What started as a seemingly isolated and quickly resolved issue - a single bulkhead that buckled during fatigue testing in November 2010 - has mushroomed into a suddenly public crisis of confidence within the Lockheed Martin F-35 programme.

Finding structural cracks in military aircraft is not uncommon during fatigue tests. But the F-35 was supposed to be different. It was the first combat aircraft launched after a revolution in digital design and simulation tools. The US Government Accountability Office (GAO) never accepted this theory, but the Department of Defense's acquisition planners did.

So the DoD adopted a strategy that called for Lockheed to deliver hundreds of F-35s concurrently during the flight test phase. Lockheed's workers would shift from assembling flight test aircraft right into early production jets, with no inefficient work stoppage or slowdown between the two phases. Then, production would escalate at a steady clip, rising by 150-200% every year to achieve the most efficient learning curve.


 © Lockheed Martin

But now, with 58 F-35s ordered so far and another 485 planned before testing ends in fiscal year 2017, DoD officials are having second thoughts, according to a leaked "quick look review" (QLR) on the programme's concurrency risks by a five-member panel of acquisition experts.

After examining multiple assessment reports over a two-week period in late October and early November, the QLR team recommended that the DoD freeze orders at the 2010 level, excluding foreign sales, of 30 aircraft until Lockheed demonstrates that the F-35's design is mature.

The report was leaked at a crucial moment for the programme's international sales efforts. Japan appeared poised to announce an order for 40 F-35s by 16 December, but reportedly postponed the final decision until 20 December. The F-35 is competing for Japan's F-X order with the Boeing F/A-18E/F Super Hornet and the Eurofighter Typhoon.

Tokyo's decision could have a major influence on South Korea's F-XIII contract decision during 2012, with the same three fighters competing for the 60-aircraft order.

A highlight in the QLR panel's 55-page report is a rarely glimpsed, detailed catalogue of all of the F-35's biggest non-classified problems and concerns. If the programme's critics had hoped for a bonanza of revelations about technical show-stoppers, however, it is likely they were disappointed.

The panel concluded that the F-35 in fact faces no technical issue that would trigger a recommendation to halt all new production. Instead, it recommends that the DoD continue building production aircraft as flight-testing continues, albeit at a reduced level.

The majority of the design problems identified in the report, such as potential immaturity of the integrated power package and complaints about the helmet-mounted display, have already been publicised. Some issues, such as wind buffeting, are described as a major risk, but the report then acknowledged that so far it is no worse than on other fighters.

The report could still mark a major turning-point in the programme's history. By recommending a flat production ramp, the panel challenges a fundamental element of the F-35's original acquisition strategy.

It is the latest in a year-long series of challenges to the concurrency strategy that began when the aluminium alloy bulkhead of a short take-off and vertical landing F-35B cracked after 1,500h of durability testing. Lockheed has acknowledged that the crack was the result of a design error. Ten months later, another crack was found in the forward root rib of a conventional take-off and landing F-35A. Further reviews found structural "hotspots" in all three variants, including a cracked support team for lift fan actuators that have limited vertical landings for three of the five F-35B test aircraft.

So far, none of the structural cracks have required Lockheed to make major design changes that would affect the entire aircraft. The QLR team also found problems that are being addressed locally, without broader design changes.

In any previous fighter programme, these issues may not have received such high-level scrutiny. But no other fighter programme has faced the cost of modifying hundreds of production fighters as flight tests reveal new problems over an 11-year period. Even if the changes are relatively minor, the cumulative cost to make the changes could be prohibitive.

The programme's internal estimates of this "concurrency cost" for the F-35 have not been revealed. A Senate report earlier in 2011 warned that the F-35 could face a similar concurrency bill as the Lockheed F-22, which was listed as $10 million per aircraft, or roughly $1.9 billion in total.

Lockheed officials have disputed the Senate's estimate, however, saying the actual concurrency cost for the F-22 was closer to $5 million per aircraft.

It is also unclear how many F-35s would be subject to the concurrency changes under the existing plan.

The QLR study warned that all 521 production F-35s delivered during the flight test phase could be affected. Lockheed, however, has argued that the F-35 airframe and hardware configuration will be frozen after the fifth lot of low-rate initial production. If the company is right, only 88 F-35s would need the full package of concurrency changes.

That leads to a broad range of cost estimates. The bill could rise to as high as $5.4 billion under the Senate's $10 million estimate for all 543 F-35s scheduled for delivery through 2017. It could also be as low as $440 million, if Lockheed's $5 million estimate for only 88 F-35s is applied.

Vice Admiral David Venlet, the head of the F-35 programme, has not released the actual cost figures, but in one December interview he described the concurrency bill as so high it "sucks the wind out of your lungs".

Lockheed, however, has taken the opposite stance. Company officials still do not accept the DoD's new concern that the concurrency strategy may be flawed. Instead, Lockheed argues that freezing production levels now would also increase costs, as manufacturing and assembly operations become more inefficient. In addition, buying production aircraft more slowly would require the services to preserve the fighters the F-35 would replace for several years more. This is the same argument that Lockheed and DoD programme officials previously made together.

The concurrency strategy has always been contested by the GAO's auditing staff. Four years ago, the office urged the DoD to reduce significantly the overlap of development and production, and to buy no more than 24 production aircraft per year for three years until Lockheed had demonstrated the basic flying qualities of each variant.

"Failure to capture key design knowledge before producing aircraft in quantity can lead to problems that eventually cascade and become magnified through the product development and production phases," the GAO said in a 2007 report.

Source: Flight International