The Lockheed Martin F-35 Lightning II has 873 unresolved deficiencies and new problems are being discovered regularly, making reducing the number of issues with the aircraft difficult.
That’s the conclusion of the latest scathing assessment of the stealth fighter from the Annual Report for the US Department of Defense’s (DoD) Office of the Director of Operational Test & Evaluation (DOT&E), released to the US Congress on 30 January.
“Although the programme is working to fix deficiencies, new discoveries are still being made, resulting in only a minor decrease in the overall number of deficiencies,” says the report.
The F-35’s problems include 13 Category 1 deficiencies. Such problems “may cause death or severe injury; may cause loss or major damage to a weapon system; critically restricts the combat readiness capabilities of the using organisation; or results in a production line stoppage,” according to the US Air Force’s (USAF) definition.
The F-35’s deficiencies are compounded by maintenance problems which hobbled the aircraft’s mission capable rate below the DoD’s goal of 80%. The mission capable rate is the percentage of aircraft capable of performing at least one mission, excluding aircraft in depot maintenance or undergoing major repairs.
“No significant portion of the fleet, including the combat-coded fleet, was able to achieve and sustain the DoD mission capable rate goal of 80%,” says the DOT&E. “However, individual units have been able to achieve the 80% target for short periods during deployed operations.”
Lockheed Martin did not respond to questions about when deficiencies with the F-35 would be fixed, saying it is still reviewing the DOT&E report.
“The F-35 continues to mature and is the most lethal, survivable and connected fighter in the world,” the company says. “Reliability continues to improve, with the global fleet averaging greater than 65% mission capable rates and operational units consistently performing near 75%.”
Some of the aircraft’s lingering problems appear to be connected to the F-35 Joint Program Office and Lockheed Martin’s recently adopted Continuous Capability Development and Delivery process, a method of delivering software fixes and additional functions every six months. The process is modeled on a Silicon Valley method of delivering bite-sized chunks of code changes to customers called agile software development.
Lockheed Martin was openly optimistic in 2019 about the agile method’s ability to turn around the F-35’s troublesome software, which totals more than 8 million lines of code. However, DOT&E says the concept has been problematic.
“Software changes, intended to introduce new capabilities or fix deficiencies, often introduced stability problems and adversely affected other functionality,” says the weapons evaluator’s report. “Due to these inefficiencies, along with a large amount of planned new capabilities, DOT&E considers the program’s current Revision 13 master schedule to be high risk.”
Hardware problems persist too. For example, USAF “units flying newer F-35A aircraft discovered cracks in the outer mold-line coatings and the underlying chine longeron skin, near the gun muzzle, after aircraft returned from flights when the gun was employed”, according to the report.
The F-35A’s internally mounted 25mm gun also remains inaccurate.
“Investigations into the gun mounts of the F-35A revealed misalignments that result in muzzle alignment errors,” says DOT&E. “As a result, the true alignment of each F-35A gun is not known, so the programme is considering options to re-boresight and correct gun alignments.”
It is not known if those changes will fix the aircraft’s problems, as further testing would be needed, notes the Pentagon. The US Marine Corps’ F-35B and the US Navy’s F-35C, which carry 25mm guns in external pods, were accurate in air-to-ground firing tests, the report says.