DOW PDF RELEASE 2026-07-10 INC. 1948 ⊙ Various ⌥ 16,798 WORDS OCR

DOW-UAP-D097, Project Sign Progress Report, 1948

▮ AI SYNOPSIS · Sonnet 4.6

DOW-UAP-D097 is an April 23, 1948 initial progress report from Air Materiel Command (AMC) at Wright-Patterson Air Force Base, addressed to the Chief of Staff, U.S. Air Force, Director of Intelligence. It documents the activities of Project Sign (Project HT-304, activated January 26, 1948), compiling a tabulated breakdown of 100 UFO incidents reported between June 1947 and January 1948. Observations span locations across the continental United States, Canada, Hawaii, Newfoundland, Alaska, Hungary, Germany, Finland, and at sea. Observers included USAF officers, commercial pilots, police, and civilians. Reported characteristics included disc, oval, or spherical shapes; high rates of climb; hovering; supersonic speeds; and occasional exhaust trails. The report also references a consultation with Dr. Irving Langmuir of General Electric and includes photographs from Incident #40.

The document is notable as one of the earliest systematic U.S. military compilations of UFO sightings, representing the formal analytical groundwork of Project Sign before its conclusions were contested at higher command levels. Enclosures referenced — including photographs, a Horten Parabola comparison, and an article titled "The Biology of the Flying Saucer" from the periodical The Aeroplane — suggest investigators were considering both conventional aeronautical and unconventional explanations. Several enclosures referenced in the cover letter do not appear in the released file, leaving the photographic evidence and image analyses unavailable for review.

▮ TOP WORDS IN THIS DOCUMENT

This file contains an initial report from the Air Materiel Command regarding Project Sign. Project Sign was a 1948-1949 U.S. Air Force program to investigate the nature and origin of unidentified flying objects (UFO). The report details 100 UFO sightings from 1947-1948. The file also contains an article excerpted from “The Aeroplane,” an aviation-focused periodical magazine published between 1911 and 1968, titled “The Biology of the Flying Saucer.”

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MCIA CONFIBENTIAL HEADQUARTERS AIR MATERI EL COMMAND DECLASSIFIED Authority: NND 927545 MCIA/ JCB/amb Wright-Patterson Air Force Base Oh 1g 23topR 1948 SUBJECT, Projeot *SIGN* TO : Chief of Staff United States Air Porce Washington 26, D. C. ATTN: Direotor of Intglligence This is an initial report on unidentifled flying objects as directed by Hq, USAF letter dated 30 December 1947, signed by General L. C. Craigle, subjeot: "Flying Disea". Quarterly reports will be submitted beginning 1 July 1948. 2. As a result of this letter, Project HT-304 was aotivated on 26 January 1948 and Technical Instruotion 2185, dated 1l February 1948, was published. Present files on Project "SIGN" represent a consolida- tion of reports received directly by Hq, AMC and those forwerded by the Director of Intelligence, USAF. 3. Schedules of activities of lighted night-flying advertising blimps have been secured and cross-checked at this Headquarters to consider them as a possible source of incident reports. 4. Inclosure l represents a tabulation and breakdown of all available reports through 1 February 1948. The following is a series of interesting observations thet were noted when reviewing the many incident cases: a. High rate of climb, as well as the apparent ability to remain motionless or hover for a considerable length of time. b. The object was described as being oval, dise or saucer- shaped 31 times. c. Associated sound was present 1l times. Reported sizes have varied from that of a 25-cent piece to 250 feet in diameter, and from the size of a pursuit plane to the bulk of six B-29 airplanes. CONFIDENTIAL NND 927545

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CONFIDEN TIẠL ANC Subject: Project "SICE" 23 APR 1948 e. Number of objects par sighting: Objects per sighting T Number of sightings 2-5 21 5-10 8 over 10 9 f. Exhaust trails were reported 23 times. 8. Speed has been estimated throughout the entire range from very slow or hovering to supersonic. Inclosures 2 and 3 are enlargements of photographe taken of Incident #40. Inclosure 4 is an evaluation of inclosure 2 by this Headquarters. Attention is invited to the marked similarity between inclosures 2 and 3, and inolosure 5. Similarity also exists between inclosures 2 and 3 and configurations 1llustrated in inolosure 6. 7. Representatives from this Headguartere visited Dr. Irving General Eleotrio Company, Langmuir of the Passarch Laborator109 "SIGN". It was the opinion of Schenectady, N. Y. to discuss Project this scientist that present available data does not encompass suffi- cient information to enable a positive identification to be made. Dr. Langmuir was reluctant to consider the so-called "flying disce" as a reality. However, It is believed at this Headquarters that it is possible to construct a low aspeot ratio airoraft that would dupli- cate many of the appearance and performance charaoteristics of reported "flying discs". Experts have agreed that this would be possible through the intelligent application of boundary layer control. FOR THE COMMANDING GENERAL: 6 Inols 1. Tabulation 2. Photo 3. Photo 4. Eval of Inol 2 5. Horten Parabola 6. Biology of Flying Saucer H. M. McCOY Colonel, USAP! Chief of Intelligence 2 NND 927545

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Incident No. 1 la 1b lc 1d le 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Date 8 Jul 47 8 Jul 47 8 Jul 47 8 Jul 47 8 Jul 47 8 Jul 47 8 Jul 47 7 Jul 47 8 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 4 Jul 47 24 Jun 47 not stated 20 Oct 47 20 Oct 47 Ят 1 CONFIDENTIAL Hour Location 5 No. Sighted Observed From 0930 0930 0930 09h5 1000 1000 1200 1010 1150 1305 Muroc Air Field, Muroc, Calif. 2 Muroc, Air Field, Muroc, Calif. Muroc Air Field, Muroc, Calif 2 Muroc Air Pield, Muroc, Calif. 2 Muroe Atr Field, Muroc, Callf. 3 Muroc Air Field, Muroc, Calif. 3 Muroc Air Field, Muroc, Calif. 1 Muroc Air Field, Muroc, Calif. 1 Area #3, Rogers Dry Lake, Muroc Air Field, Muroc, Calif. 1 Fortland, Oregon 5 Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground 1305 1305 1305 1305 2004 Milwaukee, Oregon Portland, Oregon Portland, regon Portland, Oregon Boise, Idaho 3 Ground 1 Ground 3 Ground undetermined fot stated 5 Air not stated Seattle, Washington 1305 1 Ground. 1400 1630 1700 1100 Vancouver, Washington Portland, Oregon Portland, Oregon Portland, Oregon Mount Jefferson near Redmon, Oregon 20-30 Ground 4 Ground 1 Ground 3 Ground Ground 1500 let. Rainier, Washington not stated Toronto, Canada 1320 Dayton, Ohio 9 Air 1 Ground 2 Ground 1100 Xenia, Onio - 1 Ground -CONFIDENTI NND 927545

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Incident No. 21. 22 23 25 26 27 28 29 30 30a 30b 30c 31 2 32 33 33a 330 33c 33d 33e 331 33g 34 35 CONFIDENTIAL Date Hour 1645 Location 29 Jun 47 Des Moines, Iowa 21 Jun 47 30 Jun 47 about noon 1745 Spokane, Washington Boise, Idaho 12 Jun 47 4 Jul 47 1815 2345 Weiser, Idaho West Trenton, N. J. 10 Jul 47 not stated Harnon Field, Newfoundland 10 Jul 47 2000z Harnon Field, Newfoundland 24 Jun 47 not stated Idaho 23 Jun 47 not stated Bakersfield, Calif. 7 Jan 48 1925BST Lockbourne AB, Columbus, Ohio 7 Jan 48 7 Jan 48 7 Jan 48 1925EST Lockbourne, AB, Colunbus, Ohio 19156ST Lockbourne AB, Columbus, Onio 1940 Lockbourne AB, Colunbus, Ohio mid-December early a.m. Northern Arizona 1916 not stated after dark Columbus, Ohio 7 Jan L8 133042700 Godman Field, Ky. (south of) 7 Jan 48 1400CST Godman Field, Ky. 7 Jan 48 1320CST *Godman Field, Ky. 7 Jan 48 11,20 CST 2100 from Godman Field, Ky. 7 Jan 48 14,00 Godnan Field, Ky. 7 Jan 48 1430-1600 Godman Field, Ky. 7 Jan 48 1h45 Godman Field, Ky. 7 Jan 48 1854-1906 Madisonville, Ky. 13 Oct 47 0530 14 miles north of Dauphin, Manitoba, Canada 12 Nov Lil early a.n. Ticonderoga at sea 040 miles south of Cape Blanco, 20 miles off shore) No. Sighted 18 several 2 1 10 ] 1 ] 1 1 1 1 1 1 1 1 2 -CONFIDENTIAL NND 927545 Observed - From not stated Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Air Ground Ground Ground Ground Ground Ground Air Ground Ground Boat

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-CONFIDENTIAL ING IDENT No. 36 37 38 39 40 41 42 43 44 45 46 47 48 48a 48b 480 48đ 49 50 51 52 52a 53 54 Date Hour Legation Not Stated Not Stated Boise, Idaho 12 Oet 47 1200 Cave Creek, Arizona 10 Jun 47 Not Stated Budapest, Hungary 9 Jul 47 2330 Grand Palls, Newfoundland 7 Jul 47 1600 Phoenix, Arizona 11 Jul 47 Not Stated Blendorf Field, Alaska 12 Jul 47 04302 Blendorf Field, Alaska 29 Jun 47 28 Jun 47 28 Jm 47 22 Jun 47 6 Jul 47 7 Jan 48 7 Jan 48 7 Jan 48 7 Jan 48 7 Jan 48 9 Jan 48 10 Jan 48 1645 Clarion, Iowa 1543 Roekf1eld, Wisconsin Afternoon Ilinois 1130 Greenfield, Nass. Not Stated Fairfield-Suisun Air Base, Calif. 1920-1955 Wilmington, 0h10 1925 Wilmington, 0h10 1910EST W1lmington, 0hi0 1930 W1lmington, 0h10 1920-1950 Wilmington, Oh1o 2300-2315 Danville, Kentucky 2200 Wildwood, New Jersey 3 Sept 49 29 Jul 47 29 Jul 47 28 Jun 47 16 Jan 47 23 Jul 47 1215 Oswego, oregon 1450 Hamilton Field, California After 1200 Hamilton Pield, California 1515 Lake Mead, Oregon 2230 North Sea (50 miles from the Dutch Coast) 0345Z Harmon Pield, Newfoundland -CONFIDENTIA NND 927545 No. Sighted Observed 1 Ground 1 Ground 1 Ground 5 Ground 1 Ground 1 Ground 1 Ground 18 Ground 7-10 Ground 7-10 Ground 1 Ground 1 Ground 1 Ground 1 Ground 1 Ground dround 1 Ground 1 Ground One at this Ground date, prey- lously 1 each 27 Dec,3 Jan all at 2000 o'clock. 12-15 Ground 2 Ground 2 Ground 5-6 Air 1 A1r 1 Ground

