The Model 70 first flew in December 1933 and was put forward as a contender for a USAAC contract for a primary trainer. Testing by the US Army and Navy took place shortly after this, and although pleased with the aircraft as a whole, they found the stall far too gentle for a military trainer. In order to remedy this, small spoilers (or stall strips) were added to the leading edges of the upper wings to make the stall more abrupt. Further testing followed before an initial order of 61 aircraft was placed by the US Navy in 1923. These went into production as the Model 73.
Model 73 Sportster civil production version of Model 70 flew first on November 26, 1934.
These were fitted with a 220hp Wright R-790-8 at the Navy’s request, with the US Navy designation NS-1.
Seven 1936 Model 73L3 went to the Philippines.
Seven of the 1939 A73B1 export version went to Cuba. They were delivered 1939–1940.
The Model 75 was powered by a 215 hp Lycoming and was designated by the military as the PT-13.
The Model 75 was soon replaced by the 220hp Lycoming R-680-7 powered Model A75, which became the PT-13A, B and C with the army, then in order to avoid a shortage of Lycoming engines the army requested the 220hp Continental R-670-5 be fitted in 1940. The repowered aircraft on to become the PT-17.
Three of the 1938 new production of L73L3 were built.
73 Sportster
Engine: 210hp Continental R-670
Wingspan: 32’2″
Length: 24’3″
Useful load: 915 lb
Max speed: 135 mph
Cruise: 115 mph
Stall: 45 mph
Range: 505 mi
Ceiling: 11,200′
73L3
Engine: 225hp Lycoming R-680-4 or R-680C1
A73B1
Engine: Wright R-790-8 Whirlwind, 235hp (175 kW)
Length: 25 ft 1 in
Height: 9 ft 7 in
Wing span upper: 32.2 ft
Wingspan lower: 31.2 ft
Max weight: 2699 lb
Ceiling: 12,200 ft
Max speed: 118 mph
A73L3
Engine: 235hp (175 kW) Wright R-790 Whirlwind
All Aero 