F-35B On Track.

The jump jet variant of the Lockheed Martin F-35 Lightning II Joint Strike Fighter is still scheduled to reach initial operational capability (IOC) with the US Marine Corps (USMC) in July despite ongoing difficulties with F-35 software fusion, the Pentagon's programme manager for the effort said at a press briefing on 24 March.

F-35B On Track.

"The Marine Corps understands the deficiencies and has workarounds in place," said Lieutenant General Chris Bogdan. He said the workarounds required pilots to "do some extra work" instead of relying on the aircraft to automatically respond.

The software problem involves sensor fusion, which allows the fighters to share data with one another to create a complete operational picture. "We found out that the fusion model sometimes, not all the time, [but] sometimes creates an inaccurate picture for the pilot," he said.

Lt Gen Bogdan said the software worked correctly much of the time. For example, "if there is a single ground threat, a surface-to-air missile [battery] on the range, and I have four F-35s all with their sensors on and operating into that airspace to see that one threat, what we want to have happen is ... no matter which airplane is picking up the threat, from whatever angles and sensors, to correctly identify that single threat and then pass that information [to] all four airplanes, so all four pilots are looking at the same threat in the same place at the same time". He said this happened most of the time. However, during testing, the F-35 at times has had trouble identifying how many targets it was seeing.

The programme has been using both its own engineers and outside software fusion experts to work on the problem. The USMC has been able to mitigate the issue by temporarily altering its concept of operations. Lt Gen Bogdan did not disclose specific operational details but did note that one potential workaround involved how many aircraft were paired during deployment. Teams of two aircraft had fewer difficulties with the sensor fusion issue than had those of four or more, he said. He added that, even with the deficiency, the F-35B was still far more capable than the USMC's legacy combat aircraft.

The 2B software with which the USMC intends to declare IOC "will not have all the fixes of the deficiencies we've seen in testing over the last two months," Lt Gen Bogdan added. He said the repairs would be incorporated in time for the US Air Force's (USAF's) IOC with the conventional take-off and landing A-model in 2016.

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Lockheed Martin is unlikely to receive the entire USD300 million incentive fee under its latest F-35 contract because of software problems, Lt Gen Bogdan said. He declined to specify how much the late 2B delivery would decrease the fee.