Air Force finds structural flaws in F-15s

About 40 percent of the Boeing F-15 fighters grounded after a November crash have major structural components that don't meet original manufacturing specifications, the U.S. Air Force said Wednesday.

Air Force inspectors determined 183 of 442 aircraft that remain grounded have at least one structural component known as a longeron "that does not meet blueprint specifications."

Each F-15 has two longerons, a critical support structure that runs along the length and side of the aircraft.

The Air Force said 60 percent of the fighters grounded since the Nov. 2 accident have been cleared for flight after intense inspections that included using ultrasonic equipment and special dyes that penetrate the frame to check for cracks.

The F-15, introduced in 1975 by McDonnell Douglas, is no longer in production for the U.S. Air Force. Boeing, which bought McDonnell Douglas in 1997, continues to build the plane for South Korea and Singapore.

"Aircraft-inspection results and counsel from both military and industry experts have made me confident in the safety of a portion of the fleet," Gen. John Corley, head of the Air Combat Command, said in the statement.

"As a result, I have cleared those F-15s to return to fly," he said.

Still, "deviations" in the longerons "determined not to meet blueprint specifications will be analyzed by the Air Force Air Logistics Center over the next month," the news release said.

Once the analysis is complete, the Air Combat Command "will be able to better determine which aircraft will need further inspection or repair before returning to flight," the service said.

"Those that fall outside manufacturer's specifications will require further engineering evaluation."

The Nov. 2 crash of a Missouri Air National Guard F-15C aircraft was caused by the failure of an upper-right longeron "that did not meet manufacturing specifications," the Air Force said. The pilot ejected safely and survived.

Major David Small, an Air Force spokesman, declined in an e-mail statement to say what steps, if any, the service was taking to penalize Boeing for the flaws.

Boeing spokeswoman Pat Frost said in an e-mailed statement that the company "has not seen a final Accident Investigation Report.

"However we are working with the Air Force to analyze the data gathered from fleetwide inspections. Once all of the data have been analyzed, a need for further inspection or repair can be determined," Frost said.