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CONFIDENTIAL Ineident No, 56 57 58 59 60 61 62 63 64 66 68 70 71 72 73 74 75 76 TT 79 No. Stahted Date 6 Jul 47 Hour 2045 Location 20 Jul 47 00152 4 Aug 47 14 Sept 47 Brening 055800T Birmingham, Alabana Aboard the Burgeo (at Sea one hr. fron Sydney, Australia) Bethel, Alaska Necker Island 7-10 1 1 10 Jul 47 1000 Cordroy, Canada 1 8 Sept 47 2230 8 Sept 47 2230-2300 Salt Lake City, Utah Salt Lake City, Utah 12 29 Jul 47 5 groups each con- taining 35-60 objects. 1 19 Aug 47 1205 2130 Canyon Ferry, Montana Twin Falls, Idaho Approx. 55. 2 Jun 47 10 Aug 47 14 Aug 47 24 Jun 47 Not stated 6 Aug 47 2230-2245 6 Aug 47 1045 8 0et 47 Not stated Not stated Not stated 4 Aug 47 Not stated Rehoboth Beach, Deleware 2100 Silver Springs, 0h10 1600 Placerville, Ballfornia Cascade Mountains, Portland, Oregon Philadelphia, Pa. Philadelphia, Pa. Las Vegas, Nevada Port Richardson, Alaska 1600 Boston (10 miles NW) MasS. 1 1 6 1 ] 1 1 2 24 Jun 47 App. 1500 13 Aug 47 1300 13 Aug 47 Morning 1830Z Mt. Adams, Washington Not Stated Smoke River Canyon, Idaho 1 3 July 47 30 Jun 47 Apr 47 0910 MST 1100 EST Salmon Dam, Idaho South Brookville, Maine Grand Canyon, Arizona Richmond, Virginia NND 927545 CONFIDENTI 2 10 2 Observed T2som Ground Boat A1r Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Ground Air Ground Ground Ground Ground A1r 1, others on Around other occasions

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CONFIDENHAL Incident -No. 80 81 82 83 n. 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 Date Hour 7 Jul 47 2230-2300BDT 7 Jul 47 0900 17 May 47 2030-2100 9 Jul 47 1217 7 Jul 47 1300-1400BST 14 Jun 47 1200 6 July 47 Not stated Not stated Not stated 3 Aug 47 Afternoon 6 Jul 47 1345 29 Jun 47 1300-1330 28 Jun 47 2120-2145 19 Jun 47 1215-1315 11 Jan 48 1 30 Deo 47 Location No. Sighted Observed Prom Arlington, Virginia Hielan Pield, Hawa11 Oklahoma City, Oklahoma Boise (Between Boise and Meridian) Idaho Lakeland, Florids Portland, Oregon Hollywood, California Habberbishopshiem (20 miles north) Germany Haokensack, N. J. Kansas City (100 miles west), Kansas Las Cruces, New Mexico Maxwell Pield, Alabama Colorado Springs, Colorado 30 Deo 47 1 Ground 1 1 1 5 10 Ground 1 Ground 1 Air 1 Gro und 1 Ground 1 Ground 30 Deo 47 1630 Hartford, Conneotiout 1 Air 1926PST Between Great Falls, Montana and Fairfield, California 1 A1r 1925PST Rosedale, California 1 Air 1926 Lovelock (30 miles west), Nevade 1 Ground 30 Dec 47 1925PST Between Medford and Mt. Chasta, Ore gon 1 A1r 2 Nov 47 3 Jan 48 5 Jan 48 Daybreak Houston, Texas Not stated Vassa, Finland Not stated Pretarsaart, Pinland 1 Ground 1 Ground 1 Ground -CONFIDENTIA NND 927545

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CONFIDENTIAL Incident No. 1 la 1b 1c 1d le 2 3 4 5 6 Observer's Occupation Ist It, USAF s/sgt, USAF Unknown s/Sgt, USAF Pfe, USAP Not stated Maj, USAF Major, USAF Capt, USAF Maneuvers Weather None - horizontal flignt Not stated Not stated Not stated Not stated Not stated Not stated Not stated Flying in tight circle Not stated Horizontal and tight circles lot stated Descended from an intermediate altitude in an oscillating fashion almost to the ground, then started climbing again to a very high altitude and moved off slowly in the distance. Not stated Oscillating in a downward twirl- Not stated ing movement Falling at three times the rate Not stated of a parachate Patrolman, Portland Dipping up and down in oscillat- Not stated Police Dept. ing motion Sgt, Oregon Police Following each other 7 8a 9 Patrolman, Portland Not stated Police Dept., forner Air Force pilot Patrolman, Portland Police Dept. Pri- vate pilot Patrolman, Portland Police Dept. Pri- vate pilot Capt., Harbot pilot Straight line formation; last disc fluttered very rapidly in side-way arc Straight line formation; lsst disc fluttered very rapidly in side-way are Dises would oscillate and some- times a full disc would be vis 1ble, then a half-moon shape, then nothing at all Clear with little or no cloud forma- tion Clear with little or no cloud forma- tion Clear with little or no cloud forma- tion Clear with little or no cloud forma- tion Not stated CONFIDENTIAL NND 927545

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CONFIDENTIAL Incident No • 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 30a Observer's Occupation Maneuvers Capt, United Airlines Straight-away horizontal flight Coast Guard Horizontal flight Deputy Sheriff Not stated Not stated Not stated Not stated Not stated Flipping around Not stated Not stated Not stated Private pilot Not stated Straight horizontal flight Horizontal flight Farmer Straight course - were flying about a city block apart, one behind the other Not stated Straight course Not stated Sangle fi le Not stated Flashing Not stated Horizontal flight Not stated Shooting up and down Not stated Mechanic THA Representative Horizontal flight Not stated Not stated Lt Governor Not stated West Coast Pilot, 7000 hrs. Not stated Capt, USAF, Asst Operations Officer VHF/DF Operator Climbing and descending ver- ti cally Hovering, made three 360° turns around one place. Moved to another position and circled more. Turns required 30-40 sec. Diameter estimated at 2 miles. Weather Not stated Not stated Not stated Not stated Not stated Not stated Not stated Clear as crystal Clear Cloudless and sunny Not stated Not stated Not stated Not stated Clear Bright moonlight Not stated Clear Not stated Not stated Solid overcast Overcast, 1000 ft. CONT NND 927545

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CONFIDENTIAL Incident NO o 30b 30c 30 32 33 33a 33b 33c 33đ 33e 33f 33 g 34 35 36 37 38 39 40 Observer's Occupati on daneuvers Traffic Air Controller Bobbing up and down Not stated Climbing and descending Professor and Head of Aero Engineering Lt, USAF T/Sgt, USAF Ist It, USAP PPC None None None None None Capt, USAP May have been turning Capt, USAP None Col, Ky. State Police None Capt, USAF (P11ght Leader NG 869) Not stated Unknown Not stated Judge None Second Officer, Navy CAA Official None Not stated Pilot None Hangarian Peasants Not steted Constable None Not stated Spiraled downward from 5,000 to 2,000 ft and then went upward at a 45° angle CONFIDENTIA NND 927545 Weather Overcast High overcast Clear Overcast High scattered oloud= Visibility unlimited. High scattered Not stated High overcast with BKS High scattered, visibility unlimited Clear Not stated Not stated Clear Not stated Not stated Clear ated Notestated GAVUnta bod Cumulus clouds

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CONFIDENTIAL Incident No, 41 42 43 44 45 46 47 48 48a 48b Observer's Qgeupation Colonel, USAP Ma for, USAF Bus Driver Not stated Not stated Not stated Captain, USAR Major, USAP T/sgt Cpl. Kanewyers Not stated Not stated None None Not stated None Rolled from side to side Ascending and descending Up and down and side to side Ascending and descending 480 48đ 49 50 51 52 528 53. 54 55 56 s/sgt Not stated Ascending and descending very rapidly Ascending' and descending Not stated None Knitting designer Approaching shore from Oeean then rise and fall slowly. Not stated Not stated Capt, USAP, ASST. Horizonal left to right, right to Operations Officer left like a guard in an airplane and instructor Pilot formation. ist Lt. in A1x Reseryes former B-29 Pilot Similar to a fighter airerafts maneuvers when aceompanying heavier ships. 1st It, USAP, Pilot Horizonal very elose formation Mosquito Pilot Effielent controlled evasive action Government Employee Abrupt darts s/S&t, USAY Traveling in a definite are. -CONFIDENTIAL NND 927545 Wenther Not stated Not stated Not stated Not stated Not stated Cloud banks. Not stated Not stated Cold and elear with few seattered clouds. Light seattered clouds with haze tovards 8/N. Clear with over- cast in S/N. Clear to scattered. Not stated Not stated Not stated Clear Not stated Not stated Not stated High seattered condition visibility 15 miles. Not stated

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CONFIDENTI Incident No. 57 58 59 60 61 63 64 66 68 70 71 72 Observer's oceupation. Maneuyers Bridge Construction Not stated Chief Pilot- Plying service Not stated Pilot None Storekeeper Not Stated Not stated None Not stated Not stated Not stated Hovering and fluttering, rising and descending. Executive Direct- or of Housing Authority. P1lot Horizonal Not stated It. Col, GSC Seientific Branch Research Group. Horizonal Plight Insurance Adjuster None Prospector Banking Not stated Not stated Insurance Agent Not stated Capt. AC Reserves Army Officer Not stated Not stated 73 Navigator (Constellation type aircraft) Not stated 74 75 76 Prospector Standing on edge and banking in the clouds. Trout Farm Oper. Rode up and down over the hills and hollows of the canyon floor. County Commissioner Not stated CONFIDEN NND 927545 AL Weather Clear and dark. Not stated Not stated Clear at dusk Not stated Cloudy Seattered sma11 clouds. Overcast Not stated Not stated Clear Clear Not stated Clear Clear Cloud formation seattered above 10000 ft. 5/10 scattered eumulus with tops at 10000, visibility 10 miles. Not stated Not stated Not stated

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Ineident No. 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 993 94 95 96 97 98 99 100 Observer's Oscupation. As tronomer It, USN (P80 Pilot Weather reporter Lt. Col, USAP C1v11 Service Employee Field Engineer Pilot S1gn Painter Private Pilot Not stated U. S. Army Not stated Major, USAF Administrative Asst, Rocket Sonde Section Captain Railroad Employees Capt, USAP Lt Col, Rg, EPN C-47 crew Not stated Airplane crew Immigration Service Not stated Not stated -CONFIDEN Maneuyers Not stated Not stated Not stated Not stated Ascending slowly Not stated Slow roll or barrel C1imbing Not stated Turned a corner and seemed to roll. • Descended slowly and then dropped in a spiral motion. Not stated Not stated Not stated Traveling in z1g-zag course Climbing, diving and reversal of direction which happened every few seconds. Shooting towards the east at 45° angle Descending vertically - seemed to slow down on nearing the earth Not stated Not steted Not stated Appeared to be spinning in its descent Not stated Not stated CONFIDENTIAL NND 927545 Weather Not stated Not stated Clear Scattered clouds visibility 10-12 miles. Cloudy Not stated Some clouds Clear-scattered clouds Not stated Clear Not stated Not stated CAVU Clear Clear Clear and sunny Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated

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Incident No. 1 la 1b 1c ld le 2 3 4 Color Silvery -CONFIDENTIAL Shapo Not stated Size Not stated Sound Not atated S1 lvery Reflected the sun's rays S1 Ivery Aluminum colored surface Yellowish-white White aluminum 5 6 7 8 8a 9 10 Not stated Whitish-brown Al umi num White White Like shiny chro- mium hub cap Not stated Saucer shaped Not stated None Di sc Not stated Not stated Di so Not stated None Thin metallic ob- ject, unconventional shape Pursuit ship Not stated Spherical 5 - 10 ft, diameter Not stated Distinct oval out 50 ft. 1ine; two projec- tions on upper sur- face which might have been thick fins or nobe. These crossed each other at intervals, sug- gesting either ro- tation or oscilla- tion of slow type Round Not stated Di se Not stated Di ac Not determined Disc Out of sight be- fore detailed ob- servation made Di sc Out of sight be- fore detailed ob- servation made Diso Not stated Thin and smooth on bottom; rough appearing on top Not stated -CONFIDENTIAL NND 927545 None None None None None None Not stated Not stated

