The Bristol Airplane Company is probably best known for its larger "sleeve valve" engines such as the 1675 h.p. Hercules which powered the four engined Halifax bomber and Lancaster Mk. II's. However, Bristol also produced the smaller Pegasus and Mercury engines which had "poppet" valves.

The Bristol Mercury has four valves per cylinder, an unusual number for a radial engine. They are actuated by lifter rods and valve levers. Mercury engines had a single carburetor and a gear driven supercharger.

Bristol Mercury XV's were used to power the Bristol Blenheim bomber, Westland Lysander, Blackburn Skua, and the Gloster Gladiator.