M o. C olor Shape Size Sound 1 Si 1rory Not stated Not stated Not stated la lb 1c Si Ivory Saucer shaped M ot stated None Id Reflected the aun'a rays D iac M ot stated Not stated 1® SI Ivory D i ec M ot stated None 2 A luminas colored asurface T hin metallic ob - Pursuit ship ject, unconventional shape Not stated S Yellowish-white Spherical 5-10 ft. diameter Not stated 4 W hite aluminum D istinct oval out- 50 ft. line; two projec­ tions on upper sur­ face which M ight have b een thick fins or no b a. T hese crossed each other at intervale, sug­ gesting either ro­ tation or oscilla­ tion of slow type None & K ot ab ated Bound Not stated Nona 6 W hitish-b rown D iac Not stated Nona 7 A luminum D iac Not determined M ono 8 W hite D iac Out of sight b e­ fore detailed ob ­ servation made Nono 8a W hite D iac Out of Bight b e­ fore detailed ob ­ servation made None 9 L ike shiny ohro- aium hub cap D isc Not stated Not stated 10 H ot ab ated T hin and smooth on b ottom rough appearing on top Not stated Not stated tOTiffltitt N N D 927545 I no!dent M o. C olor Shape Siie Sound 11 W hite i Saucer Not stated Not stated 12 H ot stated L ike flock of geese M ot stated L ow hturning sound 13 Resemb led metal 11c Not stated lot stated Not stated 14 L ike a nee dine L ike a ne* dine L ike a new dime Not stated 15 Silver Not stated Not stated Not stated 16 Not stated D isc Not stated Not stated 17 M irror b right A pproximately circular, no tail D iameter equal to distance b etween outb oard engines of D C 4 Not stated 16 yellow Ball Not stated Not stated 19 Reflected the sun b ri111antly L ike cigars - nueh longer than wide Not stated N one 20 Silver Round A b out 12 inches in diameter None 21 D irty white Between circle and oval - 1 n- verted saucer 17 5-250 ft. diameter 12 ft. thick L ike electric motor or dy­ namo 22 Shiny silvery Slim b ody Q uite large Not stated 23 Bright and silvery H alf-circle Not stated Not stated 24 25 G listened In tuu T oo far away to determine shape T oo far away to determine shape None 25 L uminous F lying saucer — no tail Not stated Not stated 26 Not stated Not stated Not stated lot stated 27 SiIvery C ircular in shape Same span as C -54 Not stated like a wagon wheel at 10,000 ft. 28 Not stated C omet- like Not stated Not stated 29 Not stated A lmost round Not stated Not stated 50 W hite (light) Not stated Not stated None N N D 927545 Incident -o. C olor Shape Site Sound 30a A mb er Round or oval C -47 airplane hone 30b Bright unite to amb er C one-shaped, b lunt on top and taper­ ing off toward b ottom Enormous None 30c W hite Ilight) Round C omparab le to run­ way light H one 31 W hite Not stated Not stated None 32 A mb er Not stated Not stated None 33 Sun flashes on metal or metallic Roughly circular A t the distance and altitude the ob ject appeared to b e the site of silver do 1 lai None r 33a W hite or luminous. T urned to b e more red as the sun set Round tending to b e conical Unknown - altitude ana distance too groat None 53b Sot stated C one, topped with red Not stated None 33c Si Iver with shadow Raindrop Unknown - b elieved to b e large Unknown 33d White Round at times - cone shaped Uncertain b ecause of di stance None S3® White Round 1/4 size full moon None 3Sf M etallic Not stated T remendous Sot stated 53g Not stated C one 100 ft. high, 43 ft. across None 34 Redish tinge Round L arge grapefruit Bone 35 F ire color Ball K ot stated Not stated 36 M ot stated Not stated K ot stated H ot stated 37 Reddish with b lue b ackground. Black with white b ackground Not stated 3 ft. from point of view None 38 Silver Sall Not stated hot stated feWifOfiA t N N D 927545 b • Incident M o, C o lo r Shape Slie S o u n d 39 Phosphorus Egg-shaped diacs Not ab ated Not stated UO G ray • Elliptical a 20-30 ft. Noise like jet aircraft prior to its appear- ande. No audib le sound heard while ob ject was in view. UI A luminite Round 3 ft. diameter Not Stated #2 G rayish Balloon 10 ft diameter K ot stated *3 D irty white Between a circle and an oval (Inverted saucer) 12 ft thick and 17 5-250 ft diameter Electric M otor or dynamo 44 Not stated F lying Saucers (not actually des­ crib ed as b eing this shape) Not ab ated None 45 Not stated Not stated Not stated Not stated 46 Silvery W hite Round Small Not stated 47 No definite color top side reflect­ ed light. No definite shape C -54 airplane Not determined due to the noise of airplane. 48 Red F laming Red cone Not stated Not stated 48* Bright light C ircular-like a star changing to In the sky only larger, red then to white or yellow V ery large compared to an aeroplane light None 48b Red - W hen descending C one Not determined Not stated 48c Red when moving Not stated then green and b lack to red. Not stated Not stated 48d Yellow or flame Not stated colored. Not stated Not stated 49 Not stated Pencil shaped ob ject Not stated Not stated N N D 927545 Incident No, C olor Sound • Shape Sjle 50 Stated as queer light. Referred to as saucer b ut not stated as b eing of this definite shape. Not stated Not stated 51 Silver Round Not stated Not stated 52 W hite. shiny C ircular like a b all on the b ottom b ut not completely round. 15-25 ft D iameter Not stated 52a M ilk white Not stated Not stated None 53 W hite C ircular 36 inches diameter Not stated 5U Not stated Not stated Not stated Not stated 55 Redish Not stated Not stated None 56 D in glow of light Round 2 ft. diameter None 57 Sliter to Red Not stated Not stated Not stated 58 Black Saucer (not definitely stated as b eing this shape) L arger than C -54 airplane Not stated 59 Incandescent light without appreciab le b lue and no reddish tinge Not stated • Not stated Not stated 60 Plame color D isc shaped (the after glow made it look like a cone) Barrel H ead, dinner plate and the sice of a plane flying high. Not stated 61 W hite and illuminated Not stated Site of Pigeons Not stated 62 Yellowish white Not stated Small Not stated 63 G leamed and Shismered D isc (not actually stated as b eing of this shape) 3 ft. diameter and of no great thick­ ness. Not stated 64 C olor similar Not stated to electric light. Not stated Not stated 65 lot stated Not stated 15 inches diameter Not stated 66 Bright Orange Not stated Not stated Not stated 67 Nutal color highly polish­ed chromium. top surface slightly ■ curved-larger in front than in the rear. N N D 927545 4-6 ft In length Not stated and 10-14 inches _ CON FIDE N TIA L G OH FIDE N TIA L Incident — M g, C olor Shape S ite Sound None68 Not stated D isc - appeared to have a tail. 30 ft diameter 69 W hite Not stated Not stated Bussing sound. 7 0 Not stated G iant fire cracker Not stated Bussing sound not as loud as a rocket ship. 7 1 Not stated Not stated Not stated Not stated 7 2 Silver Sphere( sat not like saucer or disc. 2-3 ft diameter Not stated 7 5 D eep G old Elliptical 15 ft long 2-3 ft in length. * Not stated 7 * Not stated T apered aharpely to a point in the front end. 30 ft. diameter None 7 5 Sky b lue Ob long like a b road rim hat with a low crown. 20 ft. long and 10 ft. thick. M ade a swishing sound. 7 6 Not stated Not stated Not stated L ike the echo of a motor. 7 7 L ight colored Only concrete evidence of fora appeared on the left tangent of the group 50-100 ft wide. ■ L oud roar 7 8 L ight gray C ircular 8 ft. diameter Not stated 7 9 Silver Not stated L arger than a Pib al b alloon when ob served through a theodolite. Not stated 80 Reflected shite light. "Blob " Small airplane None 81 Silver L arge Balloon with silver L arge diac b elow it, no attaching cab les were noticed. Not stated 82 F rosty shite Round and flat Equal to b ulk of 6 each, B-29 air­ planes with dia­ meter to thickness ratio of 10-1. & slight swishing. 83 Black e Round T wenty-five cent piece. Not stated -----------= - meldint M O. C olor Shaos SA IS. Sound 84 Shinny Round lot stated H ore or less Shrill. 85 Not stated Resemb led the XF 5U-1. Not stated Not stated 86 Not stated lot stated Not ab ated Not stated 87 NotSstated Not stated lot stated Not stated 88 Not at*ted F lying disc (not ac­ tually describ ed as b eing of this shape) Not stated Not stated 89 Silvery Round disc shaped ob ject 30-50 ft. diameter Nat stated 90 Reflected light Uniform with no protu­ b erances such as wings of an airplane Not stated Not stated 91 L ight Not stated Not stated None 92 Silver Not stated Small Not stated 93 Bluish center ri th red on its edges A ppeared to b e a disc Resemb led u shooting starj however, ob ­ servers not certain Not stated 94 Not stated Not stated Not stated Not stated 95 Not stated Not stated Not stated Not stated 96 Not stated Not stated Not stated Not stated 97 F lash of li^t Not stated Not stated Not stated 98 Brl ght light A lmost round er perhaps oval or saucer-shaped 2b -30 milesdiameter Not stated 99 Shining Brightly shining ob ject with long tall Not stated Not stated 100 Shining Not stated Not stated Not stated ---------N TIA L N N D 927545 WffIB E IffiA t Incident No. Exhaust T rail heading A ltitude F t. Speed Effect on C louds 1 K one 320° 1000-8000 ft. 300 mph Not stated la • lb 1c Not stated Northwest 7 50V -8000 ft. 350-400 mph Not stated Id K ot stated Northwest 7 000-8000 ft. 300-400 mph K ot stated le Not stated Northwest 8000 ft. 300-400 mph Not stated 2 K ot stated Not stated F rom very near the ground to very high Not stated Not stated 3 Not stated W est to east 10000-12000 ft. 200-225 mph Notstated 4 Not stated North of due east Under 20000 ft. Slower than Not maximum speed of P-80 stated 5 Not stated T wo flying south - 3 flying east M ot stated G reat speed Notstated 6 Not stated Northwesterly Undetermined T errific lotstated 7 None Southwest 30000 ft* T errific - faster than any ob ject ever seen b y him lotstated 8 None- South 40000 ft. T errific Not s tated 8a None South 40000 ft. T errific Not stated 9 Not stated South H igh over G lob e M ills T errific Not stated 10 None Northwest Not stated C ruised for Not 45 win. at conventional airline speed (180 mph) then rapidly dis­ appeared stated 11 Not stated Over north end of L ake W ash­ ington K ot stated Not stated Not stated WOE M TIA t N N D 927545 COh taE N TW r G eN F«t N N D 927545 Incident No. Exhaust T rai 1 H eading A ltitude F t. Speed Effect on C louds 12 Not stated Not stated Not stated H ot stated Notstated 13 Not stated 3 west to east. 1 north D id not appear very high T raveling so H ol fast they were out of sight In east in 2-4 seconds t stated 14 K ot stated M ot stated Not stated M oving slowly Not stated over sandy district 15 Not stated 1 headed southeast. 2 headed northeast H igh K ot stated Notstated 16 Not stated Not stated Not stated hot stated Not stated 17 Not stated north to south ab out 17 0° 9500 ft. Not stated Notstated 18 T rail stream­ ing out b e­ hind like vapor trail b ehind air­ plane on misty day - 8een over westand of T oronto K ot stated Not stated Notstated 19 L ike slight W est to east trace of steam. D isappeared immediately. One Bile high V ery fast Notstated 20 Not stated Southwest A b out 1500 ft. F ast H otstated 21 Not stated N .n.w . 