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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. He later 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 the U.S. 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 Forces 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.



Processing Information

Arranged and described by Roseann E. MacLean, 2004. Encoded by Amanda Buel, 2015.


Lenkowsky, Mandel




Leslie Lenkowsky, gift, 1989, 1989-0099, NASM


2.18 Cubic feet (2 records center boxes)


This collection includes notebooks containing scientific notes and mathematical calculations, a random assortment of journals and periodicals, published reference books, and a few advertising and promotional brochures all pertaining to American experimental military and commercial vertical flight from the late 1930s to the late 1940s. The collection also contains photographs of the following helicopters: Sikorsky XR-1, XR-4, YR-4, XR-5, XR-6, XR-6A, VS-300; Kellet XO-60 and XO-61; and Rotachute P-4. Also included are photographs of helicopters by Pitcarin, Landgraf, Greyhound Bus, Spratt, Berliner, Ochmichen, and DeBothezat.


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Collection descriptions

Archival materials




Arrangement note

The collection is arranged into the following series: Series I: Correspondence and Manuscript Notes Series II: Scientific and Mathematical Notes, Aircraft Drawings, and Published Works

Scope and Contents

The Mandel Lenkowsky Early Vertical Flight Development 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; and 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 Macmillan 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.






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Topics Periodicals
Sikorsky (USA) R-4 (H-4) Family
Sikorsky (USA) R-6 (H-6) Family
Sikorsky (USA) XR-6A
Sikorsky (USA) XR-6
Kellet XO-60 Autogiro
Sikorsky (USA) VS-300 Family
Kellet XO-61 Autogiro
Aeronautics, Military -- Research
Aeronautics, Commercial
Aeronautics, Military
Helicopters -- Flight testing
Sikorsky (USA) XR-5
Sikorsky (USA) XR-4


Mandel Lenkowsky Early Vertical Flight Development Collection, Acc. 1989-0099, National Air and Space Museum, Smithsonian Institution.

Archival Repository

National Air and Space Museum Archives

Finding Aid Online Finding Aid