According to a report in Aviation Week, test results show that the alternative engine for the F-35, the General Electric/Rolls-Royce F136, has more than 15 percent thrust margin against specification, beating out its rival, the Pratt & Whitney F135.
The tests at the U.S. Air Force Arnold Engineering Development Center (AEDC) in Tullahoma, Tennessee, are the first to officially measure the combat-rated thrust of a production-representative F136 at sea level conditions.
GE-Rolls stated, "Initial results show we have more than 15 percent margin at sea level combat-rated thrust than the specification. That's significantly beyond the thrust requirement right out of the chute." The article further notes, "Given the added margin, GE-Rolls says its baseline F136 will be able to achieve a 5 percent thrust growth through a simple digital engine control 'throttle push,' without eating into what it says could be a 25 percent maintenance-cost advantage over the F135."
The General Electric/Rolls-Royce F136 is an advanced turbofan engine being developed by General Electric and Rolls-Royce specifically for the F-35 Lightning II. The engine develops 40,000 pounds thrust in afterburner.
All initial F-35s will be powered by the Pratt & Whitney F135. After 2010, the engine contracts were planned to be competitively tendered from Lot 6 onward. The Rolls-Royce LiftSystem will be used in the F-35B STOVL variant regardless of which powerplant is selected.
On 21 July 2004, the F136 began full engine runs at GE's Evendale, Ohio facility. The engine ran for over an hour during two separate runs. In August 2005, the United States Department of Defense awarded the GE and Rolls-Royce team a $2.4 billion contract to develop its F136 engine. The contract was for the system development and demonstration (SDD) phase of the F136 initiative, scheduled to run until September 2013.
The GE/RR Fighter Engine Team includes GE Aviation in Cincinnati, Ohio, and Rolls-Royce in Bristol, England and Indianapolis, Indiana (the former Allison Engine Company, which was bought by Rolls Royce). The two companies hold 60 percent and 40 percent respectively. GE partnered with Turkey's TUSAS Engine Industries (TEI). TEI will design and manufacture critical parts for the F136 in conjunction with GE.
The US Defense budget announced on 6 February 2006 excluded the F136 — leaving Pratt & Whitney, maker of the F135 engine, as the sole provider of engines for the Lockheed Martin F-35 fighters. Congress, however, overturned this request and allocated funds for FY 2007 later in 2006. In November 2006, the General Electric/Rolls-Royce team successfully completed a 3-month preliminary design review by the F-35 Program Office and the prime contractor, Lockheed Martin.
On February 13, 2008, the GE Rolls-Royce Fighter Engine Team successfully completed its Critical Design Review (CDR) for the F136. During CDR, the U.S. Government's Joint Program Office for the F-35 Lightning II validated and approved the design of the engine. Also during the review, every aspect of the engine design was analyzed and evaluated in order to proceed with the building of the first full development engines. The process involved 80 detailed component and module design reviews, involving technical experts from the JPO, General Electric and Rolls-Royce.
On March 20, 2008, the F136 successfully completed a high-altitude afterburner testing program at the US Air Force Arnold Engineering Development Center in Tennessee, including common exhaust hardware for the F-35 Lightning II aircraft. All test objectives were reached as planned using an engine configured with Conventional Takeoff and Landing (CTOL) and Short Takeoff Vertical Landing (STOVL) common exhaust systems. The engine configuration included a production-size fan and functional augmentor allowing several run periods to full afterburner operation. The GE Rolls-Royce Fighter Engine Team successfully completed Short Take Off, Vertical Landing (STOVL) testing on an F136 engine at the GE testing facility at Peebles, Ohio on July 16, 2008.
The first complete new-build F136 engine began testing January 30, 2009, under the System Development and Demonstration (SDD) contract with the US Government Joint Program Office for the F-35 Joint Strike Fighter program. This marked the first complete engine assembled following US Government validation of the F136 design in 2008. The milestone was achieved one month ahead of schedule.
Citing the Weapon Systems Acquisition Reform Act of 2009, the GE Rolls-Royce Fighter Engine Team submitted an unsolicited fixed-price offer for the F136 to the Pentagon on September 28, 2009. The fixed-price approach would cover initial F136 engine production, beginning with the F136 second production lot. According to the GE Rolls-Royce Fighter Engine Team, the proposal would shift significant cost risk from taxpayers to the Fighter Engine Team until head-to-head competition begins between the F136 and the Pratt & Whitney F135 engine in 2013.
A May 2009 Government Accountability Office report cited the F-16 engine competition, in which 21 percent overall cost savings were realized through competition, as reason to continue F136 competitive engine funding in 2010. During 2006-2009, the Defense Department has not requested funding for the alternate F136 engine program, but Congress has maintained program funding.
On December 19, 2009, U.S. Congress approved continued funding for the F136 engine program in fiscal year 2010. The Defense Department did not request FY 2010 funding for the F136 engine program. In a report filed on June 18, 2009, the House Armed Services Committee cited Pratt & Whitney F135 engine program cost overruns of $1.872 billion as cause to continue funding the F136 competitive engine. The report also cited non-financial factors in recommending continued funding for the F136 engine, including better engine performance, improved contractor responsiveness, a more robust industrial base, increased engine reliability and improved operational readiness. Pratt has responded by raising the difficulty of managing two logistical systems. In addition, the United States Navy has said that it lacks the space on aircraft carriers to support two different engines.
On 2 November 2009, the F136 team said that they would redesign a small part of the diffuser leading to the combustor after a failure during testing. Testing resumed on January 22, 2010. The GE Rolls-Royce Fighter Engine Team is currently in the fourth year of its System Development and Demonstration (SDD) contract with the US Government Joint Program Office. The Fighter Engine Team has totaled more than 800 hours of testing on pre-SDD and SDD engines. In early 2010, full afterburning thrust was reached in testing of the first production standard engine.
Defense Secretary Robert Gates has threatened a veto of the 2011 appropriations bill if funding for the F136 is included. The House has included funding for the engine. The Senate has not passed an appropriations bill, but key committee chairmen have voiced support for competitive engines.
-- August 13, 2010
