The Admiralty had ordered a special torpedo carrying biplane (the Sopwith Special torpedo seaplane Type C, serial number 170) in February 1914 and followed it with an order in July 1914 for three similar Type C floatplanes (serial numbers 157, 158 and 159). The specification called for folding wings, bomb gear, a gun and radio. Work started at the Sopwith factory at Kingston-upon-Thames on 5 April 1914 and the three Type Cs, powered by a Salmson (Canton-Uneé) piston engine, were completed by October. They went to RNAS Calshot for evaluation in November 1914. The Special, tested that July, had failed to lift a torpedo and the new Type Cs were little better, failing to take off under load: 157 could not get airborne with a Whitehead torpedo and the other two had similar poor performance. 158 was accepted by the service on 4 February 1915 but it sank following a forced landing a few days later on 8 February. The two survivors, 157 and 159, were withdrawn from service at the end of 1915.