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Incident No . 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 25 26 27 28 29 30 Color Whi te Not stated Resembled metal l1c Like a new dime Silver Not stated Mirror bright Yellow Reflected the sun brilliantly Silver Dirty white Shiny silvery Bright and silvery Glistened in eun Luminous Not stated Silvery Not stated Not stated White (11ght) CON NTIAL Sha pe Saucer Like flock of geese Not stated Like a new dime Not stated Diso Approximately circular, no tall Ball Like cigars - much longer than wi de Round Between circle and oval - in- verted saucer Slim body Half-circle Too far away to determine shape Plying saucer - no tail Not stated Catoular in shape like a wagon wheel Come t- 11 ke Almost round Not stated NND 927545 Size Sound Not stated Not stated Not stated Low humming sound Not stated Not stated Like a new dime Not atated Not stated Not stated Not stated Not stated Diameter equal to di stance between outboard engines of DC 4 Not stated Not stated Not stated Not stated None About 12 inches in di emoter None 175-250 ft. diameter Like electric 12 ft. thiok motor or dy- namo Quite large Not stated Not stated Not stated Too far away to deternine shape None Not stated Not stated Not stated Not stated Same span as C-54 at 10,000 ft. Not stated Not stated Not stated Not stated Not stated Not stated None

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Incident No - 30g 30b 30c 31 32 33 338 33b 33c 33đ 33e 33f 33g 34 35 36 37 38 GUNI INHAL Color Shape Size Sound Amber Round or oval C-47 airplane None Bright white to amber Cone-shaped, blunt Bnormous on top and taper- ing off toward bottom None White ( 11ght) Round Comparable to run- way 11ght None White Not stated Not stated No ne Amber Not stated Not stated None Sun flashes on metal Roughly circular or metallic At the distance and altitude the object appeared to be the size of silver dollar None White or luminous. Turned to be more red as the sun set Round tending to be conical Unknown - altitude None and distance too great Not stated Cone, topped with Not stated red None Silver with shadow Raindrop Unknown - believed Unknow to be large Whi te Round at times - cone shaped Uncertain because of di stanoe None Whi te Round 1/4 size full moon No ne Metallic Not stated Tremendous Not stated Not stated Cone 100 ft. high, 43 ft. across None Redish tinge Round Large grapefruit None Fire color Ba11 Not stated Not stated Not stated Not stated Not stated Hot stated Reddish with blue background. Black with white baokground Silver Not stated 3 ft. from point of None view Ba 11 Not stated Not stated CONFIDENTIAL NND 927545

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Ine ident No. 39 40 41 42 43 44 45 46 47 48 48e 486 480 48đ 49 CONFID AL Color Shape Phosphorus Bgg-shaped dises Gray B111ptical Al uminu Round Grayish Balloon Dirty white Between a cirole and an oval (Inverted saucer) Not stated Flying Saucers (not actually des- cribed as being this shape) Not stated Not stated Silvery white Round No definite color top side refleet- ed 11ght. No definite shape Red Plaming Red cone S18e Not stated 20-30 ft. 3 ft. diameter 10 ft diameter 12 ft thick and 175-250 ft diameter Not stated Not stated Sma11 C-54 airplane Not stated Sound Not stated Noise 11ke Jet aircraft prior to 1ts appear - ande. No audible sound heard while objeet was in view. Not stated Not stated Blectrie Motor or dynamo None Not stated Not stated Not determined due to the noise of airplane. Not stated Bright light changing to red then to white or yellow Circular-like a star Very large compared None in the sky only larger, to an aeroplane 11ght. Red - when descending Cone Not determined Not stated Red when moving Not stated then grean and black to red. Yellow or flame Not stated colored. Not stated Not stated Not stated Not stated Not stated Peneil shaped object Not stated Not stated CONFIDENT NND 927545

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Ineident No, 50 51 52 52a 53 54 55 56 57 58 59 60 61 62 63 64 66 67 Color Stated as queer light. Shape Referred to as saucer but not stated as being of this definite shape. S1lver Round White, shing Circular 11ke a ball on the bottom but not completely round. Nilk white Not stated White Circular Not stated Not stated Redish Not stated Dim glou of 11ght Round Silver to Red Not stated Black Saucer (not definitely stated as being this shape) Incandescent 11ght without appreciable blue and no reddish tinge. Not stated Plame color -CONFIDENTIAL Size Not stated Not stated 15-25 ft Diameter Not stated 36 inches dianeter Not stated Not stated 2 ft. diameter Not stated Larger than C-54 airplane Not stated Sound Not stated Not stated Not stated None Not stated Not stated None None Not stated Not stated Not stated Disc shaped (the after glou made 1t look 11ke a cone) White and 111 minated Not stated Yellowish white Not stated Gleamed and Shimmered Dise (not actually stated as being of this shape) Color similar Not stated to eleetric 11ght. Not stated Not stated Bright Orange Not stated Mutal color top surface slightly highly polish- ourved-larger in front ed chronium. than in the rear NND 927545 Barrel Head, dinner plate and the size of a plane flying high. Not stated Size of Pigeons Small 3 ft. diameter and of no great thick- ness. Not stated 15 inches diameter Not stated Not stated Not stated Not stated Not stated Not stated Not stated 4-6 ft in length Not stated and 10-14 inches wide. CONFIDENTIAL

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Incident 68 70 71 72 73 74 75 76 77 78 79 80 81 82 Color Not stated White Not stated Not stated S1lver Deep Gold Not stated Sky blue Not stated Light colored Light gray Silver Reflected white 11ght. S1lver Prosty white 83 Blsek CONFIDENTIAL Shape Dise - appeared to have a tail. Not stated Giant fire cracker Size 30 ft diameter Not stated Not stated Not stated Sphere was not 11ke saucer or dise. B111pt1cal Not stated 2-3 ft diameter 15 ft long 2-3 ft in length. Tapered sharpely to a 30 ft. diameter point in the front end. Oblong 11ke a broad rim hat with a low crown. Not stated 20 ft. long and 10 ft. thick. Not stated Only concrete evidence of form appeared on the left tangent of the group. Cireular 50-100 ft wide. Not stated "Blob" 8 ft. diameter Larger than a Pibal balloon when observed through a theodol1te. Small airplane Large Balloon with silver Large dise below it, no attaching cables were noticed. Round and flat Round Equal to bulk of 6 each, B-29 air- planes with dia- meter to thielness ratio of 10-1. Twenty-five cent piece. -CONFIDENT AL NND 927545 Sound None Buzzing sound. Buzsing sound not as loud as a rocket sh1p. Not stated Not stated Not stated None Made a swishing sound. Like the echo of a motor. Loud roar Not stated Not stated None Not stated A s11ght swishing. Not stated

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CONFIDENTIAL Ineident No. 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 Color Shinny Shape Round $1ze Not stated Not stated Resembled the XP5U-1. Not stated Sound More or less Shr 111, Not stated Not stated Not stated Not stated Not stated NotSstated Not stated Not stated Not stated Not stated 81lvery Plying diso (not ao- Not atated tually described as being of this shape) Round dise shaped object 30-50 ft. diameter Not stated Not stated Not stated Not stated Reflected 11ght L1ght Unt forn with no protu- berances such as wings of an airplane Not stated Not stated None Silver Not stated Sma 11 Not stated Bluish center Appeared to be a diso with rod on Its edges Not stated Not stated Not stated Not stated Not stated Not stated Not atated Resembled a shooting Not stated star; however, ob- servers not certain Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated Flash of 11 ght Bright light Almost round or perhaps oval or saucer-shaped 26-30 miles diameter Not stated Shining Brightly shining object with long tail Not stated Not stated Not stated Not stated Not stated Shining CONFIDENTIAL NND 927545

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Incident No. 1 la 1b 1c 1d le 2 -3 4 5 6 7 8 8a 9 10 11 CONFIDENTIAL Exhaust Trail None Heading 320° Altitude Ft. Speed Effect on Clouds 1000-8000 ft. 300 mph Not stated Not stated Northwest 7500-8000 ft. 350-400 mph Not stated Not stated Northwest 7000-8000 ft. Not stated Northwest 8000 ft. 300-400 mph Hot stated 300-400 mph Not stated Not stated Not stated Not stated West to east Fron very near Not stated Not stated the ground to very high 10000-12000 ft. 200-225 mph Not stated Not stated North of due east Under 20000 ft. Slower than Not stated maximum speed of P-30 Not stated Not stated None Two flying Not statedd south - 3 flying east Northwesterly Undetermined Southwest 30000 ft. Great speed Not stated Terrific Not stated None- South 40000 ft. Terrific - faster than any object ever seen by him Terrific Not stated Not stated None South 40000 ft. Terrifio Not stated Not stated South High over Globe Mills Terrific Not stated None Northwest Not stated Not stated Cruised for Not stated 45 min. at conventional airline speed (180 mph) ther rapidly dis- appeared Not stated Not stated Over north end Not stated of Lake Wash- ington CONFIDENTIAL NND 927545

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Incident No . 12 13 14 15 16 17 18 19 20 21 22 23 24 CONFIDENTIAL Exhaust Trai l Not stated Not stated Hoading Not stated Altitude Pt. Not stated 3 west to Did not appear east. 1 north very high Speed Effect on Clouds Not stated Not stated Traveling so Not stated fast they were out of sight in east in 2-4 seconds Moving slowly Not stated over sandy district Not stated Not stated Not stated Not stated Not stated Not stated Not stated 1 headed southeast. 2 headed northeast Not stated Bigh Not stated Not stated north to south 9500 ft. about 170° Trail stream- Seshhoter ing out be- westend hind 11ke of Toronto vapor trail behind air- plane on misty day Not stated Like s11ght Weet to east One mile high Very fast trace of steam. Disappeared immediately. Not stated Southwest Not stated N.N.W. About 1500 ft. Fast 1200 ft. About 300 mph Not stated S.W. of S. 7000 ft. Slower than two-motored army plane Not stated Not stated 3000 ft. Not stated Cloud-11 ke vapor - re- tained shape and persisted for over an hour Southeast Very high Very fast Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated CONFIDENTIAL NND 927545

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-CONFIDENTIAL Incident No. 25 26 27 28 29 30 30a 30b 30c 30 32 33 33a 33Ъ Exhaust Trail Heading Altitude Ft. Speed Effect on Clouds Not stated Bast H1 gh Fast Not stated Bluish-black Not stated Not stated Not steted Cut a clear path through clouds Bluish-black Not stated 15 mi. long 10000 ft. Fast Seemed to out clouds open Not stated Not stated Not stated Did not move • Seemed to go below horizon with rotation of earth Not stated Not stated 10 flying High north; on reverse course there were only 7 300-400 mph Not stated None (ap- peared to have bluish streaks out from sides West 3000 Slow Not stated Five times length of object 120° From very near 500 mph ground to 1000 ft. after 1t started to leave vicini ty Not stated Small streak 8.8.W. trailing object 2000-3000f£t. Exceeding 500 mph Not stated Not stated Not stated different al- ti tudes Motionless Not stated White, heavy West to east 20000-50000 ft. 600*200 mph Not stated None Stationary 3000 ft. Stationary None None None visible Unknown none visible None None 210° from Godman Field Extremely high Stationary None None Not stated Not stated Not stated Not stated CONFIDENTIAL NND 927545

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-CONFIDENTIAL Incident No. 330 33₫ 33e 338 338 34 35 36 37 38 39 40 41 42 43 44 45 46 Exhaust Irall Not seen None None Not stated Not stated None Stream of fire. Not stated Not stated Not stated None Not stated Not atated Not stated Not stated Not stated Not stated Not stated Heading Altitude Pt. Appeared to be Very high. stationary. 210° from Godman Fld. Uncertain- very high. 210° from 25000 ft. Godman Pld. Approx. 210° 15000 ft. from Godman Pld. Southwest 4 miles , West to east Not stated Northwesterly Not stated Northeast Not stated Northeast 8000-10000 ft. Ngt stated Bast Not stated 30000 ft. 5000 ft. Appeared from northeast. South Not stated Northwest 1500 Pirst group s s/B, second group N/v. 1200 South Not stated Not stated Not stated Northwesterly 1000 47 Not stated Southwesterly 10000 48 Gaseous green S/M when 1t Not stated mist. left the vicinity. NND 927545 -CONFIDENTIAL Speed Appeared BAtect on Clouds None to be stationary. Stationary.Could be seen through cirrus Stationary. None 500 mph Not stated 10 uph Not stated Speed of a None meteor or falling star. 700~900 mph Not stated Not stated Not stated 350 mph Not stated Not stated Not stated Very fast Not stated 400-600 mph Not stated Great Not stated 100 mph Not stated 300 mph Not stated Past Not stated Not stated Not stated Paster Not stated than an air- plane. Paster than Not stated any aireraft he had ever seen. Gained and Not stated lost altit- ude at a terrifie rate.

