F-22 Raptor

The US Air Force Life Cycle Management Center’s (AFLCMC) F-22 Division is set to complete installation of the automatic back-up oxygen system (ABOS) in the air force’s F-22 Raptor aircraft fleet by December 2014.

In January 2012, the ABOS installation was recommended by the Air Force Scientific Advisory Board to improve the aircrew life support system, following a series of incidents, in which several F-22 pilots experienced hypoxia-like symptoms in-flight.

Built by Lockheed Martin under multiple contracts, the ABOS is integrated into the breathing regulator, and has a control panel in the cockpit within the pilot’s reach to enable manual turn-on if backup oxygen is needed.

The system is typically left in the auto position, which will automatically provide the pilot 100% oxygen in the event of a rapid decompression or low primary breathing air pressure.

Having funded a trade study of design alternatives, the F-22 Division took the Scientific Advisory Board’s recommendation and more specific requirements from the Air Combat Command-led life support system task force, and developed a strategy to address the problem.

ABOS programme manager Mike Connolly said the team put together an action plan within a week of receiving requirements from ACC and the air force.

"The ABOS is integrated into the breathing regulator."

"From there, we got approval to move forward, got funded and we executed. From notification to retrofit of the first test aircraft took six months to complete," Connolly said.

Since being declared operational in December 2005, the F-22 has frequently been grounded due to a series of hypoxia-related incidents, including dizzy spells and blackouts, experienced by pilots between April 2008 and January 2011.

Powered by two F119-100 Pratt & Whitney turbofan engines, the F-22A Raptor is a fifth generation, supersonic, tactical dual fighter jet, designed primarily as an air superiority fighter, but can also be configured to conduct ground attack, electronic warfare, and signals intelligence missions.

Image: A USAF F-22 Raptor in flight above the Mojave Desert. Photo: courtesy of Judson Broehmer.

Defence Technology