The report also cautions that “ECS (environmental control system) shutdowns are more frequent than expected and result in Obogs shutdown and cessation of breathing air to the pilot.”

Noting “some anomalies in the performance of the F-22 oxygen and anti-G delivery systems when the ECS cuts back or shuts down in-flight, or during the onset of High-G forces,” the report says the incidents “merit further analysis and testing.”

Obogs efficiency is key for flight operations, the report says. “Unlike most other aircraft oxygen generation systems, the breathing air to the F-22 pilot is not diluted with cockpit air to obtain the appropriate oxygen partial pressure (PPO2) necessary to maintain physiological function at a particular altitude, but rather it is concentrated to the necessary PPO2 by controlling the cycling of the Obogs.”