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Ine ident No.- 488 48b 48e 48đ 49 50 51 52 52a 53 54 55 56 -CONFIDENTIAL Exhaust Tra1l Heading Altitude Ft, Very faint S/W when 1t left Not stated exhaust trail the vieinity. when moving. Greenish mist when descending. Not stated S/W when it left Not stated the vicinity. None Long trail of smoke. Not stated Not stated None Not stated Not stated Not stated Not stated Not stated 210 degrees when 15000-20000 it left the vic- inity. Approximately From 4000 to due west when it very high. left the vicinity. West Very high Shoreward Not stated but said to be quite close. Not stated H1gh Southward 8000-10000 120° 6000 120° 6000 North Sea to Norfolk 22000 NNE 10000 South Bast 2000 ft Speed Bffegt on Clouds Left Not stated vieinity at very high speed. Not stated Not stated Not stated Not stated Slow Not stated Not stated Not stated Slow until Not stated over land then higher speed while leaving. Not stated Not stated Made a P-80 Not stated look 11ke 1t was motion- less in the air. Approximate - Not stated ly 750 mph. 285 mph. Not stated Equal to or greater than a Brit- 1sh Mosguito. Not stated High vel- Not stated ocity, stated to be faster than convent- ional airplane. 500-600 mph. Not stated -CONFIDENTIAL NND 927545

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Ineident No, 57 Exhaust Trall Not stated 58 59 60 61 62 63 64 65 66 68 70 71 Heading NIE (30° B of true North on horizonal plane. Not stated N/w Not stated 350° later changed to 109°. Light flame color. Prom N/ head- ing Eastward. Not stated Northern Not stated Not stated Not stated Northeasterly Not stated Northeasterly Not stated West to Bast Long stra- North to South 1ght white streak sim- 1lar to the streak left by a tracer bullet. White trail Not stated of smoke. Not stated Southeasterly 500-1000 6000 Not stated Thin streak of greyish color. South Bither smoke NB to SW or conden- sation last- ing 2 seconds. 1000-3000 May have been smoke or vapor from intense speed was aimost unite. Southeast then turned and went west. Not stated NND 927545 -CONFIDENTIAL CONFIDEN Altitude Ft. 30° off the horizon at an estinated 1/4 adle range. Speed High vel- oc1ty, sta- ted to be faster than a tracer bullet. Effect on Clouds Not stated 1000 9500-10000 6000 2000-3000 Several thousand ft. 3000 Not stated 1000 LOW 510 mph. Not stated 1000 knots Not stated Very high velocity. Not stated Paster than Not stated birds. H1gh rate of speed. Not stated Tremendous Speed. Terrific Not stated Not stated 1000-1200mph Not stated Required 3-4 Not stated seconds to travel 70° aro. Terrific Not stated Not stated Not stated Very fast. Not stated 400-500 Not stated 7000800 Not stated

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-CONFIDENTIAL Ineident No. 72 73 74 75 76 77 78 79 80 Exhaust Tra1l Heading None South Altitude Pt, Below 10000 None Basterly approximately 110° magnetie. 7000 Not stated Not stated Not stated None Bast to west Not stated Not stated 75 4000-6000 Not stated Northwest (True) Not stated Not stated Straight down. Decreasing from approxinately 25000. Not stated Bast to West Less than 15000 None Southeast Less than 500 81 82 83 84 85 86 87 88 89 Not stated None Not stated Not stated Not stated Not stated Not stated Not stated Northwest 350° Not stated Northeast North Northward Not stated Not stated Not stated Bast 6000 10000-18000 11000 7500 8500 Not stated from 5000 200 yards - 11000 NND 927545 CONFIDENTIAL Speed Tremendous 175 mph Effect on Clouds Not stated Not stated Greater than any- thing ever witnessed. Not stated Not stated 600-1200 Not Stated Not stated Not stated Not stated Inconceivable Not stated Not stated Not stated Computed at Not stated *1350 mph, however ap- peared to move with the speed of a jet aircraft. Not stated Not stated Three times Not stated that of a jet aireraft. Not stated Not stated Not stated Not stated 350 mph Not stated Not stated Not stated Not stated Not stated moving rap- Not stated pidly 210 mph Not stated

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-CONFIDENTI Incident No • 90 91 Exhaust Trail One witness thought he saw vapor trails Not stated Heading Northerly Altitude Ft. 8000-10000 Speed Not stated 92 93 94 Not stated Hone Disappeared in the south- west West Dropped from sight on north side of Mt. Tom near Holyoke, Mass. Great height Above 1000 Not stated Green and Descending ver- Prom 13000 blue flames tically High rate of speed Great speed Very high velocity 95 96 97 98 99 100 Several colors Eastward of flames - red and green predominating Not stated Not stated Not stated Not stated Not stated Not stated Not stated West to east Low 1200-1300 Not stated Not stated Not stated Grey streaks North to south Not stated were left in sky Very high rate of speed Very high rate of speed Not stated Not stated Not stated Not stated Not stated NND 927545 CONFIDENTIAL Effeet on Clouds Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated Not stated

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CONFIDENTIAL NOTE: Incident +18 It has now been definitely deterined that both the photograph and story were a hoax, perpetrated for publioity and money • Incident #84 The person making the report on this incident was determined to be an excitable person, very talkative, and possessing an ex- aggerated, Imagination and inolined to inpress people with his continuous chatter. NND 927545 CONF

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-CONFT DENTIAL REPORTED DIRECTIONS OF FLIGHT 63 38 NE 14 22 SE 34 Circling 15 Straight down 3 Direction Indefinite 64 Direction Not Stated 61 S • Where an undetermined number of ob- jeots were reported the minimum number of objects are plotted. Same object reported by different people only shown once. NND 927545 CONFIDENTI

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CONFIDENTIAL Inc 2 -CONT HAL NND 927545

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CONFIDENTIAL Inc 3 CONFIDENTIAL NND 927545

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CONFIDENTIAL Identification of Subjeot Matter (as per sample) MCIA MCIT 19 Feb 48 To meer or deman to that taken date are do To rom 0) ei the specimen: a. It is conoluded that the image is of true photographic nature, anc is not due to imperfections in the emulsion, or lack of development in the see- tion in question. The innge exhibits a "tail" indicating the proper type of distortion due to the type of shutter used, the speed of the objeot and the fixed speed of the shutter. Thie trailing off conforme to the general informa- tion given in the report. b. The report states the object was seen at approximately 2000 feet at the time of exposure. The observer also reports being able to see clearly a oanopy of enclosure. The visual acuity of an average personiwould allow for this peroeption, but certainly not much further as the subject had low visual oontrast, being gray against a gray sky. If we oan establish the distance from camera to subjeot, we will have quantity #l. The report states that a 620 camera was used, indioating several possibilities, since the 620 1a nomenclature for the spooling and width of the film we may have negatives 2t x 22", 27 x 82" and 82 x 4}". The sample subaitted had been out and it was not possible to establieh the exact frane sise. The 2} x 24" aise was ruled out, leaving 27 x 37" and 2 x 41*. If it wore the former, then the fooal length of the lens would be 4", and using 2000 feet as the approximate subject distance and the image sise at 1/64" we have an appfoximate sie of 44 feet as the diagonal of the objeot. Now if we choose the latter value of 5" for focal length, we have an approxi- mate value of 55' for the diagonal. Poits of measurement are indicated from, x to x on Exhibit *4". Янс 4 -CONFIDENTIAL NND 927545

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• CONFIDENTIAL Ephibit'Ä CONFIDENTIA NND 927545

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In 5 -CONFIDENTIAL NND 927545

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FEBRUARY 13, 1948 185 The Biolog of the Flying Saucer-I The Story of Low Aspect Ratio Aircraft By A. R. Weyl, A.F.R.Ae.S. THE AEROPLANE on both sides of the Atlantic rushed into print with claims of having observed queer, saucer-shaped aircraft which flew very fast. Some main- tained, indeed, that they had seen squadrons of such mysterious objects; others described vividly how these celestial saucers were able to descend vertically. All agreed on the saucer-like shape. Sceptics considered that, for non-aeronautical people living far from the former playgrounds of V.I. V.2, and all the rest of Hitler's " civilizatory practices, flying saucers might indeed constitute phenomena of threatening aspect, from their expert- ence of domestic disagreements. Doctors, however, hastened to assure the World that saucer-shaped or lenticular objects could well be nothing more than specks in the lenses of the eyes of the observers--the so-called musae volantes associated with high blood pressure. Teetotallers blamed the sorry consequences of imbibing intoxicating liquors for the observations. On the other hand, the U.S. Air Force considered the matter serious enough to warrant investigations into the incidents which had been reported. In the meantime, the occurrence of Flying Saucers has ceased to be news. Presumably, they have all landed. [A new crop was reported in THe AEROPLANe for January 16 last under the "Tuppence Coloured." —ED.] Aeronautical Antiquities and Iniquities As a matter of fact, saucer-shaped aeroplanes are not quite as new as some people have tried to make out. (Fig. 1.) Quite a number of aircraft have been constructed and flown with wings of the ring or disc type which could well have been mis- taken for saucers. hat-brims. spades, doughnuts, diamonds, Greek letters, pancakes, flat-fish, geometrical symbols, dinner plates, and other entirely non-aeronautical commodities. Moreover, it is quite true. and not even a minor secret, that, at present, aeronautical engineers are paying increased attention to such queer wing shapes; disc wings, for instance. permit certain disadvantages of conventional wings to be overcome. It is even thought that such shapes have been neglected too long. The blame for their neglect can be ascribed to the doctrine of the induced drag. When the Lanchester-Prandt] theory became recognized nearly 30 years ago, and when the sailplane movement proved that slender wings were a necessity for soaring, designers began striving after " good" The theory blinded their eyes agains: the possibilities of other than conventional wings. This, however, was not the fault of the theory, as Prandtl soon showed its restrictions. We have now come to reconsider the matter of wing shape in an objective way, as it is quite possible that aircraft design is approaching a cul-de-sac so long as it retains its bias in Apteroid Aerofoil (b 1 c- 6) CROSS - SECTION Fig. 1.-"Turbine flying machine" (project) of the Munich engineer Gustave Koch, 1893/1894. Tailless monoplane of low aspect ratio, propelled by a ducted fan. A 50 h.p. steam engine was deemed sufficient for this flying, motor car. The design of the duct shows intelligent anticipation. Fig. 2 (Right).—Definition of the aspect ratio of an aerofoil. The arrows signify the direction of the air flow against the wing. The terms pteroid (feather-like) and apteroid have been introduced by F. W. Lanchester. Inc 6 NND 927545 Square AR b- span c chord Sacrofoil area Aspect Ratie. AR. b "Pteroid" AR >3 "Disc"" 05K A.R. < 3 "Apteroid" A R. < 0-5 (2)% - 1.275

