All About Helicopter engines  

Many turboprops, including the Pratt & Whitney Canada PT6, are also available in turboshaft form for helicopters, the PW&C PT6B. In most helicopters the engine incorporates a simple gearbox turning an output shaft at about 6,000 rpm. This is a speed high enough for the drive torque to be modest, so the shaft and drive casing can be quite light. But the main rotor gearbox of the helicopter reduces this speed to about 250-300 rpm, so that massive construction is needed downstream. In modern helicopters the engine installation is usually above the fuselage, with the jetpipe(s) turned out sideways.

Where the helicopter will encounter sand, dust and other particles it is important to fit a particle separator over the inlet. Military and naval engines are now designed with such a separator forming an integral part of the installation. In some the air is turned through large angles before entering the compressor, so that all solids, even minute dust particles, are flung outwards and extracted.

In the GE T700 the accessory gearbox drives a blower which acts as a vacuum cleaner, sucking out the extracted material. In the outstanding T800 engine the air merely makes a sharp inwards turn to reach the compressor, `over 97 per cent' of the particles going straight on to be collected in a surrounding box. Many Russian helicopters have simple hemispherical deflectors ahead of the inlets, while Sea King/Commando helicopters can be fitted with a plain flat plate which does little to protect the engine except in cruising flight.

Helicopter engine mro

Turbomeca is one of today's leading manufacturers of low- to medium-power gas turbines for helicopters. Turbomeca engine designs allow the company to produce, sell and support these turboshaft engines. Turbomeca helicopter engine support means manufacturing of turbomeca engine spares and Turbomeca engine overhaul and microturbo engine overhaul for auciliary power units APUs is done in the UK by Turbomeca UK.

Helicopter IRCM

Thanks to terrorism, even civil helicopters are often seen with infra-red countermeasures (IRCM) intended to defeat heat-seeking missiles. The simplest answer is to add a plain box round each jetpipe so that the missile cannot `see' any hot metal. For something closer to real protection, various kinds of 'suppressor' are in use, most having the form of a large box which entrains fresh air which mixes with the hot gas before being ejected upwards or downwards. For additional protection a pulsed IRCM beacon can be added, usually above the rear fuselage. The intense IR emission is pulsed, for example by rapid-acting window shutters like some lighthouses, and this confuses the missile and causes it to break lock.

Helicopter oil coolers

Helicopters have to be able to fly slowly or even hover for long periods. This precludes the usual use of ram air for cooling, and demands special provisions to prevent overheating of the engine compartment and engine auxiliaries. Some use can be made of the rotor downwash, but the vital oil cooler needs forced draught.

In a helicopter the lubricating oil has to carry away the waste heat not only from the engine but also from the entire high-power gear train from the engine and main-rotor gearboxes, and from the various bearings and bevel gears in the drive train to the tail rotor. This demands a large oil cooler with an engine-driven fan to pump air through at high velocity, no matter what the external aerodynamics might be. In some helicopters this fan absorbs 10 per cent of the power.