F-35 Cleared For Flight; Turbine Crack Cause Identified

By on March 01, 2013 at 1:03 PM


WASHINGTON: The entire F-35 fleet has been cleared to resume flying only one week after being grounded for the second time this year. In vintage Pentagonese, this is how the return to flight was announced today to Capitol Hill:

“Upon completion and compliance with the immediate action Time Compliant Technical Directive (TCTD) issued this week to borescope inspect the LPT stage 3 turbine blades, F-35 LRIP aircraft are returned to flight status. Additionally, a 25 Effective Flight Hour (EFH) reporting cycle of creep damage will now be implemented to monitor and limit turbine creep exposure.”

Basically, it means that a potentially really serious problem — turbine blades suffering from high cycle fatigue — was not the cause of the half-inch crack which led to last week’s highly publicized grounding.

It also means that the Joint Program Office and Pratt & Whitney will be monitoring the turbine blades for what will probably be several weeks of test flights.

Here’s the press release version from the Joint Program Office which oversees the largest conventional weapons program in history: The F-35s “have been cleared to resume following engineering analysis of the turbine blade which developed a crack.

This decision concludes a cautionary flight suspension that began on Feb. 21 after a 0.6 inch crack was found on a 3rd stage turbine blade of a test aircraft at the Edwards Air Force Base F-35 Integrated Test Facility during a routine inspection.”

One of the interesting details in the JPO release is that no other cracks were found in any of the other F-35s flying.

Pratt & Whitney, who make the engines and were the lead on investigating the cause of the crack, issued a release saying that: “We believe that a key factor for the blade crack stemmed from the unique operating environment in flight test. The engine had operated more than four times longer in the high-temperature environment of the flight envelope than the typical F-35 duty cycle. The exposure in this high temperature part of the envelope led to a separation of the grain boundary on this single blade.”

The military, industry and Congress will keep watching this to make sure the problem is not systemic and does not repeat.

Comments

  • tee

    That’s great a Aircraft that must rely on After-burners to escape enemy aircraft, because it turns like a 60′s F-4 or F-5 can’t use it’s After-burners for to long or the engine will fall apart? Great Read from ” Defense-Aerospace” for more info on it and what it could mean for the JSF.

    .”The F-35’s Afterburning Engine Can’t Stand Heat”

    .http://www.defense-aerospace.com/articles-view/feature/5/143079/afterburning-engine-can%E2%80%99t-stand-heat.html

    • Ctrot

      And from what factual evidence to you come to the conclusion that the F-35 can’t use it’s afterburner? An article written by a shill like Giovanni de Briganti? Really,the hyperbole posted by you and the rest of the F-35 haters is annoying.

      Yes the F-35 is a troubled program, but no one is well served by attacking it based on ignorant, hyperbole laden strawman arguments. Doing so only weakens legitimate complaints about the program.

  • Fueldrum

    AOL defense needs to become far more objective in its analysis of this.

    “The military, industry and Congress will keep watching this to make sure the problem is not systemic and does not repeat.” Well, what will they do if it is systemic and does repeat?? Watching is hardly “making sure.”

    Yet another serious F-35 problem with no verifiable solution in hand, 16 years after the program began.

    • http://twitter.com/SMSgt_Mac SMSgt Mac

      “…what will they do if it is systemic and does repeat??” Well there is no indication it is systemic, but generally they apply a little thing called ‘Engineering’ when problems become real. But I’m sure the program appreciates someone losing sleep over non-existent strawmen. Sheesh. Yet another Low Information Voter making up a “serious F-35 problem” out of a simple mechanical part failure with no idea how long the program has been around.

      For the casual reader tripping over this thread who might not know any better due to the widespread overwrought laments from the legions of ignorami, the JSF contract was awarded just over 11 years ago, first flight of the de facto prototype (AA-1) was just over 6 years ago. The Technology Demonstration program was concluded with award of the JSF contract. During that program, Experimental Test aircraft (X-32 and X-35) were built to demonstrate design concepts and technology needed to build a desired aircraft.

      • vstillwell

        Not sure why a “low-information voter” would bother reading this article about the F-35 and comment on it. Frankly, people that throw those terms out at others are just frustrated that they don’t agree with them on something. Name calling is juvenile.
        The F-35 programs is troubled. The planes performance, so far, has not been very strong. The crack, to me, is no big deal. The overall price tag and the mountain of other problems is a big deal. Heck, even some officers in the Pentagon agree that the program has been a mess from the start.

  • tee

    I wonder if this might have something to do with the engine problem, from today’s “Wall Street Journal” — ” Pratt & Whitney unit disclosed it has broken up an alleged
    fraudulent-testing scheme by a sister United Technologies unit,
    affecting tens of thousands of engine parts used on popular business
    jets and turboprop aircraft flown by airlines around the world”:..
    .
    Was it only Business jets or ???

    .http://online.wsj.com/article/SB10001424127887324539404578338574132970026.html
    .
    also covered in. Defense-Aerospace
    .http://www.defense-aerospace.com/articles-view/release/3/143145/**updated%3A-pratt-says-faulty-testing-affected-no-military-engines.html

  • http://www.facebook.com/robert.mcgrath.1272 Robert McGrath

    Tee who died and made you avaionics expert, “turns like a 60′s F-4? I don’t think so,,and this coming from an idiot who has probably never flown a Cessna 150 is just plain stupid…The F-35 is one mean machine, and will be the work horse of our military for years to come if the idiot in charge doesnt scrap it..

  • peterhobbs

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