Boeing Stearman Model 75, part seven. The Stearman in America, part four. USAAC, USN and USAAF users

 

The Boeing Stearman Model 75 is an American biplane of which 10,626 exemplars were manufactured from 1934 until the mid 1940s. 
It served as a primary trainer for both the United States Army Air Forces (USAAF) and the United States Navy (USN) throughout World War 2. 

During late 1933 Mac Short, Harold W. Zipp and J. Jack Clark, engineers at Stearman Aircraft, took a Lloyd Stearman's design made back in 1931 and added cantilever landing gear and adjustable elevator trim tabs to come up with the Model 70, which was able to withstand +12g  and -9g forces. 
This initial Model 70 was powered by a single 210 hp Lycoming R-680 radial engine and flew for the first time on 1st January 1934, with additional test flights being performed later at Wright Field, Naval Air Station (NAS) Anacostia and NAS Pensacola. The performance pleased the USN and requested a similar model to be built under similar specifications, including a 200 hp Wright J-5 engine. This model was designated as NS-1 by the USN and 41 were ordered, with enough spares to build additional 20 machines.

In 1934 Stearman became a subsidiary of Boeing and therefore its aircraft were known as Boeing-Stearm. It was during the summer of that year when Stearman engineers improved the Model 73 (the internal denomination for the aforementioned NS-1) into the Model X75. This lead to the United States Army Air Corps (USAAC) to evaluate the plane that autumn. The Model X75 was powered either by a 225 hp Wright R-760 or a 225 hp Lycoming R-680. The USAAC accepted the model and ordered in July 1935 26 machines powered with the Lycoming engine, designated at PT-13A (PT stands for 'Primary Trainer') with the USN ordering twenty more. In August 1936 the USAAC ordered fifty PT-13As more with thirty more being ordered in October that same year and twenty-eight more in December. 

On 6th June 1941 the US Government approved the civilian version of the Model 75, designated as Model A75L3 (PT-13) and Model A75N1 (PT-17), with around 60 being sold to civilian flight schools such as Parks College of Engineering, Aviation and Technology, the export market and the many British Flying Training School Program across the USA.

This program was established at the beginning of World War 2, when the United Kingdom recognized the need to train a large number of pilots, so a large number of flying and aircrew training schools were set up across the British Empire and some neutral nations like the USA, where pilots could be trained without the risk of enemy interference. 

The British Flying Training Schools were also set up in the United States from 1941 onwards as a result of the Lend Lease Bill. Seven schools were opened (numbered from one to seven, two in Texas, two in Oklahoma and one in California, Arizona and Florida) and of those, at least five of them were equipped or had the PT-13A/PT-17 in their ranks at some point. 

On 15th March 1941 Boeing delivered its 1000th trainer to the USAAC and the 1001th trainer to the USN. Later, on 27th August 1941 the 2000th trainer was delivered to the USAAC. This feat was followed on 27th July 1944 when the company delivered the 10,000th primary trainer.

After World War 2, thousands of surplus PT-17s were sold to civilians and former military pilots. Many were modified as crop-dusters with a hopper for pesticide or fertilizer fitted in place of the front cockpit. Additional equipment included pumps, spray bars and nozzles placed below the lower wings. 

Sources:

1st https://en.wikipedia.org/wiki/Boeing-Stearman_Model_75

2nd https://en.wikipedia.org/wiki/British_Flying_Training_School_Program