The Lockheed SR-71 Blackbird remains the pinnacle of aerospace engineering, a machine that turned the impossible into the operational. However, mastering the 'Sled' requires more than just stick-and-rudder skills; it requires a deep understanding of its unique technical language and terminology.
This living glossary is a curated collection of SR-71 terminology, designed for flight simulation pilots and aviation enthusiasts who seek for a quick and useful glossary.
Note: This is a dynamic resource. VSKYLABS continuously expand this page with new technical insights, ground-op procedures, and cockpit jargon.
So...check back often for the latest updates from the 'labs!
The "Father" of the Blackbird. Developed for the CIA under the codename Oxcart, the A-12 was a single-seat, slightly smaller, and faster version of what would become the SR-71.
Aerial Refueling:
Before an SR-71 could safely accelerate past Mach 2.6, the fuel system had to undergo a specific purging process which was usually done during aerial refueling (Ground Yo-Yo was the ground process). This was not optional; it was a structural and safety requirement. As JP-7 fuel was pumped into the tanks at high pressure from the KC-135Q, the fuel tanks were purged of all atmospheric air and oxygen. Once the tanks were full, the Liquid Nitrogen (LN2) system took over, pressurizing the tanks with pure nitrogen which eliminated to possibility of auto-ignition at high speeds (above Mach 2.6) due to the extreme SR-71 surface temperature.
Aft Bypass Doors:
These duct air around the engine core and into the afterburner. At Mach 3.2, they are open wide to feed the Turbo Ramjet cycle.
AG330 (Start Carts):
The SR-71 start carts were powered by two synchronized Buick (and later Chevrolet) 454 V8 racing engines. The cart would plug into a drive shaft under the nacelle and spin the J-58 up to 3,200 RPM before the TEB (ignition chemical) was injected to start the engine.
Astro-Inertial Navigation System (ANS):
Known as the Blackbird's 'R2-D2'. This was the Blackbird’s autonomous navigation brain. It used a star-tracking telescope to fix the aircraft's position by the stars, even during the day, with an accuracy of within 300 feet while traveling at Mach 3.
AG330 (Start Carts):
The SR-71 start carts were powered by two synchronized Buick (and later Chevrolet) 454 V8 racing engines. The cart would plug into a drive shaft under the nacelle and spin the J-58 up to 3,200 RPM before the TEB (ignition chemical) was injected to start the engine.
Astro-Inertial Navigation System (ANS):
Known as the Blackbird's 'R2-D2'. This was the Blackbird’s autonomous navigation brain. It used a star-tracking telescope to fix the aircraft's position by the stars, even during the day, with an accuracy of within 300 feet while traveling at Mach 3.
Bypass Tubes:
These six external tubes wrap around the engine's core, connecting the fourth stage of the compressor directly to the afterburner. They allow the J-58 to 'bypass' its own heart when the air gets too fast for the spinning blades to handle. At speeds above Mach 2.2, the pressure in the inlet becomes so intense that it risks choking the engine core. The bypass tubes were opened to vent this high-pressure air around the turbine stages. By ducting this air directly into the afterburner, the engine began to function as a ramjet. At Mach 3.2, these tubes were carrying the majority of the air that produces thrust, allowing the core to effectively 'loaf' while the ram-air did the heavy lifting.
Chines:
The sharp, blade-like blended wings running along the sides of the fuselage from the nose to the wing roots. The chines improved the SR-71 stability especially at high AOA. The added total lift at high supersonic flight eliminated the need for canard surfaces for proper pitch-trim.
Corrugated Surfaces:
If you look closely at the wings surface of the Blackbird, they aren't smooth...they are corrugated (wrinkled). This allowed the titanium to expand vertically and horizontally without warping or 'oil-canning' the structural ribs of the wing.
D-21 ('Daughter' Mach-3 Drone):
A high-speed, unmanned reconnaissance drone designed to be launched from the back of an M-21 or a B-52. The 'D' stood for 'Daughter'. It was built to fly over 'hot' zones where a manned flight was too risky. After its mission, it would eject its camera canister and then self-destruct. It is one of the most enigmatic pieces of the Blackbird program's history.
DAFICS (Digital Automatic Flight and Inlet Control System):
The Digital Automatic Flight and Inlet Control System (DAFICS) was a critical upgrade for the Lockheed SR-71 Blackbird, replacing earlier analog systems to manage the complex interaction between the aircraft's supersonic engines and aerodynamics.The development of the DAFICS helped eliminate many of the inlet ‘unstart’ problems that had plagued the type’s Pratt & Whitney J58 engines.
Drag Chute:
The SR-71 was a massive delta-wing aircraft with no flaps. It landed fast (around 175-185 knots). It used a 40-foot diameter 'Drag Chute' for initial braking. The pilot deployed the chute just as the nose-wheel touched down.
