WASHINGTON: Fatigue testing and analysis are turning up so many potential cracks and “hot spots” in the Joint Strike Fighter’s airframe that the production rate of the F-35 should be slowed further over the next few years, the program’s head declared in an interview.

“The analyzed hot spots that have arisen in the last 12 months or so in the program have surprised us at the amount of change and at the cost,” Vice Adm. David Venlet said in an interview at his office near the Pentagon. “Most of them are little ones, but when you bundle them all up and package them and look at where they are in the airplane and how hard they are to get at after you buy the jet, the cost burden of that is what sucks the wind out of your lungs. I believe it’s wise to sort of temper production for a while here until we get some of these heavy years of learning under our belt and get that managed right. And then when we’ve got most of that known and we’ve got the management of the change activity better in hand, then we will be in a better position to ramp up production.”

Venlet also took aim at a fundamental assumption of the JSF business model: concurrency. The JSF program was originally structured with a high rate of concurrency — building production model aircraft while finishing ground and flight testing — that assumed less change than is proving necessary.

“Fundamentally, that was a miscalculation,” Venlet said. “You’d like to take the keys to your shiny new jet and give it to the fleet with all the capability and all the service life they want. What we’re doing is, we’re taking the keys to the shiny new jet, giving it to the fleet and saying, ‘Give me that jet back in the first year. I’ve got to go take it up to this depot for a couple of months and tear into it and put in some structural mods, because if I don’t, we’re not going to be able to fly it more than a couple, three, four, five years.’ That’s what concurrency is doing to us.” But he added: “I have the duty to navigate this program through concurrency. I don’t have the luxury to stand on the pulpit and criticize and say how much I dislike it and wish we didn’t have it. My duty is to help us navigate through it.”

Lockheed Martin, prime contractor on the Pentagon’s biggest program, has been pushing hard to increase the production rate, arguing its production line is ready and it has reduced problems on the line to speed things up. Speeding up production, of course, would boost economies of scale and help lower the politically sensitive price per plane.

But slowing production would help reduce the cost of replacing parts in jets that are being built before testing is complete, Venlet said. Although fatigue testing has barely begun — along with “refined analysis” — it’s already turned up enough parts that need to be redesigned and replaced in jets already built that the changes may add $3 million to $5 million to each plane’s cost.

The price of the F-35, being built by Lockheed Martin Corp. in three variants, has averaged roughly $111 million under the most recent Low Rate Initial Production (LRIP) Lot 4 contract.

The required changes to the aircraft aren’t a matter of safety or of the F-35′s ability to perform its missions, Venlet said. They’re necessary, though, to make sure the plane’s structural parts last the 8,000 hours of service life required. Nor are the weaknesses surprising in the world of fighter jets, he added. The discoveries are “not a quote ‘problem with the airplane,’” Venlet said. “It’s a fighter made out of metal and composites. You always find some hot spots and cracks and you have to go make fixes. That’s normal. This airplane was maybe thought to be a little bit better, wouldn’t have so much discovery. Well, no. It’s more like standard fighters.”

Venlet declined to say how much he thinks production should be slowed. Earlier plans called for the Pentagon to order 42 F-35s in fiscal 2011, but that was cut to 35 and more recently it was dropped to 30. Previous plans, which Venlet’s comments and the unprecedented pressure to cut the defense budget make clear will change, had been to ramp up orders to 32 in fiscal 2012, 42 in fiscal 2013, 62 in fiscal 2014, 81 in fiscal 2015 and 108 in fiscal 2016 before jumping to more than 200 a year after fundamental fatigue and flight testing is done.

Officially the “Lightning II,” the F-35 is a stealthy attack jet Lockheed is building with major subcontractors Northrop Grumman Corp. and BAE Systems for the Air Force, Navy, Marine Corps and 11 allied nations. There is a conventional take off and landing (CTOL) version, an aircraft carrier-suitable (CV) model and a short takeoff/vertical landing (STOVL) jump jet that hovers and lands much like a helicopter. The U.S. services alone are scheduled to buy 2,443 to replace a variety of older fighters, making the $379 billion program the Pentagon’s largest.

Venlet’s comments address a key issue in negotiations between the government and Lockheed for the next contract, LRIP 5. The government paid for design changes and retrofits through the first four lots, but Pentagon acquisition chief Frank Kendall issued a memo in August requiring Lockheed to bear a “reasonable” share of such costs in LRIP 5. Lockheed complained last month that the government was refusing to reimburse it for parts the company was buying in advance for LRIP 5 aircraft as the price and terms of that next production contract are negotiated.

“We negotiated the LRIP 4 contract with a certain amount of resources considered to pay for concurrent changes,” Venlet said. “We were probably off on the low side by a factor of four. Maybe five. And we’ve discovered that in this calendar year, ’11, and it’s basically sucked the wind out of our lungs with the burden, the financial burden.” On top of that, he added, the cost of concurrency changes figures to grow as more testing is done — one reason it’s important to slow production rather than testing.

“Slowing down the test program would be probably the most damaging thing anybody could do to the program,” Venlet said. “The test program must proceed as fast as possible.”

Flight testing of the F-35, though going extremely well lately, is only 18 percent complete, Venlet said. As of Nov. 29, 1,364 test flights had been flown — 896 of them in the past 10 months, despite two stoppages of a couple of weeks each to fix problems found by flying. Under a new program baseline created after the JSF project breached cost limits under the Nunn-McCurdy law, about 7,700 hours of flight tests are planned. “That’s a lot,” Venlet said, adding that number will grow if more problems are found.

Fatigue testing has barely begun, Venlet said. The CTOL variant’s fatigue testing is about 20 percent complete; the CV variant has not started yet. For the STOVL variant, fatigue testing was halted at 6 percent last year and has not resumed after a crack in a large bulkhead in the wing was found, requiring a major redesign of that part.

That bulkhead crack was one of five discoveries in the F-35B that required engineering changes, one reason former Defense Secretary Robert Gates placed it on “probation” last January and said the Marine’s plane should be canceled if the problems weren’t solved within two years. Venlet repeated earlier statements that he was sure the changes needed to take care of the problems are now in place, though he wants to await final testing of them this winter before saying it’s time for the jump jet to come off of probation.

After discovering the bulkhead crack in the B variant last year, Venlet explained, “We said, ‘Well, where else do we need to look?’ The fallout of that additional analysis has revealed additional spots that (may fail in) less than 8,000 hours of service life. We call them ‘analyzed low-life hot spots.’” In other words, he said, engineering analysis indicates those spots “are going to crack” well before the parts in question have flown 8,000 hours.

“The question for me is not: ‘F-35 or not?’” Venlet said. “The question is, how many and how fast? I’m not questioning the ultimate inventory numbers, I’m questioning the pace that we ramp up production for us and the partners, and can we afford it?”