Cracking has been found in the aft bulkhead of the BH-1 fatigue test F-35B after just 1500 hours of durability testing.
The cracks were found in the aft of five forged aluminium bulkheads which carry the aircraft’s engine and onto which the wings and other major structural components are attached, and as such they carry major loads. It is unclear whether the cracks were as a result of a design fault or an abnormal test parameter, but all flight test aircraft have been inspected and no other cracks have been found. The aircraft are to be rated for 8000 hours and fatigue testing is expected to run to 16,000 hours.
The bulkhead is one area that was addressed during the F-35’s 2004/05 SWAT weight loss campaign, and was changed from titanium to aluminium in the B model to reduce weight. The same bulkhead in the F-35A and C models is still titanium.
In the meantime, a major review of the F-35 by program head VADM David Venlet is expected to be presented to Pentagon acquisition head Ashton Carter on November 22, and then to US Defense Secretary, Robert Gates.
Compared to previous reviews, Pentagon spokesman Geoff Morrell said Venlet’s review will be a “deeper dive so as to avoid future surprises about this program,” but added no decisions were likely to be made straight after the review’s presentation.