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.[1]
On 16 November 1935, the sole aircraft (T22, later G-AECB) first flew at Hanworth Aerodrome, piloted by Harry M. Schofield. It performed well, but did not attract any orders, so the aircraft was prepared to establish a record for an Australia to England flight. On 30 July 1936, Lord Sempill, Harold "Tim" Wood, and two other crew left Croydon Airport for Australia. On 7 October 1936, during the return flight from Darwin, navigation errors occurred during the flight over the Timor Sea, and the aircraft made a successful forced landing on a coral reef (Seringapatam Reef). The crew members were immediately transported off the reef by local fishermen, and the aircraft was abandoned.[1][2]
