The Air Force—which is understood to have conducted a low-level study projecting the cost savings in the F-35 if an AETD-based engine were used—defends the project and insists the focus is on future developments. During a subcommittee hearing this month, Lieberman asked Lt. Gen. Janet Wolfenbarger, military deputy at the Office of the Assistant Secretary of the Air Force for Acquisition, whether the advanced engine program was indeed an effort to resurrect a competing engine.
“No, sir, it is not,” Wolfenbarger told him, adding that the program is trying to capitalize on advances in AFRL's Advent (adaptive versatile engine technology) initiative. “This engine could be used in a whole host of platforms should it ever reach the point of being a development program. Right now it's just a question of ensuring that we are ready to go, should we as an Air Force decide that we want to embrace this opportunity to really reduce the fuel consumption in future generations of strike aircraft, bomber aircraft [and] tactical aircraft.”
The demonstrator builds on Advent, which has been developing a suite of technologies for variable-cycle architectures to reduce fuel consumption by up to 25% and increase range by 30%. Advent architectures add a third stream of relatively cooler air flow, in addition to the standard high-pressure core flow and second stream of bypass air. The third stream is used for high power extraction and better thermal management; it also reduces installed drag and improved inlet recovery. The cooler air mass can also be mixed with the outlet flow to reduce exhaust system temperatures and infrared signature.
AETD will go even further in terms of better efficiency and power, and take the Advent concept to a pre-full-scale EMD level. Unlike the smaller cores used in the initial Advent effort, the AETD engines will be built around a larger core theoretically sized to enable future projects—such as the U.S. Navy's F/A-XX and Air Force's F-X sixth-generation fighters—to supercruise, or fly supersonically without afterburner. The size requirement also happens to match that of the F-35.
Responses to AFRL's request for proposals are due May 31 and cover Phase 1 contracts that will be awarded in August for two rival engines. This will include initial concept evaluations by February 2013, compressor rig tests in 2014, fan and core tests by mid-2015 and full engine tests as early as 2016.
GE and Rolls, which are competing against each other in the Advent program, are submitting variable-cycle growth concepts for the AETD. GE, aiming to run the first full Advent engine late this year or early 2013, says it “has been approached by Senate and House defense appropriators regarding AETD funding because they are highly interested in the program's fuel-efficiency goals and timetable, and whether they are both achievable. We believe they are achievable based on our Advent efforts over the past five years. AETD will be a sporty competition for the three engine makers.”
NOTE: Story has been edited to reflect that Ashton Carter's criticism of the F135 program was expressed during the debate over the competitive engine.