Fire Causes Friction in F-35 Test Program

F-35 program officials and experts at Pratt & Whitney are narrowing down the root cause of the June 23 F135 fire on an F-35A that grounded the fleet for 13 days and prompted its notable absence as the 2014 Farnborough Air Show in July.

The aircraft have returned back to flying status, though in a highly restricted envelope. But, the clock is ticking for when these restrictions for the test fleet will begin to cut too deeply into the project’s schedule, possibly jeopardizing the timeline for major milestones such as weapons testing and at-sea trails.

Each day that goes by without a fix – at least a temporary one to get the test jets off restricted flying status – the test program is slipping. It is unclear how much total margin there is in the program to absorb this.

Yesterday, F-35 Joint Program Director USAF Lt. Gen. Christopher Bogdan said that up to 45 days worth of testing has been missed due to the grounding and subsequent restricted flight regime on the three F-35 variants. “I’ve got SDD airplanes that at the start of this engine program could not fly the full envelope, and, therefore, our test program is delayed,” he told the ComDef 2014 conference in Washington.

Program officials conducted extensive testing on six of the 21 aircraft in the testing program and “opened up” the envelope for those six aircraft (AFs 2, 6 and 7, BF-3 and CFs 2 and 3) deemed most crucial to keeping the trails moving forward in the meantime. But, he says he must get the remaining 15 jets returned to normal flight status by the end of this month in order to keep the flight test plan on track.

“I need the rest of the test airplanes and there are 21 of them in the test program. I need all of those back to full envelope by the end of this month. Otherwise, we will start seeing some delays in future milestones that we talked about that we haven’t pushed up against yet,” Bogdan said.

Two potential fixes are in works to address the four root causes outlined by Bogdan. One, a near-term option, is a two-sortie series of maneuvers designed to “burn in” the engine in a methodical way – avoiding the microcracking that occurred as a result of the 2 sec. maneuver done on AF-27 three weeks prior to the fire. Bogdan says he is testing this procedure in hopes that it can be used to get the remaining 15 test jets back into a normal flying envelope.

Secondly, F135 manufacturer Pratt & Whitney is in the meantime crafting a prototype redesign of the engine stage that will address the rubbing that prompted the excessive temperature in AF-27.

Key test milestones ahead are getting the F-35C onboard an aircraft carrier in the fall for its first round of arrested landing and catapult takeoff trials. Also, more weapons testing is required.

Bogdan stopped short this week of declaring AF-27 a total loss; he said that there are still parts on that aircraft than can be put to use. Perhaps it will be the first F-35 can bird!