1200 ft. A b out 300 ■ph Not stated 22 Not stated S.W . of S. 7 000 ft. Slower than two-motored army plane Not stated 23 Not stated Not stated 3000 ft. Not stated Not stated 24 C loud-like Southeast vapor - re­ tained shape and persisted for over an ^ hour V ery high V ery fast Not stated CON FIDE N TIA L Incident K o. Exhaust T rail H eading A ltitude F t. Speed Effect on C louds 25 Not stated Bast H igh F ast Not stated 26 Bluish-b lack Not stated Not stated Not stated C ut a clear path through clouds 27 Bluish-b lack 15 mi. long Not stated 10000 ft. F ast Seemed to out clouds open 28 Not stated Not stated Not stated D id not Not stated move . Seemed to go b elow horizon with rotation of earth 29 Not stated 10 flying H igh north; on reverse course there were only 7 300-400 mph Not stated 30 None (ap­ peared to have b luish streaks out from sides W est 3000 Slow Not stated 30a F ive times 120° F rom very near 500 mph Not stated length of ob ject ground to 1000 ft. after it started to leave vicinity 30b Small streak S.S.W . trailing ob ject 2000-30001 ft. Exceeding 500 mph Not stated 30o Not stated Not stated different al­ titudes M otionless Not stated 31 W hite, heavy W est to east 20000-50000 ft. 600^200 mph Not stated 32 None Stationary 3000 ft. Stationary ■one 33 None None visib le Unknown none visib le None 33a None 210° from G odman F ield Extremely high Stationary None 33b None Not stated Not stated Not stated Not stated eWH DH fflA t N N D 927545 COH riDE N TIA L - Incident -J& ___ 55c 55d 55e 55f 55g 5* 55 56 57 58 59 40 41 42 45 44 45 46 *7 43 Exhaust T rill Beading A ltitude ft. Speed Rffwt on emos Not seen A ppeared to b e stationary. V ery high. A ppeared None to b o stationary. None 210° frees G odman fid. Uncertain- very high. Stationary.C ould b e seen through cirrus None 210* from G odman F id. 25000 ft. Stationary.None Not stated A pprox. 210* frat Oodamn fid 15000 ft. e 500 aph Not stated Not stated Southtreat 4 alias 10 aph Not stated None s W est to east Not stated Speed of a None meteor or falling star. Strom of fire. Northwesterly Not stated 7 00-900 mph Not stated Not stated Northeast Not stated Not stated Not stated Not stated Northeast 8000-10000 ft. 350 aph Not stated Not stated Ngt stated Not stated Not stated Not stated Nono East J00O0 ft. V ery fast Not stated Not stated A ppeared fro# northeast. 5000 ft. 400-600 mph Not stated Not stated South Not stated G reet Not stated Not stated Northwest 1500 100 *ph Not stated Not stated first group S S/E, second group N/W - 1200 300 mph Not stated Not stated South Not stated fast Not stated Not stated Not stated Not stated Not stated Not stated Not stated Northwesterly 1000 faster Not stated than an air­ plane. Not stated Southwesterly 10000 Pastor thm Not stated any aircraft ho had ever seen. Osseous green ■1st. S/W when it Not stated left the V icinity. N N D 927545 CON H DLN TIA L G ained and Not stated lost altit­ ude at a terrific rate. CON FIDE N TlA t Incident -M a___ Exhaust JX1U- Seeing. A ltitude-El. Speed Effect on C louds M l V ery faint SA when it left exhaust trail the vicinity, when noring. Not stated L eft Not stated vicinity at very high speed. 43b G reenish nist W hen descending. SA when it left the vicinity. Not stated Not stated Not stated 48c K ot stated 210 degrees when it left the vic­ inity. 15000-20000 Not stated Not stated 48d None A pproximately due west when it left the vicinity Proa 4000 to very high. • Slow Not stated 49 L ong trail of smoke. W est V ery high W ot stated Not stated 50 Not stated Shoreward Not stated b ut said to b e quite close. Slow until Not stated over land then higher speed while leaving. 51 Not stated Not stated H igh Not stated Not stated 52 Non# Southward 8000-10000 M ade a P-80 Not stated look like it was motion­ less in the air. 52* Not stated 120° 6ooo A pproximate- Not stated ly 7 50 mph. 53 Not stated 120* 6000 285 mph. Not stated 54 Not stated North Sea to Norfolk 22000 Equal to Not stated or greater than a Brit­ ish M osquito. 55 Not stated OB 10000 H igh vel- Not stated oclty, stated to b e faster than convent­ ional airplane. 56 Not stated South East 2000 ft 500-600 mph.Not stated mRflE N TWt N N D 927545 Incident -M .___ Exhaust • §2221 Effect on C louds A vUW IULN 1 fA r Budin* a m « ,r. 57 Not stated NIE (JO* E of true North on horisonal plane. JO* off the horison at an estlaated 1A ail* range. H igh vel­ ocity, sta­ ted to b e faster than a tracer b ullet. Notstated 53 Not stated NA 1000 510 nph. Notstated 59 Not stated 350* later changed to 109*. 95 00-10000 1000 knots Notstated 60 L ight flans color. Prog nA head­ ing Eastward. 6000 V ery high velocity. Notstated 61 Not stated Northern 2000-5000 Pastor than b irds. Not stated 62 Not stated Not stated Several thousand ft. H igh rate of speed. Notstated 63 Not stated Northeasterly 3000 T renendoue Speed. Not stated 64 Not stated Northeasterly Not stated T errific Netstated 65 Not stated Neat to East 1000 1000-1200aph Notstated 66 L ong stra­ ight white streak sia- ilar to the streak left b y a tracer b ullet. North to South L ow Required H seconds to travel 7 0* are. Not stated 67 W hite trail of saoke. Not stated 500-1000 T errific Notstated 68 Not stated Southeasterly 6000 Not stated Notstated 69 T hin streak of greyish color. South Not stated V ery fast. Notstated 7 0 Either moke or conden­ sation last­ ing 2 secondt NE to SV * 1. 1000-3000 400-500 Notstated 7 1 M ay have b een spoke or vapor frost intense speed, was alaoat white Southeast then Not stated turned and went west. N N D 927545 -G G N H B B ffiA t 7 000000 Notstated nets. । am a i Incident n o , Exhaust Jail.. a UUI1 I IULI1 1IH T* A tiding urm^ pt, Speed ?££.♦?$ pb ci?^g 7 2 None South Below 10000 T remendous Net stated 7 3 None Easterly approximately 110* magnetic. 7 000 17 5 »ph Not stated 7 * Not stated Not stated Not stated G reater than any­ thing ever W itnessed. Not Stated 7 5 None Bast to west 7 5 Not stated Not stated 7 6 Not stated Not stated 4000-6000 Not stated Not stated 7 7 Not stated Northwest (T rue) Not stated 600-1200 Not stated 7 6 Not stated Straight down. D ecreasing from approximately 25000. Inconceivab le Not stated 7 9 Not stated Bast to W est L ess than 15000 Not stated Not stated 80 None Southeast L ess than 500 C omputed at 1350 W h, however ap­ peared to move with the speed of a jet aircraft. Not stated 81 Not stated Northwest 6000 Not stated Not stated 82 None 350* 10000-18000 T hree times that of a Jet airoraft Not stated • 83 Not stated Not stated 11000 Not stated Not stated 84 Not stated Northeast 7 500 Not stated Not stated 85 Not stated North 8500 350 aph Not stated 86 Not stated Northward Not stated Not stated Not stated 87 Not stated Not stated from 5000 Not stated Not stated 88 Not stated Not stated 200 yards moving rap­ idly Not stated 89 Not stated East 11000 210 mph Not stated N N D 927545 CU^fiDE N TIA L Incident Bo. 90 91 92 93 9 4 95 96 97 98 99 100 Exhaust T rail -eeN H B E N TM it- • Speed Effect on C loudsH eading A ltitude F t. One witness thought he saw vapor trails Northerly 8000-10000 Not stated Not stated Not stated D isappeared in the south­ west G reat height H igh rate of speed Notstated Not stated W est A b ove 1000 G reat speed Not stated None D ropped from sight on north side of M t. T om near H olyoke, M ass. Not stated V ery high velocity Notstated G reen and b lue flames D escending ver­ tically F rom 13000 V ery high rate of speed Not stated Several colors Eastward of flames - red and green predominating L ow V ery high rate of speed Not stated Not stated Not stated 1200-1300 Not stated Not stated Not stated Not stated Not stated Not stated Notstated Not stated Not stated Not stated Not stated Notstated Not stated W est to east Not stated Not stated Not stated G rey streaks were le/t in sky North to south Not stated Not stated Notstated N N D 927545 G G iirlOE N TIA L CON FIDE N TIA L M OT E: Incident £18 It ha8 no* b een definitely determined that b oth the photograph and story were a hoax, perpetrated for pub licity and money. Incident f84 T he person waiting the report on thia incident was determined to b e an excitab le person, very talkative, and possessing an ex­ aggerated, imagination and inclined to inpress people with his continuous chatter. ----- N N D 927545 REPOST ED D IREC T IOH S OF F L IG H T CON H DE N TIA b r W W W 7 7 C ircling 15 Straight down 3 34 S D irection Indefinite 64 D irection H ot Stated 61 W here an undetermined numb er of ob ­ jects were reported the minimum numb er of ob jects are plotted® Same ob ject reported b y different people only shown once® G G N H B E N TIA fc N N D 927545 gCWE ffflA t- * Identification of Sub ject M atter (as per staple) M C U M C IT 19 F eb 48 1 1. Reference is made to the films taken b y M r. Rhoades (Incident f40) which were forwarded for examination. T he following data wore derived from a study of the specimen! a. It is concluded that the image is of true photographic nature, and is not duo to imperfections in the emulsion, or lack of development in the sec­ tion in question. T he image exhib its a "tail" indicating the proper type of distortion due to the type of shutter used, the speed of the ob ject and the fixed speed of the shutter. T his trailing off conforms to the general informa­ tion given in the report. b . T he report states the ob ject was seen at approximately 2000 foot at the time of exposure. T he ob server also reports b eing ab le to see clearly a canopy of enclosure. T he visual acuity of an average person!would allow for thio perception, b ut certainly not much further as the sub ject had low visual contrast, b eing gray against a gray sky. If wo can estab lish the di stance from camera to sub ject, wo will have quantity #1. T he report states that a 620 camera was used, indicating several possib ilities, sinoo the 620 is nomenclature for the spooling and width of the film wo nay have negatives 2| x 2^*, 2^ x 5^* and 2 g x d|*, T he sample sub mitted had b oon cut and it was not possib le to estab lish the exact frame si so. T he 2| x 2^” site was ruled out, leaving 2^ x 5$" and 2^ x 4^*. If it ore the former, then the focal length of the lens would b e 4", and using 2000 foot as the sub ject distance and the imago site at t/54", w o have an approximate site of 44 foot as the diagonal of the ob ject. V ow if we ohooso the latter value of 5" for focal length, wo have an approx!- M te value of 56* for the diagonal. Points of measurement are indicated from x to x on Exhib it "A ". approximate t eON RDE N TIA t N N D 927545 G WOE N B A t- N N D 927545 1 86 FE B RUA RY 1 3, 1 94 8 a sp ect ra tio a nd fo r the grea ter so ona fterw a rds disca rded hop eless p rop ositio n. b est given so m ew ha t ig. 5. Kitchen's doughnut of 1 91 1 N N D 927545 from w ith The B ritish su ccessfu l. A representa tive, exten sively. First Doughnut o f the idea ha s b een B ritain's co nception m o re tried m o re Fig. 4 .