The first Lockheed Martin F-35 Joint Strike Fighter has completed a 55min flight from Fort Worth, Texas, returning to flight after a six-month hiatus for modification and upgrades.
Aircraft AA-1 last flew in May, when a brief electrical system failure cut short the 19th test flight. The aircraft's maiden flight was in December 2006.
Since then, Lockheed has reworked the 270V electrical system to prevent arcing, changed out the integrated power package and incorporated other hardware and software upgrades.
F-35 on its third test flight © Lockheed Martin
The failure of a Pratt & Whitney F135 on a test stand in August ended up pacing the return to flight. This led to the decision to "proof test" the flight-test engines to ensure they were not susceptible to high-cycle fatigue failure of the third-stage low-pressure turbine blades.
The third flight-test engine was proof-tested first, and then installed in aircraft AA-1 in place of the first test engine, which had powered the first 19 flights. After ground runs and taxi tests, the F-35 was cleared to resume flight testing.
Lockheed's F-35 avionics testbed, a highly modified Boeing 737-300 called the CATBird, is also about to fly from Fort Worth. And the first short take-off and vertical landing F-35B is to roll off the assembly line on 18 December.