F-22 restrictions lifted after oxygen problem identified
An F-22 Raptor goes through maneuvers at the Arctic Thunder Airshow in Anchorage on July 28 at Joint Base Elmendorf Richardson. The F-22s at JBER and around the nation have had flight restrictions lifted after the sources of problems affecting oxygen delivery to pilots were discovered.
An F-22 Raptor ripped through the air above the packed grounds of Joint Base Elmendorf-Richardson as thousands gaped, awed and took photos of the zooming aircraft at the Arctic Thunder air show in Anchorage July 28.
Coincidentally, Arctic Thunder came just days after the U.S. Air Force lifted restrictions on the F-22s after faulty valve and clothing issues were identified. Several pilots had experienced oxygen depletion while flying the $145 million aircraft.
All F-22s were restricted from long-duration and high-altitude flights in May per Secretary of Defense guidance.
Defense Secretary Leon Panetta approved a plan to lift the restrictions on the then-grounded aircraft and the Air Force is taking corrective action on the valves.
JBER could not comment on whether or not the announcement affected the planes there or for Arctic Thunder. However, the duration and altitude restrictions would not have applied to the demonstration.
JBER had a four-month stand-down for the Raptors that ended in September 2011 after 12 Air Force pilots experienced hypoxia-like symptoms.
An Air Force task force found that the upper pressure garment and other cockpit life support equipment contributed to breathing restrictions that affected pilot physiology.
The valve allowed the vest to remain inflated in conditions where it should have released pressure in order to make it easier for pilots to breathe, which was a major contributor to their symptoms.
At Langley Air Force Base in Virginia, 1st Lt. Sarah D.A. Godfrey of Air Combat Command Public Affairs Operations said that because the stand-down was lifted in 2011, the unexplained incidents for the most part were evenly split between aircraft originating from Elmendorf and Langley Air Force bases.
ACC couldn’t discuss specifics of individual incidents, but Godfrey said symptoms were experienced in flight and the pilots used established procedures to return safely to base.
The specific contributing factors to the reduced air supply were identified during altitude chamber and centrifuge testing in which F-22 pilots were able to demonstrate breathing restrictions and impedance imposed by aircrew flight equipment. Additionally, two of 24 pilots experienced hypoxia-like symptoms during centrifuge testing, further supporting measured empirical data. Also, the Navy Experimental Dive Unit was able to identify oxygen delivery pressure drops in the F-22 Life Support System related to factors such as the diameter and air-tightness of hoses and connectors.
The Air Force determined that it must replace a valve in the upper pressure garment worn by pilots to provide support in high-altitude missions. The Air Force also identified the need to increase the volume of air provided to pilots by improving the oxygen delivery hose and its physical connections.
The restrictions will be lifted in a phased manner. First, the aircraft will fly to Japan under altitude restrictions via the North Pacific transit route. After these flights, the Air Force will recommend resuming long-duration flights, with the exception of the Alaska Aerospace Control Alert missions.
The Air Force is installing a new back-up emergency oxygen system and pursuing implementation of all Scientific Advisory Board actions. Five of the actions are complete. The remaining three include installation of a cockpit-mounted oxygen sensor, installation of an improved pilot oxygen sensor and the initial National Aeronautic and Space Administration’s report. These are set to be completed by the end of the summer.
The Air Force will then brief Panetta on the results of the modified upper pressure garment testing in early fall. Pending completion of the SAB recommendations, the NASA independent analysis, and fielding of the modified upper pressure garment, the Air Force will seek approval to remove the altitude restrictions.
After all the restrictions are removed and the back-up oxygen systems are installed, the Air Force will request resumption of the Aerospace Alert Control Alert missions in Alaska.
“Until that time, this mission will continue to be flown by other aircraft,” Godfrey said.
In a statement, Sen. Mark Begich said, “I’m pleased to hear the F-22, our nation’s greatest fighter, is expected to return to flight over the coming months. I support the Air Force’s plan which includes incremental steps to ensure the safety of our pilots before full fleet flight restrictions are lifted.
“I am especially pleased about all of the precautions being taken before the two squadrons of F-22’s from J-BER resume the Air Alert Mission in Alaska. Our Arctic Airmen’s safety is paramount.”
Godfrey said the Life Support System Task Force has worked since January to identify the root cause of previously unexplained physiological incidents during a small number of F-22 sorties. The task force leveraged the data collection and analysis efforts of prior safety investigations and the SAB that explored quantity and quality of oxygen. She said subsequent testing and analysis has concluded that physiological incidents were not caused by contaminants or by improper functioning of the aircraft’s On-Board Oxygen Generation System.
Jonathan Grass can be reached at firstname.lastname@example.org.