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...