Following the mixed success of the earlier
Monospar family of aircraft, the company designed a ten-seat light transport, the
ST-18 (later named
Croydon). Due to the longer-span wing, it was not a cantilever
monospar wing but had to be fitted with bracing struts. The ST-18 was a low-wing monoplane, with a conventional tail unit and tailwheel landing gear, and hydraulically retractable main gear. It was powered by two
Pratt & Whitney Wasp Junior radial engines mounted on the wing leading edges. It had a crew of three, and a cabin for ten passengers, a toilet and baggage compartment. ==Operational history==