The US Air Force's fleet of Lockheed Martin F-22 Raptors has returned to normal flight operations following the completion of modifications to the aircraft's life support systems. The USAF has been working steadily to remove flight restrictions on the stealthy fifth-generation fighters after the aircraft was grounded for four months in the middle of 2011 due to a series of physiological incidents.

To resume normal operations the service has modified the Combat Edge upper pressure garment and its associated hoses, valves and connectors, the USAF says. The service officially fingered a malfunctioning valve in the upper pressure garment which was not allowing the vest to deflate properly as the primary culprit behind a series of incidents resembling hypoxia. "Completion of this task eliminates the need to restrict flight operations to remain within a 30-minute flying distance from an airfield suitable for landing," the USAF says.



Meanwhile, Raptor squadrons stationed at Joint Base Elmendorf-Richardson, Alaska, have resumed flying air sovereignty mission after those aircraft received a new automatic back-up oxygen system (ABOS). "Altitude restrictions have also been incrementally removed for F-22s that have received the ABOS modification," the USAF says. "Altitude restrictions for training flights remain for non-ABOS equipped F-22 aircraft; however, those restrictions will be removed as each aircraft is modified."

The USAF says that the addition of the ABOS provides additional protection to F-22 pilots while flying at high altitudes and during "the most demanding oxygen-delivery scenarios." The first combat-coded F-22 was modified at Nellis AFB, Nevada, earlier this year in January while Alaska-based Raptors began modifications in February.

USAF officials expect the work to be completed by July 2014.

Source: Flight International