The Bristol Siddeley Nimbus, later known as the Rolls-Royce Nimbus, was a British

turboshaft A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust ...

engine developed under license by Blackburn Aircraft Ltd. from the

Turbomeca Turmo The Turbomeca Turmo is a family of French turboshaft engines manufacturered for helicopter use. Developed from the earlier Turbomeca Artouste, later versions delivered up to . A turboprop version was developed for use with the Bréguet 941 trans ...

in the late 1950s. It was used on the

Westland Scout The Westland Scout is a light helicopter developed by Westland Helicopters. Developed from the Saro P.531, it served as a land-based general purpose military helicopter, sharing a common ancestor and numerous components with the naval-orientat ...

and

Westland Wasp The Westland Wasp is a small 1960s British turbine powered, shipboard anti-submarine helicopter. Produced by Westland Helicopters, it came from the same P.531 programme as the British Army Westland Scout, and is based on the earlier piston-e ...

helicopters.

Design and development

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. In the Scout and Wasp the main rotor drive is taken from the front of the

gearbox Propulsion transmission is the mode of transmitting and controlling propulsion power of a machine. The term ''transmission'' properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differe ...

and is transmitted beneath the gas generator via a flexible coupling, while the drive for the

tail rotor The tail rotor is a smaller rotor mounted vertically or near-vertically at the tail of a traditional single-rotor helicopter, where it rotates to generate a propeller-like horizontal thrust in the same direction as the main rotor's rotation. The ...

is taken from the rear of the 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.Rolls-Royce Nimbus Turboshaft Engine original brochure

Variants

The Nimbus engines were produced in two main variants, the Mark 103/503 and the Mark 105/502. The Mark 103/503 is generally similar to the Mark 105/502 except that the former has a double-caliper

disc brake A disc brake is a type of brake that uses the calipers to squeeze pairs of pads against a disc or a "rotor" to create friction. This action slows the rotation of a shaft, such as a vehicle axle, either to reduce its rotational speed or to hol ...

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. ;Blackburn-Turbomeca A.129: ;BnN.1 Nimbus: ;BnN.2 Nimbus: ;BnN.2/1 Nimbus: ;BnN.2/2 Nimbus: ;Nimbus 500: ;Nimbus 502: (Mk.105) :Nimbus 503: (Mk.103) ;Nimbus Mk.103: ;Nimbus Mk.105:

Applications

* Saunders-Roe SR.N2,

Hovercraft A hovercraft, also known as an air-cushion vehicle or ACV, is an amphibious Craft (vehicle), craft capable of travelling over land, water, mud, ice, and other surfaces. Hovercraft use blowers to produce a large volume of air below the hull ...

Specifications (Nimbus)

References

;Notes ;Bibliography * Gunston, Bill. ''World Encyclopedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989. {{Rolls-Royce aeroengines 1950s turboshaft engines

Nimbus Nimbus, from the Latin for "dark cloud", is an outdated term for the type of cloud now classified as the nimbostratus cloud. Nimbus also may refer to: Arts and entertainment * Halo (religious iconography), also known as ''Nimbus'', a ring of ligh ...

Design and development

Variants

Applications

Specifications (Nimbus)

See also

References