Napier Lion W-12 Engine

Type: Reciprocating, W-type, 12 cylinders, liquid cooled

Power rating: 336 kW (450 hp) at 1,925 rpm

Displacement: 24 L (1,462 cu in)

Bore and Stroke: 140 mm (5.5 in.) x 130 mm (5.13 in.)

Weight: 389 kg (858 lb)

With an industrial history dating to the early nineteenth century, D. Napier and Son began building aircraft engines in the World War I era. Napier began work on a remarkable new engine, the Lion, in 1916. Its three banks of four cylinders formed a "W" or "Broad Arrow" configuration. The arrangement provided a much shorter crankcase, a stiffer and simpler crankshaft, and a more compact engine than the 12-cylinder "V" construction of other high-performance engines of the period. Napier produced the reliable and widely used Lion series from 1917 until 1932 for military, commercial, and special-purpose racing aircraft.

This early version of the Napier Lion is believed to be a Model II or IIB. Napier manufactured these models from 1918 through 1925 to power many British aircraft types, including the Handley Page H.P.15 V/1500 bomber, Supermarine Sea Lion I racer, and the Felixstowe F.5 flying boat.