—Principle of the H uth annular-biplane system m a xim um lift o f su ch W hen La n chester d o n stitu ted, u n til n o w . __ . .. r--------e4 his b o ok, m a n w a s just b egin - r n rndifn rre'd hlS *'n gs- a n d in o rder ,o •'l' w i,h a m in im um a 1p ow tL W lngs o f fa ir a spect ra tio w ere a n eces- the litH ^"? ^ ^ i,iher.e w crc a few ca r|y a ero pla nes, n ota b ly 19101 k J ”* e m o no pla n e o f S a nto s Du m on t (1909- q u te\£ xessM d “" a spect ra ,io o f o n'y 2 a n d Proved to b e n l m "6^ lhe < a rl'c? t tem p ts a t a gen uin e “a ptero id" a ero ( 910) h ^ ? G crm a n B hila i, Flick-R ein ig (1 10). It ha d a S pa n o f 7j ft., a nd p erfo rm ed in ho p s o nly A nnular A erodynamics . A ''TuPlc 'J P'r'™ "1 w ith so m e p a p er a n d a p a ir o f scisso rs sho w s tha t the sin kin g sp eed o f a circu la r disc lo a ded w ith a ^rr C .iP ,S decrca sed w hen a ho le o f su fficient dia m eter is cu t o ut in the centre (Fig. 3). This justifies the develo pm ent from the circula r disc w ing to the a nn ula r a ero foil. The theo ry o f the p heno m eno n is still so m ew ha t o b scu re. (H a vin g tried this experim ent, w e ca n co n firm tha t the cha r­ a cteristics o f a n a nn ula r a ero fo il a re certa in ly very different from those o f the p la in disc a ero foil. Our o w n experim ents w ere a dm ittedly so m ew ha t lim ited in sco p e a n d w e w ere u na b le r m o rc ^a n a n im pressio n o f the rela tive sin kin g sp eeds it did, ho w ever, a pp ea r to b e less w ith the a nn ula r a erofo il Ou r m a '" ^'“'‘o "' w ere tha t cu tting a 2.25-in . dia m eter ho le in a > J 75-in . dia m eter disc, resu lted in a m u ch fla tter glide; the sta ll w a s n ot so a b ru pt, a nd the sta b ility in the glide w a s im pro ved. W e w ere so fa scina ted w ith the experim ent tha t w e *° rcPca * a t a la ter da te o n a m o re scien tific level.— E d.) the co nvention a l a ero pla n e is co n stitu ted o f tw o b a sic a ero­ fo ils: a w ing (w hich su pp lies the lift) a n d a ta il (w hich b a la n ces a n d sta b ilizes the w ing). W e kn o w tha t su ch a n a rra ngem en t o t the tw o a erofo il co m po n en ts is b y n o m ea n s the o nly p os­ sib le o ne. The b a la ncing a nd sta b ilizin g a erofo il (ta ilp la ne) n eed n ot to b e a ft o f the lifting w ing a s a ta il. It ca n b e a rra nged a nyw here in rela tio n to the w in g. e g., a b ove it. b elo w it. o r in fro nt o f it. If the b a la n cin g a ero fo il is in fro nt o f the m a in w in g, the a ero ­ p la n e is o f the ta il-first typ e, a nd if it is a tta ched to the 1 he o rigina l idea fo r a n a nn ula r-w in g a ero pla ne ca m e G . A . Kitchen , in a b o ut 1910; he co n stru cted a b ipla ne rin g-sha ped w ings, b ut m a de n o p rogress w ith it. The sta b le m a in w ing, the ta illess a ero pla n e is crea ted. Fo r a ll these a rra ngem en ts, the con dition is tha t, in the ca se o f a w ing co m ­ p rised o f n orm a l (u nsta b le) a erofoil section s, the sta b ilizing a ero fo il exerts a cena in levera ge in rela tio n to the centre o f gra vity o f the a ircra ft. A n other p o ssib ility is to co m b in e tw o lifting w ings so tha t they w ill sta b ilize a nd b a la n ce ea ch o ther. Fo r this p u rp o se, a ll tha t is requ ired is tha t the fron t w in g sha ll p ossess, a t a ll in ci­ den ces o f flight, a grea ter effective inciden ce tha n the rea r w in g. In o ther w ords, the centre o f gra vity m u st b e n ea rer to the lea ding w ing tha n to the tra iling w in g, a nd the w hole a rra n ge­ m ent m u st b e b a la nced a ccordin gly. In this w a y, w e a rrive a t the co nceptio n o f a sta b le ta n dem a ero pla ne. If w e n ow ta ke su ch a ta n dem a rra n gem ent a n d sw eep the lea ding w ing b a ck a nd the tra iling w ing co rresp o ndin gly fo rw a rd so tha t the tips o f b oth w ings m erge in to ea ch o ther, w e o b ta in a n a nn ula r o r rin g-sha p ed w in g system . A erodyna m ica lly, it is o f m in or im po rta n ce if the sha p e is a ctu a lly circula r o r o va l, o r •* tria n gu la r o r q u a dra n gu la r sha p es co n stitu te the w in g. Fo r sim plicity s sa ke, in a ll su ch ca ses co nsidered here, the term " a nn ula r ” is a pp lied. A s m ention ed, the a erodyna m ics o f su ch sha p es ca nn ot yet b e co n sidered a s fu lly esta b lished. B u t it is p ro ved tha t lon gi­ tu dina lly sta b le w ing system s ca n b e o b ta in ed w ith su ch sha pes. S o m e typ es relying o n su ch w ings ha ve show n q uite rem a rka b le flyin g q ua lities. It is a lso p ossib le tha t, w ith a nn ula r w ings, the induced dra g is less tha n w ith co nvention a l w ings o f equ iva ­ len t a spect ra tio . In co m m o n w ith circu la r w in gs, a nn ula r w ings ha ve the rem a rka b le p ro perty tha t the lift force stea dily in crea ses w ith incidence u p to fa irly high va lu es w itho ut a sta ll. Fo r a ll kn o w n a rra n gem ents the m a xim um lift seem s to o ccur a t incidences exceedin g 30 degrees. A s su ch high a ngles o f incidence a re n ot likely to b e rea ched in flight u ninten tion a lly, it is o b viou s w hy a nn ula r w ings ha ve b ecom e reno w ned fo r their goo d-n a tu red flyin g cha ra cteristics. A n other p rop erty o f a nn ula r w in gs (first esta b lished b y Tilghm a n R icha rds) is tha t the centre o f p ressu re o f su ch w ing system s is n ea rly sta tio na ry in flight, o r tha t a tra vel o f the centre o f p ressure ca n b e o b ta ined w hich is p ositively sta b le u ntil incidences o f the o rder o f 18 degrees a re rea ched. In fa ct, n o ca se o f lon gitudin a l insta b ility ha s ever b een rep orted w ith a n a nn ula r w in g, a lthou gh the centre o f gra vity ha s o ften b een loca ted da n gerou sly fa r b a ck. The first a nn ula r-w in g a erop la n e da tes b a ck to 1908. It ha d little su ccess. Tw o typ es w ere co nstructed in su ccessio n to the design s o f a ca p a b le G erm a n a eron a u tica l engin eer. Fritz H uth, w ho w a s b y p rofession a tea cher a t a technica l scho ol (Figs. 4 a nd 6). The secon d typ e, w hich ha d a less ela b ora te a irscrew drive, flew in M a y, 1910. it w a s. ho w ever, so devo id o f p erfo rm a n ce, in sp ite o f a 50 b .h.p. en gin e, tha t it w a s fa vou r o f the “w ell-tried" co nvention o f “ n orm a l" w ings. Fo r these rea son s, a stu dy o f the histo ry o f the u se o f lo w ra tios in w ing design w ill b e o f in terest. c S p iritu a lly, the fa thers o f su ch a eron a u tica l’ exhib its w ere E n glishm en . I hey w ere p eop le o f goo d rep u ta tio n a nd b y n°cinS n S su sPect °f a erodyna m ic p erversion . . . La n chester w a s u ndou b tedly the first a erodyna m icist i f,ve ' . ght J .? a erop la n e w in gs o t circula r o r sq ua re sha p e. In his b oo k p u b lished in 1907. he referred exp ressively to su ch a pteroid w ing sha p es (Fig. 2) a nd a dva n ced the view tha t N ew to n s la w w a s va lid fo r these. The correctness o f this view w a s exp erim en ta lly p ro ved 30 yea rs la ter. In a p revio u s a rticle o n " S ta lling C ha ra cteristics o f Ta illess A ero pla nes (Thb A er o p l a n e fo r A ugust 15. 1947), the ea rly '"''re-1 ’a ^en b y F (n ow S ir Frederick) H a ndley Pa ge in the s a iling q u a lities o f w ings o f lo w a spect ra tio w a s m en tion ed. H e show ed, in a p a per rea d in A p ril. 1911. tha t m a rgin a l vo rtices PrM su re-equ a lizing flo w a ro un d the tips w ere respo nsib le Lo r.d«la y o f flow sep a ra tio n w hich ha d b een o b seived a t n ign in cidences. .s^,"^'/" th« co nn ection :-;-. . . W ith p la n es o f high ’’K1 ' ' *Lh slcnder *m « s o f n orm a l sp a n cho rd f I' n o .‘ the “"* fa cil'ty fo r the '• feedin g in " o f lin t 11 p la n c s,d« s (ie„ a t the w ing tips) to a ct a s a ive s^-Tm "i J he P k”* ? n d the llve slrea m . a nd therefo re the he- else o f Ih/S „l hC P ? n? S b a ck a l a n ea rH fr S ,a ge ,h,n in f lh p a n e o f lo w er a spect ra tio . . . ." H e then .Kea PC n m en U J l eviden ce fo r the dela y o f flow Fig. 3.—A simple experiment In annular aerofoils TH E A E ROPLA N E su fficiently in terested the m a tter to give u p a b udding in a n inefficient a ttitu de o l the p la n e a t high sp eed; a n d the from the w ing b y hea vy a n d redu nda n t S tru ctu re. H igh ga in st the in terests o f the icro pla ne (Fig. B ell) the hop e o f secu rin g o rders fro m the A dm ira lty. w a s It w a s n ot su ccessful (To be continued.) N N D 927545 p terygoid o n ea ch ha lf-w ing, the m o vem ent p ressu re w a s a resulta n t o f three distin ct experim en ta l a erop la n e o f this typ e, co nstru cted a nd tested a t B roo kla nds. a pteroid a nd tw o o f the centre o f Feb ru a ry, 1908). The R hom b oida l. b y G o rdo n C hu rchill in FE B RUA RY 1 3, 1 94 8 w a s dem o nstra ted b efore W insto n shro uded a ga in st p ub licity (m u ch ; develop m en t). This a nn ula r-w in g flight o f Kitchen 's m o dels, how ever, co n vin ced C edric Lee tha t a n a erop la n e o f su ch design w o uld b e a su ccess, a n d la te in 1910 he a cq uired the p a ten ts. A t the sa m e tim e, G . Tilghm a n R icha rds, w ho w a s a q ua lified a eron a u tica l engin eer, b eca m e A s m ention ed, the circu la r sha p e fo r the w ing is n ot in itself a decisive cha ra cteristic. Previou sly, in 1908. A . H . E dw a rds in ven ted the rin g-typ e w in g w ith rho m b o ida l o r tria n gu la r sha p e (B rit. Pa t. S pec. N o . 4519 o f " ' a nd test-flo w n b y G o rdon a t S horeha m . The flight p ilot, b ut u nlu cky fo r the regio n a l m o vem en ts; a n d w ith slight m o difica tion s co uld b e m a de to m o ve in a n y desired m a nn er w itho ut a ffectin g the gen era l efficien cy o f the p la ne.” w a s rem a rka b le a n d lucky fo r the p reciou s cra ft. A fter ha ving flow n inheren t in sta b ility o f cu rved a erofo ils m ea n s a co ntinu a l dep en dence o n extra n eo us co n tro ls ca rried a t so m e dista nce The exp erien ce w ith p ow ered a ero pla nes w a s a t first b eset w ith disa p po intm ents. Fa m in e Po in t. H eysha m , w a s a pp a ren tly n ot a spo t fro m w hich a ero na utica l experim enters co u ld derive a ny co m fo rt. “ There is n othing It a ffords high lift a t ha s a go od lift/dra g m a chin e w a s very fa st in la n ding; a nd there lift a t sm a ll a ngles is u seless, likew ise high lift/dra g ra tio a t sm a ll a ngles, a n d w ha t is requ ired is the reversa l o f the n orm a l typ e o f lift cu rve givin g little lift kt sm a ll a n gles w ith lo w va lu e o f the lift dra g ra tio to r la nding. . . ." S een fro m o ur p resen t sta te o f kn o w ledge a nd develop m en t, a nd fa cing the b urn in g p rob lem s o f p erso n a l a ircra ft fo r the m a n in the street, it w ou ld seem tha t this o pin ion is a very go od a rgum en t fo r fu rther exp erim en ta tio n a lo ng the lin es indica ted. engineerin g b urea u in o rder to jo in C edric Lee a n d to devo te his energy to the idea o f a “ sa fety ” a erop la ne. Tilghm a n R icha rds b ega n w ith system a tic exp erim en ts o n m o dels a nd o n la rge gliders. La ter, ca refu l w ind-tun nel tests (inclu ding the o b serva tion o f the p ressure distrib u tion ) w ere m a de b y him in a 2-ft. tu nn el he ha d co n stru cted a t E a st Lon do n C ollege a nd a lso in tu nn els o f the N a tio n a l Physica l La b ora to ry. The p rep a ra tio n o f the design w a s, therefo re, u nco m m on ly ca refu l to r this ea rly p eriod o f 1911-1914. In o rder to a p precia te the in ten tio ns fo r the develo pm en t, the fo llo w in g q uo ta tion fro m a p a per rea d b y Tilghm a n R icha rds in a b o ut 1912 is illu m in a ting:— ”, . . The very fa ct o f high lift o ccurring a t sm a ll a ngles m ea n s the p rovision o f la rge a rea fo r la nding sp eed resulting eq uip p ed w ith a n 80 b .h.p . ro ta ry E n gla nd o n N ovem b er 23. 