Bristol 21a / Scout F.1
The problems with the Arab engine in the Scout F led to an investigation of possible alternative power plants, and it was decided to adapt the third prototype airframe to take a new 14-cylinder two-row Brazil-Straker (later Cosmos Engineering) Mercury radial of 347hp. Designated Scout F.1, the aircraft was first flown on 6 September 1918, and proved to possess an excellent performance, establishing new unofficial climb records in April 1919.
By that time, further development of the Mercury engine had been abandoned and no more work on the Scout F.1 was undertaken.
Engine: Brazil-Straker Mercury 14-cylinder radial, 347hp
Take-off weight: 1025 kg / 2260 lb
Wingspan: 9.03 m / 29 ft 8 in
Length: 6.09 m / 19 ft 12 in
Height: 2.54 m / 8 ft 4 in
Wing area: 24.15 sq.m / 259.95 sq ft
Max. speed: 233 km/h / 145 mph