AF-4 Again

The Joint Strike Fighter aircraft that suffered an integrated power package failure yesterday, causing a fleet-wide F-35 grounding today, is the same jet that caused another grounding back in March.

The aircraft, a conventional-takeoff-and-landing variant known as AF-4, is a test plane from the system development and demonstration phase of the program, making it one of the older F-35s flying today. The Defense Department and prime contractor Lockheed Martin are negotiating Lot 5 of low-rate initial production, putting AF-4 several lots behind the newest planes coming off the line.

F-35 joint program office spokesman Joe DellaVedova told InsideDefense.com today that during the F-35 fleet's grounding earlier this year, which was caused by a generator failure and oil leak on AF-4, the integrated power package “saved the day” and helped make up for the generator's lack of power. Yesterday, the IPP “experienced a failure,” according to a statement released by the program office. No additional details were provided.

Asked whether more problems had been found on AF-4 than on other F-35s, DellaVedova said, “I don't know if they've found more problems, but it is the same airplane, so you can make that connection. It was the same airplane that started the grounding” in March.

AF-4, along with several other F-35 aircraft, are being tested at Edwards Air Force Base, CA.