US Air Force,
WASHINGTON: Senior Air Force leaders gathered for a press conference here Jan. 10 to share findings from the accident investigation board currently examining the Nov. 2 crash of a Missouri Air National Guard F-15C Eagle.
The upper right longeron — one of four metal beams that help hold the cockpit to the main fuselage — was found to have manufacturing defects, said Col. William Wignall, the head of the accident investigation.
The one longeron, already not up to design specifications, cracked apart under the stress of a 7G turn, the colonel said. This led to the other longerons failing as well, which then caused the cockpit to separate from the rest of the fuselage. The pilot was able to eject, but suffered a broken arm when the canopy snapped off.
The incident led to the grounding of the Air Force's F-15 fleet. As of Jan. 9, the Air Force approved 60 percent of F-15 A through D models to return to service with no flight restrictions
“We've had great involvement from Boeing during the investigation,” Colonel Wignall said. “In fact, they're the ones who determined the longeron was the problem. This was then confirmed by the Air Force Research Laboratory.”
During the fleet's grounding, every F-15 base conducted a series of detailed inspections. During that timeframe, nine other F-15s have been found to have similar cracks in their longerons.
The difficulty is that issues have been found with F-15s built between 1978 and 1985, across A through D models at several bases, so no one source of the problem can be isolated, said Gen. John D.W. Corley, the commander of Air Combat Command.
“This isn't just about one pilot in one aircraft with one bad part,” General Corley said. “I have a fleet that is 100 percent fatigued, and 40 percent of that has bad parts. The long-term future of the F-15 is in question.”
In the meantime, F-22 Raptor, F-16 Fighting Falcon and F-15E Strike Eagle pilots have picked up the F-15s usual mission of patrolling and defending American airspace and interests.
That has had a ripple effect among those pilots' missions, General Corley said.
“We don't have a full and healthy fleet, so we've gotten behind on training missions, instructor certifications, classes and exercises,” he said. “And in the meantime, our pilots have to be ready to deploy.”
For some of the nine F-15s that have longeron cracks, it may be cost prohibited to repair them, General Corley said. The Air Force is scheduled to retire some of these aircraft in the next fiscal year.
“We're going over each and every aircraft to make a determination,” he said. “We will take some F-15s out of the inventory. It just doesn't make sense to spend the time and money if it won't be worth it for some aircraft.”
The Air Force first began flying the F-15 in 1972 and has 665 F-15s and F-15Es in its inventory. Its replacement, the fifth generation F-22, is currently in production with active squadrons at Langley Air Force Base, Va., and Elmendorf AFB, Alaska.
