Key Points and Summary – In its early years, the F-22 Raptor fleet was plagued by a mysterious and dangerous problem causing pilots to experience hypoxia-like symptoms, including dizziness, confusion, and blackouts.
-The issue, which ultimately led to a fatal crash in 2010, forced the Air Force to ground the entire fleet in 2011.
-Investigators found no single cause but a “collage of issues,” including faulty vest valves and leaks in the oxygen delivery system.
-The grounding, however, provided a golden opportunity for maintainers, who completed a year’s worth of crucial maintenance and upgrades on the complex stealth jet.
The F-22 Raptor Oxygen Problem
Early in the F-22’s operation, some pilots reported a raft of strange symptoms when flying the stealth fighter, symptoms that included headaches, confusion, dizziness, memory gaps, and even blackouts.
Though oxygen was suspected as the culprit, a solution evaded the United States Air Force for several years. Unresolved, the issue resulted in a fatal F-22 crash in Alaska in November 2010.
In response to the accident, the US Air Force took the extraordinary step of grounding the entire Raptor fleet in May 2011, citing symptoms consistent with hypoxia.
Virtually all aircraft, both military and civilian, operate at high altitudes where there is enough oxygen to operate jet engines, but not enough for human pilots and passengers to remain conscious. To solve the problem of staying awake during flight, pilots relied on a canister of bottled oxygen to stay alive.
However, those supplies were finite, and mission mishaps or delays risked jeopardizing not only the mission but also the pilots’ lives.
To solve this problem, On-Board Oxygen Generation Systems (OBOGS) were invented in the early 1980s, providing pilots with access to unlimited oxygen supplies. OBOGS, in essence, draw air from the engine before it is burned.
The system then removes nitrogen and other impurities before it is pumped to the pilot to breathe. Although the Air Force initially outfitted pilots with breathing equipment with charcoal filters to remove potential impurities, these filters actually exacerbated the problem and were eventually removed.
The Culprit
There was no single, identifiable cause for the breathing and oxygen problems many F-22 Raptor pilots experienced. Instead, a collage of issues related to both individual components and system problems contributed to pilot issues while flying the Raptor.
The culprits were a combination of poorly-fitted valves, oxygen delivery chokepoints, and pressurization irregularities that ultimately led to symptoms similar to hypoxia.
Although the Air Force conducted multiple investigations into the oxygen issues, they first found no obvious equipment fault. However, combing through the jet and pilot equipment revealed that the pilot vest values were faulty. Intended to inflate during high-G maneuvers, the vest would sometimes remain inflated, restricting the pilot’s breathing.
The crews also discovered leaks in the oxygen delivery system, which could sometimes result in significant fluctuations in blood oxygen levels.
A Golden Maintenance Opportunity
Though the F-22 fatality, subsequent fleet grounding, and search for the culprit of the raft of hypoxia-like incidents were of grave importance, they provided the Raptor maintainers with a unique chance, and one that they took full advantage of.
An article in Air and Space Force Magazine explained what that opportunity was:
“For maintainers, the stand-down offered an unprecedented ‘opportunity … to shine,’” said MSgt. Christopher Baldwin, 1st Maintenance Squadron structural maintenance chief. Paradoxically, with the jet aircraft on the ground, “our workload seemed to increase,” he observed. “As it became apparent the grounding would be extensive, the maintenance group intensified training, having a bounty of aircraft to work on. This was combined with tackling heavy maintenance projects that normally would take an aircraft out of service for a long period.”
“The grounding allowed experienced hands to mentor newer maintainers on time-intensive fixes and other procedures they’d seldom get to practice unless the aircraft was actually broken—the stress of which makes for poor training.”
During the F-22 grounding that followed the fatal Alaska crash, F-22 maintainers rushed to implement a raft of upgrades to the F-22 fleet. Within the two-month window afforded by the grounding, they completed a year’s worth of maintenance and upgrades. Part of the issue was the Raptor’s stealth coating, a skin spread over 97 panels that was incredibly maintenance-intensive to service.
Unlike non-stealthy jets, whose internal components can be accessed by popping off an access panel, the F-22’s internal parts could be accessed by first removing 20 layers of stealth appliqué, which had to be sanded and chipped away in a labor-intensive process, then allowed up to two days to set.
How the F-22 Raptor Was Saved?
As early as 2005, a US Air Force working group, called RAW-G, or Raptor Aeromedical Working Group, had identified potential issues with the F-22, especially during high-altitude flight, and proposed solutions that, they hoped, would ensure a regular supply of oxygen to pilots. The Air Force rejected their solutions. Wary of adding costs to a program that was already one of the United States’ most expensive aerospace projects at the time, the solutions were nixed.
Facing intense media scrutiny and a vocal F-22 pilot community concerned with flying the stealth fighter, the Air Force would eventually acquiesce. In a twist of irony, they implemented many of the fixes proposed by the Raptor Aeromedical Working Group.
About the Author: Caleb Larson
Caleb Larson is an American multiformat journalist based in Berlin, Germany. His work covers the intersection of conflict and society, focusing on American foreign policy and European security. He has reported from Germany, Russia, and the United States. Most recently, he covered the war in Ukraine, reporting extensively on the war’s shifting battle lines from Donbas and writing on the war’s civilian and humanitarian toll. Previously, he worked as a Defense Reporter for POLITICO Europe. You can follow his latest work on X.
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