The Stearman (Boeing) Model 75 is an American biplane formerly used as a military trainer aircraft, of which at least 10,626 were built in the United States during the 1930s and 1940s.National Museum of the United States Air Force gives the figure 10,346 but this includes the equivalent airframes in manufactured spare parts. Stearman Aircraft became a subsidiary of Boeing in 1934. Widely known as the Stearman, Boeing Stearman, or Kaydet, it served as a primary trainer for the United States Army Air Forces, the United States Navy (as the NS and N2S), and with the Royal Canadian Air Force as the Kaydet throughout World War II. After the conflict was over, thousands of surplus aircraft were sold on the civilian market. In the immediate postwar years, they became popular as crop dusters and sports planes, and for aerobatic and wing walking use in air shows.
Design and development
In late 1933, Stearman engineers Mac Short, Harold W. Zipp, and J. Jack Clark took a 1931 Lloyd Stearman design, and added cantilever landing gear and adjustable elevator trim tabs, to produce the Model 70. Able to withstand +12g and -9g, the aircraft was powered by a 210-hp Lycoming R-680, first flew on 1 January 1934, before flight tests were conducted at Wright Field, Naval Air Station Anacostia, and Pensacola. The Navy then requested a similar model built to Navy specifications, including a 200-hp Wright J-5 engine. The resultant Model 73, was designated NS-1 by the Navy, of which 41 were ordered, including enough spares to build another 20 aircraft.
In the summer of 1934, Stearman engineers refined the Model 73 into the Model X75. The Army Air Corps evaluated the plane that autumn, powered by a 225-hp Wright R-760 or a 225-hp Lycoming R-680. In July 1935, the Army Air Corps ordered 26 with the Lycoming engine, designated the PT-13A, while the navy ordered an additional 20. In August 1936, the Army ordered an additional 50 PT-13As, followed by another 30 in October, and another 28 in December. Simultaneously, the company received orders for its primary trainer from the Argentinian navy, the Philippine Army Air Corps, and the Brazilian Air Force. In January 1937, the army ordered another 26 PT-13As.
On 6 June 1941, the U.S. government issued Approved Type Certificate No. 743 for the civilian version of the Model 75. Designated the Model A75L3 (PT-13) and Model A75N1 (PT-17), about 60 were sold to civilian flights schools such as Parks College of Engineering, Aviation and Technology, and for export.
On 15 March 1941, the company delivered the 1000th trainer to the Army, and the 1001st trainer to the Navy. Then on 27 August 1941, the company delivered the 2000th trainer to the Army. On 27 July 1944, the company delivered its 10,000th primary trainer.
The Kaydet was a conventional biplane of rugged construction, with a large, fixed tailwheel undercarriage, and accommodation for the student and instructor in open cockpits in tandem. The radial engine was usually not cowled, although some Stearman operators choose to cowl the engine, most notably the Red Baron Stearman Squadron.
Operational history Post-war usage After World War II, thousands of surplus PT-17s were auctioned off to civilians and former military pilots. Many were modified for crop-dusting use, with a hopper for pesticide or fertilizer fitted in place of the front cockpit. Additional equipment included pumps, spray bars, and nozzles mounted below the lower wings. A popular approved modification to increase the maximum takeoff weight and climb performance involved fitting a larger Pratt & Whitney R-985 Wasp Junior engine and a constant-speed propeller.
Variants Data from: United States Navy aircraft since 1911, Boeing aircraft since 1916 8,584 Model 70s, 75s and 76s were built, with additional "spares" bringing the number up to the sometimes quoted 10,346.
USAAC/USAAF designations The U.S. Army Air Forces Model 75 Kaydet had three different designations, PT-13, PT-17 and PT-18, depending on which type of radial engine was installed. PT-13 Initial production version with Lycoming R-680-B4B engine, 26 built in 1936 PT-13A Model A75 with R-680-7 engine, 92 delivered from 1937 to 1938. PT-13B R-680-11 engine, 255 delivered from 1939 to 1941. PT-13C Six PT-13Bs modified for instrument flying. PT-13D Model E75 with R-680-17 engine, 793 delivered
PT-17 Version with Continental R-670-5 engine, 2,942 delivered. PT-17A 136 PT-17s modified with blind-flying instrumentation. PT-17B Three PT-17s modified with agricultural spraying equipment for pest control near army bases. PT-17C Single PT-17 conversion with standardized Army-Navy equipment.
