Lockheed A-12 Blackbird

The A-12, the first of three different versions of the Blackbird, was secretly developed by Lockheed for the Central Intelligence Agency. The majority of Blackbirds were the SR-71 strategic reconnaissance versions used by the USAF Strategic Air Command until March 1990. Lockheed developed the Blackbird to provide a Mach 3 replacement for the U-2 spy plane. Development of the U-2 successor actually had been started in 1959 under a secret project code named Oxcart. Lockheed won the Oxcart contract in August 1959, and clandestine work by the company’s famous Skunk Works team began the following month under the direction of Chief Designer Clarence “Kelly” Johnson.

Initial specifications for the A-12 called for a top speed over Mach 3. This requirement meant that the inherent problems associated with reaching and attaining such high speeds would have to be resolved. At very high speeds, kinetic heating would subject the airframe of an aircraft to temperatures exceeding 800F (427C). Titanium alloy was the only material available at the time that could withstand these temperatures and, thus over 90 percent of the A-12 was fabricated from titanium alloy. Lockheed applied highly emissive dark blue (virtually black) paint that enabled the aircraft’s titanium skin to radiate heat two-and-a-half times faster than unpainted titanium, giving rise to the aircraft’s famed name: Blackbird. A dozen A-12s were ordered by the CIA in January 1960. The first A-12 single-seat aircraft, with its radical aerodynamically advanced delta shape and titanium airframe, was secretly flown by test pilot Louis Schalk on April 26, 1962, at the Air Force test facility at Groom Lake, Nevada.

The Pratt & Whitney J58 engine fitted to the A-12 was the first USAF engine qualified to operate for extended time at speeds exceeding Mach 3 and altitudes above 80,000 feet. The unique feature of this engine deals with bleeding a measure of the high-pressure air from the compressor and then bypassing the combustion chambers and turbine before injecting this air into the front end of the afterburner. The combination of the air bleed-bypass system feeding air directly to the afterburner works very much like a ramjet. Because conventional aircraft fuel would be too volatile at such high temperatures, a new fuel was developed called JP-7. Few in number, the Blackbirds met our nation’s strategic reconnaissance requirements for almost three decades. Typically, one of these aircraft could survey a strip of the United States 30 miles wide from coast to coast in an hour’s time.

The Museum’s Blackbird was the tenth A-12 built. This airplane was used by the CIA for five years to fly operational missions over Southeast Asia before it was retired in 1969 and put into storage at Palmdale, California. After restoration by Museum and Convair volunteers, the aircraft was transported to Balboa Park and mounted in front of the Museum in 1991.

San Diego Air & Space Museum

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