A potentially faulty pressure vest is the latest clue in a yearlong mystery over why Air Force pilots flying Lockheed Martin Corp.’s F-22 Raptor keep getting dizzy and disoriented.
Pilots have been instructed to stop using the vest during routine flight operations as the Air Force works on a fix, the service’s Air Combat Command said yesterday. The vest, part of a “G suit” used to help pilots avoid blacking out during high-speed maneuvers, “increases the difficulty of pilot breathing under certain circumstances,” according to an e-mailed statement.
A Navy dive unit assisting in the investigation found “an enormous failure rate” among pressure vests it tested, Senator Mark Warner, a Virginia Democrat who was briefed by the Air Force this week, said today.
Unable to explain episodes of dizziness, the Air Force is looking at everything from the prosaic -- hoses, masks and now G suits -- to the top-secret coatings and adhesives used in the plane’s radar-absorbing stealth skin that makes it harder to track. So far, all the engineers and investigators have come up short of a solution to symptoms that include what’s been called a “Raptor cough.”
“The bottom line is we don’t have a single causative factor,” Brigadier General Daniel Wyman, the Air Combat Command’s surgeon general, said in an interview this week.
About two dozen pilots and six ground-maintenance workers have reported symptoms associated with a lack of oxygen. There have been 11 reported incidents since the plane resumed flying operations last year after a four-month halt because of safety concerns.
A majority of F-22 pilots surveyed early last year said they “did not feel confident” in the plane’s oxygen system, according to an Air Force document released today by Warner and Representative Adam Kinzinger, an Illinois Republican. That finding contributed to the decision to halt flights last year, the service said.
Defense Secretary Leon Panetta imposed new safety measures last month that include limiting flight durations and speeding the installation of back-up oxygen systems.
No oxygen problem was detected before the Raptor was declared ready for combat in 2005.
“I don’t have any ready answers to why we are experiencing a serious problem that apparently didn’t surface during the supposedly extensive testing the Air Force did,” Thomas Christie, who was the Pentagon’s top weapons tester from 2001 to 2005, when the plane was in development, said in an interview.
The Pentagon has spent $67 billion buying 188 of the supersonic jets, which have never flown in combat. It plans to spend $11.7 billion to upgrade the planes at a time when the Pentagon is cutting spending after a decade of war in Iraq and Afghanistan.
The Raptor has been called “the most expensive, corroding hangar queen ever” by Arizona Senator John McCain, the top Republican on the Senate Armed Services Committee.
The oxygen deficiencies promise to require even more money to fix. Bethesda, Maryland-based Lockheed Martin, the world’s largest defense contractor, won a $19 million contract last week for the back-up oxygen supply system.
“It really is a conundrum,” said Jeffrey Sventek, executive director of the Aerospace Medical Association, whose annual conference last month included a briefing by the Air Force on the F-22 investigation.
The Air Force said yesterday that it’s looking at whether the equipment donned by F-22 pilots may be restricting their ability to breathe.
“Testing has determined that the upper pressure garment increases the difficulty of pilot breathing under certain circumstances,” Lieutenant Colonel Edward Sholtis, an Air Combat Command spokesman, said in an e-mailed statement. “We’re also looking at the layering of other aircrew flight equipment as contributing to that difficulty.”
The service is looking in particular at the flight suits, worn in combination with the pressure vests, by F-22 pilots at Joint Base Elmendorf-Richardson in Alaska and at Joint Base Langley-Eustis in Virginia, according to a government official briefed on the latest information.
The official, who spoke on condition of anonymity because the investigation is being handled in private, said investigators suspect the combination of clothing may be restricting a pilot’s ability to expand his chest and take a full breath.
“Obviously, the pressure suits are kind of the leading theory at this point,” Kinzinger, the Illinois lawmaker, said today on a conference call with reporters. “The thing to keep in mind is it’s just theory.”
Warner, whose constituents include pilots at Langley, said he wants to see “continued progress in the testing of suits. We’re going to stay on this until it gets resolved.”
