Designed by Mac Short and Jack Clark, one prototype of the 1933 Stearman 70 aka X-70 (Model XPT-943) was built, registered NX571Y with ATC 2-516.
The design was essentially based on the Model 6-A, retaining the same basic proportions and had a similar fabric-covered welded-steel fuselage and fabric covered wooden wings. Differences included a rounder fuselage, with the addition of aluminium-frame stringers, as well as more rounded wingtips and tail.
New features incorporated included pilot-controlled trim tabs on the elevators and single-strut landing gear.
Designed and built in 60 days, 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.
The Model 70 evolved into Model 73, 75, USN NS-1, and USAAC PT-13.
Engine: Lycoming R-680, 215hp
Wingspan: 32’2″
Length: 24’10”
Useful load: 692 lb
Max speed: 115 mph
Cruise: 90 mph
Stall: 45 mph
Range: 330 mi
Seats: 2
All Aero 