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THE AEROPLANE favour of the "well-tried" convention OT " normal" wings For these reasons, a study of the history of the use of low aspect ratios in wing design will be of interest. Spiritually, the fathers of such aeronautical exhibits were Englishmen. were people of good reputation and by means suspect of aerodynamic perversion Lanchester was undoubtedly the first aerodynamicist to give thought to aeroplane wings of circular or square shape. In his book published in 1907, he referred expressively to such "apteroid" wing shapes (Fig. 2) and advanced the Newton's law The correctness view was experimentally proved 30 years later In a previous article on * Stalling Characteristics of Tailless (THE AEROPLANE for August 15, 1947), the early interest taken by F. (now Sir Frederick) Handley Page in the stalling qualities of wings of low aspect ratio was mentioned. He showed, in a paper read in April, 1911, that marginal vortices and pressure-equalizing flow around the tips were responsible for the delay of flow separation which had been observed at He stated, in this connection:—" •.. With planes of high aspect ratio (i.e., with slender wings of normal span/chord ratio), there is not the same facility for the " feeding in" of fresh air at the plane sides (i.e., at the wing tips) to act as a link between the plane and the live stream, and therefore the live stream leaves the plane's back at an earlier stage than in the case of the plane of lower aspect ratio.. He then showed some experimental evidence separation with decrease of the aspect ratio and for the greater maximum lift of such wings. When Lanchester published his book, man was just begin- ning to spread his wings, and in order to fly with a minimum expenditure in power, wings of fair aspect ratio were a neces- Nevertheless, there were a few early aeroplanes, notably the little " Demoiselle monoplane of Santos Dumont (1909. 1910), which had an aspect ratio of only 2 and proved to be One of the earliest attempts at a genuine "apteroid " aero- plane was an experiment by a German architect, Flick-Reinig (1910). It had a span of 7) ft., and performed in hops only. 186 FEBRUARY 13, 1948 Fig. 3.—A simple experiment in annular aerofoils. A simple experiment with some paper and a pair of scissors shows that the sinking speed of a circular disc loaded with a paper clip is decreased when a hole of sufficient diameter is cut out in the centre (Fig. 3). This justifies the development from the circular disc wing to the annular aerofoil. The theory of the phenomenon is still somewhat obscure. (Having tried this experiment, we can confirm that the char- acteristics of an annular aerofoil are certainly very different from those of the plain disc Our own experiments were admittedly somewhat limited in scope and we were unable to form more than an impression of the relative sinking speeds: it did, however, appear to be less with the annular aerofoil. Our main conclusions were that cutting a 2.25-in. diameter hole in a 5.375-in. diameter disc, resulted in a much flatter glide; the stall was not so abrupt, and the stability in the glide was We were so fascinated with the experiment that we hope to repeat it at a later date on a more scientific level.Ep.) The conventional aeroplane is constituted of two basic aero- foils: a wing (which supplies the lift) and a tail (which balances and stabilizes the wing). We know that such an arrangement of the two aerofoil components is by no means the only pos- The balancing and stabilizing aerofoil (tailplane) need not to be aft of the lifting wing as a tail. arranged anywhere in relation to the wing, e.g.. above it, below If the balancing aerofoil is in front of the main wing. the aero- plane is of the tail-first type, and if it is attached to the Fig. 5. Kitchen's doughnut of 1911. Fig. 4.—Principle of the Huth annular-biplane system. main wing, the tailless aeroplane is created. For all these arrangements, the condition is that, in the case of a wing com- prised of normal (unstable) aerofoil sections, the stabilizing aerofoll exerts a certain leverage in relation to the centre of Another possibility is to combine two lifting wings so that they will stabilize and balance each other. For this purpose, all that is required is that the front wing shall possess, at all inci- dences of-flight, a greater effective incidence than the rear wing. In other words, the centre of gravity must be nearer to the leading wing than to the trailing wing, and the whole arrange- ment must be balanced accordingly. In this way, we arrive at the conception of a stable tandem aeroplane. If we now take such a tandem arrangement and sweep the leading wing back and the trailing wing correspondingly forward so that the tips of both wings merge into each other, we obtain an annular or ring-shaped wing system. Aerodynamically, it is of minor importance if the shape is actually circular or oval, or if triangular or quadrangular shapes constitute the wing. simplicity's sake, in all such cases considered here, the term " annular" is applied. As mentioned, the aerodynamics of such shapes cannot yet be considered as fully established. But it is proved that longi- tudinally stable wing systems can be obtained with such shapes. Some types relying on such wings have shown quite remarkable It is also possible that, with annular wings, the induced drag is less than with conventional wings of equiva- tent aspect ratio. In common with circular wings, annular wings have the remarkable property that the lift force steadily increases with incidence up to fairly high values without a stall. known arrangements the maximum lift seems to occur at As such high angles of incidence are not likely to be reached in flight unintentionally. it is obvious why annular wings have become renowned for their good-natured flying characteristics. Tilghman Richards) is that the centre of pressure of such wing systems is nearly stationary in flight, or that a travel of the centre of pressure can be obtained which is positively stable until incidences of the order of 18 degrees are reached. fact, no case of longitudinal instability has ever been reported with an annular wing, although the centre of gravity has often been located dangerously far back. The first annular-wing aeroplane dates back to 1908. had little success. Two types were constructed in succession to the designs of a capable German aeronautical engineer, Fritz Huth, who was by profession a teacher at a technical school The second type, which had a less elaborate airscrew drive, flew in May, 1910; it was, however, so devoid of performance, in spite of a 50 b.h.p. engine, that it was soon afterwards discarded as a hopeless proposition. Britain's First Doughnut The British conception of the idea has been far more successful. As it is constituted, until now, the best representative, its history may be given tried extensively: somewhat more The original idea for an annular-wing aeroplane came from G. A. Kitchen, in about 1910; he constructed a biplane with ring-shaped wings, but made no progress with it. The stable NND 927545

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FEBRUARY 13, 1948 187 THE AEROPLANE flight of Kitchen's models. however. convinced Cedric Lee that an aeroplane of such. design would be a success, and late in 1910 he acquired the patents. At the same time, G. Tilghman Richards, who was a qualified aeronautical engineer, became, sufficiently interested in the matter to give up budding engineering bureau in order to join Cedric Lee and to devote his energy to the idea of a " safety " aeroplane. Tilghman Richards began with systematic experiments on models and on large gliders. Later, careful wind-tunnel tests (including the observation of the pressure distribution) were made by him in a 2-ft. tunnel he had constructed at East London College and also in tunnels-of the National Physical Laboratory. preparation of the design was, therefore, uncommonly careful for this early period of 1911-1914. In order to appreciate the intentions for the development, the following quotation from a paper read by Tilghman Richards about 1912 is illuminating:- The very fact of high lift occurring at small angles neans the provision of large area for landing speed resultin n an inefficient attitude of the plane at high speed: and th dependence on extraneous controls carried at some distance from the wing by heavy and redundant structure. lift at small angles is uscless, likewise high lift/drag ratio at small angles, and what is required is the reversal of the normal type of lift curve giving little lift at small angles with low value of the lift/drag ratio for landing. Seen from our present state of knowledge and development. and facing the burning problems of personal aircraft for the man in the street, it would seem that this opinion is a very good argument for further experimentation along the lines indicated. The experience with powered aeroplanes was at first beset with disappointments. Famine Point, Heysham, was apparently not a spot from which aeronautical experimenters could derive any comfort. The original Kitchen biplane with a 50 b.h.p. rotary engine was wrecked by a gale, during 1911, before flight tests could be made. After reconstruction some flights were performed with it at Shoreham during 1911-12; yet it never gave any proof of superior qualities. The biplane had ailerons of the original Farman variety, between the wings. biplane arrangement was given up in favour of the monoplane. A subsequent experimental monoplane was nicknamed the " Secret-Circle Plane or " Doughnut," the experiments being shrouded against publicity (much against the interests of the development). This annular-wing aeroplane (Fig. 7) was equipped with an 80 b.h.p. rotary and test-flown by Gordon England on November 23. 1912, at Shoreham. The flight was remarkable and lucky for the pilot, but unlucky for the precious craft. After having flown a large circuit on the first attempt, the pilot noticed, when coming in to land, that the aeroplane was exceedingly tail-heavy and getting out of control. the elevator being insufficient. At about 150 ft. above the ground the inevitable stall took place; but the pilot managed somehow to drop his mount upside down on to telegraph wires and escaped without personal injury With the reconstructed and improved monoplane many sticcessful flights were made by Gordon England, N. S. Percival Fig. 6.-Huth annular biplane of 1909. Fig. 7.—Cedric Lee Monoplane No. 1 of Tilghman Richards, 1912. and Gordon Bell. Finally it came to grief when flown by Cedric Lee himself without previous training. After a good flight he managed to put it into a river. Another incident happened with subsequent annular monoplane: the elevator jammed and broke in flight. The aeroplane merely pancaked to the ground, again preserving the health of its pilot, E. C, Gordon England, These types in their final form had lateral control effected by differential deflection of the elevators It was realized that this elevon control was not very effective for lateral manœuvres, yet the lateral stability of the wing proved so great that the provision of ailerons seemed superfluous. The longitudinal stability was always satisfactory, once the centre of gravity was Because of the great inherent -fore-and-aft stability, a separate elevator was, at one time, located on top of the vertical fin and permitted the fitting of special ailerons For directional control a vertical rudder stern of the fuselage at the trailing edge of the wing. of tricycle undercarriage was employed. - In respect of performance, the wind-tunnel tests indicated that a better lift/drag ratio could be expected than with : comparable conventiona aeroplane. However, no conclusive evidence for this has, as yet, been presented The third British monoplane of this type also had an 80 b.h.p. rotary engine, but this time it was located aft and, further, drove the airscrew by means of an extension shaft. Unlike its pre- decessors, no dihedral was provided, and because of this the flying qualities were found to have been greatly improved. From early in 1914 until the outbreak of the 1914-18 War this unconventional aeroplane by Gordon Bell): it was lems frequently fore demonstrated flown (mostly Winston Churchill in the hope of securing orders from the Admiralty, Altogether, 11,000 miles were flown in about 128 hours, and even people not previously trained as pilots were able t fly it. In May, 1914, two such aeroplanes were being designe for participation in the Gordon-Bennett Race of 1915. When the 1914-1918 War terminated the work. it had clearly grown far beyond the stage of an untried project and could have well been termed a successful experiment with every prospect of becoming a practical proposition In 1919-20 Tilghman Richards succeeded in persuading the Air Ministry to place an order for a further experimental after communicating this decision Major-General Bagnall-Wild, the promoter of the idea, retired, and red tape killed an intelligent intention. It is only fair to record that aeronautical progress has suffered from. the failure to have this development continued. Tilghman Richards stated many years ago: There is nothing mysterious about the annular plane. It affords high lift at large angles. lift/drag ratio for machine was very fast in flight, for its day, and extremely slow in landing: and there being three distinct regions of lift, one apteroid and two pterygoid on each half-wing pressure was a resultant of three distinct regional movements; and with slight modifications could be made to move in any desired manner without affecting the general efficiency of the plane." As mentioned, the circular shape for the wing is not in itself a decisive characteristic. Previously, in 1908. A. H. Edwards invented the ring-type wing with rhomboidal or triangular shape (Brit. Pat. Spec. No. 4519 of February, 1908). experimental aeroplane of this type, An "The Rhomboidal," was constructed and tested at Brooklands. It was not successful. (To be continued.) NND 927545

