Mentions Oxygen System Problems, But Cites Pilot Error As The Cause Of The Accident

The USAF has released its official report on an accident which occurred November 16th of last year in Alaska in which a pilot was lost and an F-22 Raptor was destroyed.

In the report, the Air Force says that during the flight At the fire protection system (FPS) detected a bleed air leak in the center bleed air ducting from both engines. In response to the FPS, the Integrated Vehicle Subsystem Controller (IVSC) asserted the C BLEED HOT caution ICAW while it requested the Environment Control System (ECS) to isolate the center bleed system. “CAUT” was displayed in the heads up display (HUD) advising the pilot of the caution ICAW.

The report seems to indicate that the pilot may have attempted to start the flow of emergency oxygen to his face mask, but was unable to do so. "The lack of airflow to the (pilot's) oxygen mask and the fact that the mask was up and secured in place at the time of impact suggests the (pilot) would have attempted to activate the EOS for continued airflow. However, analysis of the EOS from the wreckage determined it was not activated," the report reads.

The report suggests that the distraction caused by trying to activate the emergency oxygen system was the primary cause of the accident. It says the pilot input a combination of right forward stick and right pedal which initiated a 240 degree descending right roll at greater than 45 degrees per second. "At the completion of these stick and pedal inputs (the pilot) had rolled through inverted, experienced less than 1 g of gravitational force, and went from a RWD to LWD attitude, and the descent rate of the aircraft significantly increased.

These control inputs appeared to be inadvertent because:

• They had no clear goal or objective.
• They resulted in an unusual attitude.
• During ground simulation, when the pilot member repositioned his torso to visually
• acquire the manual EOS activation ring, he inadvertently actuated the stick and
• pedals.
• The MP (pilot) made no attempt to correct the MA’s (aircraft's) unusual attitude for 30 seconds after
• completion of these inputs.

"The inadvertent operation of the flight controls placed the (aircraft) in an unusual attitude which was unnoticed by the MP. This resulted in the MP’s unrecognized spatial disorientation.

The report does list several factors it calls "non-contributory" to the accident, including sudden incapacity or unconsciousness, efforts of G-Forces, and hypoxia. The report says the evidence does not support any of those factors as contributing to the accident.

FMI: http://usaf.aib.law.af.mil/ExecSum2011/F-22A_AK_16%20Nov%2010.pdf