Despite a Napier petrol-motor dirigible balloon design of 1902, it was 1918 before Napier seriously entered the aero engine market with the advanced 12 cylinder “Lion II” broad arrow engine of 450 bhp. This largely aluminium alloy, water cooled, double overhead camshaft engine with 4 valves per 2 litre cylinder, was developed for a 20 year period during which it powered over 150 aircraft types, both civil and military worldwide. The Fairey III D and F aircraft types for example served the RAF and RN squadrons for bombing torpedo and reconnaissance duties in between 1920 and 1935. Squadrons of Vickers “Virginia, Vernon and Victoria” heavy aircraft provided military transport in many parts of the globe.
Winning the Schneider Trophy for Great Britain in 1922, a 500 bhp Supermarine “Sealion” flying boat, Napier went on to develop the ”Lion” to give 900 bhp output for the 1927 Schneider race won by a Supermarine “S5” seaplane at 281.6 mph. When supercharged to give 1350 bhp the aero “Lion” briefly took the world air-speed record in 1929 in the lovely Gloster VI “Golden Arrow” floatplane at 336mph.
Always innovative in its aero engines Napier, through the designs of Major Frank Halford produced an “H” configured series of engines from 1930. The 3 types produced differed in their 4-stroke valve. The 16 cylinder “Rapier” of 390 bhp had push rod operated overhead valves, the 24 cylinder “Dagger” of 1000 bhp double overhead cam valves, while the 24 cylinder water cooled “Sabre” developed to 3000 bhp had skew gear driven sleeve valves. This engine powered the fast “Typhoon” and “Tempest” fighter bombers of the WW2 D-Day offensive as well as in defence against the “V1” flying bombs at home.
It was in powering gas-turbine helicopters that Napier took the lead after WW2. The 2 free-turbine “Gazelle” engines in the RAF Bristol “Belvedere” twin rotor machine and the Westland “Wessex” series for the RN anti submarine and air-sea rescue squadrons. Two special 3500 bhp “Eland” turbo prop engines powered the 44 seat Fairey “Rotodyne” which took the helicopter speed record in 1957. The same year Napier “Scorpion” liquid-fuel rocket booster engines were tested in a “Canberra” bomber which gained the world altitude record at 70,300 feet.