In this article:
SR-71, KC-135Q and JP-7
The SR-71 Blackbird would be a very short-ranged aircraft were it not for air refueling, limited to around 2,000 NM. Multiple air refuelings extended the range of the aircraft to the limits of crew endurance. Many missions have exceeded 12,000 NM. Forward basing of the SR-71 and KC-135Q tankers permitted faster response, shorter range, shorter duration missions, fewer air refuelings, and greater overall efficiency.
KC-135Q crews and their aircraft were unique from the rest of the Air Force in several ways. Their aircrews in fact were the only one certified in Blackbird’s specific radio-silent rendezvous procedures, and their boom operators were the only ones qualified to refuel the SR-71. The Q-model tankers had special plumbing between their fuel tanks, allowing them to transfer JP-4 and JP-7 fuel between various tanks. Their engine could burn transfer JP-4 or JP-7 fuel. If the SR-71 landed somewhere JP-7 fuel was not available, the Q-model tankers flew in with the fuel and, through the use of transfer hoses on the ground, were able to refuel the SR-71.
How to get better gas mileage in an SR-71 Blackbird flying at Mach 3
David Peters, former SR-71 pilot, explains how to get better gas mileage in a Blackbird flying at Mach 3;
‘We had some gimmicks we used to make fuel. Each plane was different but the techniques were very close. As soon as we started the climb away from the tanker I would select tank two manually and even sometimes go to manual aft transfer to get the CG aft as soon as possible. After level off at Mach 3 I would get the CG situated where the trim was at zero for a slight cruise climb thus eliminating induced drag. Next I would have the aft doors in A position and manipulate the speed to close the forward doors as much as by possible without creating an unstart. This might be anywhere from 3.0 to maybe as high as 3.04 or 5.
‘Much of this was dependent on outside temperature. If it was colder than standard you could do even better. Hotter than standard not so good but always better than the plan. Using these techniques and a few more I would often see fuel flows below 3600 lbs/hr/per engine at Mach 3. Ed and I rarely came back from a mission with less than 5,000 lbs more fuel than the flight plan called for. There are a lot of those things involved. Flying the SR required a great deal of stick and rudder abilities under some circumstances but I always told people it was primarily a cerebral machine. You had to have very deep understanding of how it worked to get the job done.’
Skill and knowledge
Peters concludes;
‘I have said many times before, much to the contrary of the engineers that DAFICS [digital automatic flight and inlet control system] really screwed up what the airplane was capable of just like everything we seem to do anymore it took the skill and knowledge of the operator pretty much out of the equation. But that is another discussion.’
Be sure to check out Linda Sheffield Miller (Col Richard (Butch) Sheffield’s daughter, Col. Sheffield was an SR-71 Reconnaissance Systems Officer) Twitter X Page Habubrats SR-71 and Facebook Page Born into the Wilde Blue Yonder Habubrats for awesome Blackbird’s photos and stories.
Photo credit: David Peters and TSgt. Michael Haggerty / U.S. Air Force
