CORE VALUES

The primary engine for the F-35B Joint Strike Fighter is suffering growing pains and currently "running 190 degrees above our desired temperature," say Pratt & Whitney specialists as they work to squeeze more power out of the design in the test program.

Company officials say they have plans to cut the 190F of extra heat in the short takeoff and vertical landing (Stovl) configuration engines by "more than half this summer." The specific area of concern is the "rotor inlet temperature margin," William J. Gostic, vice president of F135 programs, told AW&ST. The immediate fix involves adjusting the engine's bypass ratio to optimize air flow through the engine's core where the most extreme temperatures are experienced. JSF engine manufacturers have the unique problem of designing a Stovl propulsion system with a variable bypass ratio that supports conventional engine operations in addition to periodically supplying thrust for the wing-mounted roll posts and the tail-mounted three-bearing swivel module.

"Currently, we do not have the level of [rotor inlet temperature] margin we desire to have at the end of the [demonstration and] development program," which is still about two years away, Gostic says. He also points out that there is no military requirement for the margin and that the Stovl engine has already demonstrated the 40,550-lb. specification level of thrust.

Some propulsion analysts suggest that the engine's combustor--where fuel and air are mixed and ignited--is too small because, to save money, it was derived from the F-22 engine. As a result, it doesn't have the necessary airflow without additional bypass air. Increasing bypass air can rob an engine of efficiency.

AT THE SAME TIME, CONGRESS--backed by its investigative arm, the Government Accountability Office (GAO)--has rushed to shore up support for the alternative engine program run by General Electric and Rolls-Royce. The Pentagon's top civilian and military leaders--but not the JSF program office--wanted to kill the program in a move to cut $400 million from the defense budget.

The GAO says, however, that the decision was made without an up-to-date analysis that would have shown a "20% savings from competition [that] would allow a break-even point to occur at about 1,700 engines--not 2,500." Additional savings would come from reliability improvements while maintaining the industrial base, enhancing readiness, instilling contractor incentives for better performance, ensuring an alternative if the current engine develops problems and improving international participation.

Ironically, congressional authorization committees have recommended cutting JSF's budget by $1.2 billion and reducing production to five or zero aircraft (from the 16 requested) in Fiscal 2008 by saying the risk of concurrently developing and putting the aircraft into low-rate production is too high. Pentagon and aerospace industry officials say concurrency is the only way to avoid stretching the schedule and driving up costs. Some aerospace industry officials say the move is simply part of the bargaining process to decrease production and create short-term top-line budget cuts.

John Warner (R-Va.), chairman of the Senate Armed Services Committee, says he strongly supports continuing the two engine programs for another year.

"In that period, we'll have the first test flight of the Pratt & Whitney engine and I think that's an important milestone as we, at the end of this year, begin to review once again whether we go forward with the joint program," Warner says. "And also it gives the Pentagon the opportunity to reexamine its own decision process. The first . . . was driven by budgetary concerns and the next process, I hope, will [be] more in the best interest to achieve competition and to affect the cost statements."