Mandel Lenkowsky Early Vertical Flight Development Collection

National Air and Space Museum, Archives Division

Accession No. 1989-0099

NASM ref no. WF-149389

National Air and Space Museum
Smithsonian Institution
Washington, DC

Roseann E. MacLean

Biographical note

Mandel Lenkowsky was a civil and aeronautical engineer. He attended the Guggenheim School of Aeronautics at New York University from September 1933 until June of 1937. Subsequently he attended the School of Engineering at Princeton University from October to November of 1943. His post graduate work detailed the development of rotary wing aircraft. Lenkowsky was employed as an aeronautical draftsman at US Naval Air Station, Lakehurst New Jersey from February 1941 until June of 1941. In August of 1941, Lenkowsky was employed by the Army Air Forces (A.A.F.) Materiel Center, as a project engineer. Lenkowsky resigned from the Army Air Force at Wright Field in Dayton, Ohio, in October of 1944 to dedicate full time to the completion of his book on the development of the helicopter.

Scope and content note

The Lenkowsky Collection contains correspondence, manuscript notes, notebooks of scientific and mathematical notes, periodicals, and published reference materials about experimental, military and commercial vertical flight from the 1930s to the 1940s. The collection includes photographs of the Sikorsky XR-1, XR-4, YR-4, XR-5, XR-6, XR-6A, VS-300; Kellet X0-60 and X0-61, Rotachute P-4 helicopters, as well as the Berliner, DeBothezat, Greyhound Bus, Landgraf, Ochmichen, Pitcairn, and Spratt helicopters. The collection contains chapters from Mandel Lenkowsky's unpublished manuscript, The Helicopter, and his correspondence with Macmillion Publishing Company. The book was scheduled for publication in the summer of 1945. In his correspondence, Lenkowsky stated he would like to focus primarily on the development of the Focke helicopter (Germany 1934-37) and was trying to secure rights to mention it in his book. There is no evidence in the collection that Lenkowsky completed the book or that it was ever published. Series I Correspondence Manuscript notes Series II Scientific and mathematical notes Published Works (Government /Civilian) Books Newspapers/periodicals Reference materials Photographs Miscellaneous materials

Acronyms

CAA	Civil Aviation Authority
A.A.F.	Army Air Forces
A.S.M.E.	American Society of Mechanical Engineers

Series I: Correspondence and manuscript notes

This series covers correspondence between Mandel Lenkowsky and the military service and Macmillion Publishing Company regarding the possibility of publishing his manuscript on the development of the helicopter. The manuscripts appear to be unfinished works of Mandel Lenkowsky on the helicopter. The dates of this material range from 1941 until May 20 of 1945.
Box	Folder

1	1	Correspondence, Coast Guard and Selective Services 1941-1945
	2	Correspondence-Government Agencies: Civil Service, War Department, Navy, WMC, etc. 1943-1945
	3	Correspondence- Klemin, Summerill Tubing, Spicer Manufacturing Corp., Sikorsky (1943-1944)
	4	American Helicopter Society letter with membership list May 20, 1945
	5	Correspondence with Macmillion Publishing Company (1944-1945)
	6	Type written manuscript entitled: "Outline for Proposed Helicopter Book"
	7	Mandel Lenkowsky "The Helicopter Today: Its Background and Its Future" [1943
	8	"Helicopter Problems," "Early Helicopters," "Successful Helicopters," and "Sikorsky's Helicopters" [Lenkowsky?, unfinished chapters
	9	"Let's Take a Ride in the XR-4", "Types of Aircraft", "Preface", and "The How and Why" [Lenkowsky?, unfinished chapters]
	10	"Preface", "Ch. 1-Meet the Helicopter" and "Ch.2 The Mechanics of Flight", 1943 [Lenkowsky?, unfinished chapters]
	11	Miscellaneous notes and parts of publications regarding rotary wing aircraft
	12	US Congress, House. H.R. 10605 Public no.787, 75th Congress. Chapter 852. 3D sess., 6/30/1938 [authorizing funds for the development of rotary wing and other aircraft
		Pierre Faure "Thirty Years in the Service of Aviation; Louis Breguet" [1938?, translated 1944
		Comparison of Rotor "Outline of Report for Reeves", "Some Final Thoughts", [Lenkowsky?] 12/12/1944
		Gilbert Magill "Rotor craft" [with illustrations] n.d.

Series II: Other materials

This series contains scientific and mathematical notes, aircraft drawings, and published works. The published works are organized by aircraft model, then company or government institution. It also contains two poems written about the helicopter, photographs of the XR-1, XR-1A, XRG-XRGA, XO-6, Debothezat, Berliner, Ochmichen, Pitcairn, Landgrat, VS-300, Greyhound Bus, Sprah, Kellet XR-8 ,XR-4, XR-5, XR-6 also XR-6A, YR-4, YR-4B helicopters, military and civilian, personal photos. The photos are arranged by aircraft type, then chronologically.
Box	Folder

1	13	Project Record Computation Book, project record no. MX-245 [February 23, 1942-December 1943: XR-6 Engine, YR-4A, XR-8 Blades]

