September 24, 2012
Credit: Credit: Rolls Royce
Graham Warwick Washington
It has been almost three decades since the U.S. last set out to develop an all-new combat-aircraft engine, but more than 50 years since the turbojet gave way to the turbofan. Now the U.S. is embarking on development of a new generation of fighter engine with an architecture it considers as fundamental an advance as the turbofan was over the turbojet.
Being part of a research effort that could produce the dominant combat-aircraft engine of coming decades is critical for industry. So General Electric and Pratt & Whitney are breathing easier after being selected by the U.S. Air Force Research Laboratory (AFRL) for the Adaptive Engine Technology Development (AETD) program to mature fuel-efficient, high-thrust powerplants for post-2020 upgrades to the Lockheed Martin F-35 and future “sixth-generation” combat aircraft.
AETD is a follow-on to AFRL's $524 million Adaptive Versatile Engine Technology (Advent) program under which GE Aviation and Rolls-Royce North American Technologies will demonstrate engines in 2013. Selection for AETD is a coup for Pratt, which in 2007 lost out to GE and Rolls in the Advent competition, but a blow for Rolls, which did not receive the nod for the follow-on program.
“When we were not selected for Advent, we did a lot of our own rig work,” says Jim Reed, Pratt & Whitney's director of advanced engine programs. “But that only mattered if we were selected for AETD. We had to build a strong proposal.” At stake is the potential development of fuel-efficient engines to upgrade the F-35 after 2020 and to power future Air Force and Navy air-dominance fighters that could enter service around 2030.
The last time the U.S. embarked on development of an all-new combat engine was in the early 1980s with the launch of the Joint Technology Demonstrator Engine (JTDE) program, which led to Pratt & Whitney powering both the Lockheed Martin F-22 with the F119 and the F-35 with a further development of that engine, the F135.
Having succeeded in killing the GE/Rolls-Royce F136 alternative engine for the F-35, Pratt's supporters in Congress threatened to cut funding for AETD, fearing it was a backdoor maneuver to a competitive engine. But Air Force reassurances that its goal is to mature technology and not to develop an engine—coupled with the selection of Pratt over Rolls—should defuse criticism of AETD.
“We will not produce a prototype engine, but run core engines,” says Tim Lewis of AFRL's Propulsion Directorate. “All three proposals were technically acceptable, but funding drove us to select two of the three,” he says. Rolls states that it is “disappointed by this decision but . . . continues to work with the Air Force Research Laboratory on important programs such as Advent and HEETE [Highly Energy-Efficient Turbine Engine].”