With a displacement of 540 cubic inches (9 litres) the Mongoose had a maximum power output of 155 horsepower (115 kilowatts).

A Mongoose engine powers the sole remaining airworthy Hawker Tomtit, based at Old Warden.

The Mongoose is a five-cylinder, single-row, air-cooled radial piston engine.

[1] An unusual feature of the Mongoose is the vertical position of the lower cylinder, a design thought likely to promote oil fouling of the spark plugs.

Note:[3] An Armstrong Siddeley Mongoose IIIC powers the sole remaining airworthy Hawker Tomtit, K1786/G-AFTA, owned and operated by the Shuttleworth Collection this aircraft flies regularly throughout the summer months.