2	1	Project Record Computation Book, Project Record no.1 [March 29, 1943]
	2	Project Record Computation Book, Project Record no. 2 [October 27-29, 1943]
	3	Project Record Computation Book miscellaneous, [Rotary Wing Parachute, 6 pages dispersed]
	4	Mathematical notes, Sikorsky reports on helicopters and miscellaneous models [including: R-1A, R-4B, R-5, R-6A, XR-8, XR-9, XR-10] ca. 9/4/1941-2/2/1945
	5	Miscellaneous mathematical notes and manuscript notes written about the history of helicopters, rough drawing of a helicopter, drawings of airfoils, June 1945 [models including XR-4, XR-8, R-6A ,engine P-V XHRP-1, Focke 284, referencing several technical manuals
	6	Miscellaneous materials on limits of helicopter design, [Diehl, Bernett, and Howard, 1952]
	7	Helicopter Flight Demonstration; [VS -300, XR-4], 4/20/1942
	8	Flight Demonstration of the XR-4 Aircraft Project List for 1943, (4/27/1942)
	9	Army Air Forces Memorandum Report on XR-4, A.A.F.41-18874; (12/30/1942)
	10	Army Air Forces Memorandum Reports on YR-4B, A.A.F.42-107237; [12/7/1943 and 6/13/1944]
	11	Some Considerations of Roughness Experienced During Helicopter Flight, model YR-4A; 4/18/1944
	12	Flight Test Measurements of Stress and Motion of the Main Rotor Blades; Model YR-4A, 5/18/1944
	13	Army Air Forces Specification for A.A.F. model R-4B [10/2/1943: Sikorsky Aircraft Model VS-316-A-2
	14	Army Air Force Specification on A.A.F. Model R5-A; Information on Load Distribution for XR-5 (3/23/1944), Drawing of XR-5 Helicopter, Rotor Hinge locations 1944
	15	Army Air Forces Specification for A.A.F. Model R-6A; [1/10/1944]
	16	Sikorsky Aerodynamics Report Utility Cargo Twin Engine Helicopter; 5/17/1944
	17	Basic Instruction Manual for Army Pilots and Mechanics for model Y0-60 Aircraft. Report number 000.10 (8/7/1943)

3	1	Army Air Forces Memorandum Reports on Y0-60, A.A.F.42-13607; serial numbering-47-1668-A and addendum #1
	2	XR-1A Three view Platt-Le Page Aircraft Company 9/15/1941, 5x700
	3	XR-6, XR-6A Sikorsky Aircraft General Arrangement Drawing VS-06-01-1001, 9/16/1943
	4	XO-61 Autogiro Pitcairn three view drawing #7111, 8/11/1941
	5	Miscellaneous drawings of helicopters
	6	An Aerodynamic Analysis of the Autogiro Rotor 1934, Wind Tunnel Tests of a 10ft Diameter Gyroplane Rotor 1935; National Advisory Committee for Aeronautics
	7	The American Helicopter Society, Inc.- Semi Technical Bulletin No.1 May 1944, The American Helicopter Quarterly, Jan 1946
	8	Bibliography of Rotary Wing Aircraft US Army Air Forces 1945; Greyhound Looks Ahead to Integrated Air-Bus Service
	9	Contribution to the Aerodynamics of Rotating -Wing Aircraft, Dec 1939, Part I and II; G Sissingh,
	10	The Flight of Helicopter; H.B. Squire; Oct 1935 [pages are stuck together please do not photocopy]
	11	Journal of the Aeronautical Sciences, May 1942, April 1943, June 1943, Sept. 1936
	12	"Lectures on Rotary Wing Aircraft", Alexander A. Nikolsky Oct. 1, 1943
	13	National Advisory Committee for aeronautics Technical Note No.626, Static Thrust Analysis of the Lifting Airscrew by Montgomery Knight and Ralph A. Hefner, December 1937
	14	Notes on Helicopter Design Theory: A Series of Lectures Delivered March-April 1944 at Princeton University; Alexander A. Nikolsky (1944)
	15	Performance of Rotating Wing Aircraft, by K. Hohenemser, No. 871, July 1948 National Advisory Committee for Aeronautics [Ingenieur-Archive, Vol.8, December 1937]
	16	Physical Principles of the Helicopter. Lecture Notes by J.A. J. Bennett Department of Aeronautical Engineering, Princeton University, n.d.
	17	"Rotary Wing Aircraft: A series of articles", Aircraft Engineering [1/1940-8/1940] ; James A.J. Bennett
	18	Rotorplane Airworthiness (Part-06); Papers by Montgomery Knight and Walter Castles[1/29/1942]

4	1	The Story of the Helicopter by Devon Francis, 1946
	2	A Study of Auto-gyro Rotor Blade Oscillations in the Plane of the Rotor Disc by John Wheatley
	3	Transactions of the A.S.M.E, April 1939
	4	Various newspaper/periodical clippings concerning the helicopter [19]
	5	Four news articles on the early helicopter [1939-1945]
	6	Helicopter Poetry: "The Stump Jumper's Lament"; "The Hell Cop"
	7	Photographs Model X0-61, X060 and Rotachutes P-34 also photographs of Kellet Aircraft Corp. employees. Early 1940's
	8	Photographs, various group shots involved with the XR-5, X060 captions on back of some photos, YR-4B rotor and hub
	9	Photographs "Manny", XR-4, XR-5, XR-6 also XR-6A, YR-4, YR-4B Photographs ca.28 Mar 1945 [ 5-11-1942]
	10	Photographs XR-1, XR-6, XR-6A, Debothezat, Berliner, Ochmichen, Pitcairn, Landgrat, VS-300, Greyhound Bus, Sprah, Kellet XR-8