The U.S. Air Force has “high confidence” that it has solved a yearlong mystery over why at least a dozen pilots flying the F-22 Raptor jet fighter became dizzy and disoriented.
Major General Charles Lyon, director of operations for the Air Combat Command who led a task force to solve the problem, said yesterday a valve that regulates oxygen flow into a Raptor pilot’s pressure vest was too weak to prevent the vest from inflating unnecessarily and restricting a pilot’s ability to breathe.
“I have high confidence we have eliminated the major contributors to the problem,” Lyon told a Pentagon news conference.
A stronger valve will be installed and tested by the end of the year, he said. Until then, the F-22, made by Bethesda, Maryland-based Lockheed Martin Corp., will be restricted to lower altitudes so pilots don’t need a pressure vest.
Lyon said he doesn’t know the cost of all the fixes, which include a back-up emergency oxygen system, “but it’s in the millions” of dollars.
Lyon’s briefing added new details to the Pentagon’s announcement last week that it had begun taking corrective action.
While the valve has performed satisfactorily for pilots of older F-15 and F-16 fighters, the F-22 is designed to fly at higher altitudes, which requires continuously pumping more oxygen to the pilots, Lyon said. The valve wasn’t strong enough to prevent that higher pressure oxygen from inflating the pilots’ vests at lower altitudes.
“It’s inflating before it should,” Lyon said of the vest. “So it’s like putting a corset around your chest.”
F-22 pilots haven’t worn the pressure vests since June because of that concern, and there have been no unexplained hypoxia-related incidents since March, he said.
Reports of unexplained hypoxia -- lack of oxygen -- sent the Air Force on a yearlong investigation that required studying everything from hoses and masks to the plane’s radar-absorbing stealth skin.
“In the end, there is no smoking gun,” Lyon said. While all the parts to the pilots’ life-support system, including the valve in question, worked as designed, they didn’t work well enough together in the F-22’s unique performance envelope, he said.
The Raptor, conceived during the Cold War as a fighter for the 21st Century, is a “hybrid” that flies at high speeds and high altitudes. Considered a fourth generation stealth aircraft, it has a top speed of about 1,500 miles per hour (2,410 kilometers per hour), more than twice the speed of sound, and a service ceiling of roughly 65,000 feet (19,800 meters), although the exact figures are classified.
“We hadn’t had any other airplanes that had done that,” Lyon said.
The Pentagon has spent $67 billion to buy 188 of the supersonic jets from Lockheed Martin, the world’s largest defense contractor. It plans to spend an additional $11.7 billion to upgrade the planes at a time when the military is cutting spending after a decade of war in Iraq and Afghanistan.
The possibility of contamination from toxins in the cockpit air was ruled out after thousands of samples of gases and compounds were studied, and “we found nothing remarkable,” Lyon said.
In a signal of the military’s confidence in the plane, Defense Secretary Leon Panetta authorized the deployment of a squadron of F-22s to Kadena Air Base in Japan last week.
Asked why the planes were deployed before all the fixes are completed, Lyon said, “When we deploy the F-22, it reassures our allies and our friends. We send them the very best that we have from the aviation component.”