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Rolls Royce Gem Turbo-shaft Engine |  |
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Rolls Royce Gem Turbo-shaft Engine | |
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| Apart from the Napier Gazelle engine the Rolls Royce Gem is the only truly British helicopter engine. The engine originally known as the RS 360 was developed in the early 1970s for a new multi role Westland helicopter. The engine is a complex British answer to the Lycoming T53 or perhaps the GE T700/CT7, the engine is a three spool machine featuring mechanically independent HP and LP compressors and a power turbine. The engine is of modular construction consisting of seven modules, a reduction gearbox module, a turbine shaft module, a LP compressor module, an accessory module, a HP spool and combustion chamber module, LP turbine module and a free power turbine module.
The Gem is a magnificent self contained engine, the 510 engines with mechanical fuel controls are suitable for ground running as they are equipped with power turbine governors. The engine is equipped with standard tachometer generators for HP and PT spool speed measurement and the LP spool is equipped with a reluctance type magnetic speed probe. In addition to hydromechanical fuel controls an electronic protection unit monitors power turbine inlet temperature and LP spool speed, the unit has the ability to reduce fuel flow to keep the engine operating within safe limits.The output shaft speed of this engine is a useful 6000 rpm with a three spoke flexible coupling. The Gem 530 adopts a Hamilton Standard electronic fuel control system consisting of an engine mounted simplified hydromechanical control and an airframe mounted electronic engine control (EEC). The EEC accepts signals from sensors mounted on the engine and drives a stepper motor built into the hydromechanical control unit resulting in precise fuel metering under all engine conditions. Ground running of the Gem 530 without the EEC is tricky as there are no governors, limited control is possible by using the engine mounted power lever. A slightly unusual engine the Gem appears to have limited success and is not fitted to many different aircraft types. It is also an obsolete design, a possible similar replacement is the collaboratively produced RTM322 unit.
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| Rolls Royce Gem Turboshaft Gas Turbine Engine (Gem 510) |
| Power Output.....................900-1200 BHP (Depending on the Version) RPM...................................Nh= 43,400rpm Nl=37,600 rpm Npt= 27,738rpm LP Compressor...................4 Stage Axial with Bleed Valve HP Compressor..................Centrifugal Impellor Air Mass Flow.....................7.5 Lbs/Sec Overall Pressure Ratio.........12:1 Combustion Chamber..........Reverse Flow Anular with 17 Vapourising Burners Compressor Turbines..........1 Stage Axial each Power Turbine....................2 Stage Axial with reduction gearbox in the nose, output shaft speed 6164 rpm ratio 4.5:1 Layout................................Coaxial Shaft Three Spool with Accessory Gearbox, Modular Construction Starting...............................Starter Generator Ignition...............................Two Tourch Ignitors with High Energy Plugs Fuel System........................Gear pump with Hydromechanical or Electronic Fuel Controls, Electronic Protection System. Oil System...........................Return System with Pressure and Scavenge pumps, Engine Mounted Tank and Oil cooler Weight................................407 Lbs Applications........................Two in Westland Lynx Helicopter |
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Gem Plug "N" Play Control and Instrumentation Box |
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| It is possible to construct a control box for ground running the Gem 510 engine. The box is simply plugged into the wiring harness connector, the box provides monitoring instruments for all spools, EGT and controls for starting. A press-button contactor spools the engine up to light up speed and the throttle is slowly opened until light up occurs. A gentle increase in throttle position brings the engine to a cool safe 55% idle speed. Electronics inside the box monitor HP spool speed and automatically de-energize the starter generator at approximately 40%. Just plug and Play! Starting power is provided by two meaty car batteries connected to the box input. The PT governor is locked at the minimum position and the gas generator held at around 55%. |
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| Plug and Play Box: Gem engine at idle |
