Better, cheaper engines: the Versatile Affordable Advanced Turbine Engines programme underlines the shift towards affordability in the minds of Pentagon planners

Interavia Business & Technology, March, 2002 by Nick Cook

Some bad news for Europe's aero-engine industry, acutely sensitive as it is to the merest suggestion of government subsidies for its opposite number in the US. The United States is preparing to launch a follow-on to the hugely successful Integrated High Performance Turbine Engine Technology (IHPTET) programme, a project widely credited with having maintained and sustained US market dominance in key sectors of the business over the past decade.

While IHPTET was focused primarily on performance, the priorities for the follow-on effort, the Versatile Affordable Advanced Turbine Engines (VAATE) programme, have shifted because affordability is now being given at least the same weight as performance in the minds of Pentagon planners. The shift is visible in the cost-driven specification of the F-35 Joint Strike Fighter (JSF) and in the growing number of unmanned aerial vehicle (UAV) and combat UAV (UCAV) programmes under study by the US Air Force and US Navy. VAATE will also read across into new commercial engine programmes at General Electric and Pratt and Whitney.

And there's the rub. Every time a government launch-assistance package is announced in Europe, America complains about it, accusing Europe of bending trans-Atlantic trade laws by funding back-door subsidies for its aerospace industry. It happened late last year when EC approval was granted to a UK government loan of 250 million [pounds sterling] to Rolls-Royce to support development of the Trent 900, the UK company's powerplant offering for the Airbus A380, and the Trent 600, another Trent derivative aimed at the still-fluid Boeing 747X market. Then and previously, the UK and its EC neighbours countered the suggestion that rules were being flouted by trotting out the old refrain that the US commercial engine industry is supported by the hundreds of millions of defence dollars poured into programmes like IHPTET by the US government. There is no question that US commercial engine companies have benefitted enormously from such programmes. The GE90, for example, makes use of a number of derivative IHPTET technologies, including single-crystal high pressure turbine blades and vanes, boltless blade retention, composite fan blades and low pressure turbine brush seals. The PW4084's hollow titanium fan-blades and advanced single-crystal turbine blades are among a number of technologies that are said to have spun out of IHPTET.

Headline goal

The goal of the three-phase IHPTET programme, which started in 1987, was to double `propulsion capability' across a broad range of aero-engine products -- including commercial engines -- by the beginning of the 21st century. The effort has been backed jointly by the USAF, USN, US Army, the National Aeronautics and Space Administration (NASA), the Defense Advanced Research Projects Agency (DARPA) and US engine manufacturers. The headline goal of VAATE is to improve the affordability of next-generation military propulsion systems by ten times relative to today's state of the art military product: the Pratt and Whitney (P&W) F119 in the Lockheed Martin F22A Raptor and its derivative, the F135, in the Lockheed Martin/Northrop Grumman/ BAE Systems F-35.

When the IHPTET programme is complete in 2005, it will have demonstrated a 100 per cent increase in the thrust-to-weight ratio of turbofan engines relative to their counterparts of a generation ago. It has also shown that a 35 per cent decrease in production and maintenance costs is achievable in today's manufactured products. The results have been fed into many contemporary engine projects. The completion of IHPTET Phase I in 1991 -- after it had successfully demonstrated a 31 per cent improvement in combat engine thrust-to-weight ratios -- led, for example, to the supercruise capability of the F-22.

Taking over from IHPTET

VAATE will take over from IHPTET Phase III as the latter winds down in the next three years. It has been in planning since 1997 and, like IHPTET, will address different engine classes -- large and small turbofans, turboprops, turboshafts and expendable engines for missiles -- only this time with a markedly sharper emphasis on affordability. "IHPTET was not quite as focused on affordability, because in 1987 cost wasn't such a big issue," said Timothy Lewis, performance analysis group leader at the Propulsion Directorate, Turbine Engine Division, of the US Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base, Ohio. "But in future cost is going to be critical." AFRL has devised a `capability/cost index' in which key contributors to propulsion affordability -- the main ones being thrust-to-weight ratio, fuel consumption, development, production and maintenance costs -- will combine to produce a `metric' that engine makers can use as a measure of progress when assessing their own products. VAATE officials are confident they can meet the programme's aggressive targets and milestones owing to a range of new materials and health-monitoring technologies that were not available to them a decade ago. VAATE's ten times affordability goal is to be achieved by 2017, with an interim six level improvement in affordability (relative to the F119) set for 2010.