SR-71 aerial refueling challenges and risks.
The SR-71 required refueling roughly every hour. Although refueling proved challenging, SR 71 pilots were always up for the task.
After takeoff, their first task was typically refueling. They would sometimes take off from Kadena Air Force Base in Okinawa with enough fuel to complete the entire flight.
No refueling is required Although it was known as a Yo-Yo, upkeep was a nightmare. With a 65,000-pound fuel load, the SR-71 had to reach Mach 3+ immediately after takeoff for a number of our missions. The crew chief had to completely refuel the aircraft using the Yo-Yo process, filling the tanks with 80,000 pounds of fuel. They then defueled 15,000 pounds of JP-7 to leave a 65,000-pound fuel load and a jet that could reach Mach 3+ right away once the nitrogen pressurization system was operational.
Refueling posed unique challenges because sight was low due to the triangular forward glass and because the pressure suit helmet produced unwanted reflections. The SR-71 had to fly beneath the tanker since the container, which received the fuel, was below the cockpit. Typically, one would consume 11,000 gallons or 70,000 pounds of JP7 fuel.
Refueling usually happened at a height of roughly 25,000 feet. The aircraft became thrust-limited, meaning that drag increased as it approached the stall speed for this particular aircraft, as the weight grew and the airspeed had to be maintained down to accommodate the slower tanker (there was no additional thrust available without afterburner). In order to maintain position at that point, the pilot had to slightly open one throttle into the after-burner range.
The pilot had to use rudder to balance the asymmetry or accept some sideways flight when using one afterburner. It’s interesting to note that the pilots created the left afterburner maneuver to cause a tiny rightward yaw in the plane. Hence, just the left quarter panel had defogged air, and if necessary, one may benefit from it. During each flight, the pilot had to refuel two to four times, which required a lot of work.
Sources: Aloysius Casey and Rich Graham.
Lindsey Sheffield Miller
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