Major F35B Component Cracks
(Source: Aviation Week’s Ares blog; posted Nov. 17, 2010)
The cracks have appeared in the STA 496 bulkhead, located just aft of the main landing gear, of the F-35B static test airframe. (Alcoa illustration)
PARIS --- The F-35 Joint Strike Fighter has encountered a new, serious problem as a bulkhead on an F-35B fatigue test airframe developed cracks after only 1,500 hours of tests that are due to last 16,000 hours.

“The aft bulkhead of the F-35B BH-1 fatigue-test specimen has developed cracks after 1,500 hours of durability testing,” Aviation Week’s Ares blog reported yesterday. “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.”

This incident again raises questions about the technical viability of Lockheed Martin’s redesign of the aircraft, especially for the F-35B STOVL version, and about the company’s claims that its simulation systems are so good that flight testing can safely and drastically be cut back to lower costs.

Lockheed Martin issued the following statement on the issue:

"During a recent durability ground test, fatigue cracks were discovered in the aft bulkhead of BH-1, an F-35B ground test aircraft. The cracks were discovered during a special inspection when a test engineer discovered an anomaly; the aircraft has logged approximately 1500 hours of durability testing. Precautionary inspections were conducted on all flight test aircraft and the CTOL ground test aircraft. No additional cracks were found and flight testing has not been impacted.

“The root cause investigation is underway and will determine if the cracks were caused by a test anomaly that is not indicative of flight conditions, an engineering issue or a material failure. Durability testing is conducted early in the development of a new aircraft program to avoid costly sustainment issues later in the life of the aircraft."

A knowledgeable source confirmed to that the frame in question is the STA 496 bulkhead, and added that “by all accounts, so far, the undercarriage loads are in the mix, which brings into focus a debate that was had some time ago about whether or not the full spectrum of the [Conventional Take-Off and Landing] loads should be used as well as those for the STOVL scenarios ([Vertical Landing] and, possibly, Ski-Jump)” for the fatigue test program.

Click here to read the Ares report on the Aviation Week website.


Lockheed Finds Cracks in F-35B Test Aircraft (excerpt)
(Source: Fort Worth Star-Telegram; posted Nov. 17, 2010)
Lockheed Martin has discovered a potentially significant problem with one model of its F-35 joint strike fighter, the company reported Wednesday.

The news comes just days before an important Pentagon meeting on the program's continuing delays and rising costs.

Lockheed issued a statement saying its Fort Worth engineering staff had found cracks in the rear bulkhead -- a major structural part weighing about 300 pounds -- of an F-35B ground test plane undergoing fatigue testing.

The cracks were found after the plane had been subjected to the equivalent of about 1,500 hours of flight time. The airplane's structural components are designed to last at least 8,000 hours.

Lockheed said the cracks were found in a special inspection after engineers discovered unusual data from test instruments.

The latest problem comes at a key juncture for the troubled F-35, which, at an estimated $382 billion, is the costliest weapons program ever.

Pentagon officials have been reviewing the program for weeks to determine how to expedite testing and fix failing components, particularly of the short-takeoff-vertical-landing F-35B designed for the Marines.

A Defense Acquisition Board plans to meet Monday to review cost and test data and approve any changes in budgets and schedules.

There have been unconfirmed reports that senior Pentagon officials were at least considering the possibility of canceling the F-35B model to focus on getting the other two versions tested and into service.

Lockheed did not disclose when the inspection took place but said it had inspected all of the other flight test aircraft and the ground test F-35A model. "No additional cracks were found, and flight testing has not been impacted," the company said.

Eight F-35s are now in flight testing, including four F-35Bs.
Four more are built and being prepared for flight testing, and six have been built for ground testing. (end of excerpt)

Click here to read the full story, on the Star-Telegram website.


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