1912. A lto gether, 11.000 m iles w ere flo w n in a b ou t 128 hou rs, a nd even p eo ple n ot p revio usly tra ined a s p ilots w ere a b le to fly it. In M a y, 1914. tw o su ch a ero pla nes w ere b ein g design ed fo r p a rticipa tio n in the G o rdo n-B enn ett R a ce o f 1915. W hen the 1914-1918 W a r term ina ted the w o rk, it ha d clea rly grow n fa r b eyo nd the sta ge o f a n u ntried p roject a n d co uld ha ve w ell b een term ed a su ccessfu l exp erim ent w ith every p rospect o f b eco m in g a p ra ctica l p rop osition . In 1919-20 Tilghm a n R icha rds su cceeded in p ersu a din g the A ir M in istry to p la ce a n o rder fo r a fu rther exp erim en ta l a ero p la n e. B u t a w eek a fter co m m u nica tin g this decisio n M a jo r-G enera l B a gn a ll-W ild, the p ro m oter o f the idea , retired, a nd red ta pe killed a n intelligent in ten tion . It is o n ly fa ir to reco rd tha t a ero na utica l p ro gress ha s suffered fro m the fa ilure to ha ve this develo pm en t co ntinu ed. A s Tilghm a n R icha rds sta ted m a ny yea rs a go :— a n d G o rdo n B ell. Fin a lly it ca m e to grief w hen flo w n b y C edric Lee him self w itho ut p revio us tra in in g. A fter a go od flight he m a na ged to p ut it in to a river. A no ther in ciden t ha p pened w ith a su b seq uen t a nn ula r m o no pla ne: the eleva to r ja m m ed a n d b ro ke in flight. The a ero pla ne m erely p a n ca ked to the grou nd, a ga in p reservin g the hea lth o f its p ilot, E . C . G ordon E n gla n d. These typ es in their fin a l form ha d la tera l co ntro l effected b y differentia l deflectio n o f the eleva tors. It w a s rea lized tha t this elevon co n trol w a s n ot very effective fo r la tera l m a m ru vres, yet the la tera l sta b ility o f the w ing p roved so grea t tha t the p ro visio n o f a ileron s seem ed sup erflu ou s. The lon gitu dina l sta b ility w a s a lw a ys sa tisfa ctory, o nce the centre o f gra vity w a s p ro perly loca ted. B eca u se o f the grea t in heren t fore-a n d-a ft sta b ility, a sep a ra te eleva to r w a s, a t o ne tim e, lo ca ted o n to p o f the vertica l fin a nd p erm itted the fittin g o f specia l a ileron s. For direction a l co n trol a vertica l rudder w a s a tta ched to the stern o f the fu sela ge a t the tra iling edge o f the w in g. A form o f tricycle u n derca rria ge w a s em ployed. — In respect o f p erform a n ce, the w ind-tun nel tests in dica ted tha t a b etter lift/dra g ra tio co uld b e expected tha n w ith a co m pa ra b le co nvention a l a ero pla n e.' H o w ever, n o co n clusive eviden ce fo r this ha s. a s/yet, b een p resen ted. The third B ritish m on op la n e o f this typ e a lso ha d a n 80 b .h.p . ro ta ry engine, b ut this tim e it w a s loca ted a ft a nd. fu rther, drove the a irscrew b y m ea n s o f a n exten sion sha ft. U n like its p re­ decessors, n o dihedra l w a s p rovided, a nd b eca use o f this the flying q ua lities w ere fo un d to ha ve b een grea tly im pro ved. Fro m ea rly in 1914 u ntil the o utb rea k o f the 1914-18 W a r this u nco nvention a l a ero pla ne w a s freq uently flow n (m o stly . _ . a la rge circu it o n the first a ttem p t, the p ilo t n oticed, w hen co m ing in to la n d, tha t the a ero pla ne w a s exceedin gly ta il-hea vy a n d getting o ut o f co ntro l, the eleva tor b eing in sufficient. A t a b ou t 150 ft. a b o ve the gro un d the inevita b le sta ll to o k p la ce; b ut the p ilo t m a na ged so m ehow to dro p his m o un t u p side do w n o n to telegra p h w ires a nd esca p ed w itho u t p erson a l in jury. W ith the recon structed a nd im pro ved m o no p la n e m a ny su ccessfu l flights w ere m a de b y G ordon E n gla nd. N . S . Perciva l m ysterio us a b o ut ths a n nu la r p la ne, la rge a n gles, ha s n o b urb le p oin t, a nd ra tio fo r w ings w ith a b o dy. The in flight, fo r its da y, a nd extrem ely slo w b eing three distinct region s o f lift, o ne The o rigin a l Kitchen b ipla ne w ith a 50 b .h.p. ro ta ry engin e w a s w recked b y a ga le, du rin g 1911, b efore flight tests co uld b e m a de. A fter recon stru ctio n so m e flights w ere p erfo rm ed w ith it a t S ho reha m during 1911-12; yet it n ever ga ve a ny p roo f o f su p erio r q ua lities. The b ipla ne ha d a ileron s o f the o rigina l Fa rm a n va riety b etw een the w ings. V ery so on the b ipla ne a rra ngem en t w a s given u p in fa vo ur o f the m o no pla n e. A su b sequ en t exp erim en ta l m on op la n e w a s n ickn a m ed the “ S ecret-C ircle Pla n e " o r “ Do ughnu t." the experim ents b ein g TH E A E ROPLA N E M A RCH 5, 1 94 8 TH E A E ROPLA N E iu\*ra - RVD D Ut (C ontinu'd from page 185. February 13 last.) Fig. 1 0.—Principle of the Willoughby Delta design. 279 N N D 927545 The Biology of the F lying Saucer— II By A. R. W eyl, 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, ' ‘ T H E S E C R E T-C IR C LE "C ON S PIR A C Y," m entio ned p re­ vio usly in co nn ectio n w ith circula r-a ero foil a ero pla nes, did n ot la ck co ngen ia lly in ven tive sp irits. E a rly in 1913 a n engin eer in Dijo n, M . B o urgo in , m a de experim en ts w ith a n a n n ula r­ w ing a erop la ne. The tests w ere u nsa tisfa ctory. On e fea tu re o f this design w a s the p ro vision m a de fo r va ryin g the w ing incidence in flight. M o re recently, a sim ila r idea w a s su ggested b y N . H . W a rren a nd Th. R . Yo un g (Fig. 8). In 1937 they secu red a p a tent (B rit. Pa t. S p ec. N o . 508.022 o f Decem b er, 1937) fo r a n on - sta lla b le m o n op la ne o f rhom b oida l sha p e (i.e.. lea ding w ing sw ept b a ck a nd tra iling w ing sw ep t fo rw a rds w ith the w in g tips m erged together). This w a s p ro vided w ith a co nvention a l ta il a t the stern o f a lo ng fu sela ge a nd a n um b er o f a dva nta ges Fig. fl.—Project by Warren and Young for a light twin- engined two-seater of 90 h.p. (1937). The elevator is fitted between fin and fuselage. There is no tailplane. w ere cla im ed. In 1943 a m o del fo r a tw o -sea ter fighter w ith ta il tu rret show ed the sepa ra te ta il o m itted; sp ecia l em pha sis w a s la id o n the tria ngula r sha p e o f ea ch w ing a nd the effect o f sw eep w a s relied u p o n. N othing m ore ha s b eco m e kn o w n since, ho w ever, b ut it is w o rth n oting tha t the p roject ha d b een b a sed o n so un d a ero dyn a m ic co nsidera tio ns. In 1933, the a nn ula r w ing o f the G erm a n scu lp to r A n tes crea ted a m ild sensa tion b eca u se o f the go o d p erform a n ce o f m odels m a de to this co n cep tion (Fig. 9). S om ew ha t p ecu lia r w a s the a ero dyn a m ic co nception o f the rho m b oida l a nn ula r a erop la n e o f P. N esb itt W illo ughb y, a Fig. 9.—M odel of the "annular wing” of A ntes, 1 933. leading up to their use for supersonic flight. q ua lified a ero na utica l engin eer (Fig. 10). The W illou ghb y Delta C o. o f Lon do n ha d ta ken u p the develo pm en t o f this idea in 1931 a n d su fficient m ea n s w ere a va ila b le to m a ke ra ther exten sive tests. The p rinciple is b est describ ed a s a ta ndem m on op la n e w ith tw o a ero fo il-sha p ed p a rts co nn ecting the lea ding w ing w ith the tra ilin g w ing n ea r the tip s. The "side w ings" ha d a erofo il sha p e n ot o n ly in their lo ngitu din a l cross-section (i.e., in the direction o f flight), b ut a lso la tera lly. This w a s co nsidered a cha ra cteristic fea tu re a nd su b ject to p a ten ts. It w a s cla im ed tha t the vo rtex distrib u tio n in duced b y su ch sha p e ga ve a n u n usu a lly high a erodyna m ic efficien cy in sp ite o f the sm a ll sp a n o f the a ero pla ne. In a ddition , it w a s p o in ted o ut tha t the m a xim um lift w a s shifted to very high in ciden ces. M o reo ver, the " side w in gs" shou ld redu ce the dra g o f engin e n a celles fitted u n dern ea th them . A ll this w a s sa id to b e p roved b y exten sive w in d-tun nel experim enta tion here a n d a b roa d. Design s o f p a ssenger tra ns­ C o rt a ircra ft rea ching w eights o f 40.000 lb . w ere p rep a red o n the a sis o f m o del tests m a de a t the N a tion a l Physica l La b ora to ry a nd elsew here. The results m ust ha ve b een so enco ura ging tha t a n exp erim en ta l m o no pla n e w ith tw o 125 b .h.p . M en a sco en gines a nd w eighing 2.540 lb . w a s co n stru cted la te in 1938 (Fig. II). This a erop la n e flew in deed a n d w a s even p u b licly dem o nstra ted (inclu din g o n e-en gin e flight) a t a G a rden Pa rty in M a y, 1939. S hortly a fterw a rds the exp erim en ter w a s killed in a n u n exp la in ed cra sh du rin g a flight test. Fro m p ressure p lo ts o ver the “ side p la n es " w hich ha ve b een p u b lished, a p pa rently trim cha nges co uld b e exp ected a t va rio u s inciden ces. These co m po nents w ere thu s ca pa b le o f p ro du cin g lo ngitudina l in sta b ility a n d it is n ot im prob a b le tha t this a nd p oo r co ntrol efficiency m a y ha ve co ntrib uted to the a cciden t. There w a s a lso evidence o f a sta ll a t n orm a l in ciden ces, a lthou gh o f a very m ild cha ra cter a n d w ith little a p p a rent decrea se in the lift co efficien t (w hich, how ever, w o uld n ot exclude the p resence o f fluctua tin g lift fo rces). in A no ther su ggestion fo r a n a nn ula r w in g w a s m a de b y L. Peel, in 1944. This, ho w ever, w a s co ncerned less w ith the a ero dyn a m ic p rop erties o f su ch w ing system s tha n w ith the a rra n gem ent o f tw o engin es fa cin g ea ch o ther w ith their a ir­ screw s. in o rder to o verco m e the to rqu e rea ctio n. A p heno m en on o f w hich a ero dyn a m ic experim enters w ere a lw a ys w ell a w a re, b ut w hich a ircra ft design ers fa iled to u tilize, w a s tha t w ind-tun nel tests clea rly p roved goo d-n a tured sta llin g p rop erties o f w ings ha vin g very sm a ll a spect ra tio s. Yet even in the very ea rly da ys w hen centres o f gra vity w ere fa r to o fa r b a ck o n the o ld b o x-kites, the sq u a re sha p e o f ta ilpla nes, then u na ccou nta b ly in vo gu e, m a y ha ve sa ved the p ilot's b a co n m o re tha n o nce b y its refusa l to sta ll u n der extrem e p rovoca tio n. La ter o n science ca m e a nd p roved tha t a ta ilpla n e o f " goo d " a spect ra tio w a s m o re efficien t. It w a s. b ut it m a de the sta ll w o rse w hen the centre o f gra vity ha p pened to b e ra ther a ft. The in teresting thin g is tha t a ero toils o f circu la r o r sq ua re sha p e w ere tested in the ea rly da ys a t in ciden ces u p to 90 degrees, w hile o n n orm a l a ero foils tests w ere restricted to ra ther sm a ll inciden ces o nly, genera lly exclu ding the ra n ge o f sta ll. 280 M A RCH 