Curtiss-Wright CW-20T

1940 civilian airliner prototype.

1 Commando tested by Curtiss-Wright

The CW-20T was a private venture by Curtiss-Wright aimed at the civilian market, and designed by Curtiss chief aircraft designed George A. Page Jr. It resulted from 25 letters of intent by various US airlines, which convinced the company to go ahead with the project. As one of the first pressurized, "sub-stratospheric", airliners of its time, it was a direct response to Boeing's 307 Stratoliner and Douglas' DC4E prototypes. The CW-20T featured a double-bubble fuselage, a new design aimed at better sustaining pressurization constraints, but the prototype was actually not pressurized. The engines were two 1,700-hp Wright R-2600B-17A 14-cylinder Twin Cyclones, a company design, which were deemed to be a more efficient solution than four smaller powerplants. They were equipped with full-feathering, three-bladed Curtiss-Electric C-533-D propellers, yet another company product. The aircraft initially featured a twin-tail empennage, but testing showed poor yaw stability and it was modified in early 1941 to a single tail.

Plans changed as the USA was drawn into World War II, and the USAAF ended up becoming the aircraft unique customer when it ordered 200 units as the C-46 Commando in September 1940 and purchased the sole CW-20T protoype as the C-55 in March 1941 for testing.