Lockheed SR-71 Blackbird SR-71C

The SR-71C was a one-off: a single aircraft, serial 61-7981, and the thirty-second and last airframe of the SR-71 programme, whose production totalled 29 SR-71As, two SR-71Bs and this one SR-71C. It was never a planned production version. It was improvised as a replacement trainer after the second of the two SR-71B two-seaters, 61-7957, was lost on 11 January 1968, when a double generator failure was followed by a double flameout on approach; the crew ejected safely. With only one trainer left, the decision was made to assemble a replacement from parts that were already available.

Those parts came from two very different sources. The rear half was taken from the first YF-12A, serial 60-6934, the interceptor prototype that had been damaged beyond repair by fire at Edwards Air Force Base in a landing mishap on 14 August 1966. The front half was a forward fuselage that had never been meant to fly at all: Lockheed had built it as an engineering mock-up for static ground testing, which the Hill Aerospace Museum describes as a functional engine mock-up of an SR-71A forward fuselage. Lockheed engineers mated the two sections at the company's Palmdale facility in California, producing a two-seat trainer. Sources differ slightly on the date: the Hill Aerospace Museum calls it the last SR-71 manufactured, in 1968, while other accounts place the completion of the thirty-second airframe in 1969.

Its mixed origin earned 61-7981 a nickname of its own, a rarity among Blackbirds, which were collectively known as "Habu": it became "The Bastard". The name had nothing to do with temperament; the aircraft was, as one account puts it, two airframes flying in very close formation.

The SR-71C first flew on 14 March 1969, with Lockheed test pilot Robert J. Gilliland at the controls and Steve Belgeau as reconnaissance systems officer. The crew reported trim and control problems, and when the aircraft was delivered to Edwards Air Force Base for Air Force acceptance testing the issues came into clearer focus. A team of Air Force test pilots flew it 16 times over several weeks to track them down. The variable inlets and their bypass doors were not staying in step with each other, and the rudders had to be trimmed away from their streamlined position, which added drag. The Air Force had Lockheed fit a beta (yaw) indicator, which showed four degrees of yaw while a Nomex yaw string stayed centred, indicating no yaw at all. This is the origin of the long-told story that the SR-71C was not quite straight and flew with a yaw at supersonic speed. The real culprit was more mundane: the pitot boom was out of alignment by the same four degrees, so the flight computers were receiving a false reading. Once that was corrected, the aircraft flew just like the B model.

On 3 September 1970, after flight testing, the SR-71C was delivered to the 9th Strategic Reconnaissance Wing at Beale Air Force Base, California. There it helped train many of the pilots who went on to fly the SR-71 on operational missions, and it was a natural choice for familiarisation flights with VIPs. The only operational difference from the B model was that the C had one fewer internal fuel tank, so its refuelling procedures were slightly different.

Its flying career was short. It made its last operational flight on 11 April 1976 and was removed from flying status on 24 June 1976 with 737.3 hours on the airframe, 180.9 of which had been flown by the rear section while it was still part of the YF-12A; its own time as an SR-71C amounted to 556.4 flight hours. Accounts of what followed differ: one says it was kept at Beale as a standby for the surviving B model, while the Hill Aerospace Museum states that it was moved into long-term storage at Lockheed's Palmdale plant.

Its final home was settled in April 1990, when, after Utah Senator Orrin G. Hatch intervened, the aircraft was assigned to the Hill Aerospace Museum at Hill Air Force Base, Ogden, Utah. Moving it proved a project in itself. Members of the Air Force Heritage Foundation of Utah, the 67th Aerial Port Squadron and the 405th Combat Logistics Support Squadron travelled to California to work out how to disassemble, package and transport it. In August 1990 the aircraft was broken down into three major pieces plus smaller components for carriage in a C-5 Galaxy, but no cargo aircraft was immediately available. In spring 1991 two trips with large flat-bed trucks moved most of the palletised components, and in August 1991 the final airlift carried the larger sections. Reassembly by the 405th, museum volunteers, Air Force reservists and active-duty personnel took about two months, and the SR-71C went on display in October 1991; one account gives the date as 16 October 1991. It remains there on loan from the US Air Force Heritage Program, still the only aircraft of its designation. Some secondary references give it an incorrect 64-series serial, 64-17981.