US Defense for Acquisition, Technology and Logistics Under Secretary Frank Kendall and Air Force Lieutenant General Christopher C. Bogdan have revealed that the root causes of stability issues in software being tested for the F-35 Lightning II stealth multirole fighter have been identified.
Kendall and Bogdan told a Senate Armed Services Committee that the instability in 3i software and 3F software caused the shut down of sensors once every four hours in Lockheed Martin's combat aircraft, thereby increasing the number of reboots in flight.
The cause of the issue was the timing of software messages from the sensors to the main F-35 fusion computer.
However, the problem has now been resolved with the new software containing stability improvements meaning sensors only needed to be restarted after more than ten hours.
Commenting on the software glitch, Kendall and Bogdan said: "We are cautiously optimistic that these fixes will resolve the current stability problems, but are waiting to see how the software performs in an operational test environment.
"We have three Operational Test (OT) jets flying with the new software and expect 50 hours of additional OT testing by 29 April."
As of 13 April this year, the improved version with the new software had flown 29 sorties and 75 hours.
The F-35 aircraft has approximately eight million lines of code, in addition to another 16 million lines of code on the off-board systems.
The aircraft is being developed in three models including the F-35A conventional takeoff and landing (CTOL) variant, the F-35B short take-off and vertical-landing (STOVL) variant, and the F-35C carrier-based catapult assisted take-off but arrested recovery (CATOBAR) variant.
Image: Lockheed Martin's F-35C Lightning II fighter jet. Photo: courtesy of Andy Wolfe.