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MARCH 5, 1948 279 THE AEROPLANE The Biology of the Flying Saucer-II By A. R. Weyl, A.F.R.Ae.S. i the recipe i ede the here to operation to peone ine (Continued from page 185, February 13 last.) qualified aeronautical engineer (Fig. 10). The Willoughby "CONSPIRACY," mentioned pre- of London had taken up viously in connection with circular-aerofoil aeroplanes, did idea in 1931 and sufficient means were available to make rather not lack congenially inventive spirits. Early in 1913 an engineer extensive tests. in Dijon, M. Bourgoin, made experiments with an annular- The principle is best described as a tandem monoplane with wing aeroplane. The tests were unsatisfactory. of this design was the provision made for varying the wing trailing wins near the to connecting the leaning wind werothi trailing wing near the tips not only in their longitudinal cross-section (i.e., in the direction of flight), but also laterally. This was considered a More recently, a similar idea was suggested by N. H. Warren and Th. R. Young (Fig. 8). In -1937 they secured a patent (Brit. Pat. Spec. No. 508,022 of December, 1937) for a non- stallable monoplane of rhomboidal shape (i.e., leading wing swept back and trailing wing swept forwards with the wing tips merged together). This was provided with a conventional tail at the stern of a long fuselage and a number of advantages characteristic feature and subject to patents It was claimed hat the vortex distribution induced by such shape gave ar i han i was hit i ery hah hate no more pen ma the aeroplane dyn addition, he as pointed hut it the In addition, it was pointed out that the " side wings should reduce the drag of engine nacelles fitted underneath them. All this was said to be proved by extensive wind-tunnel experimentation here and abroad. Designs of passenger trans- port aircraft reaching weights of 40,000 lb. were prepared on the basis of model tests made at the National Physical Laboratory that an experimental monoplane with two 125 b.h.p. Menasco engines and weighing 2,540 lb. was constructed late in 1938 This aeroplane flew indeed and was even publicly demonstrated (including one-engine flight) at a in May, 1939 Shortly afterwards the experimenter was killed in an unexplained crash during a flight test. published, apparently trim changes could be expected at various These components were thus capable of producing longitudinal instability and it is not improbable that this and poor control efficiency may have contributed to the accident. decrease in the lift coefficient however, would not exclude the presence of fluctuating lift forces). RUDDER Fig. 8.-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. were claimed. In 1943 a model for a two-seater fighter with tail turret showed the separate tail omitted; special emphasis was laid on the triangular shape of each wing and the effect of sweep was relied upon. Nothing more has become known since, however, but it is worth noting that the project had been based on sound aerodynamic considerations. created a mild sensation because of the good performance of models made to this conception (Fig. 9). Somewhat peculiar was the aerodynamic conception of the rhomboidal annular aeroplane of P. Nesbitt Willoughby, a 11 11 75° Fig. 9.—Model of the "annular wing" of Antes, 1933. Fig. 10.-Principle of the Willoughby Delta design. Another suggestion for an annular wing was made by This, however, was concerned less with the aerodynamic properties of such wing systems than with the arrangement of two engines facing each other with their air- screws, in order to overcome the torque reaction. A phenomenon of which acrodynamic experimenters were but which aircraft designers failed to utilize, was that wind-tunnel tests clearly proved good-natured stalling properties of wings having very small aspect ratios. Yet even in the very early days when centres of gravity were far too far back on the old box-kites, the square shape of tailplanes. then unaccountably in vogue, may have saved the pilot's bacon more than once by its refusal to stall under extreme provocation Later on science came and proved that a tailplane of "good" aspect ratio was more efficient. It was, but it made the stall worse when the centre of gravity happened to be rather aft. The interesting thing is that aerofoils of circular or square shape were tested in the early days at incidences up to 90 degrees, while on normal acrofoils tests were restricted to rather small incidences only, generally excluding the range of stall. NND 927545

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THE AEROPLANE 280 MARCH 5, 1948 argument against disc wings, The best aerofoil sections in use prior to about 1925 had a plain camber which implies travel of the centre of pressure when the incidence varies; the length of such travel is linked up with the wing chord Hence the change in trim or stability is, with such aerofoil sections, greater with large-chord wings. On this consideration of fore-and-aft stability and control, designers had some justification for their decision against experimenting with disc wings. discisio aerofoil sectors ed already been used in fishe while had practically no travel of the centre of pressure and hence did not suffer from this disadvantage of the disc wing. The whole argument, however, lost its importance imme- diately M. M. Munk proved that very efficient aerofoil sections could be designed with a completely (or nearly so) stationary centre of pressure. It is, therefore, right to say that from that time all conditions existed for a practical evolution of disc-wing aeroplanes. F. Handley Page converted an aerofoil, leaving an aspect ratio of 6.25, into six square-aerofoil portions by five slots. each parallel to the chord of the wing. By so doing he hoped to have the low drag of a normal wing combined with the high stalling angle of the disc-type slight improvement wing Although a very was claimed, the principle was that of eating the cake and having it too: the induced drag is respon- sible for the stalling properties of the disc wing and you cannot have the benefits of the high drag without suffering its disad- vantages. Moreover, in order to have the effect of the disc wing, the provision of mere slots is insufficient. vortices need room to deploy On the whole, however, the idea proves that at least one practical aircraft designer had realized that there was some- thing in wings of abnormally small aspect ratio. There were other, although not quite as well thought out, antecedents of the disc-wing aeroplane. In the first soaring- flight competition on the Rhoen (1920), Friedrich Richter, a urly naval pilot of 20 stone or so, performed on a triplan lider with wings having an individua aspect ratio of far less than three. H. Hayden secured, in 1922, a patent for a rhom- boidal wing with an aspect ratio of nearly unity, claiming for such a shape high lift and good flying qualities. In 1925 he constructed a glider with a wing having an aspect ratio of only 2.25. The wing was nearly triangular in shape, with its apex leading, and a pronounced wash-out towards the tips (Fig. 12); no lateral controls were fitted. The tailplane with the elevator was fitted underneath the trailing edge at the Fig. 11.-Willoughby's " Delta 8" experimental monoplane of 1938. an observant student of laboratory could have noticed the extraordinary capacity of circular or square shapes and that at very high Yet, apart from a few broad-minded experimenters, no designer drew the conclusion that wings of such shapes promised safety practisad experience that Aying in the though it was known from " second regime,,Carly at the stall, was positively dang Pous. -Parker's " Spiral Dive"—-was attributed, in those days, to high incidences, and that most of the lightly loaded rectangular wings used at that period rendered the stall relatively innocuous. However, accidental stalling was then, as now, the cause of the majority of all And the nose dive following inadvertent stalls was well known to be of the most serious consequences. laboratory experiments on aerofoils of very small aspect ratio and the results were generously published (how closely secret they would be kept to-day!). Eiffel showed that the ratio of the resultant forces reached maxima for small aspect ratios and that slender wings gave the greatest drag at 90 degrees inci- . dence, whilst disc wings had then the least resistance of all. Riabouchinsky proved that the maximum lift with disc wings was reached at incidences of the order of 40 degrees, whilst with normal aspect ratios (exceeding a value of 4) the maximum lift took place at incidences of 12 to 14 degrees. only. their critical incidence disc wings gave a gradual decrease whereas wings of normal aspect ratio gave very abrupt and unsteady tests by Dines on flat plates in natural wind confirmed this information and that the cambered aerofoils as well was also proved (by Riabouchinsky). O. Foeppl showed from system- atic wind-tunnel tests that a square aerofoil behaves, in respect of its lift curve, in a remarkably different manner from one having an aspect ratio of 1.5, although wall interference and Reynolds Number may have somewhat affected the results of Later, Prandtl was eager to point out that his aerofoil theory did not hold for very small aspect ratios, and that, in fact, the induced drag of disc wings was less than the theory suggested. In spite of this, however, nobody seems to have heeded the possibilities implied and the " Battle of the Aspect Ratios" was decided in favour of slender wings. To be fair, it must be pointed out that there was one serious Fig. 13.—A French project of G. Abrial, 1929. Fig. 12.—Experimental Hayden glider, 1925. Span, 19.7 ft. : length, 13-85 ft.; wing area, 173 sq. ft. All-up. weight, No lateral control. stern of a fuselage. Flying experiments in Styria were said to have proved satisfactory flying qualities. Some early tailless aeroplanes, such as certain expérimental types of Rene Arnoux, had rather stub wings and heavily reflexed (i.e., positively stable) aerofoil sections A 1929 design of G. Abrial showed an aspect ratio of 2.88. with, however substantial tip discs (which have the effect of increasing the aerodynamic aspect ratio) and wind-tunnel experiments indi- cated a creditable performance (Fig. 13). Russian attempts. in particular the parabola type of Tscheranowsky, too, were experiments with aspect ratios of three and even less (Figs. 14 and 15). Their resemblance in shape to the latest designs of super-sonic aeroplanes is remarkable. A Modern Pioneer Further interest in the aerodynamics of dise wings was displayed by research workers with the arrival of Juan de la Cierva's Autogiro. This was indeed something like a circular wing, and performance estimates were based on the properties of such wings. Yet the question of stalling stability did not arise, because of the rotor properties. research engineer of the Sare heal miner of the ation Advisor cole econ Committee for Aeronautics (N.A.C.A.), who proved independent lines of development. a capable of follow to In about 1930 Charles H. Zimmermann subjected the properties of disc wings to NND 927545

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MARCH 5, 1948 281 THE AEROPLANE wing structures as well as for the possibility of housing every- thing within a wing Hence there are very real design reasons for the preference of disc wings, quite apart from the eased accommodation of short-span aeroplanes. Some Remarkable Results Zimmermann established that the optimum aspect ratio was found between the values of 0.75 and 1.5. These values include both square and circular wing shapes. For a given wing section (Clark Y) the latter gave the highest lift coefficient, 1.85 at 45 degrees incidence, compared with a value of 1.24 at 14 degrees incidence for an aspect ratio of six. Furthermore, an important result was evidence that at an aspect ratio of unity (square or elliptical wings), and at an aspect ratio of 0.9 (wing with faired tips), no tendency to autorotation could be found A circular wing (aspect ratio of 1.27) indicated the possibility of autorotation (i.e., spinning) at incidences below that of maximum lift. The possibility of spinning before the actual stall is reached is, indeed, extra- ordinary. All these results refer to tests with the Clark Y aerofoil section. Less established was the contention that disc wings would give improved lateral and longitudinal stability at low incidences This seems still to be a moot point of the Flying Saucer. In Fig. 16, Fig. 17, and Fig. 18 some characteristic results of C. H. ZIMMERMANN'S TESTS (NACA TECHN. REP No 431 Fig. 14.—A Russian ' parabola' glider of 1924. extensive wind-tunnel investigation and the published reports still form development. the resulis confirm, qualitatively, the experiments made 20 years before. But, as mentioned earlier, these experiments had been practically forgotten. Zimmermann's target has been the development of a really fool-proof aeroplane for amateur pilots. It is no use hiding the fact that in nearly all accidents in which blame is attributed to an "error of judgment " on the part of the pilot, the aeroplane is actually at fault. The most common causes are the consequences of inadvertent stalling Once this is completely remedied, the overwhelming majority of accidents will become mere incidents or just fun, and instead of coroners and hospitals. aircraft manufacturers and repair shops will have the benefit. On such very sound lines (which seem to be generally acknowledged, but still far too often ignored). Zimmermann directed his main attention the stalling problem. He proved that small variations in the aspect ratio made profound differences and that the shape of the wing tips also had a great influence. At the same time he confirmed that the induced drag of circular or square wings is by no means as prohibitive as the simple theory of the "horseshoe" vortex line would indicate. He also proved that it was simply the induced drag due to the predominant influence of the marginal vortices which brought about the behaviour at high incidences; the idea that the provision of oblique slots might help in this connection proved. however, abortive. An advantage which Zimmermann's research brought to light was that disc wings gave less profile drag at smal incidences (high-speed flight). because of the reduction of thi relative thickness of the aerofoil sections. This drag reduction has indeed become one of the main reasons for disc wings being adopted for aeroplanes capable of flying at speeds at which the compressibility of the air needs to be considered For supersonic flight disc wings, seem, at present, to be a necessity. Alternatively, for a given aerofoil thickness ratio, he height available for structure and storage (power plants) is greatest within a disc wing; this makes for light and stifl LIFT CORERICIENT IP SHAPE CLARK Y SECTION 20° ANGLE OF INCIDENCE Fig. 16.-N.A.C.A. tests by C. H. Zimmermann which prove the extraordinary stalling qualities of disc wings. Zimmermann's wind-tunnel experiments of 1932 are given. It is seen from Fig. 18 that the difference between the incidence of maximum lift and the gliding angle at maximum lift (amax- a max) remains fairly independent of aspect ratio, and of the order of 9 to 13 degrees. This would mean that the attitude of the disc-type aeroplane, when flattening out, would not greatly differ from that of conventional aeroplanes. In particular, there would be no need to provide high under- carriages for disc aeroplanes as their gliding path is steep. This is an important difference from wings with leading-edge slots. In practice, however, the landing of disc-wing aeroplanes gives rise to undercarriage problems. As the induced drag increases rapidly with the reduction of flying speed, when the aeroplane flattens out prior to touching-down, the gliding angl steepens abruptly. This is particularly true of tailless designs and the result is a strong tendency to pancake to the ground as soon as the pilot flattens out. Thus to avoid the necessity of fitting undercarriages able to stand the strain of abnormally high sinking speeds, it has been found practical to land with power on. For a tailless aeroplane with an aspect ratio of three. M. B. Morgan found that, without flaps, the trimmed gliding angle at 160 m.p.h. was three degrees; it increased to 17 degrees at 126 m.p.h.. while the stalling speed was 115 m.p.h. pronounced steepening of the This between the aeroplane and the proposition. lidi helicopter akes attracer an attractive Fig. 15.-A ' parabola' aircraft by B. I. Tscheranowsky. Another peculiarity of the disc wing established by Zimmermann was its sensitivity to the shape of the wing-tips NND 927545