PT-18 Version with Jacobs R-755-7 engine, 150 built. Further production was cancelled as the engines were needed for other types of trainers. PT-18A Six PT-18s modified with blind-flying instrumentation.
PT-27 USAAF paperwork designation given to 300 D75N1/PT-17 aircraft supplied under Lend-Lease to the Royal Canadian Air Force. The last example built, FK108, had a canopy installed.
US Navy designations NS Up to 61 Model 73B1 delivered, powered by Wright J-5/R-790 Whirlwind radialsBowers 1989, pp. 252–253. N2S Known colloquially as the "Yellow Peril" from its overall yellow paint scheme. N2S-1 Model A75N1 with Continental R-670-14 engine, 250 delivered. N2S-2 Model B75 with Lycoming R-680-8 engine, 125 delivered in 1941. N2S-3 Model B75N1 with Continental R-670-4 engine, 1,875 delivered. N2S-4 Model A75N1 with Continental R-670-4 and -5 engines, 457 delivered of 579 ordered, including 99 PT-17s diverted from U.S. Army orders. N2S-5 Model E75 with Lycoming R-680-17 engine, 1,450 delivered.
Company designations Stearman 70 Company designation for prototype, powered by Lycoming radial engine, designated XPT-943 for evaluationBowers 1989, pp. 251–252. Model 73 Initial production version, 61 built for U.S. Navy as NS plus export variants Model 73L3 - Version for the Philippines, powered by R-680-4 or R-680C1 engines, seven builtBowers 1989, p. 253. Model A73B1 - Seven aircraft for Cuban Air Force powered by Wright R-790 Whirlwind, delivered 1939–1940 Model A73L3 - Improved version for the Philippines, three builtBowers 1989, p. 254. Stearman 75 (or X75) Evaluated by the U.S. Army as a primary trainer, the X75L3 became the PT-13 prototype. Variants of the 75 formed the PT-17 family. Stearman 76 Export trainer and armed version of the 75 with a gun ring and one or two fixed forward firing machine guns. A76B4 - 5 built for Venezuela. A76C3 - 15 built for Brazil. B76C3 - 15 built with cameras for Brazil. 76D1 - 16 built for Argentina and three for Philippines as BT-1. S76D1 - seaplane version of 76D1 for Argentina 76D3 - 24 built for Philippine Constabulary as BT-1 armed advanced trainer, and 24 built for Cuba.
Other designations Stearman XPT-943 Designation assigned to the X70 evaluated at Wright Field
Stearman Kaydet Name used for aircraft in Royal Canadian Air Force service
American Airmotive NA-75 Single-seat agricultural conversion of Model 75, fitted with new, high-lift wingsTaylor 1965, p. 178.
Operators
Argentine Air Force Argentine Navy received 16 Model 76D1s 1936 to 1937Bowers 1989, p. 268. and 60 N2S Kaydet post-war; all were retired by the early 1960s
Bolivian Air ForceAndrade 1979, p. 159
Brazilian Air Force Model A75L3 and 76.Andrade 1979, p. 158
Royal Canadian Air Force received 301 PT-27s under Lend Lease.Bowers 1989, p. 265.
Republic of China Air Force received 150 PT-17s under Lend-Lease,Bowers 1989, p. 262. and 104 refurbished aircraft post war in Taiwan. The ROCAF used them until 1958.Bowers 1989, pp. 260–261.
Colombian Air ForceAndrade 1979, p. 159
Cuban Air ForceAndrade 1979, p. 159
Dominican Air ForceAndrade 1979, p. 159
Hellenic Air Force
Guatemalan Air ForceAndrade 1979, p. 159
Honduran Air Force
Imperial Iranian Air Force
Israeli Air Force purchased 20 PT-17s.Nordeen 1991, p. 27.
Mexican Air Force
Nicaraguan Air Force
Paraguayan Air ForceAndrade 1979, p. 159
Peruvian Air Force
Philippine Constabulary Air Corps Philippine Army Air Corps Philippine Air Force
United States Army Air Corps/United States Army Air Forces United States Marine Corps United States Navy
Venezuelan Air Force
Yugoslav Air Force
Surviving aircraft
A considerable number of Stearmans remain in flying condition throughout the world, as the type remains a popular sport plane and warbird.
