NATIONAL HARBOR, Md. -- The U.S. Defense Department official in charge of the F-35 fighter jet program said he hopes to have a fix in place for a defective engine part by the end of the year.
Speaking Monday at the Air Force Association's annual conference, Air Force Lt. Gen. Christopher Bogdan said engine-maker Pratt & Whitney, part of United Technologies Corp., is developing a replacement component for the fan section of the F135 engine.
"We're hoping before the end of the year, we'll have at least the prototype," he told reporters after a presentation on the acquisition program. "If the prototype works, we'll put that in."
The Pentagon hasn't released an official cause of the engine fire that led to a temporary grounding of the F-35 fleet and ongoing flying restrictions for the Lockheed Martin Corp.-made aircraft. A so-called root cause analysis is expected by the end of the month. Officials have traced the problem to "excessive rubbing" during an earlier test flight between a titanium fan blade and surrounding material, a synthetic polymer known as polyamide.
Three weeks before the F-35A conventional Air Force model aircraft caught fire during takeoff June 23 at Eglin Air Force Base, Florida, it was flown in a manner designed to test the performance of its g-force, roll and yaw within designed limits known as the flight envelope.
While the maneuver only last two seconds or so, it triggered an unexpectedly high level of rubbing between the titanium blade in the fan section of the F135 engine and the polyamide. The metal reached temperatures of as high as 1,900 degrees Fahrenheit — compared to the normal level of about 1,000 degrees — and resulted in micro-cracking.
Pratt & Whitney has pledged to cover the cost of the engine fix, which includes redesigning that part of the propulsion system to create more space in the so-called trench area. Bogdan declined to specify how much it will cost until the root-cause analysis is completed.
A prototype part may be tested as early as mid-October, Bogdan has said. Meanwhile, the program office is developing a new engine break-in procedure as a short-term fix to better analyze how it performs under increasing loads, he has said.
"There is no engine today going into a Lockheed Martin airframe that won't have the fix," Bogdan said on Monday. If the prototype part isn't ready by the end of the year, "we'll do some burn-ins of production engines."
There are currently about 100 F-35s in the U.S. fleet. Pratt & Whitney has delivered roughly 150 F135 engines.
His presentation on Monday was essentially a rehash of one he gave a couple of weeks ago at the National Press Club. While he acknowledged the engine problem threatens to delay the program by 30 days to 45 days, Bogdan said he expects the Marine Corps will still begin operational flights of the F-35B jump-jet variant next July as scheduled, followed by the Air Force in 2016 and the Navy in 2018.
Problems with such components as the helmet, carrier hook and lightning protection have either been solved or are in the process of being addressed, Bogdan said. "These are all past problems," he said.
Meanwhile, new issues have emerged with such areas as the engine, the Autonomic Logistics Information System, or ALIS (pronounced "Alice") -- which determines whether the plane is safe to fly -- mission data files and simulators.
Still, Bogdan said he's more concerned with the program's programmatic and financial issues than its technical challenges. Automatic budget cuts known as sequestration are scheduled to return in fiscal 2016 -- coinciding with a planned dramatic rise in production of aircraft, he said.
The Pentagon is currently negotiating with Lockheed to buy 43 planes as part of the eighth lot, or installment, Bogdan said. That figure is slated to increase to 57 aircraft in Lot 9, 74 aircraft in Lot 10 and 119 aircraft in Lot 11, he said. The number of aircraft being purchased is set to double over the next three years and triple over the next five years, he said.
"There is a significant ramp coming," he said.
While funding for the program was relatively shielded from sequestration cuts so far, it must continue in order for the program office to work to control costs and maintain predictability, Bogdan said. Of the overall effort, he said, "It's not too big to fail, it's too important to fail."
The Joint Strike Fighter is the Pentagon's most expensive weapons acquisition program, estimated to cost a total of $398.6 billion for a total of 2,457 aircraft. That breaks down to a per-plane cost of $162 million, including research and development.