The power behind Air 9000

Defence has chosen its Additional Trooplift Helicopter; now it must choose between two excellent engines to propel it.
Engines are an important feature of any aircraft and helicopters are no exception. Various engine characteristics including fuel economy and maximum power output will have a great effect on the overall performance of the machine. Reliability is obviously crucial to prevent unscheduled contact with the ground, but the frequency and cost of maintenance will impact heavily on fleet availability and the overall price of ownership.

It follows then that deciding what type of engine should power your new fleet of troop lift helicopters is a move that would not be taken lightly. For the 12 new MRH 90 Additional Trooplift Helicopters it selected last year Defence has two options: the Rolls Royce/Turbomeca RTM322 or the General Electric T6E1 variant of the T700 helicopter engine.

The RTM322 has been selected by three of the four "home" nations of the European NH Industries NH90 maritime and tactical transport helicopter. France, Germany and the Netherlands have a requirement for up to 399 of the twin-engined NH90.

The RTM322 is a two-shaft engine featuring a three-stage axial and close-coupled centrifugal compressor driven by a two-stage gas generator turbine. The combustion system is a large-volume, reverse-flow annular type with vaporisers. A two-stage power turbine drives a coaxial shaft passing through to the engine front. The engine is controlled by a FADEC (Full Authority Digital Engine Control) system.

According to Turbomeca it was designed from the outset to suit a wide-range of military and commercial helicopter designs, but can also be employed in fixed-wing, maritime and industrial applications. The engine offers a variety of different drive configurations, a choice of three starting systems, and mission-specific options including a high-efficiency inlet particle separator and infra-red suppressor. A comprehensive helicopter health and usage monitoring system is also available, providing extensive engine self-diagnostic capabilities.

The RTM322 first flew in 1986 in a Sikorsky S-70C Black Hawk. It has since undergone successful US government-sponsored flight evaluation in a US Navy SH-60B, amassing over 1,000 hours of flight in the H-60 series of aircraft. The RTM322 offers a "drop-in" upgrade for the Black Hawk family of aircraft that according to Turbomeca offer cost, support and performance benefits. The RTM322 is also the alternative power plant for the Sikorsky S-92 helicopter.

The initial production order for the RTM322 to power 44 Royal Navy Merlin HM Mk1 helicopters was received in 1992, and the type entered service in 1998. The RTM322 also powers 22 EH101 HC Mk3 utility helicopters now being delivered to the Royal Air Force, and 67 AgustaWestland WAH-64 Apache attack helicopters now entering service with the British Army. Rolls-Royce Turbomeca has also been awarded a Ministry of Defence (MoD) tri-service support contract covering all three RTM322 applications in UK service.

The GE T700/T6E1 is being co-developed and will be co-produced by GE and Avio SpA of Italy. Avio SpA is responsible for 50 percent of the design and testing of the certification engines and will assemble and test the production engines for Italy's NH 90 helicopters at their Brindisi plant.

The T700 baseline engine was originally designed for the US Army's UH-60A Blackhawk. The US Army also chose two later versions, the -701 and -701C, for its advanced attack helicopter, the AH-64 Apache and for the UH-60L Blackhawk. A civil version of the baseline engine, the CT7-2, powered the Bell 214ST and the Sikorsky S-70, a Blackhawk derivative.

According to GE the T700/T6E growth engine retains the rugged, reliable and maintainable design features of its T700 predecessors while delivering over 2,500 shaft horsepower. They say a Full Authority Digital Electronic Control reduces pilot workload and enhances maintainability.

Existing ADF helicopters such as the Blackhawk, Sea Hawk and the Seasprites use version of the T-700 which, while different to the T6E series, offers an amount of commonality. On the other hand the RTM322 is in an earlier phase of its development cycle and is, so far, in much wider use in NH90 based helicopters than the GE offering

The choice of engine has been the subject of analysis by the Air 9000 industry team, an entity that includes Eurocopter and their subsidiary Australian Aerospace. No comment was forthcoming from any of the players though a common theme was that both are excellent engines and that the choice is up to the customer.

As this issue of ADM closed for press it was understood that a recommendation was with the Minister for Defence, Senator Robert Hill, and that a decision was imminent. The Minister is not a man to rush such issues but as an Australian configuration for the MRH 90 must be settled without delay if delivery schedules are to be met it is to be hoped that a decision has been made by the time you read this.

By Daniel Cotterill, Canberra