Argentina
308 – N2S-5 airworthy at the Argentine Naval Aviation Museum in Bahía Blanca, Buenos Aires.
Australia 75-6488 – B75N1 registered as VH-EYC, airworthy, owned by Steven Bradley, South Australia 5134 75-7462 - B75N1 - registered as VH-PWS, airworthy, owned by Michael Murphy, Royal Aero Club of Victoria. 75-8314 – E75 Registered as VH-USE, airworthy, owned by Raalin, Western Australia 6208
Austria 75-2606 – PT-17 Registered as OE-CBM, airworthy, Austrian Aviation Museum, Vöslau 75-230 - PT-13B Registered as OE-ABS, airworthy, Austrian Aviation Museum, Vöslau 75-5032 – PT-17 Registered as OE-AMM, airworthy at Hangar-7, Salzburg
Brazil K-132 – A75L3 on display at the Museu Aeroespacial in Rio de Janeiro K-210 – A76C3 on display at the Museu Aeroespacial in Rio de Janeiro 38010 – N2S-3 on display at the TAM Museum in São Carlos, São Paulo
Canada 41-8621 – PT-17 airworthy at the Canadian Warplane Heritage Museum in Hamilton, Ontario. 42-17456 – PT-13D owned by Daniel Jones of Lacombe, Alberta. 5284 – N2S-3 under restoration to airworthy with Daniel Jones of Lacombe, Alberta 5293 – N2S-3 owned by J. Kurtin of Collingwood, Ontario 30083 – N2S-4 on display at the Reynolds-Alberta Museum in Wetaskiwin, Alberta 61105 – N2S-5 with Bruce Bond of Sarnia, Ontario 75-3498 – PT-17 airworthy owned by Great River Aviation Ltd. of Whitehorse, Yukon o/a Klondike Airways. PT-17 airworthy at the Canadian Aviation Museum in Windsor, Ontario.
Colombia FAC-62 – PT-17 airworthy FAC-1995 – PT-17 airworthy
Czech Republic
75-3125 – former RCAF PT-27 airworthy at Tocna airport
Iceland T5-1556 – PT-17 airworthy with Erling Pétur Erlingsson in Hafnarfjörður, Capital Region. It is the oldest airplane in Iceland. It was brought to the country in 1941 by the aircraft carrier and damaged in an accident in 1943.
Indonesia PT-13D is on display at Dirgantara Mandala Museum in Yogyakarta. The aircraft is painted in Taloa Academy of Aeronautics livery.
Israel 2752 – PT-17 is airworthy at the Israeli Air Force Museum in Hatzerim.
Mexico EPS-6084 – PT-17 on static display at the in Santa Lucía, Zumpango.
Netherlands 75-7027 – PT-13B is airworthy, registered as PH-TOX, owned by Joe Brewer and based at Oostwold Airport. 75-7213 – N2S-3 is airworthy, registered as N9912H, owned by the Nordsiek family and based at Breda International Airport. 75-5864 – PT-13D Kaydet is airworthy, registered as N1944S based at Texel International Airport
New Zealand 75-647 – PT-17 airworthy with R. J. S. Jenkins in Ardmore, Auckland. 75-2055 – PT-17 airworthy with R. B. Mackley in Milford. 75-2100 – PT-17 airworthy with Classic Aircraft Sales Limited in Blenheim. 75-2724 – PT-17 airworthy with B. L. Govenlock in Hastings. 75-3132 – PT-17 airworthy with the Antonievich Family Trust in Pukekohe. 75-3655 – PT-17 airworthy with M. P. Cantlon in Mount Maunganui. 75-4245 – PT-17 airworthy with the Strome Farm Trust in Drury. 75-5064 – PT-13D airworthy with the Stearman Syndicate in Drury. 75-5907 – PT-13D airworthy with Stearman 03 Limited in Mount Maunganui. 75-8025A – N2S-3 airworthy with M. J. Dean in Mount Maunganui.
Peru PT-17 is on display at the Instituto de Estudios Históricos Aeroespaciales del Perú, Miraflores, Lima.
Spain PT-13 on display at the in Cuatro Vientos, Madrid. PT-17 on display at the Fundación Infante de Orleans in Cuatro Vientos, Madrid.
Switzerland