Skunk Works

I turned to Dave for help and advice during that period of U-2 test flights in the summer of 1955, when our test pilots began reporting “duct rumble” at fifty thousand feet, describing the sensation as driving down a deeply rutted road on four uneven tires. In an airplane as fragile as the U-2, such severe shaking was a serious problem. The cause was flying at a slant so that more air was entering one of the twin air-intake ducts than the other. The problem landed directly in my lap since I had designed the intakes. Dave helped me design a splitter to enhance more even airflow and that helped to alleviate the problem, but not entirely. At fifty thousand feet, pilots were continuing to experience a roughness, although not to the point of watching their wing flaps so that they broke into a cold sweat. I told Kelly, “We’ve got it under control, but it won’t go away. I have no idea why it happens only at fifty thousand feet.” He didn’t either. He just told our pilots: “Avoid flying at fifty thousand whenever possible. You should be up higher than that anyway.” Pratt & Whitney finally solved the problem completely a year or so later by revising the fuel control for a better match of air and fuel into the engine.

But our test pilots had a lot more on their minds than rumbling ducts. Landing the U-2 on its two tandem wheels was neither easy nor routine. Our veteran test pilots warned Kelly that training CIA pilots to fly the U-2 and not getting one or more killed in the process was going to be a major challenge. Pilots were also apprehensive when hitting clear air turbulence and watching those long thin wings flapping like a bird’s, worrying that the next big gust would snap them off entirely. And, by the way, there were no ejection seats in the early models of the airplane. Ejection seats would add thirty pounds above a regular seat, so to save precious weight, the CIA decided to dispense with them altogether.

U-2 pilots would be trained to fly 9-hour-and-40-minute missions, flying round-trip on deep-penetration flights over the Soviet Union. The pilot needed an iron butt for ten-hour flights. “I ran out of ass before I ran out of gas,” some U-2 drivers would later complain—and who could blame them? A pilot was jammed inside a cockpit smaller than the front seat of a VW Beetle, laced into a bulky partial-pressure suit, his head encased in a heavy helmet, hooked to an oxygen breathing tube, a urine tube, and fighting off muscle cramps, hunger, sleepiness, and fatigue. If the cabin pressure and oxygen supply cut off, a pilot’s blood would boil off in seconds at more than thirteen miles above sea level.

The U-2 was a stern taskmaster, unforgiving of pilot error or lack of concentration. No U-2 pilot, no matter how tired, would risk a few winks and leave the driving to his autopilot. The airplane demanded extraordinary pilot vigilance from the moment of takeoff. It was designed for an immediate steep climb, but it was critical to keep the wings level because they stored a very heavy fuel load and as the U-2 rose in the sky the fuel expanded under diminishing air pressure. One wing would sometimes feed the fuel into the engine more quickly than the other and that upset the airplane’s delicate balances. To regain this balance the pilot had to activate pumps that moved fuel from one wing to the other. Another very tricky aspect of flying this particular machine was maintaining carefully controlled airspeed. A pilot could fly up to 220 knots during a climb with a special gust control turned on that stiffened the wings and allowed it to hit wind gusts of up to fifty knots. But he also had to guard against climbing too slowly, that is, below 98 knots, or the airplane would stall and fall out of the sky. Above 102 knots the airplane experienced dangerous Mach or speed buffeting. So the slowest it could safely go was right next to the fastest it could go as it climbed steeply to above sixty-five thousand feet. And the shuddering felt the same whether it was the result of going too fast or too slow, so a pilot had to keep totally alert while making corrections. A mistake might make the buffeting worse and shake the airplane to pieces. And to make life more interesting, our test pilots reported that sometimes during a turn the inside wing would be shaking in stall buffet while the outside wing was shaking even more violently in Mach buffet.

Once the pilot reached seventy thousand feet he tried to maintain 400 knots true airspeed, about as fast as a commercial jetliner, and keep the engine from overheating and operating at maximum efficiency.