| Nimbus | |
|---|---|
 | |
| Nimbus Mark 103 | |
| Type | Turboshaftaircraft engine |
| Manufacturer | Bristol Siddeley |
| First run | July 1958 |
| Major applications | Westland Scout Westland Wasp |
| Developed from | Turbomeca Turmo |
TheBristol Siddeley Nimbus, later known as theRolls-Royce Nimbus, was a Britishturboshaft engine developed under license byBlackburn Aircraft Ltd. from theTurbomeca Turmo in the late 1950s. It was used on theWestland Scout andWestland Wasp helicopters.[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.
In the Scout and Wasp the main rotor drive is taken from the front of thegearbox and is transmitted beneath the gas generator via a flexible coupling, while the drive for thetail rotor 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.[2]
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-caliperdisc 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.
Data fromFlight global archive[3] and[4]
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