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• THE AEROPLANE 282 MARCH 5, 1948 pseudo-circular and pseudo-square wings thus exhibit This also applies to the ground effect, l.e., the landing qualities. The provis.on or oblique nozzle- shaped slots at the tips yielded no useful results. square-cut tips were found to be a disadvantage, with respect to drag, as well as to other qualities. Later N.A.C.A. research by F. E. Weick and Robert Saundefs referred to aspect ratios of the order of 3 in connection slotted auxiliary Vevions flaps for the trim of tailless aeroplanes. This constituted the first investigation of what has known to-day as the " Delta i.e., the combination sweep-back with low aspect ratio. Such shapes are of special interest for aeroplanes capable of flying through the trans-sonic Zimmermann The results of Zimmermann's research that a number of otherwise quite respectable designers were tempted into experimentation with disc-wing aeroplanes. accordance with Zimmermann's views, all these designs were intended to be of the safety-first type of privately the early phase from the more recent interest in Flying Saucers. n 1934 Farman was stimulated into exis was seen in his wing with an aspect ratio of only 1.9. F-1020 monoplane which otherwise had a long fuselage with a conventional tail. It was said to have proved very stable in flight, but was not further heard of. parasol monoplane with a completely circular wing, a camber flap in the trailing edge and tested in the U.S.A. (in 1934), with indifferent results. shown in flight in news reels. At about the same time Raoul J. Hoffmann, of St. Peters- burgh, Florida, an eminent aeronautical engineer of Austrian origin (known as the first to prove-in 1913—that the ratio C//C, governs optimum climb and glide with minimum sinking speed, took up development of the disc-wing aeroplane. Hofimann's Flying Saucer was a tailless aircraft with an aspect ratio of slightly over 2. The first type was an ultra- light single-seater with 36 b.h.p. Later a side-by-side two-seater with an 85 b.h.p. Cirrus engine was constructed and flew well: the wing tips served as ailerons and the elevators formed part of the trailing, edge. aerofoil sections employed were N.A.C.A. M.6 basically, with N.A.C.A. M.l at the tips. Both are sections designed by. M. M. Munk. The former is a reflexed- camber section with a practically stationary, centre of pressure; the latter is symmetrical The central structure of the wing, the fuselage and the fin was of welded-steel tube; the wing had three spars. little two-seater was stated to fly well and to exhibit very good stability. seems, however, that the controllability, particular directionally, was not satisfactory. The vision from the cockpit must have been very restricted a moot point with all these designs. A speed range from 28 m.p.h. to 135 m.p.h. was claimed. The empty weight was given as 900 lb., and the wing loading was 5.5 lb./sq. ft. One remarkable characteristic observed during the flying tests of Hoffmann's aircraft was that, when coming in to land. the approach was steep: yet prior to the flattening out and just before touching down, the glide flattened. 120 I MAX D.MIN 100 MAX/ "O MIN - - - - - -- CLARK Y AEROFOIL SECTION (NACA REP. No 439) MAX UFT COEFFICIENT RATIO MIN DRAG COEFFICIENT 60 60° INCIDENCE AT MAX LIFT 40 40° GUDING ANGLE AT MAX. LIFT 20 INCIDENCE GLIDING ANGLE AR ASPECT RATIO (-b'%) Fig. 17.—These results from Zimmermann's wind-tunnel tests on disc wings (1932) clearly show the characteristics of low aspect ratio aerofoils. CR 25 FORCE RESULTANT AERODYNAMIC LD 2-0 - Trio —20 LIFT/ORAG OPTIMUM 15 -0 1-0 CLARK Y AEROFOIL SECTION (NACA ZIMMERMANN, REP. No. 431) LIFT / DRAG AR ASPECT RATIO (- b') 18.—Further results from Zimmermann's tests shown here also indicate the advantages to be gained from disc wings. contradict the experience referred to above, and it was attributed to a ground effect arising from the rake of the It is indeed reasonable to expect that the presence of the ground would affect the formation an extent which may markedly influence the behaviour of disc wings during take-off and landing. Hoffmann projected a pusher and a twin-engined version, but these types R. J. Hoffmann and C. L. Snyder at South Bend, Indiana. wing shape was very similar. It resembled a semi-circle flying with its straight side as the leading edge; to this wing, ailerons corresponded to that of the previous Hoftmann type: serofoils with little centre-o -pressure travel were used. Again, The latest type had its tailplane and elevator separately located over the wing trailing edge (similar to plane " of De Rougé). It seems that the longitudinal control at certain incidences was not satisfactory. The ailerons which formed part of the wing shape and reduced the aspect ratio to a value of 1.75 had a triangular shape and were greatly skewed (taking into account the oblique flow over the wing The engine was a 70 b.h.p. Le Blond radial; a tricycle undercarriage was fitted. With the pilot alone, a gliding, speed of 23.5 m.p.h. was recorded (the gliding angle of 21 degrees was measured, with a sinking speed undercar per second, hath eng be accome slated by he maxy undercarriage without flattening out of the glide. mum speed was 86 m.p.h., and the take-off was stated to require 5 secs. in zero wind. Several more Arup types seem to have been constructed and flown during 1935, The flying qualities were praised- gliding angles of 1:2.6 being quoted- performance figures sounded extremely good. Yet, for reasons never disclosed, the production stage was not reached and the development ceased abruptly. It is worth noting that Charles Zimmermann himself has taken no part in this development, was an interested spectator at demonstration flights with an Arup monoplane at Langley Field. An Italian " Tortellino" At the time of the Arup development (1934), F. Piana Canova, an Italian, began to embark on a development for a tailless aeroplane with a low aspect ratio. In May, 1935, he secured patents for a rhomboidal wing, one diagonal of which coincided with the direction of flight. be located at the lateral apices, elevator and rudder at the rear apex, while the airscrew was in front of the leading apex. Another patent related to bi-convex aerofoils with ducts and control valves for the pilot, enabling the latter to neutralize the negative pressure on the forward ventral surface when at negative incidences. The latter patent was, apparently, never submitted to flight experiments. (To be continued.) NND 927545

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MARCH 19, 1948 337 THE AEROPLANE The Biology of the Flying Saucer-III By A. R. Weyl, A.F.R.Ae.S. Previous articles in this series appeared in " The Aeroplane" for February 13 and March 5 Wot live Canov pries erecrade in Turin avid at Rome of five Canova projeets (described in the previous instal- ment of this article). It is interesting to note that the Canova dise-wing types did not make use of reflexed-camber aerofoils. Stability and trim could, therefore, be secured only by an upwards delection of enlarged clevators. Early in 1935, an'open glider of the constructed 15 Minen end Mhe "Zocali" tpe was successful flights with it. (with the enlarged elevator) be performed. motion was experienced; turns were of question- able steadiness. In this respect, insufficient damping in and yaw are With winch-launching, reached altitudes of 600 ft. On the basis of this design, a light aeroplane was developed and the Italian Government financed the construction of two larger experimental aeroplanes, including one A fatal accident described as reflecting on the technical merits of the design. authorities to minds and to Fig. 19.—An American " Flying Flapjack" with two engines. It crashed while under test (1938). A Return to Childish Things Aeroplanes with a long, deep tail affixed to a small-span wing form a development of the low-aspect wing in another direction. Although the overall aspect ratio is low with such system is not that of a disc more akin to primitive an arrangement, the winkites or, better, to the paper dart of our school days which, as we may be able to remember with some mental effort, exhibited quite remarkable flying qualities and made better use of our school books than we ever expected. A representative of this aboriginal type is shown in Fig. 19. It crashed during the first tests (which would not seem very surprising in view of the arrangement of engines and airscrews). Another less eccentric arrangement was the French Payen single-seat racer of 1935. This was a daring experimental type with a 400 b.h.p. radial engine. An improved type, this time more reasonable—a 70 b.h.p. light aeroplane-was constructed in 1936. To a very small, conventionally tapered wing, a large triangular tail was fitted; the wing alone had lihedral, and the overall aspect ratio was about 1.76. No lights have been reported o1 one of these Payen aeroplanes. but take-off attempts with the second suggested that with the small span the torque reaction of the airscrew cannot be adequately dealt with. A third design (in 1938) the " Flêchair" single-seat fighter project, therefore. incorporated two coaxial counter-rotating airscrews driven by two 100 b.h.p. engines mounted in tandem in the long fuselage. The pilot's cockpit was located at the root of the fin, and a single-track undercarriage was adopted. There were, however, far too many untried features in this unusual design to make it a serious proposition. Nothing more has been heard of Payen's efforts. The modern characterized phase of the by Flying Saucer aeroplane two distinct developments. One is is the helicopter-aeroplane, the other is the trans-sonic or supersonic aeroplane. Both have become unfortunately—-essentially military developments; the progress is hence shrouded in the usual pretentious secrecy (which implies that the potential enemy knows everything) while the work is gravely hampered by elaborate security precautions. The helicopter-aeroplane is not a novel idea. Many years ago, for (famous for his electrical experiments with high-frequency phenomena) secured a patent for a tailless aeroplane equipped with a large lifting airscrew permitting a vertical ascent. In 1921 Claud Dornier secured a patent for a conventional 100 Cl 100 G -120 8 120 • 100 100 LIFT COEFFICIENT (× 100) SQUARE WING 8 LIFT COEFFICIENT (X -60 - 40 20 DRAG COEFFICIÉNT (× 100). do Poet ort 80830986 ASPECT RATIO 1 SQUARE WING • D + 10 20 DRAG COEFFICIENT (x 100) Fig. 20.—Lift and drag of wings of different aspect ratio. (Left) Wind- tunnel results obta ned at Goettingen, in 1920; Goettingen 389 aerofoil with 10 per cent. thick- ness and square wing tips. (Right) A reduction of the results to aspect five. ratio an by of the Prandel Aerofoil Theory Thered of rage drag, shows that square aerofoil (aspect ratio one) does of not follow the theory. Its induced drag is less than dicted by pre- the "horse- shoe vortex" assump- tion. NND 927545

