WASHINGTON – The F-35 will not get its full combat capability package until late fall of 2017, a delay of about four months from the original plan, according to a top general.

Testing of two earlier versions of the F-35 software, Blocks 2B and 3i, took longer than expected, Joint Program Office (JPO) Chief Lt. Gen. Christopher Bogdan wrote in his March 23 written testimony before the House Armed Services subcommittee on tactical air and land forces. The Marine Corps declared initial operational capability (IOC) with Block 2B last summer; meanwhile, the Air Force needs Block 3i to declare its jets operational this year.

Testing of Block 3F, which will give the jets full warfighting capability, started later than planned because the program office had to spend more time fixing Blocks 2B and 3i, Bogdan wrote. As a result, Block 3F will likely be completed about four months late, and will be delivered in late fall of 2017, Bogdan told lawmakers.

However, Bogdan noted that this delay is an improvement over the JPO's projection a year ago, and is not expected to impact the Navy's ability to declare its F-35C jets operational in 2018. The four-month delay will also have no impact on coalition partners' capabilities, he wrote.

The schedule risk is primarily due to software "stability" issues, seen in both Blocks 3i and 3F. In essence, a timing misalignment of the software of the plane's sensors and the software of its main computers are causing a "choking" effect, where the jet's systems shut down and have to be rebooted. However, the JPO and contractor Lockheed Martin have identified the root cause and plan to flight test an updated software load at Edwards Air Force Base, California, sometime in the next few weeks, officials have said.

The program office has established a "Red Team," made up of experts from the Navy, Air Force and outside the Pentagon to take an in-depth look at the issue, Bogdan told reporters after the hearing. The Red Team has already begun its study and will report back in about a month, he said.

"We brought them together and we're sending them down to Lockheed to try to figure out, do we have the root cause analysis right on these problems? Are we going after the right issues?" Bogdan said. "Because it's very easy to just make a fix to the software, but if you don't fix the fundamental issues going on those fixes only will last so long and they will pop up again."

Success of Block 3F mission systems hinges on the program office resolving the problems with Block 3i, Director of Operational Test and Evaluation Michael Gilmore wrote in his written testimony. The stability and functionality problems in the initial versions of Block 3F, inherited from Block 3i, were "so significant that the program could not continue flight test," he wrote.

While Bogdan stressed the Block 3F delays will not impact IOC, he acknowledged they could affect how ready the jets are for the formal initial operational test and evaluation (IOT&E) phase of development, currently planned to start in 2017.

Gilmore estimated Block 3F capabilities will not be ready for IOT&E until 2018 at the earliest.

"The Block 3F schedule, even with significant improvements in software stability, deficiency resolution, and flight test rates, still appears to extend into 2018 before the capabilities will be ready and certified for IOT&E," Gilmore wrote.

Email: lseligman@defensenews.com

Twitter: @laraseligman

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