A choice of engines for the Joint Strike Fighter looks increasingly certain, with US Congress likely to fund continued development of the General Electric/Rolls-Royce F136 as an alternative to the Pratt & Whitney F135 primary powerplant.
With three key committees voting to provide the full $480 million in funding for fiscal year 2008, the GE/R-R Fighter Engine Team (FET) looks set to stay on schedule to have the F136 available to power theF-35 beginning with the fourth low-rate initial production batch in FY2012.
That schedule reflects a $70 million cut in FY2007 funding inflicted by US Department of Defense efforts to terminate the F136 system development and demonstration contract awarded in August 2005. "The restructuring moved the milestones out three months, but we are still aligned with ISR [initial service release] in 2012, as per the original plan," says FET president Jean Lydon-Rodgers.
P&W, meanwhile, is working toward initial service release of the F135 in 2009, ready to power the first production batch of F-35s. Three development engines have been delivered to Lockheed to support flight testing of the first F-35A, aircraft AA-1, and STOVL ground testing is under way to qualify the F135 and R-R lift system to power the firstF-35B in May 2008, says Bill Gostic, vice-president F135 programmes.
Testing of the CTOL engine in its ISR configuration is under way at P&W's West Palm Beach, Florida test site, while STOVL flight release testing has resumed after an engine was damaged when a deliberate hard stall of the shaft-driven lift fan caused the shaft to break (Flight International, 5-11 June). As JSF primary powerplant provider, P&W is responsible for clearing the lift system for use with both the F135 and F136.
The first production-configuration F136, meanwhile, is scheduled to begin testing late in 2008. First flight, in the CTOL F-35A, is planned for late 2010, and the F136 is to fly in the STOVL F-35B in 2011. The GE/R-R team's development contract includes six flight-test engines.
In the meantime, the FET plans to continue testing two pre-SDD engines. One has just completed control system testing at GE's Peebles outdoor test site in Ohio and will be used to test the production-configuration fan and augmentor. STOVL testing with the F-35B's R-R-developed lift system will begin in February on a new test stand.
With some international partners looking to buy their initial F-35s in LRIP 3, Lydon-Rodgers says the FET is in talks with the JSF programme office on how to offer them the option of the F136. "The UK and the Netherlands are the primary concern for the F136," she says. As the test aircraft will remain in the USA initially, one option is to re-engine them with the F136 before they are delivered in-country, she says.
While the two engines will have the same thrust because they have to be interchangeable, Lydon-Rodgers says the F136 will produce that thrust at lower temperatures than the F135 because it was designed later, after redesign of the F-35 to overcome weight problems. This increase in temperature margin will reduce life-cycle cost, improve hot-day combat capability and provide for affordable growth, she says.
Gostic says a shortfall in temperature margin in the F135 has been overcome with the ISR configuration now on test. He says the engine can provide 5% more thrust with no change to the core size, using fan and cooling improvements. A further 10% growth has been identified, but requires core, inlet and exhaust changes.
Source: Flight International
