The US Air Force has removed the majority of operating restrictions previously imposed on its Lockheed Martin F-22 fighter pilots, but is continuing to limit the maximum altitude to which the type can be flown.
Around 21,000 sorties have been completed without incident since the USAF lifted a safety-related grounding order imposed for three months late last year, says Maj Gen Larry Wells, commander of its Ninth Air Force organisation. The suspension was introduced following an investigation ordered after several pilots had reported encountering hypoxia-like symptoms while flying the stealthy type. This traced the problem to issues with the Raptor's onboard oxygen generation system's oxygen schedule and Combat Edge upper pressure garment.
Several restrictions initially imposed after a return-to-flight decision was approved, including the need to remain within 30min flying time of a landing site, have now been removed, but pilots still must stay below an imposed limit of 35,000ft (10,700m), Wells says. This can be increased to 40,000ft if a high-altitude flight suit is being worn. A new pulse oximeter system to monitor the pilot's health and warn of any hypoxia-like event is now being used inside the helmet, in place of an earlier finger-mounted design.
Source: http://www.flightglobal.com/news/articl ... ns-379056/