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Cracks on an F-35B’s primary support structure found last year are more extensive than previously thought, triggering a halt in ground-based durability testing until the fourth quarter of this year.
The initial cracks were found on section 496, a primary wing carrythrough bulkhead, last fall, prompting officials to stop the ground-based testing at hour 9,400 during the second life’s worth of use — or second 8,000 hr. of equivalent flight hours — to investigate the issue.
Since then, cracking also has been discovered on adjacent bulkheads, according to Joe Dellavedova, spokesman for the F-35 Joint Program Office. “Subsequent inspection of surrounding structures in light of this discovery found additional cracks in two of the other adjacent bulkheads,” he says.
Because the discoveries were found to occur beyond the first 8,000 hr. of use, the issue is not affecting flight operations for the young F-35B fleet. These issues are also, thus far, limited to the B model that employs a sophisticated lift-fan for vertical takeoff and landing operations for the U.S. Marine Corps. The U.K. and Italy also are expected to buy the F-35B.
It's gonna replace the A-10 huh?
So just before that daft bint comes on here stealing oxygen (becky the troll?), this was in the second life, ie. after the first 8000 hour life?
Are bulkheads usually part of a mid life maintenance program?
Another thing, does the F35b test bed simulate the engagement and disengagement of the fan for an equivelant number of flying hours? For example, perhaps (like some jet engines) the F35b would (maybe it does) have 2 tests, starts and flying hours, so the maintenance routing for a F35B is either 8,000 flying hours or (for example) 2,000 fan engagements, whichever is first.
Surely some of the catapult aircraft are similar?
reply to post by punkinworks10
In the case of the F-15 and so many others it was money. It was cheaper to build them just slightly too thin, and from testing they were strong enough to last the planned life cycle. Then the life cycle was extended, and now there is an issue.
The aft bulkhead of the F-35B BH-1 fatigue-test specimen has developed cracks after 1,500 hours of durability testing, Ares has learned. This is less than one-tenth of the planned fatigue test program, which is designed to prove an 8,000-hour airframe life with a safety factor of two.
The bulkhead design was modified in the course of the jet's weight-saving redesign in 2004-05, switching from forged titanium - proven on the F-22 - to a new aluminum forging process developed by Alcoa.
According to Lockheed Martin,"the cracks were discovered during a special inspection when a test engineer discovered an anomaly." The company says that flight-test aircraft have been inspected and found crack-free and that flight testing has not been affected.
Engineers are still investigating the failure and it is not yet known whether the cracks reflect a design fault, a test problem (for example, a condition on the rig that does not reproduce design conditions) or a faulty part.
If the bulkhead design is found to be at fault, it will be a serious setback for the F-35B program, potentially imposing flight restrictions on aircraft already in the pipeline or requiring expensive changes on the assembly line.
Six F-35Bs are included in the LRIP-2 contract, now in the mate or final assembly stage, and nine in the 17-aircraft LRIP-3 batch - which are intended to support initial Marine Corps training and operations. If a redesign is necessary it could also delay deliveries of LRIP-4 aircraft.
Bulkheads are a major structural component of the F-35, carrying the major spanwise bending loads on the aircraft. They are produced from forgings weighing thousands of pounds, which are machined into the final shape. They are among the longest lead-time items in the airframe, being built into mid-body sections produced by Northrop Grumman.
The F-35A and F-35C bulkheads are still made of titanium, as are similar bulkheads on the F-22.
Correction: Northrop Grumman asks us to point out that the parts in question are built into the wing/centersection assembly made by Lockheed Martin.
reply to post by punkinworks10
Yeah sorry, I read Drognridrs post as a critic of UK manufacturing and America is best.
I agree too many cooks is a major issue especially with my experience on Eurofighter Typhoon.