American biplane military training aircraft in use 1934 through WWII
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. 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 &amp; 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-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-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-18A Six PT-18s modified with blind-flying instrumentation.
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.
Up to 61 Model 73B1 delivered, powered by Wright J-5/R-790 Whirlwind radials
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 designation for prototype, powered by Lycoming radial engine, designated XPT-943 for evaluation
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 built
;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 built
(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.
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.
Designation assigned to the X70 evaluated at Wright Field
Name used for aircraft in Royal Canadian Air Force service
 Single-seat agricultural conversion of Model 75, fitted with new, high-lift wings
Brazilian Air Force Model A75L3 and 76.
Royal Canadian Air Force received 301 PT-27s under Lend Lease.
Republic of China Air Force received 150 PT-17s under Lend-Lease, and 104 refurbished aircraft post war in Taiwan. The ROCAF used them until 1958.
Colombian Air Force
Imperial Iranian Air Force
Israeli Air Force purchased 20 PT-17s.
Mexican Air Force
Nicaraguan Air Force
Paraguayan Air Force
Peruvian Air Force
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.
Specifications (PT-17).
"Data from" United States Military Aircraft since 1909General characteristics* Crew: 2* Aspect ratio: * Airfoil: * Propellers: 2-bladed fixed-pitch propeller
Performance* Endurance: * g limits: * Roll rate: * Time to altitude: in 17 minutes 18 seconds
Armament
In popular culture.
An iconic movie image is a Stearman cropduster chasing Cary Grant across a field in "North by Northwest" (the airplane that chased Grant was actually a Naval Aircraft Factory N3N Canary; the plane that hits the truck is a Stearman).
A heavily modified PT-17 variant was used as the Tornado in the Sonic The Hedgehog 2 Film.
See also.
Aircraft of comparable role, configuration, and era
References.
Notes.
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Videography.
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