F-35 software instability in both blocks 3i and 3f causes certain aircraft sensors, including the radar, to shut down for minutes at a time before fully recovering, according to a key official.

F-35 Program Executive Officer (PEO) Air Force Lt. Gen. Christopher Bogdan testified Wednesday that miscommunication between sensors and the main computers in the aircraft mistime during takeoff, building up little delays to the point where sensors shut off. As an example, he said the radar will recover, but it takes minutes to regain the picture that it had.

Bogdan said the program is experiencing these sensor shutoffs at a rate of once every four hours of flight time. Calling this “not good,” Bogdan said he needs the rate to be closer to once every eight to 10 hours. Block 3f is the final software iteration and the one with which the aircraft will achieve full operational capability.

Bogdan said the program performed a root cause analysis after discovering the problem a few months ago. He said F-35 prime contractor Lockheed Martin [LMT] has a number of fixes in the works that the program will flight test starting next week in the next version of Block 3i software. The program will know in the next month or so if those fixes work, he said.

“If those fixes work … then the impact of this problem to Air Force (initial operational capability) will be minimal,” Bogdan told the House Armed Services (HASC) tactical air and land forces subcommittee.

When asked what fixes Lockheed Martin had in the works, company spokesman Mark Johnson said Wednesday that the issues addressed are “primarily driven by the radar system.” Contradicting Bogdan’s testimony, Johnson said no other sensors are challenged. Johnson said Lockheed Martin’s confidence is high, pending flight test results, that these stability issues can be fixed in time for IOC.

Citing the F-35’s eight million lines of code, Bogdan said it is not unusual for both legacy and modern fifth-generation airplanes to have to reset one of the sensors in flight or have an automatic reset. He said if it happens more frequently, or at critical times, then it affects the pilot’s ability to get the mission done.

Bogdan said the software instability issue will probably delay the end of flight test about four months. This will not impact Navy F-35C IOC, he said, because schedule margin is available, but it would “clearly” impact how ready the airplanes are for initial operational test and evaluation (IOT&E), a critical milestone in weapon system development.

Navy F-35C IOC shall be declared when the first operational squadron is equipped with 10 aircraft and Navy personnel are trained, manned and equipped to conduct assigned missions. Based on the current F-35 schedule, the F-35C will reach the IOC milestone between August 2018 and February 2019, according to Joint Program Office (JPO) spokesman Joe DellaVedova.

Director of Operational Test and Evaluation (DOT&E) Michael Gilmore told the House panel Wednesday these instability instances only occurred in Block 2b once every 30-plus hours. He said the initial versions of Block 3i don’t provide any more combat capability than Block 2b, because it was supposed to be a rehosting of Block 2b with a new processor.

The goal, Gilmore said, is having the time between instability incidents to be long enough for a “very low probability” they occur during a multi-hour combat mission, which he said can comprise several hours. Gilmore said his office will “certainly” be looking at whether eight hours will be sufficient in IOT&E.

Government Accountability Office (GAO) Director of Acquisition and Sourcing Management Issues Michael Sullivan testified Wednesday that while the software instability issues are “very serious,” the program was able to work through issues with software Block 2b and he hopes it can do the same with blocks 3i and 3f. The timing issue, he said, is critical because programs ideally enter IOT&E with those types of problems resolved as opposed to adding that burden to operational testers.

Gilmore, in his annual report, believed that the F-35 program’s current goal of entering IOT&E by August 2017 was unrealistic and may not take place until as late as August 2018 (Defense Daily, February 1).