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

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76
Seerct NOFORN
Chapter 2
and could not survive the stresses of loops and barrel rolls. Moreover,
the original U-2s were placarded, which meant that they could not be
flown at sea level faster than 190 knots in smooth air or 150 knots in
rough air. At operational altitude, where the air was much less dense,
they could not exceed Mach 0.8 (394 knots). Speeds in excess of
these limits could cause the wings or tail section to fall off.
Airspeed was a very critical factor for the U-2. At maximum alti­
tude only 6 knots separated the speeds at which low-speed stall and
high-speed buffet occurred. Pilots called this narrow range of accept­
able airspeeds at maximum altitude the ..coffin corner" because at
this point the U-2 was always on the brink of falling out of the sky. If
the aircraft slowed beyond the low-speed stall limit, it would lose lift
and begin to fall, causing stresses that would tear the wings and tail
off. A little too much speed would lead to buffeting, which would
also cause the loss of the wings or tail. Flying conditions such as
these required a U-2 pilot's full attention when he was not using the
autopilot. Airspeed was such a critical factor that Kelly Johnson
added a vernier adjustment to the throttle to allow the pilot to make
minute alterations to the fuel supply. 50
Among the unique devices developed for the U-2 was a small
sextant for making celestial .. fixes" during the long overflights.
Because cloud cover often prevented U-2 pilots from locating naviga­
tional points on the earth through the periscope, the sextant turned out
to be the pilots' principal navigational instrument during the first
three years of deployment. When clouds were not a factor, however.
the periscope proved highly accurate for navigation. During the final
tests before the aircraft became operational. U-2 pilots found they
could navigate by dead reckoning with an error of less than I nautical
mile over a 1.000-nm course.5'
FINAL TESTS OF THE U-2
Flight-testing of the U-2 continued throughout the fall and winter of
1955-56 in order to test all the various systems. By mid-January
1956. SAC officials were so impressed that they also wanted to pur­
chase a fleet of these planes. On 30 January. DCI Dulles agreed to
" Cunningham int.:rview (TS Codeword): John Parangosky. intt:rview by Donald E.
Wdzenhach. tape recording. 6 March 1986 (S): information supplied by James
Ch..:rbonneaux to Donald E. Wdzenhach (S).
" Cunningham interview (TS Codeword).
Seci:et