Even though manufacturer Lockheed Martin continues to build the aircraft at its Marietta, Ga., factory, the company is unable to do required flight testing for each aircraft as it leaves final assembly. Nor can government test pilots from the Pentagon's Defense Contract Management Agency (DCMA) fly their acceptance flights for new aircraft as they are readied for delivery.
"Our final assembly is scheduled through December 2011. That is still ongoing at Marietta. We delivered aircraft 4181, and that was on June 22, to the Air Force, so they have that as their aircraft," said Lockheed spokeswoman Stephanie Stinn. "After that aircraft, we can't do the required acceptance flights."
Technically, four aircraft have been delivered to the Air Force, but are being stored at Marietta pending the lifting of the flight restrictions. When the Air Force resumes F-22 flight operations, those aircraft will be flown to Langley Air Force Base (AFB), Va.
Two further aircraft, 4182 and 4183, have been completed, but the company and DCMA can't do required flight testing on those jets, Stinn said. The aircraft are being stored in a near-flight-ready status, she said.
Aircraft "4182 and 4183 were scheduled to deliver in July, but they're not in a position to do any sort of test flights, so we can't deliver," Stinn said. "Maybe early August, but we don't have a definitive date."
Aircraft 4182 and onwards, which have not undergone any of their acceptance flights, have yet to receive their final stealth coatings. The coatings are applied only after a number of flight tests have been completed, and as a result, a backlog is slowly building up.
Before the stealth coatings are applied, the aircraft fly coated only with a primer.
The Raptors have been "stood down" since May 3, according to Air Force spokeswoman Capt. Jennifer Ferrau, due to a suspected problem with the aircraft's oxygen generator.
According to one Air Force document, after reviewing work on a study of the F-22 On-Board Oxygen Generation System (OBOGS), the chief of Air Combat Command, Gen. William Fraser, instituted a temporary flight restriction for the F-22 and directed a Class E Safety Investigation.
The investigation, which began in January, includes the OBOGS installed in the A-10, F-15E, F-16, F-22, F-35 and T-6 aircraft. Fraser appointed Maj. Gen. Steve Hoog, commander of Ninth Air Force, as the investigating officer.
The flight restriction applies to all F-22 crews, but test pilots at Edwards AFB, Calif., are operating under a flight waiver that allows them to fly certain test sorties. Air Force officials at Edwards could not immediately say what kind of test sorties those aircraft are flying.
The grounding is hurting the readiness of operational F-22 pilots, who cannot maintain their currency on the twin-engine jet. The Air Force is using simulators to ease the problem as much as it can.
"Pilots and ground crew continue to train in simulators and perform ground tasks to stay as proficient as possible. Once the aircraft are cleared to fly again, there will be a period where the pilots will need in-flight training to become fully proficient on the aspects of flying that simulators cannot replicate," Ferrau said. "Some live flight is required for high-G maneuvering flight, a true outside visual, and in-flight decision-making in a dynamic environment where simulators are lacking."