Most Air Force F-15s Get Green Light to Fly

American Forces Press Service ^ | Jim Garamone

[SandRat]

WASHINGTON, Jan. 10, 2008 – About 60 percent of the Air Force’s F-15 Eagle fighter fleet has been found fit and ready to again defend the skies over the homeland or perform overseas missions, senior U.S. military officers said here today.

An F-15A Eagle lands at Hickam Air Force Base, Hawaii Jan. 9, 2008. Photo by Tech. Sgt. Shane A. Cuomo, USAF   
(Click photo for screen-resolution image);high-resolution image available.

About 260 F-15s were returned to full operational duty Jan. 8 after receiving nose-to-tail inspections following the Nov. 2 midair breakup of a Missouri Air National Guard jet as it flew south of St. Louis during a training mission, senior Air Force officers told reporters today at the Pentagon following today’s release of the accident investigation report. Much of the Air Force’s nearly 700 F-15s had been grounded since the incident.

The report cited the failure of a structural component called a longeron as causing the F-15C to break into two parts. Although injured, the pilot was able to successfully eject from the aircraft and parachute safely to earth.

“We are ... lucky that this pilot survived,” said Air Force Gen. John D.W. Corley, commander of Air Combat Command, at Langley Air Force Base, Va. ACC furnishes airpower for stateside defense and overseas military purposes. The F-15 constitutes the backbone of United States’ domestic air defense assets, said Corley, who wears a second hat as air component commander for U.S. Joint Forces Command, at Norfolk, Va.

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.

When the upper-right-hand longeron broke, the remaining structure along the forward fuselage was unable to distribute the loads in that area, which caused the aircraft to break into two at a point just aft of the cockpit area, explained Air Force Col. William Wignall, president of the accident investigation board.

“This is not just a bad part, this is a bad part that’s been under huge stress” for nearly three decades, Corley said.

The accumulated fatigue and stress on that part caused it to crack and eventually to break, he said.

F-15 aircraft returned to duty have undergone extensive inspections, said Air Force Maj. Gen. Thomas J. Owen, commander of Warner Robins Air Logistics Center, Air Force Material Command, Robins Air Force Base, Ga. Owen’s unit is responsible for logistics support for various Air Force aircraft, including F-15s.

“No (operational) restrictions will be imposed on the aircraft that have passed the inspections, although future recurring inspections will be required to the upper-right and left longerons,” Owen said.

About 182 F-15 A through D models manufactured between 1978 and 1984 remain out of service pending additional tests, officials said. Nine other F-15s have been found to have longeron-fatigue cracks and have been grounded. About 441 F-15s in the Air Force inventory are model A through D, while 224 others are of the newer E series.

Inspections performed on the F-15 fleet are more than 90 percent complete. They include thorough checks of hydraulic and electrical lines, fasteners, aircraft fuselages and skins, and all internal structural components, including the longerons, Owen explained.

Air Force Material Command and its partners in industry “remain committed to the defense of our nation and the safety of the men and women who operate the F-15 aircraft throughout the world,” Owen said.

[Tenacious 1]

It sounds like the F-15 is good to go for another 30 years or so.

Well worth it.

[Husker8877]

My girlfriend’s dad worked on the radar systems for the F-15 years ago, so he is very happy they got their structural problem worked out.

He has nothing but respect for the aircraft.

[furquhart]

There are F-15A’s still flying?

[Doe Eyes]

It sounds like the F-15 is good to go for another 30 years or so.?

Yes, about 60%, the other 40% are trash.

[MediaMole]

According to the serial 78-522, the aircraft in that photo is an early F-15C.

[RightWhale]

What’s a longeron? Is that what holds the wing together?

[Erasmus]

They’re structural members that run from front to back, just under the skin. Among other things, they hold the (transverse) bulkheads in position.

I believe longerons are placed in significant compression or tension when the aircraft is undergoing severe pitch changes, e.g., during landing and high-G takeoff.

[Erasmus]

To clarify, I meant to say “under the skin of the fuselage.”

[ops33]

From Wikipedia

“In aircraft construction, a Longeron is a thin strip of wood or metal, to which the skin of the aircraft is fastened. Longerons are attached to formers (also called frames), in the case of the fuselage, or ribs in the case of a wing, or empennage. In very early aircraft, a fabric covering was sewn to the longerons, and then stretched tight by painting it with dope, which would make the fabric shrink, and become stiff.”

[SandRat]

Not beign AF you got me.

[RightWhale]

Apparently it is part of the skeleton they attach the skin to.