Electronic Compartment (E-bay):
Chines:
The sharp, blade-like blended wings running along the sides of the fuselage from the nose to the wing roots. The chines improved the SR-71 stability especially at high AOA. The added total lift at high supersonic flight eliminated the need for canard surfaces for proper pitch-trim.
Corrugated Surfaces:
If you look closely at the wings surface of the Blackbird, they aren't smooth...they are corrugated (wrinkled). This allowed the titanium to expand vertically and horizontally without warping or 'oil-canning' the structural ribs of the wing.
D-21 ('Daughter' Mach-3 Drone):
A high-speed, unmanned reconnaissance drone designed to be launched from the back of an M-21 or a B-52. The 'D' stood for 'Daughter'. It was built to fly over 'hot' zones where a manned flight was too risky. After its mission, it would eject its camera canister and then self-destruct. It is one of the most enigmatic pieces of the Blackbird program's history.
DAFICS (Digital Automatic Flight and Inlet Control System):
The Digital Automatic Flight and Inlet Control System (DAFICS) was a critical upgrade for the Lockheed SR-71 Blackbird, replacing earlier analog systems to manage the complex interaction between the aircraft's supersonic engines and aerodynamics.The development of the DAFICS helped eliminate many of the inlet ‘unstart’ problems that had plagued the type’s Pratt & Whitney J58 engines.
Drag Chute:
The SR-71 was a massive delta-wing aircraft with no flaps. It landed fast (around 175-185 knots). It used a 40-foot diameter 'Drag Chute' for initial braking. The pilot deployed the chute just as the nose-wheel touched down.
Electronic Compartment (E-bay):
The electronic compartment was located just aft of the pilot’s station. This pressurized and air-conditioned space contained most of the communication and navigation equipment as well as the stability augmentation system, autopilot, flight reference, Mach trim, and other electronic systems.
Expansion Gaps:
Because metal expands when heated, the SR-71 was designed with "loose" skin panels on the ground. During a Mach 3 dash, the airframe would actually grow by several inches in length and width. This is why the aircraft famously leaked JP-7 fuel on the tarmac; the "skin" didn't truly seal until the heat of high-speed flight expanded the titanium panels to fit together perfectly.
Pressure Suit (Full Pressure Suit):
Because the SR-71 operated in a near-vacuum at 80,000 feet, the crew could not survive with a simple oxygen mask. They wore a Full Pressure Suit which was the direct precursor to the suits used by Space Shuttle astronauts.
Spikes:
The conical 'nose' inside each engine nacelle. At speeds above Mach 1.6, the spikes move rearward to control the position of the supersonic shock-wave, slowing incoming air to subsonic speeds before it enters the engine. Crucial for effective high-Mach propulsion.
SR-71B:
The dual-control trainer version of the Blackbird. It is easily identified by its elevated rear cockpit for the instructor pilot and two ventral fins under the engine nacelles to compensate the structural differences in the fuselage design.
TEB (Triethylborane):
A chemical used for engine ignition. Because JP-7 was so hard to light, the SR-71 injects a shot of TEB, which ignites spontaneously on contact with air, to start the engines and light the afterburners. This produces the signature green flash in the exhaust.
Because metal expands when heated, the SR-71 was designed with "loose" skin panels on the ground. During a Mach 3 dash, the airframe would actually grow by several inches in length and width. This is why the aircraft famously leaked JP-7 fuel on the tarmac; the "skin" didn't truly seal until the heat of high-speed flight expanded the titanium panels to fit together perfectly.
Forward Bypass Doors:
Located around the inlet, these were opened to 'dump' excess air if the engine can't 'swallow' it fast enough, preventing a pressure buildup that would 'spit' the shockwave out.
Green Flash:
A visible green flash in the SR-71 engine nozzles was a known signature of TEB (Triethylborane) ignition.
Habu:
The legendary nickname given to the SR-71 by the local people of Okinawa, Japan. The 'Habu' is a deadly black pit viper found on the island; when the locals saw the dark, sleek titanium aircraft taking off from Kadena Air Base, they saw a striking resemblance to the snake. The name became a badge of honor for the crews.
Green Flash:
A visible green flash in the SR-71 engine nozzles was a known signature of TEB (Triethylborane) ignition.
Habu:
The legendary nickname given to the SR-71 by the local people of Okinawa, Japan. The 'Habu' is a deadly black pit viper found on the island; when the locals saw the dark, sleek titanium aircraft taking off from Kadena Air Base, they saw a striking resemblance to the snake. The name became a badge of honor for the crews.
