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A recently declassified NASA report suggests the Air Force could have more effectively investigated problems with the F-22 Raptor and responded to pilots who experienced symptoms of oxygen deprivation or hypoxia.
The report also "concurs with much of what the Air Force has done" to determine why the expensive, stealthy jet has caused some pilots to feel dizzy or disoriented.
However, it cited a lack of information sharing and approaches to treating pilots that varied from base to base. It also took a critical look at how the Air Force examined the problem early on in their attempt to find the elusive "smoking gun."
NASA completed the 120-page report in August 2012. The Daily Press recently obtained a redacted copy through a Freedom of Information of Act request.
Among the highlights:
NASA recommends adjusting oxygen levels in relation to altitudes. However, the Air Force says it wants to seek more data before making those changes.
The Air Force developed guidelines to treat pilots with unexplained cases of hypoxia. However, different bases tried specific approaches that, while beneficial, were not shared throughout the service. The Air Force said what NASA deems as inconsistency could be seen as being flexible.
The report describes pilots with ear blockages that clear in the middle of the night, "waking them up to the sound of a loud explosion." Other pilots describe how it takes "a couple of days" to recover from the fatigue of a flight. In response, the Air Force says pilots in many aircraft complain of delayed ear blocks, and the condition is not unique to the F-22. As for fatigue, the Air Force says NASA's observations were made before improvements reduced breathing stress among pilots.
The investigative process generated much information, but didn't necessarily lend itself to the challenge posed by the Raptor, which not only examined individual systems, but now those systems interacted.
Raptor pilots began experiencing unexplained symptoms of hypoxia as early as 2008. Most incidents happened at Langley Air Force Base in Hampton and Joint Base Elmendorf-Richardson in Alaska, the NASA report says.
In 2011, the Air Force grounded the entire fleet as it investigated the problem. It lifted the stand-down after four months even though investigators did not determine what specifically caused the problem.
Last year, the Raptor made national headlines when two pilots from the Virginia Air National Guard based at Langley told "60 Minutes" they were not comfortable flying the aircraft, even though they believed in it. That spurred Sen. Mark R. Warner to get involved, and it led Defense Secretary Leon Panetta to impose flight restrictions and demand the installation of an automatic, backup oxygen system.
Later in the year, Air Force leaders announced they believed the problem had been largely solved through a combination of measures. One key fix involved a pressure vest meant to inflate during periods of intense acceleration, known in pilot parlance as pulling high Gs.The vest was inflating at the wrong time, which restricted breathing. Pilots were told not to wear the vest while the valve was redesigned.
Last month, Raptor pilots began flying with vests again, using a newly designed valve. Pilots have reported no problems, and the Air Force cleared pilots to fly at 52,000 feet, up from a restriction of 44,000 feet, said Lt. Col. Tadd Sholtis, a spokesman for Air Combat Command.
The Air Force has not logged an unexplained hypoxia incident since March 2012.
The service asked NASA in May 2012 to review the Raptor investigation, as well as the protocols the Air Force established to deal with the incidents. Leading the probe was NASA's Engineering and Safety Center, which pulled in experts from throughout NASA.
The 14-member team included four people from NASA-Langley, including the team leader.
The NASA team lists "high concentrations of oxygen at lower levels" as something that could have led to breathing problems. Restricted breathing combined with previous problems regarding the upper pressure garment worsened the problem.
Sholtis said adjusting the oxygen schedule of the Raptor -- the concentration of oxygen at different altitudes -- is something that merits further study, but the Air Force isn't necessarily buying NASA's recommendation.
"Although NASA and others point to the effects of too high a concentration of oxygen at lower altitudes, there are factors that argue against a rush in that direction," Sholtis said last week.
He said experts also point to the advantages of "pre-breathing" higher oxygen levels before climbing to high altitudes -- which happens quickly in a Raptor.
"And many Navy pilots have been flying on 100 percent oxygen for years with no known impact on safety or health," Sholtis said. "So we're seeking more information and consensus among experts before we adjust that schedule."
NASA recommended the establishment of an F-22 Medical Consult Service as a resource for flight surgeons who treat pilots with more long-term problems stemming from hypoxia. That came after a review of Air Force guidelines on how to respond to incidents.
The study found "anecdotal evidence" that a specific approach at Langley Air Force Base worked well: exposing pilots to hyperbaric oxygen treatments. But no pilots at Elmendorf-Richardson in Alaska received similar care.
Yet if the treatment "is beneficial or curative, as it appears to be, then it should be applied equally for any pilot presenting with similar symptoms," the study says.
The study also said complex cases were put in the hands of less experienced flight surgeons.
"On more than one occasion, relatively junior medical officers have in fact contacted a more senior NASA flight surgeon for advice on how to manage such cases," the study says.
Referring to the Langley approach, Sholtis said Raptor bases made minor changes to general treatment guidelines to account for variables they encountered.
"What NASA saw as an inconsistent application of the plan could be interpreted in a different light as necessary flexibility," he said.
He said the Air Force already has the type of central consultation service that NASA recommended. It is the Hyperbaric Division of the Aeromedical Consultation Service at the USAF School of Aerospace Medicine.
Since the NASA report, the Air Force "has more clearly stated the division's responsibility and its availability to consult with F-22 bases in our Medical Response Plan," Sholtis said.
The main Air Force working group generated great amounts of data "that has been variously described as unwieldy and confusing," the report says. Sharing information appeared to be a problem.
"The different sets of data contained different types of information," the report says. "Not all information was contained in all sets. One needs to combine summaries to gain a fuller picture of any single event."
A more efficient process would have consolidated information in a single, easy-to-navigate source. NASA said the Air Force's main investigative body -- the Root Cause and Corrective Action (RCCA) team -- was designed to find specific "broken" items, although it was sensitive to how different systems in the Raptor may have interacted.
Still, it concludes: "The RCCA process was a systematic approach, but was not necessarily appropriate for identifying system level problems."
Sholtis said the investigative process improved over time. Prior to the four-month stand-down in 2011, the Air Force considered Raptor problems as single incidents at individual bases. But starting in 2011, the Air Force began to take a broader, more systematic look at the problem.