5, 1 94 8 Thus, a n o b serva nt stu den t o f la b o ra to ry tests co uld ha ve n oticed the extra ordina ry ca pa city o f circu la r o r sq ua re sha p es to give a very gra du a l, in no cen t sta ll, a n d tha t a t very high in cidences. Yet, a p a rt from a few b ro a d-m inded exp erim en ters, n o design er drew the co n clu sion tha t w ings o f su ch sha p es p ro m ised sa fety in flight, thou gh it w a s kn o'w n fro m ea rly p ra ctica l experien ce tha t flyin g in the “ seco n d regim e," i.e., a t the sta ll, w a s p o sitively da n gerou s. It is true tha t sp in nin g— Pa rker’s " S pira l Dive "— w a s a ttrib u ted, in those da ys, to high inciden ces, a n d tha t m o st o f the lightly lo a ded recta n gu la r w in gs u sed a t tha t p erio d rendered the sta ll rela tively in no cuo us. H o w ever, a ccidenta l sta lling w a s then , a s n ow , the ca u se o f the m a jo rity o f a ll cra shes. A nd the n o se dive fo llo w in g in a dverten t sta lls w a s w ell kn o w n to b e o f the m o st seriou s co nsequ en ces. E iffel. R ia b ou chinsky, Din es. Pra n dtl, etc., b ega n their la b ora tory exp erim en ts o n a ero fo ils o f very sm a ll a spect ra tio a nd the results w ere gen erou sly p ub lished (how clo sely secret they w o uld b e kep t to -da y!). E iffel sho w ed tha t the ra tio o f the resulta n t fo rces rea ched m a xim a fo r sm a ll a sp ect ra tio s a nd tha t slen der w ings ga ve the grea test dra g a t 90 degrees in ci­ . den ce, w hilst disc w in gs ha d then the lea st resista nce o f a ll. R ia b ou chin sky p roved tha t the m a xim u m lift w ith disc w in gs w a s rea ched a t in ciden ces o f the o rder o f 40 degrees, w hilst w ith n orm a l a spect ra tio s (exceeding a va lu e o f 4) the m a xim u m lift too k p la ce a t incidences o f 12 to 14 degrees o nly. B eyo nd their critica l in ciden ce disc w in gs ga ve a gra du a l decrea se o f the lift fo rce, w herea s w ings o f n o rm a l a spect ra tio ga ve a very a b ru pt a n d u n stea dy o ne. 1 he tests b y Dines o n fla t p la tes in n a tu ra l w ind co nfirm ed this in form a tion a nd tha t the o b serva tio n a p p lied to ca m b ered a erofo ils a s w ell w a s a lso p ro ved (b y R ia b ou chinsky). O. Fo ep pi sho w ed fro m system ­ a tic w ind-tu nn el tests tha t a sq u a re a ero foil b eha ves, in respect o f its lift cu rve, in a rem a rka b ly different m a nn er from o n e ha vin g a n a spect ra tio o f 1.5, a lthou gh w a ll in terferen ce a nd R eyno lds N um b er m a y ha ve so m ew ha t a ffected the resu lts o f the tests. , . La ter, Pra n dtl w a s ea ger to p o in t o u t tha t his a ero foil theo ry did n ot ho ld fo r very sm a ll a spect ra tio s, a nd tha t, in fa ct, the induced dra g o f disc w ings w a s less tha n the theo ry su ggested. In sp ite o f this, how ever, n ob ody seem s to ha ve heeded the p ossib ilities im plied a nd the “ B a ttle o f the A sp ect R a tio s w a s decided in fa vo u r o f slender w ings. To b e fa ir, it m u st b e p o in ted o ut tha t there w a s o ne serio us Fig. 1 2.—E xperimental H ayden glider, 1 925. Span, 1 9.7 ft. ; length, 1 3-85 ft. ; wing area, 1 73 sq.ft. A ll-up weight, 310 lb. N o lateral control. a rgum ent a ga in st disc w ings. The b est a ero foil sectio ns in u se p rio r to a b o ut 1925 ha d a p la in ca m b er w hich im plies tra vel o f the centre o f p ressure w hen the in ciden ce va ries; the length o f su ch tra vel is linked u p w ith the w ing cho rd. H en ce the cha nge in trim o r sta b ility is, w ith su ch a ero fo il sectio ns, grea ter w ith la rge-cho rd w ings. On this co n sidera tio n o f fo re-a nd-a ft sta b ility a n d co ntrol, design ers ha d so m e ju stifica tio n fo r their decisio n a ga in st experim en tin g w ith disc w ings. Yet q u ite u sefu l a erofo il sectio ns ha d a lrea dy b een u sed in flight w hich ha d p ra ctica lly n o tra vel o f the centre o f p ressu re a n d hen ce did n ot su ffer fro m this disa dva n ta ge o f the disc w in g. The w ho le a rgu m en t, how ever, lost its im po rta n ce im m e­ dia tely M . M . M u n k p roved tha t very efficien t a ero fo il section s co uld b e design ed w ith a co m p letely (o r n ea rly so ) sta tion a ry centre o f p ressure. It is. therefo re, right to sa y tha t fro m tha t tim e a ll co nditio ns existed fo r a p ra ctica l evolu tio n o f disc-w ing a erop la nes. F. H a n dley Pa ge co nverted a n a ero foil, lea vin g a n a spect ra tio o f 6.25, in to six sq u a re-a erofo il p ortio ns b y five slo ts, ea ch p a ra llel to the cho rd o f the w in g. B y so doing he hop ed to ha ve the lo w dra g o f a n orm a l w ing co m b in ed w ith the high sta llin g a n gle o f the disc-typ e w in g. A ltho u gh a very slight im p rovem en t w a s cla im ed, the p rincip le w a s tha t o f ea tin g the ca ke a nd ha ving it to o: the in duced dra g is respo n­ sib le fo r the sta llin g p rop erties o f the disc w ing a nd yo u ca nn ot ha ve the b en efits o f the high dra g w itho ut su ffering its disa d­ va n ta ges. M o reover, in o rder to ha ve the effect o f the disc w ing, the p rovision o f m ere slots is in sufficient. M a rgin a l vo rtices n eed ro om to deplo y. On the w hole, ho w ever, the idea p ro ves tha t a t lea st o ne p ra ctica l a ircra ft designer ha d rea lized tha t there w a s so m e­ thing in w ings o f a b n orm a lly sm a ll a sp ect ra tio . There w ere o ther, a lthou gh n ot q uite a s w ell thou ght o u t, a ntecedents o f the disc-w ing a ero pla ne. In the first so a rin g­ flight co m petition o n the R ho en (1920), Friedrich R ichter, a b u rly n a va l p ilot o f 20 sto ne o r so , p erfo rm ed o n a tripla n e glider w ith w ings ha vin g a n in dividua l a spect ra tio o f fa r less tha n three. H . H a yden secured, in 1922, a p a tent fo r a rhom - b oida l w ing w ith a n a spect ra tio o f n ea rly u nity, cla im ing fo r su ch a sha p e high lift a n d goo d flyin g q u a lities. In 1925 he co nstructed a glider w ith a w ing ha ving a n a spect ra tio o f o n ly 2.25. The w ing w a s n ea rly tria n gu la r in sha p e, w ith its a p ex lea ding, a nd a p ro no un ced w a sh-ou t to w a rds the tips (Fig. 12); n o la tera l co ntro ls w ere fitted. The ta ilpla n e w ith the eleva tor w a s fitted u n dernea th the tra iling edge a t the Fig. 1 3.—A French project of G . A briel, 1 929. stern o f a fu sela ge. Flying experim en ts in S tyria w ere sa id to ha ve p roved sa tisfa cto ry flyin g q ua lities. S o m e ea rly ta illess a ero p la n es, su ch a s certa in exp erim en ta l typ es o f R ene A rn ou x, ha d ra ther stub w ings a n d hea vily reflexed (i.e., p o sitively sta b le) a erofoil sectio ns. A 1929 design o f G . A b ria l show ed a n a spect ra tio o f 2.88, w ith, how ever, su b sta ntia l tip discs (w hich ha ve the effect o f in crea sin g the a erodyna m ic a spect ra tio ) a n d w ind-tun nel exp erim en ts indi­ ca ted a credita b le p erform a n ce (Fig. 13). R ussia n a ttem pts, in p a rticula r the p a ra b o la typ e o f Tschera no w sky, to o, w ere exp erim en ts w ith a spect ra tios o f three a nd even less (Figs. 14 a nd 15). Their resem b la nce in sha p e to the la test designs o f su per-so nic a ero pla nes is rem a rka b le. . A M odern Pioneer Further in terest in the a ero dyn a m ics o f disc w ings w a s disp la yed b y resea rch w o rkers w ith the a rriva l o f J u a n de la C ierva ’s A u togiro . This w a s indeed so m ethin g like a circula r w in g, a nd p erform a n ce estim a tes w ere b a sed o n the p rop erties o f su ch w ings. Yet the q uestion o f sta llin g sta b ility did n ot a rise, b eca u se o f the ro to r p ro perties. The rea l p ion eer o f the disc w in g w a s a very a b le A m erica n resea rch engineer o f the N a tion a l A dviso ry C o m m ittee fo r A ero n a u tics (N .A .C .A .), w ho p roved ca pa b le o f fo llo w in g in dependen t lines o f develo pm ent. In a b ou t 1930 C ha rles H . Z im m erm a n n su b jected the p ro perties o f disc w ings to N N D 927545 a nd repa ir sho ps w ill to b e genera llyseem parabola' aircraft by B . I. Tscheranowsky M A RCH 5, 1 9M f'f j^—A Russian ‘parabola* glider of 1 924 . A ^CU O •K M N CI Fig. 1 6.—N .A .C.A . tests by C. H . Zimmermann which prove the extraordinary stalling qualities of disc wings. extensive w in d-tun nel in vestiga tio n a n d the p ub lished rep orts still fo rm the b a sis o f p resen t develo pm ent. In p la ces, the resu lts co nfirm , q ua lita tively, the experim ents m a de 20 yea rs b efo re. B ut. a s m en tion ed ea rlier, these exp erim en ts ha d b een p ra ctica lly fo rgo tten. Z im m erm a n n's ta rget ha s b een the develo p m en t o f a rea lly foo l-proo f a erop la n e for a m a teur p ilo ts. It is n o u se hidin g the fa ct tha t in n ea rly a ll a ccidents in w hich b la m e is a ttrib u ted to a n “error o f judgm ent"’ o n the p a n o f the p ilo t, the a ero p la n e is a ctua lly a t fa ult. The m ost co m m o n ca uses a re A t the sa m e tim e he co nfirm ed tha t the in du ced dra g o f circu la r o r sq ua re w ings is b y n o m ea n s a s p ro hib itive a s the sim ple theory o f the " horseshoe " vo rtex lin e w ou ld in dica te. H e a lso p ro ved tha t it w a s sim p ly the in du ced dra g due to the p redo m in a n t influence o f the m a rgin a l vo n ices w hich b rou ght a b ou t the b eha vio ur a t high in ciden ces; the idea tha t the A n a dva n ta ge w hich Z im m erm a n n's resea rch b ro ught to light w a s tha t disc w in gs ga ve less p rofile dra g a t sm a ll in cidences (high-sp eed flight), b eca use o f the reduction o f the rela tive thickn ess o f the a ero foil sectio ns. This dra g reductio n ha s indeed b ecom e o ne o f the m a in rea so ns fo r disc w ings b ein g a do pted fo r a ero p la n es ca p a b le o f flyin g a t sp eeds a t w hich the co m pressib ility o f the a ir n eeds to b e co n sidered. For sup erson ic flight disc w ings seem , a t p resent, to b e a n ecessity. A lterna tively, fo r a given a erofo il thickn ess ra tio . a ckno w ledged, b ut still fa r to o o ften igno red), Z im m erm a n n directed his m a in a tten tio n to the sta lling p rob lem H e p roved tha t sm a ll va ria tio ns in the a spect ra tio m a de p ro fou nd differen ces a n d tha t the sha p e o f the w ing tips a lso ha d a grea t the co n sequ en ces o f in a dverten t sta lling. On ce this is co m p letely rem edied, the o verw helm in g m a jo rity o f a ccidents w ill b ecom e m ere incidents o r just fu n , a nd in stea d o f co ro ners a n d ho spita ls, a ircra ft m a nu fa cturers ' ha ve the b enefit. On su ch very so un d lin es (w hich w in g stru ctu res a s w ell a s fo r the p ossib ility o f ho usin g every­ thin g w ithin a w in g. r^cn cc there a re very rea l design rea so ns fo r the p reference o f disc w ings, q u ite a p a rt from the ea sed a cco m m o da tion o f short-spa n a erop la n es. . Some Remarkable Results Z im m erm a nn esta b l.shed tha t the o ptim u m a spect ra tio w a s fo un d b etw een the va lues o f 0.75 a n d 1.5. These va lues in clude b oth sq ua re a nd circula r w ing sha p es. Fo r a given w ing section (C la rk Y) the la tter ga ve the highest lift co efficien t. 1.85 a t 45 degrees in cidence, co m p a red w ith a va lu e o f 1.24 a t 14 degrees in ciden ce fo r a n a spect ra tio o f six. Fu rtherm ore, a n im po rta n t resu lt w a s evidence tha t a t a n a spect ra tio o f u nity (sq ua re o r elliptica l w in gs), a nd a t a n a spect ra tio o f 0.9 (w in g w ith fa ired tips), n o tendency to a u to ro ta tio n co u ld b e fo un d. A circula r w ing (a spect ra tio o f 1.27) in dica ted the p o ssib ility o f a u to ro ta tio n (i.e.. sp inn ing) a t incidences b elo w tha t o f m a xim um lift. The p o ssib ility o f sp inn ing b efo re the a ctua l sta ll is rea ched is. indeed, extra ­ o rdin a ry. A ll these results refer to tests w ith the C la rk Y a ero foil section . Less esta b lished w a s the co n ten tio n tha t disc w ings w o uld give im pro ved la tera l a nd lo ngitu din a l sta b ility a t lo w in ciden ces This seem s still to b e a m oo t p o in t o f the Flyin g S a ucer. In Fig. 16. Fig. 17. a nd Fig. 18 so m e cha ra cteristic resu lts o f the height a va ila b le fo r strictu re a n d stora ge (po w er p la nts) is grea test w ithin a disc w ing; this m a kes fo r light a nd Z im m erm a nn s w ind-tun nel experim ents o f 1932 a re given . It is seen from Fig 18 tha t the differen ce b etw een the incidence o f m a xim um lift a n d the glidin g a ngle a t m a xim um lift (“m a x « a m a x) rem a in s fa irly in dep en den t o f a spect ra tio , a nd ,h.e. .