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

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Sec,el NOFOPIN
Chapter 2
68
power-to-weight ratio of 2.7: I was almost 20 percent less efficient
than the preferred P-31 version:"
To conduct lengthy missions over hostile territory, the U-2
needed to carry a large amount of fuel. Kelly Johnson used a
'·wet-wing" design for the U-2, which meant that fuel was not stored
in separate fuel tanks but rather in the wing itself. Each wing was di­
vided into two leak-proof compartments, and fuel was pumped into
all the cavities within these areas; only the outer 6 feet of the wings
were not used for fuel storage. The U-2 also had a I 00-gallon reserve
tank in its nose. Later, in 1957, Johnson increased the fuel capacity of
the U-2 by adding 100-gallon "slipper" tanks under each wing, pro­
jecting slightly ahead of the leading edge.
One of the most important considerations in the U-2's fuel sys­
tem was the need to maintain aircraft trim as the fuel was consumed.
The aircraft therefore contained a complex system of feed lines and
valves draining to a central sump, which made it impossible to pro­
vide the pilot with an empty/full type of fuel gauge. None of the first
50 U-2s had normal fuel gauges. Instead there were mechanical fuel
totalizer/counters. Before the start of a mission, the ground crew set
the counters to indicate the total amount of fuel in the wings, and then
a flow meter subtracted the gallons of fuel actually consumed during
the flight. The pilot kept a log of the fuel consumption shown by the
counters and compared it with estimates made by mission planners
for each leg of the flight. As a double check. U-2 pilots also kept
track of their fuel consumption by monitoring airspeed and time in
the air. Most pilots became quite expert at this. Several who did not
came up short of their home base during the 20 years these planes
were flown:'
INITIAL TESTING OF THE U-2
Preliminary taxi trials began on 27 July 1955, when the first run down
the newly completed runway took the plane to 50 knots. Lockheed's
chief test pilot, Tony Le Vier, was at the controls. A second taxi trial
"' OSA Hiswry. chap. 8. p. 13 (TS Codeword).
" Information supplied by Norman Nelson. former director of Lockheed's Skunk Works.
10 Donald E. Welzenbach, 14 March 1986 (U): Miller, ltickheed U-2. pp. 77, 96.
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