The Central Intelligence Agency and Overhead Reconnaissance; the U-2 and Oxcart Programs, 1954-1974

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Secret NOFORN
Chapter 2

In designing the U-2 aircraft, Kelly Johnson was confronted with two major problems—fuel capacity and weight. To achieve intercontinental range, the aircraft had to carry a large supply of fuel, yet, it also had to be light enough to attain the ultrahigh altitudes needed to be safe from interception. Although the final product resembled a typical jet aircraft, its construction was unlike any other US military aircraft. One unusual design feature was the tail assembly, which—to save weight—was attached to the main body with just three tension bolts. This feature had been adapted from sailplane designs.

The fragility of the wings and tail section, which were only bolted to the fuselage, forced Kelly Johnson to look for a way to protect the aircraft from gusts of wind at altitudes below 35,000 feet, which otherwise might cause the aircraft to disintegrate. Johnson again borrowed from sailplane designs to devise a "gust control" mechanism that set the ailerons and horizontal stabilizers into a position that kept the aircraft in a slightly nose-up attitude, thereby avoiding sudden stresses caused by wind gusts. Nevertheless, the U-2 remained a very fragile aircraft that required great skill and concentration from its pilots.

The wings were also unique. Unlike conventional aircraft, whose main wing spar passes through the fuselage to give the wings continuity and strength, the U-2 had two separate wing panels, which were attached to the fuselage sides with tension bolts (again, just as in sailplanes). Because the wing spar did not pass through the fuselage, Johnson was able to locate the camera behind the pilot and ahead of the engine, thereby improving the aircraft's center of gravity and reducing its weight.

The wings were the most challenging design feature of the entire airplane. Their combination of high-aspect ratio and low-drag ratio (in other words, the wings were long, narrow, and thin) made them unique in jet aircraft design. The wings were actually integral fuel tanks that carried almost all of the U-2's fuel supply.

The final major design feature was the lightweight, bicycle-type landing gear. The entire structure—a single oleostrut with two lightweight wheels toward the front of the aircraft and two small, solid-mount wheels under the tail—weighed only 208 pounds yet could withstand the force of touchdown for this 7-ton aircraft. Because both sets of wheels were located underneath the fuselage, the U-2 was also equipped with detachable pogos (long, curved sticks with two small wheels on them) on each wing to keep the wings level during takeoff. The pilot would drop the pogos immediately after takeoff so