The Saro-Percival Mailplane was a three-engined monoplane mail plane designed by Edgar Percival, and built by Saunders-Roe Limited (Saro) at Cowes in 1931, the aircraft first flying early in 1932.

It was a low-winged monoplane with a wooden wing[2] and plywood fuselage powered by three 120 hp (89 kW) de Havilland Gipsy III engines.

Starting on 15 June 1932, the Mailplane (G-ABLI) flew from Stanley Park Aerodrome (Blackpool) to Karachi, India taking a total of five days, 23 hours and 50 minutes.

Both the new Cruiser and the Mailplane were displayed at the first Society of British Aircraft Constructors (SBAC) Show at Hendon Aerodrome on 27 June 1932.

[9][10] One further development was the Spartan Cruiser III, with an aerodynamically-refined fuselage accommodating eight passengers, a modified windscreen and a trousered main undercarriage.

[11] Specifically, the aircraft possessed a greater than average aerodynamic efficiency and a particularly low minimum drag coefficient.

In such a configuration, the aircraft could achieve an endurance of six hours and a cruising range of approximately 700 miles, although the payload could be increased beyond this if the distance of the journey was shortened.

[13] The fuselage, which was composed entirely of metal, closely conformed with the design principles present in the hulls of Saro's series of flying boats, although this did not extent to its shape.

The wing had a three-ply covering that provided considerable torsional stiffness; it was thickened and further stiffened at areas close to the fuselage to form a walkway to the cabin door.

Both the rudder and elevators were provided with horn balances while trimming of the tail was achieved via a screw jack that was operated by a wheel in the cockpit.

The tanks were interconnected by large balance pipes; fuel pumps were used to supply each engine, feeding directly into their carburetor.

[4] The fuselage of a Cruiser III (G-ACYK) is on display at the National Museum of Flight, East Fortune, Scotland.

[19][20] Data from British Civil Aircraft since 1919,[4] National Advisory Committee for Aeronautics[21]General characteristics Performance