Air Force pilots flying the "Dragon Lady" no longer experience decompression sickness during their high-altitude flights, according to officials with the U-2 Program Office here.
Commonly referred to as DCS, decompression sickness is caused by the formation of nitrogen bubbles in the blood and tissue following a sudden drop of air pressure.
For U-2 pilots, who routinely fly missions above 70,000 feet, this has been a major concern.
"Our pilots were seeing an increased number of DCS incidents due to long missions," said Col. Fred Kennedy, the Command and Control, Intelligence, Surveillance and Reconnaissance Division chief. "Air Force senior leaders became aware of the problem, and made fixing it their No. 1 priority for our program."
The fix -- dubbed the Cabin Altitude Reduction Effort, or CARE, program -- beefs up the U-2's structure, replaces the legacy cockpit pressure regulator and safety valve, and includes modifications to the engine bleed schedule. That permits engineers to nearly double the cockpit pressure experienced by a U-2 pilot, from 4.4 pounds per square inch to more than 8 psi.
"What our folks have done is to drop the apparent altitude in the cockpit from 29,500 feet to 15,000 feet - roughly the difference between Mount Everest and Pikes Peak (Colo.)," Kennedy said. " CARE basically eliminates the risk of DCS and allows our U-2 pilots -- who might otherwise have been removed from flying status -- to keep flying."
A total of 27 U-2 airframes have been outfitted with CARE, ahead of schedule and under cost. The total outlay for the program was $8.7 million, officials said.
To date, there have been no reported DCS incidents since the modifications.
"This is a big deal for the U-2 community," Kennedy said. "Healthy pilots mean more missions and more extraordinary ISR capability for our warfighters."http://www.af.mil/News/ArticleDisplay/tabid/223/Article/467537/u-2-modifications-reduce-decompression-sickness.aspx