Documents / FOIA release
This is a CIA History Staff monograph by Gregory W. Pedlow and Donald E. Welzenbach, published in Washington in 1992 and approved for release in 2011. It covers the CIA's manned overhead reconnaissance program from 1954 to 1974, which developed and flew the U-2 and the A-12 OXCART. It traces the U-2's development, the overflights of the Soviet Union, the downing of Francis Gary Powers on 1 May 1960, and later operations. One section is titled U-2s, UFOs, and Operation BLUE BOOK.
“Nathan F. Twining”2 pages
CO5653421 UNCLASSIFIED Chapter 2 76 (0129581.13[111[1]>10<25Yrs [S] 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 hi g h-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 win g s 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 usin g 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.'4 Amon g 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 locatin g navi g a- 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 1 nautical mile over a 1,000-nm course." 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 interview (TS Codeword): John Parangosky. interview by Donald E. Welzenbach. tape recording. 6 March 1986 (S): inrormation supplied by o Donald E. Welzenbach (S). " Cunningham interview (TS Codeword). UNCLASSIFIED
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FOIA release, from the cia-readingroom collection. The PDF is mirrored here; the original link is under it. 406 pages are in the text index: search them above, or from the library's search.