% der < °fu9 L° 13 degrees. 1 his w ou ld m ea n tha t the a ttitu de o f the disc-typ e a ero pla ne, w hen fla tten in g o u t. w ou ld n ot grea tly differ fro m tha t o f co nvention a l a ero p la n es. In p a rticula r, there w o uld b e n o n eed to p rovide high u n der­ ca rna ges 'o r disc a ero pla nes a s their gliding p a th is steen slo ts ‘S 3n im POr,a nl differen ce from w ings w ith lea din g-edge In p ra ctice, ho w ever, the la nding o f disc-w in g a erop la nes gives rise to u n derca rria ge p ro b lem s. A s the induced dra g increa ses ra pidly w ith the reduction o f flying sp eed w hen the a erop la n e fla tten s o ut p rior to to uching-do w n, the gliding a ncle sltTfw n x ihrn ntlu 7 hie ^.H ^iik.i.. ___ r E ¥ ^a uiu p.y, IH D p uru vuia ny true o t ta illess design s a nd the resu lt is a stro ng tenden cy to p a nca ke to the grou n d a s so on a s the p ilot fla tten s o u t. Thu s to a vo id the n ft.essity J 1"!1' u nderca rria ges a b le to sta nd the stra in o f a b no rm a lly high sin kin g sp eeds, it ha s b een fo un d p ra ctica l to la n d w ith p ow er o n. u Fn A ’a i,lcss a ero pla n e w ith a n a spect ra tio o f three M i ' f? u n d lha ,‘ *ilhout fla p s, the trim m ed gliding . IM m .p h. w a s three degrees; it increa sed to 17 degrees a t 1.6 m .p h.. w hile the sta lling sp eed w a s 115 m .p .h. This p ron ou nced steep en ing o f the gliding a ngle m a kes a m erger b etw een the a ero pla n e a n d the helico pter a n a ttra ctive p ro po sition . A n o ther n ecu lia rity o f the disc w in g esta b lished b v Z im m erm a n n w a s its sensitivity to the sha p e o f the w ina -tin s N N D 927545 TH E A E ROPLA N E M A RCH 5. 1 94 8TH E A E ROPLA N E regio n. A SUCT RA TIO ( b’ >) a n d p seu do-circula r significa n t d.flerences. Pancakes A la Zimmermann iseu do -circu la r a nd p seudo -sq u a re w ings thu s exhib it _^_______.2_______ This a lso a pp lies to the grou nd effect, i .e., the la nd.ng q ua lities. 1 he o t o b liq ue n ozzle­ sha p ed slo ts a t the tips yielded n o u sefu l results. In a n y ca se, sq ua re-cu t lips w ere fo un d to b e a disa dva n ta ge, w ith resp ect to dra g, a s w ell a s to o ther q ua lities. p rovis.on La ter N .A .C .A . resea rch b y F. E . W eick a nd R o b ert S a u ndefs referred to a spect ra tio s o f the o rder o f 3 in co n nection w ith slo tted a uxilia ry V evio ns fla p s fo r the trim o f ta illess a ero pla nes. This co nstitu ted the first investiga tion o f w ha t ha s b eco m e kn o w n to -da y a s the ” Delta W ing," i.e., the co m b .n a tion o f sw eep -b a ck w ith lo w a sp ect ra tio . S uch sha p es a re o f specia l in terest fo r a ero pla nes ca pa b le o f flyin g thro ugh the tra ns-so nic The resu lts o f Z im m erm a n n 's resea rch w ere so con vin cin g tha t a n um b er o f o therw ise q uite respecta b le design ers w ere tem pted in to experim en ta tio n w ith disc-w ing a ero p la n es. In a ccorda n ce w ith Z im m erm a nn 's view s, a ll these design s w ere intended to b e o f the sa fety-first typ e o f p riva tely o w n ed a ircra ft. This distinguishes the ea rly p ha se fro m the m o re recen t in terest in Flyin g S a u cers. In 1934 Fa rm a n w a s stim u la ted in to exp erim entin g w ith a w ing w ith a n a sp ect ra tio o f o n ly 1.9. This w a s seen in his F-1020 m o no p la n e w hich o therw ise ha d a lo ng fu sela ge w ith a co nvention a l ta il. It w a s sa id to ha ve p roved very sta b le in flight, b ut w a s n ot further hea rd o f. A n exp erim en ta l p a ra so l m o no pla n e w ith a co m pletely circula r w in g, a ca m b er fla p in the tra iling edge a n d severely skew ed a ileron s w a s tested in the U .S .A , (in 1934), w ith indifferent results. It w a s show n in flight in n ew s reels. , , A t a b ou t the sa m e tim e R a o ul J . H o ffm a n n, o f S t. Peters- b urgh, Florida , a n em in en t a ero na utica l engineer o f A ustria n o rigin (kn ow n a s the first to p ro ve— in 1913 tha t the ra tio C ’ IC i govern s o ptim um clim b a nd glide w ith m inim um sin kin g sp eed, to ok u p develo pm en t o f the disc-w ing a erop la ne. H o ffm a n n's Flying S a u cer w a s a ta illess a ircra ft w ith a n a spect ra tio o f slightly o ver 2. The first typ e w a s a n u ltra ­ light sin gle-sea ter w ith 36 b .h.p . La ter a side-b y-side tw o-sea ter w ith a n 85 b .h.p . C irrus en gin e w a s co n stru cted a n d flew w ell, the w ing tips served a s a ilero ns a nd the eleva to rs fo rm ed p a rt o f the tra ilin g edge. The a ero foil sectio ns em plo yed w ere N A C A . M .6 b a sica lly, w ith N .A .C .A . M l a t the tips. B o th a re sectio ns design ed b y M M M u n k. The fo rm er is a reflexed- ca m b er section w ith a p ra ctica lly sta tion a ry, centre o f p ressu re, the la tter is sym m etrica l . , , . cThe centra l structure o f the w ing, the fu sela ge a n d the fin w a s o f w elded-steel tu b e; the w ing ha d three sp a rs. this little tw o -sea ter w a s sta ted to fly w ell a n d to exh'b it very goo d sta b ilitv It seem s, ho w ever, tha t the co n tro lla b ility, in p a rticula r directio n a lly, w a s n o t sa tisfa ctory. 1 he visio n fro m The co ckp it m u st ha ve b een very restneted- a m oo t p oin t w ith a ll these design s. A sp eed ra nge fro m 28 ,m ,P ^% ,35a !^p'h; w a s cla im ed. The em p ty w eight w a s given a s 900 lb ., a n d the w ing lo a ding w a s 5.5 Ib ./sq. ft. ... . „ . One rem a rka b le cha ra cteristic o b served du rin g the flyin g tests o f H offm a n n s a ircra ft w a s tha t, w hen co m ing in to la nd, the a p pro a ch w a s steep ; yet p rior to the fl itten in g o ut a n d just b efo re to uching do w n , the glide fla tten ed. This w ou ld 8------------ O H IM ¥ A S A t CT r a tio ( •'•! u 3 A E ROIOK ILCIION CA M P N o 4 3’) iN CiM N CI A l M A X Lil G lON G A N G U g ¥ Fie 1 7—These results from Zimmermann's wind-tunnel lefts on disc wings (1932) clearly show the characterist.es of low aspect rat.o aerofo.ls N N D 927545 1 8 .—Further results from Zimmermann’s tests shown here also indicate theadvantages to be gained from disc wings. seem to co ntra dict w a s a ttrib u ted to a the experience referred to a b o ve, a n d it gro un d effect a risin g fro m the ra ke o f the w ing-tip s. It is indeed rea son a b le to exp ect tha t the p resen ce o f the grou nd w o uld a ffect the fo rm a tio n o f the m a rgin a l vo rtices to a n exten t w hich m a y m a rkedly influence the b eha viou r o f disc w ings during ta ke-o ff a nd la nding. H o ffm a nn p ro jected a p u sher a nd a tw in-engined versio n, b ut these typ es did n ot m a teria lize. A fu rther develo p m en t w a s the A rup m on op la n e o f R . J . H o ffm a nn a nd C . L. S nyder a t S o uth B en d, In dia na . The w in g sha p e w a s very sim ila r. It resem b led a sem i-circle flyin g w ith its stra ight side a s the lea ding edge; to this w in g, a ileron s w ere a dded a s specia l tips. T he a spect ra tio p ra ctica lly A ga in,co rrespo n ded to tha t o f the p reviou s H o ffm a nn typ es, a ero foils w ith little centre-o f-pressu re tra vel w ere u sed. T he la test typ e ha d its ta ilpla n e a n d eleva to r sep a ra tely lo ca ted o ver the w ing tra iling edge (sim ila r to the “ E lytro - p la ne " o f De R ou gd). It seem s tha t the lo ngitudina l co ntrol a t certa in in ciden ces w a s n ot sa tisfa cto ry. T he a ileron s w hich fo rm ed p a rt o f the w ing sha p e a n d reduced the a sp ect ra tio to a va lu e o f 1.75 ha d a tria n gu la r sha p e a n d w ere grea tly skew ed (ta kin g in to a ccou n t the o b liqu e flow o ver the w ing tips). T he engine w a s a 70 b .h.p . Le B lon d ra dia l; a tricycle u n derca rria ge w a s fitted. W ith the p ilot a lo ne, a gliding sp eed o f 23.5 m .p.h. w a s recorded (the w ing lo a ding w a s a b ou t 3.3 Ib ./sq . ft.) a nd a glidin g a ngle o f 21 degrees w a s m ea su red, w ith a sin kin g sp eed o f 12.3 ft. p er secon d, w h.ch ca n b e a ccom m oda ted b y a stu rdy u nderca rria ge w ithou t fla ttenin g o ut o f the glide. The m a xi­ m u m sp eed w a s 86 m .p .h.. a nd the ta ke-o ff w a s sta ted to requ ire 5 secs, in zero w in d. S evera l m o re A ru p typ es seem to ha ve b een co n stru cted a nd flow n during 1935. The flyin g q u a lities w ere p ra ised— glidin g a n gles o f I : 2.6 b eing q uo ted— a nd the p ub lished p erform a n ce figu res so un ded extrem ely go o d. Yet. fo r rea so ns n ever disclosed, the p roduction sta ge w a s n ot rea ched a nd the develo pm ent cea sed a b ru ptly, it is w o rth n oting tha t C ha rles Z im m erm a n n him self ha s ta ken n o p a rt in this develop m en t, b ut he w a s a n in terested sp ecta tor a t dem o nstra tion flights w ith a n A rup m o no p la n e a t La ngley Field. A n Italian “ Tortelllno ” A t the tim e o f the A ru p develop m ent (1934), F. Pia n a C a n ova , a n Ita lia n , b ega n to em b a rk o n a develo p m en t fo r a ta illess a ero pla n e w ith a lo w a spect ra tio . In M a y, 1935, he secu red p a ten ts fo r a rho m b o ida l w ing, o ne dia go n a l o f w hich co incided w ith the direction o f flight. The a ileron s w ere to b e loca ted a t the la tera l a p ices, eleva tor a n d ru dder a t the rea r a pex, w hile the a irscrew w a s in fro nt o f the lea ding a pex. A n other p a tent rela ted to b i-co nvex a erofo ils w ith ducts a nd co n tro l va lves fo r the p ilot, ena b ling the la tter to n eutra lize the n ega tive p ressure o n the fo rw a rd ventra l su rfa ce w hen a t n ega tive incidences. The la tter p a tent w a s, a pp