F-35 Fire: In Search Of A Solution

The long-delayed operational debut for the Lockheed Martin F-35 Joint Strike Fighter is at risk of further slippage due to a safety-critical problem with its Pratt & Whitney F135 engine for which no single root cause has yet been identified. Senior leaders initially dismissed the fire that damaged F-35 AF-27 at Eglin AFB, Florida, on June 23 as a “one-off incident,” as U.S. Marine Corps commandant Gen. James Amos called it in mid-July. However,  at least five engines have been removed from F-35s after showing signs of premature wear.
The JSF flight-test team has until the end of this month to demonstrate and validate an operational work-around that will allow aircraft in the 21-strong systems development and demonstration (SDD) fleet to fly without the onerous flight restrictions that were imposed after the fire. If that is not done in time, the flight-test schedule that supports initial operational capability (IOC) dates will be in jeopardy.
The F135 engine’s size and 6,500‑lb. weight may contribute to uniquely high loads and deflection forces in maneuvering flight.
Meanwhile, Pratt & Whitney is working on redesigned engine components that are intended to prevent the problem from recurring, with the objective of lifting restrictions on the JSF training and tactics development fleet. While the investigation into the fire and related defects is ongoing, 38 possible causes have been narrowed down to four. Pratt’s proposed design changes are planned on the assumption that further investigation will validate those findings and is intended to address any of the likely root causes.
The JSF program office declines to give details of the damage to AF-27 and says that it has not yet established whether the $205 million fighter (its program acquisition cost, according to the 2013 Selected Acquisition Report) can be restored to flyable condition. For Pratt & Whitney, the risk to the F-35 schedule emerges as another major test program—the Bombardier CSeries airliner—remains on hold due to a problem with a new P&W engine.
Five F135 engines have been pulled from F-35s after failing an inspection regime that was instituted after the June 23 fire. One of the failed engines was removed from F-35 CF-9 (the ninth production F-35C), an aircraft with fewer than 70 flight hours.
aviationweek