| Air
Combat Command officials cleared a portion of the F-15 Eagle
A through D model aircraft Jan. 9 for flying status and recommended
a limited return to flight for Air Force units worldwide following
engineering risk assessments and data received from multiple
fleet-wide inspections. However, almost 200 aircraft are still
grounded, some may never fly again.
The return to fly order and recommendation applies only to
those F-15 aircraft, about 60 percent of the total Air Force
F-15 A through D fleet, that have cleared all inspections and
have met longeron manufacturing specifications. The order and
recommendation follows more than two months of stand-down actions
after an Air National Guard F-15C aircraft experienced catastrophic
structural failure and broke apart in flight during a basic
fighter maneuver training sortie in Missouri Nov. 2, 2007. (see
video
animation)
Technical study of the F-15’s recovered wreckage determined
that the component in question did not meet the manufacturer’s
structural specifications and had developed cracks that caused
it to fail, according to the report. According to the investigation's
findings, 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 long-term future of the F-15 is in question
Much of the U.S. Air Force’s 665 F-15s had been grounded
since the incident. 441 F-15s in the Air Force inventory are
model A through D. During the fleet's grounding, every F-15
base conducted a series of detailed inspections. After the preliminary
examination, 224 F-15E aircraft were returned to service as
they were not affected by this specific problem. As of Jan.
9, the Air Force approved 260 of these aircraft (60 percent)
to return to service with no flight restrictions. The remaining
182 of the aircraft, manufactured between 1978 and 1984 are
remained out of service pending additional tests. Inspections
determined that these aircraft have at least one longeron that
does not meet blueprint specifications. Deviations in these
longerons will be analyzed at the Warner-Robins Air Logistics
Center. The analysis is expected to take approximately four
weeks to complete. Once the analysis is complete, Air Combat
Command will be able to better determine which aircraft will
need further inspection, or repair, before returning them to
flight.
Sofar nine of the inspected F-15s have been found to have longeron-fatigue
cracks and have been grounded. The Air Force is scheduled to
retire some of these aircraft this year as it may be cost-prohibitive
to repair them. "We're going over each and every aircraft
to make a determination," Gen. John D.W. Corley, the commander
of Air Combat Command 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 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,. "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 Air Force first began flying the F-15 eagle in 1972. The
Eagles are currently being replaced by the fifth generation
F-22 Raptor, currently in production with active squadrons at
Langley Air Force Base, Va., and Elmendorf AFB, Alaska. As F-15s
operations were brought to 'stand down', 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. According to Gen. Corley, 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." Foreign air forces operating
the F-15 Eagle followed the USAF and reduced operations of their
Eagles to the minimum.
While the US Air Force may have other alternatives
for air superiority fighters (such as the F-22 Raptor), the
Japanese, Saudi and Israeli air forces face a major problem
regarding their fleets of first line aircraft.
(Updated: January 11, 2008)
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