But the U-2 program has seen more cases of DCS over the last decade than at any other time in its 56-year history. Since the war in Afghanistan started, in 2001, the average number of cases reported each year has almost doubled. More important, before 2002, no cases severe enough to hinder U-2 operations were reported, but between 2002 and 2009, there were 16 confirmed severe cases, five of which were deemed life-threatening. Nine of the pilots who experienced serious DCS symptoms reported long-lasting or permanent brain damage.
A study published in the July 2011 issue of the journal Aviation, Space, and Environmental Medicine analyzed 40 years of the military’s medical records to find possible reasons for the shift. Three major factors seem to be contributing to the increase. First, pilots are flying more often. With a demanding new role—providing ground combat support in Afghanistan—U-2 pilots are flying 70 percent more hours on 122 percent more sorties than they did during the cold war.
U-2 pilots are also flying for longer stretches. During the cold war, flights rarely lasted longer than eight hours; now ground operations require U-2s to stay in the air for up to 12 hours. As a result, severe DCS cases over the last decade are concentrated among the pilots flying out of the primary support base for combat operations in Iraq and Afghanistan.
Finally, fundamental changes in the work pilots are doing may also be making things worse. The study found that even mild exercise, including motions as simple as pressing foot pedals or raising an arm to flip a switch, can greatly increase the risk of DCS. Unlike cold war reconnaissance, today’s missions require pilots to do much more in the cockpit—operating a radio, inputting navigational data, adjusting sensors—so the new mission itself could be partly responsible for releasing nitrogen bubbles through a pilot’s bloodstream.
Lieutenant Colonel Sean Jersey, a physician and one of the study’s authors, cites a potential fourth factor: stress. In the Soviet flyover days, U-2 pilots would head out to a target, snap pictures, and fly back. They could even sleep part of the way, letting the airplane fly on autopilot. Today, pilots must quickly react to changes on the battlefield, acting as a mobile relay station for communications and an eye in the sky for troops fighting on difficult terrain. They’re also in constant contact with the soldiers on the ground, often during combat.
“Emotionally, I think they’re wrung out from that,” says Jersey. “When you’re talking to somebody on the radio and there’s gunfire in the background…you’re not taking a nap while that’s happening.”
Lieutenant Colonel Blake Smith is a U-2 pilot who retired early last year. He often served as director of operations for the 99th Expeditionary Reconnaissance Squadron, to which the U-2 is assigned, during the shift toward combat support missions, and he knew the pilots and their problems well. He remembers that when he joined the program in 1998, DCS was mostly a non-issue. Pilots might complain of minor joint pain, but once they were back on the ground and rested, their symptoms would generally get better.
“Years ago, whenever you mentioned you had a little bit of DCS, the reaction from the medical forces, and the reaction from the Air Force for that matter, was not as thorough and robust as it is now,” says Smith.
What changed, he says, was the sudden appearance of DCS cases that affected the pilots’ central nervous systems, something no one in the program was used to handling. On the way home from flying a long-duration combat mission for Enduring Freedom in late 2002, Major Greg Kimbrough suffered severe symptoms. Having been trained to expect joint pain and a headache, he had no idea that his inability to read fine print or recognize his landing field was indicative of decompression sickness. “What we got when we went through our initial training was the basics of it,” says Kimbrough, “and that was all based on past events,” when the cases were minor.
By the time he was having major symptoms at altitude, Kimbrough’s cognition was so compromised that it never occurred to him to call for help. Somehow he was able to land his U-2 safely, but he has little memory of the last hours of the flight.