a rently, n ever su b m itted to flight exp erim ents. (To be continued.) M A RCH 1 9, 1 94 8 TH E A E ROPLA N E The Biology of the F lying Saucer— III By A. R. W eyl A.F .R.Ae.S. Previous articles in this seriesappeared in “ TheAeroplane" for February 13 and March 5 W IN D-TU N N E L TE S TS w ere m a de in T u rin a nd a t R o m e o f live C a n ova p rojects (describ ed in the p revio u s in sta l­ m ent o f this a rticle). It is in terestin g to n ote tha t the C a n ova disc-w in g typ es did n ot m a ke u se o f reflexed-ca m b er a erofo ils. S ta b ility a nd trim co uld, therefo re, b e secured o nly b y a n u p w a rds deflectio n o f en la rged eleva to rs. E a rly in 1935. a n 'o p en glider o f the "Z oeglin g" typ e w a s co n stru cted b y a M ila n firm a nd M . A . G a rb ell m a de fa irly su ccessful flights w ith it. H e repo rted tha t the lon gitudin a l sta b ility (w ith the en la rged eleva tor) w a s go od a nd tha t p a ra chu te-like la n din gs co u ld b e p erfo rm ed. The la tera l sta b ility cha ra cteristic, how ever, p ro ved deficient, sin ce a ” Dutch-roll " m o tio n w a s exp erien ced, turn s w ere o f q uestion ­ a b le stea din ess. In this resp ect, insu fficien t da m ping in ftill a nd ya w a rc m ention ed. W ith w inch-la un ching, this glider rea ched a ltitudes o f 600 ft. On the b a sis o f this design , a light a ero pla n e w a s develo ped a n d the Ita lia n G o vernm en t fina n ced the co nstruction o f tw o la rger experim enta l a ero p la n es, inclu ding o ne w ith 130 b .h.p . G ipsy engin e. A fa ta l a cciden t describ ed a s “ n ot n ecessa rily reflecting o n the technica l m erits o f................... a u tho rities to cha nge their m in ds develo pm ent. A erop la nes w ing fo rm a the design ." ca used the a nd to term in a te this A R eturn to C hildish w ith a lo ng, deep ta il Thin gs a ffixed to a develo pm ent o f the low -a sp ect w ing sm a ll-spa n in a n other direction . A lthou gh the o vera ll a spect ra tio is lo w w ith su ch a n a rra n gem en t, the w ing system is n ot tha t o f a disc. It is m o re a kin to p rim itive kites o r, b etter, to the p a per da rt o f o ur scho ol da ys w hich, a s w e m a y b e a b le to rem em b er w ith so m e m en ta l effort, exhib ited q u ite rem a rka b le flying q ua lities a nd m a de b etter u se o f o u r scho olb oo ks tha n w e ever expected. A representa tive o f this a b origin a l typ e is sho w n in Fig. 19. It cra shed during the first tests (w hich w ou ld n ot seem very su rp risin g in view o f the a rra n gem ent o f en gines a n d a irscrew s). A n other less eccen tric a rra n gem en t w a s the Fren ch Pa yen sin gle-sea t ra cer o f 1935. This w a s a da ring experim enta l typ e w ith a 400 b .h.p. ra dia l engine. A n im p roved typ e, this tim e m o re rea son a b le— a 70 b .h.p . light a erop la n e— w a s co n stru cted in 1936. To a very sm a ll, co nvention a lly ta p ered w in g, a la rge tria n gu la r ta il w a s fitted; the w ing a lon e ha d dihedra l, a nd the o vera ll a spect ra tio w a s a b ou t 1.76. N o flights ha ve b een rep orted o f o ne o f these Pa yen a ero p la n es, b ut ta ke-off a ttem p ts w ith the seco nd typ e seem to ha ve su ggested tha t w ith the sm a ll sp a n the to rqu e rea ction o f the a irscrew ca nn ot b e a dequ a tely dea lt w ith. rig. 1 9.—A n A merican “Flying Flapjack" with two engines. It crashed while under test (1938). A third design (in 1938) the “Flecha ir" sin gle-sea t fighter p ro ject, therefore, inco rpo ra ted tw o co a xia l co un ter-ro ta ting a irscrew s driven b y tw o 100 b .h.p . en gines m o un ted in ta ndem in the lon g fu sela ge. The p ilot’s co ckp it w a s lo ca ted a t the ro o t o f the fin, a nd a single-tra ck u nderca rria ge w a s a do pted. There w ere, how ever, fa r too m a ny u ntried fea tu res in this u nu sua l design io m a ke it a seriou s p rop osition . N othin g m o re ha s b een hea rd o f Pa ych's efforts. T he m odern p ha se o f the Flyin g S a ucer a ero pla ne is cha ra cterized b y tw o distin ct develop m en ts. On e is the helicop ter-a ero pla n e, the o ther is the tra n s-so nic o r su perso nic a ero p la n e. B o th ha ve b eco m e— u nfo rtu na tely— essentia lly m ilita ry develop m en ts; the p ro gress is hen ce shro u ded in the u su a l p reten tio u s secrecy (w hich im plies tha t the p o ten tia l enem y kn ow s everything) w hile the w ork is gra vely ha m pered b y ela b o ra te secu rity p reca u tio ns. The helicop ter-a erop la ne is n ot a n ovel idea . M a n y yea rs a go , fo r insta n ce. N icola Tesla (fa m ou s fo r his electrica l experim ents w ith b igh-freq uency p hen o m en a ) secured a p a tent fo r a ta illess a ero pla n e equ ipp ed w ith a la rge lifting a irscrew p erm ittin g a vertica l a scen t. In 1921 C la u d Dornier secu red a p a tent N N D 927545 fo r a co nvention a l Fig. 20 —Lift and drag of wings of different aspect ratio. (Left)Wind- obtained at G oettingen, in 1 920; G oettingen 389 aerofoil with 1 0 per cent, thick­ ness and square wingtips. (Right) A reduction of the results aspect five. Prandtl ratio an of by the A erofoil Theory of the induced drag. shows square aerofoil (aspect ratio of one) does not follow the theory. Its induced drag is less than pre­ dicted by the “horse-shoe vortex" assump­ tion. TH E A E ROPLA N E M A RCH 1 9, 1 94 8 8- 1 01 3 J A N G LE Of IN CIDE N CE (DE G RE E S) a ero p la n e w ith ta ke-o ff a s helico pter (B rit. Pa t. S p ec. N o. 161,948). E a rlier still (in 1916), the G erm a n , F. B endem a nn , a n oted resea rch w o rker o n a irscrew s, co ndu cted a secret develo pm ent o f a n a ero p la ne w ith a la rge tilting a irscrew ca p a b le o f risin g a nd descendin g a s a helicop ter. The develop m en t o f this a ir o b serva tio n p ost w a s la ter disco n­ tinu ed in view o f the A ustria n helico pter exp erim en ts b y Th. v. Ka rm a n a n d Petro czy. __ Fro m his ea rly exp erim en ts w ith lifting a irscrew s, F. B en dem a nn fo un d tha t ho verihg w itho ut fo rw a rd m ovem en t co u ld b e a chieved— w hen the p ow er lo a ding o f the a ircra ft w a s less tha n a b ou t 9 lb ./b .h.p. W ith fighter a ero p la n es, su ch low p ow er loa dings w ere a lrea dy then b ein g a pp roa ched, a nd o pera tion a l exp erien ce ha d indeed show n tha t certa in sin gle- sea ters co uld, u n der fa vou ra b le co ndition s, b e held in a ttitudes a pp roa ching tha t o f hoverin g (la ter the Fo kker D.V J 1 b ipla ne, w ith a la rge a irscrew , b eca m e reno w ned fo r this trick in a ir co m b a t o n the W estern Fro nt). A ttem p ts to revive the p roject a t a la ter da te fa iled, a nd w ith the su icide o f its p ro m oter (w ho ha d gon e in to the C ivil S ervice), a ll in terest in the develo pm en t cea sed. C ha rles W . Z im m erm a n n , m ention ed ea rlier a s stim u la to r o f the disc w ing, a pp ro a ched the co n cep tion o f the helico pter a ero p la ne o n the b a sis o f his results w ith low a spect ra tio w ings. H e secured b a sic p a tents a n d co nstru cted during 1934-35, in the cella r o f his hom e, a m a n -ca rryin g a ircra ft o f his design . This ha d a w ing o f o nly 7-ft. sp a n , w ith tw o a irscrew s driven b y tw o 25 b .h.p. engin es. Du e to p ersistent engin e trou b le, n o flights w ere m a de; the little a ircra ft sho w ed, how ever, a ll the essen tia l fea tu res o f the p resen t typ es. In 1937 he gra n ted a licence fo r his p a ten ts to the C ha n ce- V o ught A ircra ft Divisio n o f the U n ited A ircra ft C o rp ora tio n in S tra tfo rt, C o nn ecticut, a n d jo in ed this firm fo r the fu rther develo pm ent o f his idea s, ft is p ossib le tha t the p ub lic co n ceptio n o f the m ysterio us “ Flyin g S a u cers ” ha s o rigin a ted fro m this develop m en t. Z im m erm a n n's intention m a y ha ve b een the develop m en t o f a sa fety-first a erop la ne fo r the p riva te o w ner. The U .S . N a vy, how ever, too k a n in terest in the p o ssib ilities o f the helico pter­ a ero pla n e. a nd the w ork do ne a t p resent is p u rely fo r m ilita ry p urp oses. In 1942 a lo w -po w ered p ilo ted sca le m o del typ e v-173 w a s co nstru cted. This w oo den a ircra ft m a de m a ny flights a nd p roved tha t the idea s u nderlying the design w ere p ra ctica l. The p rin cip le is tha t, a t high sp eed a nd w hen cru ising, the a ircra ft sha ll fly a s a n a ero pla n e, w hile fo r slow sp eed a n d hoverin g it flies a s a helico p ter. H ence the a irscrew s a re a t the sa m e tim e ro tors a nd m ust ha ve a ra ther la rge dia m eter. W ith the V -173 the p rob lem o f the p ron e p ositio n to r the p ilot w a s stu died, a nd there is rea son to b elieve tha t the la test typ es ha ve a dop ted this fea tu re. A fu rther step to w a rds the rea liza tio n o f a n a va l gun -spo tter a n d a fighter fo r u se fro m a ircra ft ca rriers ha s b een the C ha nce- V o ught XF5U -1 sin gle-sea ter (1946), fo r w hich a sp eed ra n ge from 40 m .p .h. la nding sp eed to o ver 425 m .p .h. ha s b een cla im ed; in gen era l, it fo llow s the V -173 m o del. (See p. 185, February 13.) The a spect ra tio o f the w ing is less tha n u n ity. S trictly sp ea kin g, ho w ever, it is n ot a gen uine ta illess a ero pla ne b eca use o f the a tta chm ent o f a trim m in g eleva to r to b oth sides o f the w in g. The rea son fo r su ch excrescences is the n eed to loca te RA TIO Fig. 21. — L i f t curves of aerofoils of different aspect ratios. (Left) Wind-tunnel results obtained, in 1 920, at G oet- G oettingen 389 and square tips. The absence of stall at normal incidence is in evidence, for aspect ratios up co a value of two. (Right) Reducing the values, by the Prandtl theory, to an aspect ratio of five, shows that wings of very small aspect ratio do not follow the theory in respect of the induced- incidence correc­ tion. co n tro l o rga n s directly in the slip strea m o f the p a ddle-like a irscrew ro to rs. The tw in ru dders, to o. a re in the slip strea m . U n like the V -173 typ e, the XF-5U -I ha s a n a ll-m oving ta il' su rfa ce a nd the u nderca rria ge is retra cta b le. 1 his in terestin g hyb rid ha s a m o dern m eta l stru cture. Tw o s a ,t a n d W h,tney R -2000-2 engin es o f 1,350 b .h.p. ea ch (a t 2,700 r.p.m .) a re m o un ted w ithin the w in g, entirely b uried a nd co oled b y fo rced dra u ght. W a ter in jectio n fo r tem p o ra rily b oo stin g the p ow er is o ne o f the engine fea tures. v^J ^'3' Dro *,'cm w a s •he design o f a tra n sm ission gea r w hich a llo w s b o th ro tors to b e driven fro m either o f the en gin es — this is a n ecessity in ca se o f a n engine fa ilure. The fo ur- b la ded ro to rs a re co ntra -rota tin g so tha t there is n o residu a l to rqu e a nd a rc gea red dow n to a b ou t o ne-fifth o f the engin e sp eed, hen ce their su b sta ntia l dia m eter. The w ing lo a ding is ra ther high, rea chin g the o rder o f 40 Ib ./sq . ft. The Real Flying Saucer ? S in ce this experim en ta l typ e w a s p ro du ced, fu rther p ro gress ha s b een m a de in the develop m en t. It seem s tha t a xia l-flow ga s tu rb in es ha ve b een in sta lled, a nd it is q u ite p ossib le tha t a co m b in ed p rop ulsion w ith therm a l jet a n d a irscrew rotor is a lrea dv u n der test. W ith this, fo r slo w flight (ta ke-o ff, clim b a nd la nding) the ro tors a re driven b y the ga s turb ines, w hile a t high sp eed the ro to rs a re declutched a nd fea thered a nd p ure jet p rop ulsio n is u sed. This w o uld, incidenta lly. Fig. 22.