![]() Having become recognised as a designer of military aircraft, following the supply of Model 15 to both the US Army (PW-9) and US Navy (FB-1), the company designed the Boeing Model 21 to meet a US Navy requirement for a primary trainer. This was an equal-span biplane, incorporating an unusually wide wing centre-section, and introduced N-type interplane struts to eliminate wing incidence-bracing wires. The divided-axle main units of the tail-skid landing gear had rubber bungee shock absorbers, plus provision for easy conversion to operation with floats. The pilot and pupil were accommodated in tandem open cockpits. Power was provided by a Lawrance J-1 radial engine. ![]()
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