At more than 170 knots on landing, the SR-71 Blackbird was already operating in a narrow band where small aerodynamic penalties turned into large control problems. That reality explains why a single photograph showing one engine at idle while the other sits in full afterburner still gets pilots talking: it captures a moment when the aircraft’s systems design mattered as much as stick-and-rudder skill.
A very straightforward explanation is provided by Lionel “Stormy” Boudreaux, who was described as “one of only 12 pilots who flew operational sorties in both the U-2 and the SR-71.” In his dissection of the picture, he refers to it as a practice single-engine go-around: It is a picture of a practice Single-engine go-around. In this image the left engine is in idle, the right engine is in full afterburner. Pilot has closed left rudder fully, and is just turning into a right bank – all in order to maintain the aircraft straight. Moreover, he has retracted landing gear. The design of the SR was very unique and the gear could be retracted by either the left or the right hydraulic system which was also a design feature of the SR, according to Boudreaux.
This is a simple but savage operational issue: the engines of the Blackbird are far apart and at low speed the loss of thrust on one side causes a major yawing movement. It can be counteracted by rudder input and a turn into the good engine, but the configuration of the SR-71 adds one more trap- one that does not present itself until the landing gear has already been raised, during the recovery. Boudreaux outlined the mechanism in a simple language: “Besides banking into the good engine and full rudder against the yaw, it was critical to retract the gear. Why? Because the nose gear down with the aircraft flying in a huge yaw, the nose gear acted like a canard or a fin stuck out in the airflow, causing the yaw to become even greater.”
The reminder of that “fin in the airflow” effect is that landing gear is not merely a structural system, but also an aerodynamic shape inserted into the flow at the time when the aircraft is slow, high in angle-of-attack and already struggling to counteract asymmetric thrust. On a Mach 3+ aircraft in which the chines and vertical tails were designed to provide the highest stability and signature control at high speed, the nose gear has become an unwanted control surface at the most inopportune moment. In a single-engine go-around, when the pilot is maneuvering to maintain the aircraft heading during acceleration and clean-up, the additional yaw connection may put the plane on the border of controllability. Boudreaux’s emphasis is unambiguous: “It would quickly be out of control if the gear could not be raised, specifically the nose gear. During certain low-speed conditions in this situation, the recovery would not be possible if the nose gear could not be retracted.”
The technical solution was duplicity towards the direction, which was most appropriate to survivability. According to Boudreaux, the SR-71 was unique in that it was able to retract the gear on either hydraulic side: “the SR-71 is the only aircraft I know of that has 2 methods (using hydraulics of either side) to retract the gear.” Such a decision represents a philosophy of design that can be observed throughout the Blackbird program – systems designed about a handful of extreme operating points. The materials choice of 85% of the structure of the aircraft depended on the titanium, which was the choice of materials depending on heat and strength maintained at a high speed. It also employed JP-7 fuel as propellant and heat sink, a systems level method of controlling temperatures that would have overwhelmed conventional designs.
In the same spirit, the landing gear architecture treated retraction as a controllability requirement, not merely a housekeeping step after takeoff. “Most aircraft have a normal and an emergency method to lower the gear, but only one system to retract the gear,” Boudreaux explained, before adding why the Blackbird diverged: “it was so critical to get that nose gear retracted at low speeds during single-engine operations that Lockheed designed it so that if either engine failed the landing gear could still be retracted.”
The drama of the photo is enhanced by the last twist of Boudreaux: “What are the odds that during a practice single-engine approach was made even more exciting by having the engine that was to power the practice single-engine approach and go-around blowup! This made the practice turn into a real single-engine go-around!”
That combination, the high approach speed, the strong yaw due to asymmetric thrust, and the nose gear that might increase the issue, demonstrates how the reputation of the SR-71 was achieved in meticulous details. It was not just a record plane in altitude and speed; it was an aircraft where both hydraulic systems had to be capable of removing the gear in the fewest minutes possible on the plane when it was most required by the pilot.
