Lockheed Martin has started final assembly on the last F-22A Raptor ordered by the US Air Force, but the delivered fleet remains grounded over concerns about the pilot's breathing system inside the cockpit.

Lockheed has mated the fuselage sections of the F-22A with USAF serial number 09-4195. In final assembly, the company's workers in Marietta, Georgia, will instal the wings, tails, landing gear and Pratt & Whitney F119 engines, among other avionics integration and check-out tasks.

The last of 195 aircraft ordered by the USAF, including 185 remaining operational airframes, is now scheduled for delivery early in the second quarter of 2012.

The updated schedule is delayed slightly from the company's plan last year to deliver the last F-22A before March. Lockheed halted deliveries to the USAF while the F-22 was ordered grounded by the Air Combat Command after 3 May.


 © US Air Force

That order continued to be in effect after this article went to press, although the fleet's status could change quickly.

Although the fleet is technically grounded, some F-22As have been allowed to fly for specific reasons. As Hurricane Irene approached the US east coast in late August, the USAF scrambled F-22As and other fighters away from Langley AFB, Virginia.

USAF officials have confirmed that hypoxia was ruled out as a potential cause of the fatal F-22 crash at Joint Base Elmendorf-Richardson, Alaska, last November. The actual cause of the incident has not been released.

That unexplained crash and a string of reports of hypoxia illness prompted the USAF to voluntarily stand down the F-22A fleet. The service is continuing to study aircraft onboard oxygen generating systems (OBOGS) for the F-22A and several other aircraft, including the Lockheed F-35A.

The OBOGS investigation is led by a scientific advisory committee chaired by Gregory Martin, a retired USAF general and fighter pilot.

Source: Flight International