IGV (Inlet Guide Vanes):
The Inlet Guide Vanes were a set of variable-angle blades located at the very front of the J-58 compressor. They acted as the 'traffic controllers' for the air entering the engine's core. At low speeds, the IGVs were angled to allow the engine 'gulp' air more easily. As the aircraft accelerates toward high Mach numbers, these vanes rotated (scheduled by the engine control system) to a 'cambered' position. At high Mach numbers the IGVs adjusted their angle to ensure the air enters the first stage of the compressor at the perfect angle, preventing a 'compressor stall'. The IGVs worked in correlation with the Bypass Tubes. While the tubes bleeded off air to the afterburner, the IGVs managed what's left to keep the engine core spinning safely.
Inert Tank Pressurization:
To prevent the JP-7 fuel from becoming explosive at high temperatures when flying at speeds that exceed Mach 2.6, the fuel tanks were pressurized with nitrogen. This 'inerting' process displaced all compressed air (thus oxygen) from the tanks, ensuring the fuel could not ignite inside the airframe.
J-58 (JT11D-20) Engine:
The J-58 was the world's first engine capable of operating in a continuous afterburning mode for hours at a time. It wasn't a plain jet engine; it was a 'Turbo-Ramjet' hybrid. Above Mach 2.2, six massive 'bypass tubes' opened up, taking air from the fourth stage of the compressor and ducting it straight into the afterburner. This turned the engine into a Ramjet, where the faster the plane went, the more efficiently it produced thrust. At Mach 3.2, the J-58 (turbo) engine itself only provided about 18% of the total thrust. The rest was generated by the unique pressure dynamics of the Spikes and the Inlet.
JP-7 Fuel:
A specialized, low-volatility kerosene developed specifically for the SR-71. It has such a high flashpoint that it was famously used as a coolant for the airframe before being burned in the engines. You could drop a lit match into a bucket of JP-7 and it would not ignite. JP-7 ignition for engine start and afterburner was made by the use of TEB (Triethylborane).
KEAS (Knots Equivalent Airspeed):
KEAS was the primary reference for the structural and aerodynamic limits of the Blackbird. It represents the "real" pressure of the air hitting the airframe. KEAS corrects for the compressibility of air at high speeds and high altitudes, giving the pilot a 'true' sense of the aerodynamic load on the wings.
M-21 (The 'Mother' Ship):
A heavily modified version of the A-12 designed to carry and launch the D-21 drone. The 'M' stood for 'Mother'. It featured a second seat for the Launch Control Officer and a large pylon on the back to hold the drone. The program was tragically cancelled after a mid-air collision during a D-21 launch.
Mission Equipment Bay (Q-bay):
Inert Tank Pressurization:
To prevent the JP-7 fuel from becoming explosive at high temperatures when flying at speeds that exceed Mach 2.6, the fuel tanks were pressurized with nitrogen. This 'inerting' process displaced all compressed air (thus oxygen) from the tanks, ensuring the fuel could not ignite inside the airframe.
J-58 (JT11D-20) Engine:
The J-58 was the world's first engine capable of operating in a continuous afterburning mode for hours at a time. It wasn't a plain jet engine; it was a 'Turbo-Ramjet' hybrid. Above Mach 2.2, six massive 'bypass tubes' opened up, taking air from the fourth stage of the compressor and ducting it straight into the afterburner. This turned the engine into a Ramjet, where the faster the plane went, the more efficiently it produced thrust. At Mach 3.2, the J-58 (turbo) engine itself only provided about 18% of the total thrust. The rest was generated by the unique pressure dynamics of the Spikes and the Inlet.
JP-7 Fuel:
A specialized, low-volatility kerosene developed specifically for the SR-71. It has such a high flashpoint that it was famously used as a coolant for the airframe before being burned in the engines. You could drop a lit match into a bucket of JP-7 and it would not ignite. JP-7 ignition for engine start and afterburner was made by the use of TEB (Triethylborane).
KEAS (Knots Equivalent Airspeed):
KEAS was the primary reference for the structural and aerodynamic limits of the Blackbird. It represents the "real" pressure of the air hitting the airframe. KEAS corrects for the compressibility of air at high speeds and high altitudes, giving the pilot a 'true' sense of the aerodynamic load on the wings.
M-21 (The 'Mother' Ship):
A heavily modified version of the A-12 designed to carry and launch the D-21 drone. The 'M' stood for 'Mother'. It featured a second seat for the Launch Control Officer and a large pylon on the back to hold the drone. The program was tragically cancelled after a mid-air collision during a D-21 launch.
Mission Equipment Bay (Q-bay):
The mission equipment bay was located immediately aft of the E-bay and could be pressurized or unpressurized depending on specific equipment needs. This compartment provided space for installation of cameras and sensors, test packages, and/or ballast as dictated by mission requirements.
