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FLASHBACK: Lockheed SR-71A Blackbird

  • Published
  • By Tony R. Landis
  • Air Force Materiel Command History Office

Big Tail - One of a Kind Variant

Shortly after the first SR-71’s began flying operational missions over North Vietnam, the Air Force was looking into ways of expanding the capabilities of the aircraft. With the interchangeable noses, mission planners had to make a choice of flying either optical cameras or side-looking radar, depending upon the mission requirements and the weather over the target area. Unfortunately several missions were rendered useless when weather over the target area prevented the use of the optical camera systems installed. There was also the possibility that future ground defenses had the ability to reach the SR-71 from behind since it carried no aft facing countermeasures.

In 1974, the Air Force identified a requirement for aft facing ECM requirement on the SR-71. Several proposals examined by the Air Force included conformal packages, belly pods as well as an extended tail fairing. After researching all the possibilities, the extended tail appeared to be the most viable option based on lowest cost, added volume and least aerodynamic drag. The new “Big Tail” assembly is 13-feet, 9-inches long and weighs 1,273 lbs. with 49 cubic feet of space to carry 864 lbs. of payload. The primary payload consisted of aft facing ECM as well as the 24-inch Optical Bar Camera. The new assembly needed to articulate 8.5 degrees up and down to clear the runway during take-off and landing.

The tenth SR-71 built (61-7959) was selected to receive the new modification. This aircraft was already being used for flight test duties at Palmdale at the time so there would be no effect on the operational fleet. Between April and November 1975, ‘959 received the modification with the new tail fairing; necessary modifications included a 51-inch adapter unit for the new tail, air conditioning for cameras and other equipment as well as routing the fuel vent along the upper surface of the tail. In addition to the tail modification, chine bays were modified to accommodate the 24-inch Optical Bar Camera.

With the stress and vibration testing completed, ‘Big Tail’ was taken out for the first high-speed taxi test on November 20, 1975 by Lockheed test crew Darrell Greenamyer (pilot) and Steven Belgeau (Reconnaissance Systems Officer-RSO). Two weeks later, on December 3, the same crew took Big Tail up on its first flight. Lasting just over one hour, the crew performed basic flight checks as well as tail deflections and fuel dump tests. With each test flight with the same Lockheed crew, Big Tail flew to higher speeds and altitudes achieving Mach 3 at 75,000 ft during the 6th flight on January 28,1976. Prior to turning the aircraft over to Air Force test crews, Greenamyer performed 4 solo flights to prove the system could be run by just a single crewmember. The RSO’s seat occupied by a ballast dummy affectionately known as “Sierra Sam”.

Once Lockheed crews proved the system worked, the Air Force took over all flight testing. Tom Pugh and Bob Riedenauer became the pilots and RSO duties went to William Frazier and John Carnochan with the first Air Force flight taking place on May 5, 1976. Over the next 6 months these Air Force crews made 23 flights in ‘Big Tail’, testing various camera systems in the tail and chine bays, as well as new ECM systems such as the DEF I, DEF J and DEF A-2.

Although ‘Big Tail’ proved to be a viable system, the Air Force chose not to pursue the concept any further.  After only 36 flights with the extended tail, ‘959 made its last flight on October 29, 1976, then simply placed in outdoor storage at Palmdale. Though it only had a total of 866 hours of flight time and a total of 304 flights to its credit, ‘959 became a source of spare parts for other flight test SR-71s until it was finally transferred to the Air Force Armament Museum at Eglin AFB, Florida in the fall of 1991.

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