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THE AEROPLANE 338 120 100 80 LIFT COEFFICIENT (x ANGLE OF INCIDENCE (DEGREES) 8 aeroplane with take-off as helicopter (Brit. Pat. Spec. No. 161,948). Earlier still (in 1916), the German, F. Bendemann, a noted research worker on airscrews, conducted a secret development of an aeroplane with a large tilting airscrew capable of rising and descending as a helicopter. development of this air observation post was later discon- helicopter experiments by Th. v. Karman and Petroczy. experiments ' F. Bendemann found that hovering without forward movement could be achieved-when the power loading of the aircraft was With fighter aeroplanes, such low power loadings were already then being approached, and operational experience had indeed shown that certain single- seaters could, under favourable conditions, be held in attitudes approaching that of hovering (later the Fokker D.VII biplane, with a large airscrew, became renowned for this trick in air combat on the Western Front). Attempts to revive the project at a later date failed, and with the suicide of its promoter (who had gone into the Civil Service), all interest in the development Charles W. Zimmermann, mentioned earlier as stimulator of the disc wing, approached the conception of the helicopter basis of his results with low aspect ratio He secured basic patents and constructed during 1934-35, in the cellar of his. home, a man-carrying aircraft of This had a wing of only 7-ft. span, with two airscrews driven by two 25 b.h.p. engine trouble, no flights were made: the little aircraft showed, all the essential features of the present types, In 1937 he granted a licence for his patents to the Chance- Vought Aircraft Division of the United Aircraft Corporation n Stratfort, Connecticut, and joined this firm for the further development of his ideas. conception of the mysterious " Flying Saucers" has originated from this development. Zimmermann's intention may have been the development of a safety-first aeroplane for the private owner. The U.S. Navy, however, took an interest in the possibilities of the helicopter- aeroplane, and the work done at present is purely for military In 1942 a low-powered flights and proved that the ideas underlying the design were he principle is that, at high speed and when cruising, th aircraft shall fly as an aeroplane, hovering it flies as a helicopter. Hence the airscrews are at the same time rotors and must have a rather large diameter. With the V-173 the problem of the prone position for the pilot was studied. and there is reason to believe that the latest types have adopted this feature. A further step towards the realization of a naval gun-spotter and a lighter for use from aircraft carriers has been the Chance- Vought XFSU-1 single-seater (1946), for which a speed range from 40 m.p.h. landing llows the V-173 model. February 13Seneral, it 1 The aspect ratio of the wing is less than unity. speaking, however, it is not a genuine tailless aeroplane because of the attachment of a trimming elevator to both sides of the wing. The reason for such excrescences is the need to locate MARCH 19, 1948 120 8. 100 80 ASPECT RATIO • (SQUAR 60 40 D+ 0 • ANGLE OF INCIDENCE ( DEGREES, +- 20 Fig. 21. - Lift curves of aerofoils of different aspect ratios. (Left) Wind -tunnel results obtained, in 1920, at Goet- tingen, with Goettingen 389 aerofoil and square tips. The absence of stall at normal incidence is in evidence, for aspect ratios up to a value of two. (Right) Reducing the values, by the Prandtl theory, to an aspect ratio of five, shows wings of that very small aspect ratio do not follow the theory in respect of the induced- Incidence correc- tion. control organs directly in the slipstream of the paddle-like airscrew rotors. too, are in the slipstream. Unlike the V-173 type, the XF-SU-1 has an all-moving tail surface and the undercarriage is retractable. This interesting hybrid has a modern metal structure. Pratt and Whitney R-2000-2 engines of 1,350 b.h.p. each (at ,700 r.p.m.) are mounted within the wing, entirely buried anc Water injection for temporarily boosting the power is one of the engine features. A special problem was the design of a transmission gear whis alla sessio tons to bodin engine lither of there fines this is a necessity in case of an engine failure. bladed rotors are contra-rotating so that there is no residual torque and are geared down to about one-fifth of the engine speed, hence their substantial diameter. The wing loading is rather high, reaching the order of 40 lb./sq. ft. The Real Flying Saucer ? Since this experimental type was produced, further progress has been made in the development. It seems that axial-flow gas turbines have been installed, and it is quite possible that a combined propulsion with thermal jet and airscrew With this, for slow flight (take-off, climb and landing) the rotors are driven by the gas turbines, while at high speed the rotors are declutched and feathered and pure jet propulsion is used. This would, incidentally, ZERO LIFT PROFILE DRAG COEFFICIENT AT 0-008 0-006 FLAT PLATE -- SQUARE TIPS ROUNDED TIPS NACA 24 SECTIONS RN - 2-7 × 10% DVL. TESTS T/C 0-04 0-08 0-12 0-16 AEROFOIL THICKNESS RATIO 0-20 - 0-24 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).

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MARCH 19, 1948 339 0•3 Cop 0-2 RN e -0-43x10% THE AEROPLANE M. B. Morgan has recently communicated the following values for the limit of stability at the stall from this graph:— Upper limit of the Angle of Sweep-back (referre‹ o the & chord) beyond which self-stall can be expected Aspect Ratio Required Degrees 651 FLAT PLATE T-O 0-05 0-01 T/C 0-4 0-5 0-6 THICKNESS RATIO 0-7 0-8 09 Fig. 23.—Increase of zero lift profile drag with thickness ratio of symmetrical aerofoil section. The saving in profile drag is one of the advantages of disc wings because of their thinner aerofoil section. (Data from Gerber, Zurich Report No. 6). explain Saucers the extraordinary ability of the reported " Flying " to be able to fly very fast and high, and also to hover, ascend and descend with practically no forward speed. other aircraft is known to do that. On the other hand, it is inconceivable that whole squadrons of such unconventional aircraft could already be observed at air exercises. for military developments to progress as quickly as all that. For operation with gas turbines a speed range from zero (i.e., hovering flight) to more than 500 m.p.h. has been claimed for the Chance-Vought-Zimmermann helicopter-aeroplane. Technically, there is little reason to doubt that such an amazing speed range can be attained with the combination power plant mentioned Incidentally, as there is not as yet a standard term for the combination of an aeroplane with an helicopter, " helicoplane The other line of engineering approach which has led to the disc-wing of near-saucer appearance from the trend towards very high flying speeds within the sonic range of velocities, and in particular, at great altitudes. As now commonly realized, the compressibility of the gaseous medium sets a speed limit for conventional aeroplanes. reached when the speed of flight approaches sufficiently to the velocity at which sound is propagated through the air. " acoustic velocity" depends solely on the air temperature. is, therefore. lower at altitude. compressibility effects begin to be felt at lower speeds when flying at altitude * shock stall, due to the compressibility of the air, sets in, the lift is catastrophically decreased (hence the justification for the expression " shock stall "), the drag rises to enormous longitudinal stability is grossly impaired by a rapid backwards shift of the aerodynamic centre as well as by fluctuations in the flow pattern at the wing. experience of phenomena of such distressing nature has given to two distinct aims in aeronautical rose la te dist of the phenomena to higher Mach Numbers; the other aim is to find wings which would permit flight within or through the trans-sonic regime. The alternative. through.' is still a necessary impediment of definition, since we do not know yet if stable, steady possible within the trans-sonic regime (extending from about 0.8 to 1.2 Mach Number) while there is certainly that beyond this trans-sonic regime, i.e., within the supersonic regime, stable, steady fight can be predicted. Two simple means have become known which delay the occurrence of the " shock stall" until much higher (but still leading either as sweep back or as sweep forward. Farnborough discovery of nearly 30 years ago, when high top speeds of airscrews were investi- gated-is the adoption of very thin aerofoil sections. latter leads. as we have pointed out already, straight to aerofoils of low aspect ratio when. for reasons of structural stiffness. a certain wing thickness is required. In the discussion of the " Stalling Characteristics of Tailless Aeroplanes shown AEROPLANE for April 25. that at low speeds. during take-off and landing. swept-back wings suffer from the disadvantage of instability at the stall. With pronounced sweep-back, swept-back wings of normal aspect ratios exhibit the vice of " self-stalling." due to premature tip stall. It was also shown that this vice can be remedied by reducing the aspect ratio, and a curve based on extensive wind-tunnel tests (THE AEROPLANE for July 11. 1947. p. 47, Fig. 8) proved that there is a aspect ratio and angle of sweep-back in this connection. It is thus advisable to. sweep-back with low-aspect ratio when safe stalling is required. Considerations of high speed lead to a similar combination, since both features tend to as a result, the rare case of two quite different aspects of an engineering problem pointing to an identical solution been the development of ; more or less triangular. disc wings, termed " Delta- are trespassing into the wings is that when the shock stall occurs, the backward shift of the centre of pressure is less than with induced drag does not count quantitatively at these high speeds. Development of such abnormal aeroplane types began in Germany during the War, following the progress accomplished in jet and rocket propulsion since 1937, which had shown that was a practical proposition. experimental delta-wing types had been brought to initial flying tests when the War came to a close. The German development had two distinct aims, resulting in two separate lines of approach. The immediate target neces- sitated by the Allied bombing raids, was the creation of very fast jet fighters or fighter-bombers which could surpass in speed even the Me 262. Secondly, there was the long-term develop- ment of a supersonic aeroplane capable of flying over very long such as from Europe to America and back, and dropping a bomb or two on the way. It is perhaps not too fantastic to surmise that this development had some connection with the research on atomic bombs and bacteriological warfare instituted by the Hitler Gang. placed with enterprising laced which enterprising gers, nora bly with the orien brothers and Messerschmitt (both pets of the Reichsluftministerium), with the Gotha Works, Henschel, Junkers, Heinkel and Arado (a Government enterprise), etc. In order to facilitate experiments with rather unusual aircraft types and to enable an exchange of ideas and experiences, a special research aerodrome was built at Oranienburg (near Berlin) with all facilities for flight testing (in particular, very long wide runways and repairs and modifications were provided). under the command of a capable technician, Lf.-Col. Knemeyer. On this aerodrome, all the initial and development tests with novel prototypes had to be made. When the Russians collected the aerodrome, they were agreeably surprised to discover some of the most progressive aircraft ever constructed. It has since become certain that they have made intelligent use of this aero- nautical treasure as well as of the technicians collected then and interested in the develop- ment, at least one, the well-known Junkers works at Dessau, has been completely transferred to Russia, lock, stock and barrel. Most of the scientists and designers were urged to volunteer for development work in Russia. Few could afford to refuse. among the interceptor were the following:-One at Oranienbur orten tailless delta-wing, which had been damaged during tests and was undergoing repair; another Horten tailless jet-fighter was just ready for its first tests. There was also the latest version of the Lippisch-Junkers development of the Me 163-C: design; an experimental Gotha, and several research gliders. Hitler's Last Secret Weapon The German long-term development of an aeroplane capable of reaching truly supersonic speeds discarded the It was based on the ram-jet or aerodynamic pro- pulsive duct (* Athodyd")-the simplest engine ever invented. The ram-jet, a widely discussed invention by the genial Réné Lorin in 1912, had been experimented with in Germany, notably by the Austrian Eugen Saenger (for whom a special laboratory built by the German authorities in 1938), by Otto abst. of Focke-Wulf nade by Alexander Lippisch (formerly known as an eminent sailplane designer and research worker on tailless aeroplanes). progress had been made with the combustion of solid fuel in Such fuel took the form of solid blocks of specially prepared coal which lined the walls of the duct. ment had been perfected by the German Research Institute

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