[1] The Nimbus is a turboshaft engine comprising a gas generator section, which consists of a three-stage compressor, (two axial stages and one centrifugal stage), driven by a two-stage turbine in conjunction with an annular combustion chamber, and a power output section consisting of a single-stage free turbine driving an output shaft via a two-stage reduction gearbox.

The fuel system is designed to control and govern the engine under all operating conditions and to provide safeguards against malfunctions, the pilot selecting rotor speed and the governing element automatically maintaining the rotor speed within close limits under varying conditions of load.

The lubrication system is self-contained, the oil tank being integral with the air intake casing.

Engine and helicopter accessories are mounted on a gearbox located on the air intake casing.

The Mark 103/503 is generally similar to the Mark 105/502 except that the former has a double-caliper disc brake incorporated in the output drive shaft to provide adequate braking of the helicopter's rotor in the high winds encountered over the deck of a fast moving ship, whereas the 105/502 has a single caliper unit.