F-35: Blade Bummer

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Department of Defense

The F-35 engine turbine blade that failed in a 2007 test.

The news that the Pentagon’s fleet of 51 F-35 fighters has been grounded because of a half-inch crack in one of its engine’s turbine blade is one of those problems that can truly be called a teething issue: it’s something that happens on most every high-tech jet engine that is pushing the engineering envelope.

Pentagon officials over the weekend suggested waiting for Pratt & Whitney, the maker of the F-135 powerplant that powers the F-35, could take a week to 10 days.

Sometimes such problems are natural; sometimes not.

All involved want to make sure that whatever caused the crack is unique to that particular blade and not a threat to all F-35 engines. A single-engine warplane like the F-35 could be doomed by a disintegrating turbine blade.

This isn’t a new problem with the F-35 powerplant; a similar blade cracked during testing in 2007. “Most likely root cause is resonant response to aerodynamic excitation by the upstream 54 vanes in STOVL operation,” an investigation into that earlier failure concluded. “No indication that defects in material properties or single crystal orientation significantly contributed to the failures.”

News of the grounding comes at a sensitive time, as F-35 advocates try to convince the Australian government this week to stick to its original plan to buy 100 of the jets. The grounding is only the latest in a series of problems for the program, which has been plagued by delays and cost overruns.

The U.S. military plans on spending $396 billion for 2,457 of the planes, making it the most costly weapons system in the history of the world (the planes, built by Lockheed Martin, are slated to cost $332 billion; Pratt’s price for the engines is projected to be $64 billion). But the program’s problems, and looming defense-spending cuts, are likely to cut the program, perhaps by as much as half, defense officials say privately.

The grounding affects the F-35s being built for the Air Force, the Marines and the Navy because all three variants use the same engine (“Putting all your engines in one basket,” one defense official says). There had been a plan to develop competing engines for the F-35 – as there were for the older F-15s and F-16s the F-35 is slated to replace – but the Pentagon and Congress agreed two years ago to scrap an alternative engine, saying it wouldn’t be worth the added investment.