Key findings released for UK’s F-35B crash

The mostly unclassified UK Defence Safety Authority service inquiry investigation into the loss of a United Kingdom Royal Air Force 617 Squadron F-35B Lightning II (BK-18) aims to make recommendations in order to prevent reoccurrence.

The accident was notable for being the first loss of a UK F-35B and the third loss of an F-35B globally at that time.

The aircraft ditched into eastern Mediterranean waters off the north coast of Egypt, while attempting take-off from the HMS Queen Elizabeth on 17 November 2021.

The pilot successfully ejected in the UK’s first ever ejection using an Mk16E seat, landing back on the deck, while the aircraft decelerated before impacting the sea off the end of the flight deck ramp.

The BK-18 floated semi-submerged beside the ship for a short period before subsequently sinking. A “large red object” identified as BK-18’s left intake blank was seen emerging from the aircraft’s auxiliary intake and recovered by sea boat during the sinking.

The aircraft was later discovered intact, inverted on the seabed at a depth of 2,000 metres before it and all detached items were transported back to the UK.

The published report concluded that a protective red gear intake blank (cover), designed to prevent foreign object debris from entering the airframe during storage, had remained inside the F-35 before launch and likely led to an immediate safety engineering issue.

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That issue had subsequently given rise to the aircraft crash situation on take-off and was later found to have damaged the front face of the engine.

“Based on all the evidence, the panel concluded that the left intake blank was at the front face of the engine compressor during the aircraft launch and determined this to be the causal factor (via contact with variable inlet vanes, resulting in insufficient thrust for a successful launch),” the report said.

“The panel concluded that not removing all elements of red gear at the same time was a contributory factor. The panel further concluded that the omission of a handover which included red gear was also a contributory factor.

“The panel concluded that it was almost certain that wind dislodged the left intake blank in BK-18 from its installed position and moved it to a point at which it could not be seen externally on the night of 16 November 2021.”

The report also found that intake blank covers becoming dislodged (likely by windy conditions) in the aircraft was not previously perceived as an airworthiness threat before the incident, use of white light was likely required to see them and items located in the aircraft’s intake duct could only be discovered by personnel climbing into the duct to check (as they were not visible from the ground and no previous UK aircraft had this unobservable area).

The panel concluded that normalisation to blanks falling out or becoming detached was a contributory factor. The Director Military Aviation Authority also observed trends within the Lightning Force regarding failure to follow process in general.

Previous operations had reportedly often found intake blanks which had been dislodged or “blown out” during deployment.

These incidents include an intake plug found ingested in a USAF F-35A in September 2014, an intake blank found low power ground run in a USMC F-35B in September 2015, an intake blank found in a USAF F-35A in July 2018, and an intake blank found during low speed abort in a US Navy F-35C in January 2020.

The United Kingdom independently reported an engine intake blank found dislodged and wrapped around the lower lift fan door in December 2018, an aircraft exhaust blank blown across a runway in February 2019, a new F-35B intake blank found with peeling safety lettering in May 2021, an engine exhaust blank was lost overboard in May 2021 and another in November 2021.

“Given that the F-35 was an international program, UK reporting was but a small piece of the overall picture,” the report said.

“The panel considered it more than likely that other red gear (intake covers) issues were going unreported across the F-35 community, so the threat to air safety was under appreciated.

“The panel concluded that this lack of reporting, assessment, and analysis of air safety events relating to red gear was a contributory factor.

“The panel found that the UK had omitted an important safety step when writing the see-off Air Engineering Standing Order, that if implemented could have led to the discovery of BK-18’s intake blank. The panel concluded that the UK omission of an independent check of the common duct immediately prior to flight was a contributory factor.”

The sunken F-35 wreckage was assessed as beyond economic repair, and additional recovery costs of £2.63 million equated to a total cost, at time of loss for £81.8 million.