The clip features a quick, practice contact in “tanker manual” configuration followed by a disconnect, in preparation for a normal contact and subsequent refueling.
The cool video in this post shows a rendezvous between an SR-71 Mach 3 spy plane (flown by BC Thomas) and a KC-135Q tanker (with George Lester as boom operator) for a quick, practice contact in “tanker manual” configuration followed by a disconnect, in preparation for a normal contact and subsequent refueling.
As told by Paul F Crickmore in his book Lockheed Blackbird: Beyond the Secret Missions (Revised Edition), it’s impossible to overemphasise the essential role played by the KC-135Q tanker crews, without whom successful prosecution of the SR-71 mission would have been impossible. It became apparent to Strategic Air Command (SAC) that the tanker force dedicated to supporting SR-71 operations would need to be expanded beyond the original 21 Q-model aircraft and in 1967 the decision was made to modify an additional 35 aircraft. Some 20 KC-135As from the 70th AREFS, 43rd BW at Little Rock AFB, Arkansas, and 15 from the 306th AREFS, 306th BW at McCoy AFB, Florida were therefore converted.
However, to save costs these aircraft weren’t equipped with the full avionics suite found on the KC-135Qs stationed at Beale and were known informally as ‘partial Qs’. These additional ‘135s lacked the AN/ARN-90 TACAN and LORAN A (the latter was subsequently removed from the Beale aircraft). Instead, these partial. Qs relied upon an AN/ARC-50, known as ‘Comm 3’, to provide air-to-air distance measurement for the rendezvous between tanker and receiver.
There were two types of rendezvous used by KC-135Qs during missions in support of the SR-71. Other than differences in timing, these two procedures were identical. The first, known as the ‘cold’ rendezvous, was used when the receiver was subsonic prior to the air refuelling, such as for the initial fuel on-load after take-off or during pilot qualification training. The ‘hot’ rendezvous was used when the receiver was supersonic prior to the air refuelling, which was usually the case during an operational mission or ferry flight.
The KC-135Q could simultaneously carry a maximum of 74,490lb of JP-7 (until the Boeing X-51 Waverider Mach 5 unmanned experimental aircraft the SR-71 had been the only aircraft in the world that burned JP-7) and 110,000lb of JP-4 for its own engines. To account for changes in the aircraft’s CG during refuelling operations, 850lb of ballast was added to the lower nose compartment. The refuelling operation was conducted at 355 Knots Indicated Airspeed (KIAS; red-line speed for the KC-135Q) and within a block altitude of FL260-270, a height lower than SR-71 crews preferred, but as high as a fully laden KC-135Q could reach while maintaining 355KIAS.
Approaching the end of the air-refuelling task, the SR-71 was at the limits of its subsonic heavy-weight performance envelope and the pilot would often engage one afterburner and cross-control the aircraft to mitigate against the effects of asymmetric thrust in order to stay in contact with the tanker. Much later in the programme, tests conducted with KC-135Rs showed a 20KIAS increase in the tanker’s maximum speed, allowing the SR-71 to refuel at 375KIAS, a considerable improvement, especially during heavy-weight operations.
Lockheed Blackbird: Beyond the Secret Missions (Revised Edition) is published by Osprey Publishing and is available to order here.