—Increase of profile drag with section thickness, at zero lift. The importance of the tip shape is obvious. The data refer to an aspect ratio of five (From D.V.L. wind­ tunnel tests at low turbulence). N N D 927545 N N D 927545 Fig. 23.—Increase of zero lift profile drag with thickness ratio of symmetrical aerofoil secticin. The saving in profile drag is one of the advantages of disc wings because of their thinner aerofoil section. (Data from G erber, Zurich Report N o. 6). exp la in the extra o rdin a ry a b ility o f the rep orted “ Flyin g S a ucers " to b e a b le to fly very fa st a nd high, a nd a lso to hover, a scen d a n d descend w ith p ra ctica lly n o fo rw a rd sp eed. N o o ther a ircra ft is kn o w n to do tha t. On the o ther ha nd, it is in con ceiva b le tha t w hole sq u a dro ns o f su ch u nco nvention a l a ircra ft co u ld a lrea dy b e o b served a t a ir exercises. It is ra re fo r m ilita ry develop m en ts to p rogress a s q uickly a s a ll tha t. For o pera tio n w ith ga s tu rb ines a sp eed ra nge fro m zero (i.c., hovering flight) to m o re tha n 500 m .p .h. ha s b een cla im ed fo r the C ha n ce-V o u ght-Z im m erm a n n helico p ter-a ero pla n e. Techn ica lly, there is little rea son to dou b t tha t su ch a n a m a zin g sp eed ra nge ca n b e a tta in ed w ith the co m b in a tion p ow er p la nt m en tion ed. In cidenta lly, a s there is n ot a s yet a sta n da rd term fo r the co m b in a tion o f a n a erop la n e w ith a n helicop ter, the n a m e “ helico pla ne " is tenta tively su ggested. The o ther lin e o f engin eering a p pro a ch w hich ha s led to the disc-w in g a ero pla ne o f n ea r-sa u cer a pp ea ra n ce derives fro m the trend to w a rds very high flyin g sp eeds w ithin the so n ic ra n ge o f velo cities, a n d in p a rticula r, a t grea t a ltitudes. A s n o w co m m on lv rea lized, the co m pressib ility o f the ga seou s m edium sets a sp eed lim it fo r co nvention a l a erop la n es. This lim it is rea ched w hen the sp eed o f flight a pp roa ches su fficiently to the velo city a t w hich so un d is p ro pa ga ted thro ugh the a ir. This “ a cou stic velocity ’’ dep en ds so lely o n the a ir tem pera tu re, a nd is, therefo re, lo w er a t a ltitu de. H ence, co m p ressib ility effects b egin to b e felt a t lo w er sp eeds w hen flyin g a t a ltitude. W hen the “ sho ck sta ll," due to the co m p ressib ility o f the a ir, sets in. the lift is ca ta stro phica lly decrea sed (hence the justifica tio n fo r the expressio n " sho ck sta ll ”), the dra g rises to eno rm o us va lu es, a nd the lo ngitudina l sta b ility is grossly im pa ired b y a ra p id b a ckw a rds shift o f the a ero dyn a m ic centre a s w ell a s b y fluctu a tion s in the flow p a ttern a t the w in g. The exp erien ce o f p hen o m en a o f su ch distressin g n a tu re ha s given rise to tw o distinct a im s in a eron a utica l resea rch. On e is to dela y the o nset o f the p heno m en a to higher M a ch N um b ers; the o ther a im is to fin d w in gs w hich w ou ld p erm it flight w ithin o r thro ugh the tra n s-so nic regim e. The a lterna tive. “ w ithin o r throu gh, is still a n ecessa ry im pedim en t o f definitio n, sin ce w e do n ot kn o w yet if sta b le, stea dy flight w ill b e a t a ll p ossib le w ithin the tra ns-so n ic regim e (exten din g from a b o ut 0.8 to 1.2 M a ch N u m b er) w hile there is certa in ly tha t b eyon d this tra ns-so n ic regim e, i.e.. w ithin the su person ic regim e, sta b le, stea dy flight ca n b e p redicted. Tw o sim ple m ea n s ha ve b ecom e kn ow n w hich dela y the o ccurren ce o f the "sho ck sta ll" u ntil m u ch higher (b ut still su b so nic) flyin g sp eeds a re a tta ined.- One is sw eep o f the , lea ding edge o f the w in g, either a s sw eep b a ck o r a s sw eep fo rw a rd. The o ther— a Fa rn b oro u gh discovery o f n ea rly 30 yea rs a go. w hen high top sp eeds o f a irscrew s w ere in vesti­ ga ted— is the a dop tion o f very thin a erofoil section s. The la tter lea ds, a s w e ha ve p o in ted o ut a lrea dy, stra ight to a ero fo ils o f low a spect ra tio w hen , fo r rea so ns o f structu ra l stiffness, a certa in w ing thickn ess is requ ired. In the discu ssio n o f the “ S ta lling C ha ra cteristics o f Ta illess A ero pla n es" (The A er o p l a n e fo r A p ril 25. 1947), it w a s sho w n tha t a t lo w sn eeds. i.e., during ta ke-o ff a nd la nding, sw ept-b a ck w in gs su ffer fro m the disa dva n ta ge o f in sta b ility a t the sta ll. W ith p ro no un ced sw eep -b a ck, sw ep t-b a ck w ings o f n orm a l a spect ra tios exhib it the vice o f “ self-sta llin g." due to p rem a tu re tip sta ll. It w a s a lso show n tha t this vice ca n b e rem edied b v reducin g the a sp ect ra tio , a nd a cu rve b a sed o n exten sive w ind-tu nn el tests (The A er o p l a n e fo r J u ly II. 1947. p . 47. Fig. 8) p roved tha t there is a distinct rela tion b etw een a spect ra tio a nd a ngle o f sw eep -b a ck in this co nn ection . TH E A E ROPLA N E M . B . M o rga n ha s recen tly co m m un ica ted the fo llo w in g va lues fo r the lim it o f sta b ility a t the sta ll fro m this gra ph:— Upper limit of the A ngle of Sweep-back (referred to the j chord) beyond which self-stall can be expected A spect Ratio Required Degree* 65 1 54 2 4 6 3 38 4 25 6 1 4 8 5 1 0 It is thus a dvisa b le to co m b ine sw eep -b a ck w ith low -a spect ra tio w hen sa fe sta lling is requ ired. C o nsidera tio ns o f high sp eed lea d to a sim ila r co m b in a tion , since b oth fea tu res tend to dela y the shock sta ll. W e ha ve, a s a result, the ra re ca se o f tw o q uite different a sp ects o f a n en gin eering p rob lem p o intin g to a n identica l so lution . The in evita b le resu lt ha s b een the develop m en t o f a rro w ­ sha ped. m o re o r less tria ngula r, disc w ings, term ed " Delta ­ W ings," fo r flight a t sp eeds w hich a re trespa ssing into the tra n s-so nic velocity regim e. A n other a dva n ta ge o f su ch w ings is tha t w hen the shock sta ll o ccurs, the b a ckw a rd shift o f the centre o f p ressure is less tha n w ith n orm a l w ings. The induced dra g do es n ot co u nt q ua ntita tively a t these high sp eeds. Develop m ent o f su ch a b n orm a l a ero pla ne typ es b ega n in G erm a n y during the W a r. fo llo w in g the p ro gress a ccom plished in jet a nd ro cket p rop u lsio n since 1937. w hich ha d sho w n tha t flight a t so n ic velocity w a s a p ra ctica l p rop ositio n. A few experim en ta l delta -w in g typ es ha d b een b rou ght to in itia l flying tests w hen the W a r ca m e to a clo se. The G erm a n develop m en t ha d tw o distinct a im s, resu ltin g in tw o sepa ra te lines o f a pp roa ch. The im m edia te ta rget n eces­ sita ted b y the A llied b o m b in g ra ids, w a s the crea tion o f very fa st jet fighters o r fighter-b om b ers w hich co u ld su rp a ss in sp eed even the M e 262. S eco ndly, there w a s the lon g-term develo p­ m ent o f a su person ic a erop la n e ca p a b le o f flying o ver very lo ng dista nces, su ch a s fro m E u rop e to A m erica a nd b a ck, a nd drop ping a b o m b o r tw o o n the w a y. It is p erha p s n ot to o fa nta stic to su rm ise tha t this develop m en t ha d so m e co n nectio n w ith the resea rch o n a tom ic b om b s a nd b a cterio lo gica l w a rfa re institu ted b y the H itler G a n g. Fo r the im m edia te ta rget, o rders fo r intercep tor-fighters w ere p la ced w ith enterprisin g firm s, n ota b ly w ith the H o rten b rothers a nd M esserschm itt (b oth p ets o f the R eichsluftm inisteriu m ), w ith the G o tha W o rks. H en schel. J u nkers. H einkel a nd A ra do (a G o vern m en t enterprise), etc. In o rder to fa cilita te experim ents w ith ra ther u nu sua l a ircra ft typ es a nd to ena b le a n excha n ge o f idea s a n d exp eriences, a sp ecia l resea rch a erodro m e w a s b uilt a t Ora nienb urg (n ea r B erlin) w ith a ll fa cilities fo r flight testin g (in p a rticu la r, very lo ng w ide ru n w a ys a nd w o rksho ps fo r rep a irs a nd m o difica tion s w ere p rovided). This w a s p la ced u n der the co m m a n d o f a ca pa b le techn icia n, Lt-C ol. Knem eyer. On this a ero dro m e, a ll the in itia l a nd develo pm en t tests w ith n ovel p roto typ es ha d to b e m a de. W hen the R u ssia n s co llected the a ero dro m e, they w ere a greea b ly su rprised to discover so m e o f the m o st p rogressive a ircra ft ever co nstru cted. It ha s since b ecom e certa in tha t they ha ve m a de in telligen t u se o f this a ero ­ n a u tica l trea su re a s w ell a s o f the techn icia n s co llected then a n d a fterw a rds. Of the G erm a n firm s in terested in the develop­ m ent. a t lea st o n e. the w ell-kn ow n J u nkers w orks a t Dessa u, ha s b een co m p letely tra nsferred to R ussia , lock, stock a nd b a rrel M o st o f the scientists a nd designers w ere u rged to vo lun teer fo r develo pm ent w o rk in R u ssia . Few co uld a fford to refuse. A cco rding to relia b le in fo rm a tion , a m o ng the intercep tor p roto typ es a t Ora nienb urg, a t the tim e o f the Occup a tion , w ere the follow ing:— On e H orten ta illess delta -w in g, w hich ha d b een da m a ged during tests a n d w a s u n dergo in g rep a ir; a no ther H o rten ta illess jet-hghter w a s ju st rea dy fo r its first tests There w a s a lso the la test versio n o f the Lipp isch-J un kers’ develo pm ent o f the M e 163-C ; a n other a dva nced J u nkers design ; a n exp erim enta l G o tha , a n d severa l resea rch gliders. • H itler's Last Secret Weapon The G erm a n lon g-term develop m en t o f a n a ero pla ne ca p a b le o f rea ching tru ly su perso nic sp eeds disca rded the ga s-tu rb ine jet engine. It w a s b a sed o n the ra m jet o r a erodyn a m ic p ro­ p ulsive du ct (“ A tho dyd ")— the sim p lest engine ever invented. The ra m -jet. a w idely discussed invention b y the gen ia l R ini Lo rin in 1912. ha d b een experim en ted w ith in G erm a ny, n o ta b ly b y the A ustria n E u gen S a en ger (for w ho m a sp ecia l la b ora tory ha d b een b u ilt b y the G erm a n a uthorities in 1938), b y Otto Pa b st, o f Focke-W ulf. a nd b y o thers Follow ing a suggestio n m a de b y A lexa n der Lipp isch (fo rm erly kn ow n a s a n em in en t sa ilpla n e designer a n d resea rch w orker o n ta illess a ero pla nes), p rogress ha d b een m a de w ith the co m b ustio n o f so lid fu el in ra m -jets. S uch fu el to ok the fo rm o f so lid b locks o f sp ecia lly p rep a red co a l w hich lined the w a lls o f the du ct. This develo p­ m en t ha d b een p erfected b y the G erm a n R esea rch In stitute- fo r S o a rin g Flight. (To be continued.)