Designed to Spec T.16/48, the P.115 was to have been powered by an Armstrong Siddeley Cheetah seven-cylinder radial engine, to replace the Percival Prentice. Boulton Paul drew up an alternative engine choice, using the new de Havilland Gipsy Queen 71 which was rated at 400 hp (300 kW), geared and supercharged. The P.115 would have had a top speed of 139 kn (160 mph; 257 km/h) and cruising speed of 122 kn (140 mph; 226 km/h), at 5,000 ft (1,500 m), climbing to 10,000 ft (3,000 m) in 10 minutes.
P.116
Boulton Paul also submitted the P.116 for T.16/48, powered by a supercharged 295 hp (220 kW) de Havilland Gipsy Queen 50.