Sunday, March 21, 2010

U-2 Spy Plane Keeps 'Em Flying Under Pressure

Unmanned drones don't worry about decompression sickness (DCS), but high-flying spies do. A short feature article and slide show in today's New York Times considers the U-2 spy plane's Cold War history and newfound value in the skies over Afghanistan.

Most of us associate DCS, or the bends, with ascending too rapidly from undersea depths. Rapid decompression from a pressurized fuselage at high altitude is every bit as dangerous. U-2 pilots "wear spacesuits because their blood would literally boil if they had to eject unprotected at such a high altitude," the article reports, and 2006, a U-2 pilot almost crashed after drifting in and out of consciousness during a flight over Afghanistan. The pilot, Kevin Henry, now a retired Air Force lieutenant colonel, said in an interview that he felt as if he were drunk, and he suffered some brain damage. At one point, he said, he came within five feet of smashing into the ground before miraculously finding a runway.

Civilian aviators, and certainly commercial airline passengers, very rarely encounter such circumstances. But the risk of the bends is always on the mind of alert military air crews who depend on pressure suits or pressure-demand oxygen systems to breathe. The conditions are just short of spaceflight. At maximum cruise altitude, around 70,000 feet (plenty high enough to see the curvature of the Earth), the U-2's cabin is only pressurized to about 30,000 feet. In commercial airliners, operating at typical cruise altitudes of 30,000–40,000 feet, the cabin is pressurized to 6,000–8,000 feet.

Such high-pressure risks give us yet one more reason to admire our men and women in uniform—or spacesuits, as the case may be—and keep those hyperbaric oxygen chambers at the ready. Fly right!

(NYTimes photo: U-2 pilot USAF Maj Eric Schontz stretching and breathing pure oxygen one hour preflight.)

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