The Air Force isn’t declaring the case solved.
“The upper pressure garment is not ‘the’ cause of physiological incidents, and we still have other variables to work through before we can determine what the major factors are and how they interact to produce the number of unexplained incidents we’ve seen,” Sholtis said.
The pressure vest is made by Sewing Technology Inc., a closely held company based in Buffalo, New York, according to the Air Force. Lisa Donhauser, a co-owner of the company, said the Air Force hasn’t contacted her about any concerns with the pressure vest, which the company has made for F-15 and F-16 jets.
“I do not believe that this vest would be contributing to this situation, as thousands of these vests have been worn and produced over the last 20-plus years without any concern that I am aware of,” she said today in an e-mailed statement.
The Air Force probe focused initially on the plane’s On-Board Oxygen Generating System built by Honeywell International Inc. Honeywell, based in Morris Township, New Jersey, has said the system, which provides enriched oxygen to the pilot, is performing as designed.
Retired General Gregory Martin, who headed a study of the F-22 for the Air Force Scientific Advisory Board, told reporters in March that the system “might not produce as much oxygen as it would when it was not under G,” or a high level of acceleration. Still, he said the oxygen level was “never in an area of concern.”
The oxygen system is “a common design,” Charles Oman, a senior research engineer and lecturer who specializes in aerospace physiology at the Massachusetts Institute of Technology in Cambridge, Massachusetts, said in an interview. “That’s why everyone was so mystified.”
Wyman, the surgeon general, said the oxygen system in the F-22 is unique because it funnels highly concentrated oxygen directly to the pilot, instead of being mixed with air from the cockpit. While the F-22 also operates at higher altitudes and air speeds than other fighters, Wyman said evaluations show its oxygen system “works as advertised.”
With answers still elusive, critics of the plane such as Pierre Sprey say the toxic coatings used for the stealth skin may be entering the plane’s air intakes and fouling the oxygen flow.
“That’s the No. 1 candidate,” Sprey, who was an Air Force architect of the F-16 fighter and the A-10 ground-attack plane in the 1970’s and 1980’s, said in an interview. “There’s no candidate that comes closer to filling the bill on the evidence.”
Raptor pilots also have reported suffering from a persistent cough and vertigo, symptoms not associated with classic hypoxia, or deprivation of oxygen, Sprey said.
The stealth coatings theory also may explain why five ground-crew technicians also have reported symptoms, even though they are never in the air using the oxygen system.
“This airplane is constantly being reglued, which is why the maintenance guys came down with these symptoms,” Sprey said.
While the Air Force is investigating that theory, it has no evidence to support it, Sholtis said.
“If the stealth coating, adhesives or other materials were off-gassing or otherwise leaking contaminants into the pilot’s air supply, you would expect to see significant amounts of harmful chemicals or other evidence of toxicity” when air samples are chemically analyzed, Sholtis said by e-mail.
Difficult to Say
“We don’t see the evidence,” he said. “So it’s difficult for us to say with any confidence that that kind of contamination is occurring.”
Sventek, a physiologist who ran oxygen chambers for the Air Force for decades, said he is skeptical of the stealth-skin theory.
“I would find it hard to believe that once the skin is cured that there would be any off-gassing,” or release of toxic gases into the air, he said. “That would be a stretch.”
Senate Armed Services Committee Chairman Carl Levin indicated the Air Force was doing all it could to get to the bottom of the oxygen mystery.
“The long-term modernization programs certainly depend on the F-22 being safe for our pilots to fly, but there is no reason at this point to believe that the Air Force cannot solve this current problem,” Levin, a Michigan Democrat, said in a statement.
The F-22 can be used in combat if needed even with its undiagnosed problems, Deputy Defense Secretary Ashton Carter said at a May 30 forum in Washington.
With 11 unexplained incidents out of 12,000 sorties since the flight ban was lifted last year, the hypoxia rate remains relatively low, Wyman, the surgeon general, said.
“We have pilots flying daily, and this isn’t happening to them,” he said.