The U.S. Air Force's fleet of F-22 Raptor fighters has been grounded since May 3 due to toxins entering the cockpit via the aircraft's life support systems, sources with extensive F-22 experience said.
Service leaders grounded the stealthy twin-engine fighter after pilots suffered "hypoxialike symptoms" on 14 occasions. The incidents affected Raptor pilots at six of seven F-22 bases; the exception is Tyndall Air Force Base, Fla.
But despite an investigation that has spanned nearly three months, no one yet knows what toxin or combinations of toxins might have caused the incidents, nor is it clear exactly how the chemicals are entering the pilots' air supply, sources said.
Toxins found in pilots' blood include oil fumes, residue from burned polyalphaolefin (PAO) anti-freeze, and, in one case, propane. Carbon monoxide, which leaves the blood quickly, is also suspected.
"There is a lot of nasty stuff getting pumped into the pilots' bloodstream through what they're breathing from that OBOGS [On-Board Oxygen Generation System]. That's fact," one former F-22 pilot said. "How bad it is, what type it is, exactly how much of it, how long - all these things have not been answered."
The blood tests were performed after each of the 14 incidents in which pilots reported various cognitive dysfunctions and other symptoms of hypoxia. One couldn't remember how to change radio frequencies. Another scraped trees on his final approach to the runway - and later could not recall the incident.
"These guys are getting tested for toxins and they've [gotten] toxins out of their bloodstreams," the source said. "One of the guys was expelling propane."
This source, along with the others, requested anonymity for fear of retribution.
The line of inquiry may shed new light on the death of Capt. Jeff "Bong" Haney, a 525th Fighter Squadron pilot who was killed when his F-22 crashed last November near Anchorage. Sources said that in Haney's last few radio calls before his jet disappeared, he sounded drunk, a classic sign of hypoxia. Haney was known as a prodigiously skilled aviator who was in line to attend the elite Air Force Weapons School.
Air Force officials have said they have not yet completed the investigation into the crash.
Asked for comment about the possibility that F-22 pilots had been exposed to carbon monoxide, an Air Force spokesman, Maj. Chad Steffey said, "The safety of our aircrews is paramount, and the Air Force continues to carefully study all factors of F-22 flight safety."
Asked about other toxins, Steffey referred questions to the Air Force Safety Center at Kirtland AFB, N.M., where officials did not repond by press time.
Officials with Lockheed Martin, which builds the aircraft, said they are cooperating with the investigation but cannot comment further.
Carbon Monoxide?
Beside the various toxins found in the pilots' blood, carbon monoxide is another potential cause of the hypoxia incidents.
The gas, one of many generated as exhaust by the plane's jet engines, might be getting into the cockpit, sources said.
Part of the problem, at least for pilots flying from Joint Base Elmendorf-Richardson, Alaska, where many of the known incidents have occurred, may be the startup procedures used in winter, one source said.
Because of the harsh climate, pilots often start their jet engines inside a hangar before taking off. That could allow exhaust gases to be trapped in the building, sucked back into the engines, and ingested into the bleed air intakes that are located within the engines' compressor sections that supply the OBOGS, sources said. The layout, sources added, is standard for modern jet aircraft.
But another source said that many of the hypoxia incidents have occurred well into flights or even during a day's second mission, long after the plane has left the Elmendorf hangar.
The U.S. Navy had problems with the OBOGS on its F/A-18 Hornet, which sucked carbon monoxide into its oxygen system during carrier operations. Between 2002 and 2009, Hornet aviators suffered 64 reported episodes of hypoxia, including two that killed the pilots, according to the July-August 2010 issue of "Approach," a Navy Safety Center publication.
The Navy modified the planes' OBOGS, has had no recent similar incidents and is not currently investigating the systems, Naval Air Systems Command officials said.
USAF Expands Investigation
In January, a safety investigation board led by Maj. Gen. Steven Hoog began looking into the the OBOGS on the F-16, F-15E and F-35 fighters; the A-10 attack jet and the T-6 trainer, according to May statements by officials with the service's Air Combat Command, which oversees combat aircraft.
In May, Air Force Secretary Michael Donley had ordered the service's Scientific Advisory Board to conduct a "quick-look study, gather and evaluate information, and recommend any needed corrective actions on aircraft using on-board oxygen generation systems," according to a July 21 statement by service officials.
The release indicated that the service is now looking at more types of aircraft: the B-1 and B-2 bombers and the CV-22 tilt-rotor and "other aircraft as appropriate."
According to the release, the investigation is conducting a "series of carefully controlled in-flight tests, the team will examine the subsystems identified in reported incidents. These include the pressurization system, mask and cockpit oxygen levels."
The release said the Scientific Advisory Board investigation followed the grounding of the F-22 fleet, but did not say whether it superseded, replaced or is merely accompanying the Hoog investigation.
One source said that F-22 test pilots at Edwards AFB, Calif., last week started flying sorties as the investigate OBOGS concerns as part of the Air Force safety investigation.
Air Force officials have confirmed only that some test pilots at the base are flying their jets under a special waiver granted to them to test an unrelated software upgrade.
However, the operational fleet remains grounded, with pilots and ground crews practicing in simulators as much as they can. But that is not a real solution because the pilots won't be able to maintain currency, one former F-22 pilot said.
"After 210 days, they've got to start retraining everybody," he said.
It would take weeks for the instructor pilots at Tyndall to re-qualify themselves and then start to train others, the former pilot said. Pilots with lapped currencies would be re-qualifying each other.
It would take four to six weeks afterward to re-qualify the operational squadrons. Service officials confirmed that 12 Raptors are stranded at Hill AFB, Utah, but declined to identify their squadron. The jets came to the desert base for a Combat Hammer exercise in which pilots and ground crews practice loading and releasing live air-to-ground weapons. Service officials said the jets are from the 1st Fighter Wing at Langley AFB, Va.
Meanwhile, Lockheed can't deliver new Raptors to the Air Force because the company and the Pentagon's Defense Contract Management Agency are unable to fly required test sorties needed to certify the jets meet specifications. Four aircraft have technically been delivered to the service but can't fly to their new home at Langley AFB.
At least two additional aircraft have been completed but remain at the factory undelivered.
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