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  • GAO Discloses New JSF Stealth Problems
    Posted by Bill Sweetman 4:19 PM on Apr 08, 2011

    Dozens, even hundreds of early Joint Strike Fighters could require rework because of manufacturing defects that make them less stealthy, according to the Government Accountability Office in its latest report.

    When the GAO issued its preliminary report on the JSF in mid-March, I noted:
    The GAO also hints about "emerging concerns about ... stealth-related issues" - which to those of us who have been through the history of LO, sounds a bit ominous.
    The new report goes into more detail:
    Defense Contract Management Agency officials noted difficulties in manufacturing outer mold lines, resulting from tight tolerance specifications and multiple manufacturing methodologies among the different JSF parts suppliers. The manufacturing processes are new and different from legacy practices.

    Inability to meet the outer mold line requirements could have major impacts on cost as well as stealth requirements and capabilities.

    This problem is not expected to be resolved until the June 2015 time frame after which a large number of aircraft will have been built and would need to be retrofitted for any design changes.

    Program officials stated some redesign activities have begun and will take into the 2013 timeframe to begin developing the changes, their costs, and implementation. The effects of these changes could extend out into 2015, but will be prioritized to reduce performance and cost impacts.
    I've asked Lockheed Martin and the program office to comment on this, but here is some context.

    When an airplane is illuminated by radar, several things happen. One of them is that the radar energy generates surface electrical currents that flow over the skin -- it's been compared to St Elmo's fire. Physical or electrical discontinuities -- steps and gaps, or where composites touch metal -- can cause  complex scattering and compromise stealth.

    Avoiding or managing the problem is a big deal in stealth design. Many early stealth aircraft made heavy use of putties and other sealants on panel gaps. That's undesirable, because if the sealants have to be removed and replaced it not only takes time directly, but may ground the aircraft while multiple layers of sealants and coatings are allowed to set.

    On the F-22, a lot of major panel joints were saw-toothed. With the F-35, however, the idea was to avoid that complexity and instead build the aircraft to higher tolerances.

    As for "multiple manufacturing methodologies among the different JSF parts suppliers", this reminds me of research for a 2003 Air & Space story about the origins of Airbus: the visionary goal of having pieces from France, Germany and Britain turn up in Toulouse and just snap together took a lot of very difficult work.

    How many aircraft could require modification? Plans call for the US to have ordered 132 aircraft through 2013 (contract year) and 275 by 2015.

    In addition to this developing story, the GAO also says that a new estimate of procurement cost from 2017 onward -- and a new acquisition program baseline, essential for a new Milestone B approval -- will not be completed until late 2011.

    The GAO notes, too, that the Pentagon's projected procurement costs between now and 2016 depend on international partners buying 223 aircraft in that period. That's actually more than the US Air Force plans to buy in the same years. Various factors, the GAO says "may result in reduced or deferred foreign buys." I'd call that a good possibility.

    There is some good news in the report: with the latest schedule extension and more development money, the GAO sees less risk in the development program than before.

    Finally -- and anyone who wants to comment with "the GAO is always negative" had better read this first -- Appendix II of the new GAO report is an extensive and detailed "we told you so."

    Tags: ar99, tacair, jsf, gao

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