The F136 advanced turbofan engine for the F-35 Lightning II Joint Strike Fighter (JSF) will almost certainly have its future decided in political debate in Washington rather than through technical progress in the engineering laboratory. But while the proposed alternate engine for the JSF is controversial on Capitol Hill – the Obama administration and Defense Secretary Robert Gates oppose its development – the engine is making progress in the test arena.

GE Aviation said on December 6 it hit a milestone when, together with Rolls-Royce PLC, it launched tests on its sixth F136 engine, surpassing a major test goal for 2010. GE and Rolls-Royce have a 60-40 partnership on the F136 engine, while Rolls-Royce also manufactures the LiftFan system for the F-35B short takeoff/vertical landing (STOVL) version of the F-35B.

Opponents of the F136 engine say that a single engine type for the JSF is sufficient and that the Pratt & Whitney F135, currently employed on all flying JSFs, has proven itself. Supporters of the F136 argue that no real competition between the two engines was ever held and that an alternate engine provides much-needed insurance for the JSF program.

Retired Air Force Lt. Gen. Stephen G. Wood, a recent commander of U.S. air forces in Korea, piloted F-16 Fighting Falcons with two kinds of engines and saw more than 4,200 F-16s enter service around the world with a mix of GE and Pratt & Whitney power plants. Now, Wood is senior vice president, defense relations, for Rolls-Royce North America, Inc.

“The GE/Rolls-Royce F136 developmental program is 80 percent complete and the F136 will be ready to begin flight test next year,” said Wood in a December 8 interview. “The risk is too great to allow only one propulsion system for the F-35, which will make up over 85 percent of our nation’s fighter force in 20 years.”

Wood said that if current plans continue, in little more than a decade the Air Force, Marine Corps and Navy fighter inventory will be dominated by the JSF, with only a handful of F-15E Strike Eagles, F/A-18E/F Super Hornets and F-22 Raptors serving alongside the F-35 Lightning II Joint Strike Fighter. Although the F-35 program was restructured recently for the third time in two years, Gates and other officials say the nation is still depending upon the aircraft.

“Continued competition between F-35 engine makers will force both parties to produce a better engine,” Wood said.

According to GE, the F136 team has compiled more than 850 test hours so far this year, with a goal of reaching 1,000 hours by year’s end. Four F136 engines are testing concurrently for the first time at three locations.

GE said in a press release that its team’s decision in 2005 to resize the F136 engine with a larger core and higher-flow fan is proving fortuitous, as testing has shown the engine will enter production with cooler running temperatures. “That will translate into a long-term maintenance cost advantage,” GE says.