NASA Blackbird Research Program:
Beginning in 1969, NASA operated two YF-12A aircraft and one SR-71A (temporarily designated
YF-12C for political reasons). The joint NASA-Air Force program continued for ten years. In 1990, after the Air Force formally retired the Blackbirds, NASA arranged to acquire two SR-71A models and the sole remaining SR-71B trainer for use as research aircraft. The Air Force retired the SR-71 fleet in 1990, but two airframes were reactivated for operational service in 1995. They were retired again in 1997. NASA operated the SR-71 between July 1991 and October 1999 for research purposes and to support the Air Force reactivation program. After retirement from NASA service, all remaining Blackbird airframes were allocated to museums and former operating agencies for permanent display.
Pressure Suit (Full Pressure Suit):
Because the SR-71 operated in a near-vacuum at 80,000 feet, the crew could not survive with a simple oxygen mask. They wore a Full Pressure Suit which was the direct precursor to the suits used by Space Shuttle astronauts.
RS-71:
The Blackbird original designation was RS (Reconnaissance-Strike). However, prior to its official introduction, General Curtis LeMay directed that the designation be reversed to SR. In an ironic twist, during the public announcement, President Lyndon B. Johnson inadvertently referred to it by its earlier RS designation. Although it looks like a simple reversal of letter, the RS and SR represents different roles in military designation language:
The Blackbird original designation was RS (Reconnaissance-Strike). However, prior to its official introduction, General Curtis LeMay directed that the designation be reversed to SR. In an ironic twist, during the public announcement, President Lyndon B. Johnson inadvertently referred to it by its earlier RS designation. Although it looks like a simple reversal of letter, the RS and SR represents different roles in military designation language:
- RS = Reconnaissance Strike.Suggests a multi-role aircraft, capable of both intelligence gathering and offensive operations.
- SR = Strategic Reconnaissance. Places full role emphasis on strategic reconnaissance.
RSO (Reconnaissance Systems Officer/Operator):
The 'Backseater'. While the pilot flew the plane, the RSO was the mission's 'Brain'. The RSO managed the ANS (Astro-Inertial Navigation), the Sensors (cameras/radar), and the complex Defensive Systems (ELINT/ECM) to jam enemy radar. The RSO had no forward-facing window...only two small side windows, meaning that they had to trust the instruments and the pilot completely at all phases of flight!
RCS (Radar Cross-Section):
In the contexts of the SR-71 Blackbird:
In the fall of 1957 the CIA commissioned a study to determine the probability of detecting an airplane by radar with respect to its speed, altitude, and radar cross-section (RCS). This analysis indicated that supersonic speed significantly reduced the ability of conventional radar systems to detect an aircraft. For RCS reduction, most peripheral assemblies of the A-12 and SR-71 were made of composite plastic laminates.
Sensors:
While the SR-71's speed and altitude were legendary, its true mission was 'Sensor Management'. The aircraft was essentially a modular flying laboratory. However, unlike the engines or the airframe, the specific resolutions and capabilities of these systems remain largely Classified.
Skunk Works:
Lockheed Martin's Advanced Development Programs entity. They develop Lockheed's highly classified development programs and exotic aircraft platforms. The SR-71 was developed at Lockheed's Skunk Works, led by Clarence "Kelly" Johnson, who is the man behind the Blackbird concept and design.
Spikes:
The conical 'nose' inside each engine nacelle. At speeds above Mach 1.6, the spikes move rearward to control the position of the supersonic shock-wave, slowing incoming air to subsonic speeds before it enters the engine. Crucial for effective high-Mach propulsion.
SR-71B:
The dual-control trainer version of the Blackbird. It is easily identified by its elevated rear cockpit for the instructor pilot and two ventral fins under the engine nacelles to compensate the structural differences in the fuselage design.
TEB (Triethylborane):
A chemical used for engine ignition. Because JP-7 was so hard to light, the SR-71 injects a shot of TEB, which ignites spontaneously on contact with air, to start the engines and light the afterburners. This produces the signature green flash in the exhaust.
TEB Counter (The "Green Flash" Reserve):
Because the JP-7 fuel used in the SR-71 was so chemically stable, it could not be ignited by a simple spark. Every time a pilot starts an engine or lights an afterburner, a metered 'shot' of Triethylborane (TEB) was injected. Each engine nacelle carried a pressurized tank containing roughly 20 ounces of TEB. This provides enough for approximately 16 shots per engine. In the cockpit, the TEB counter tracks these shots. Every time the throttle was moved from the cut-off to idle gate, or into the afterburner range, the counter clicked down. Once the counter hit zero, that engine could not be restarted, and the afterburners could not be re-lit.
Titanium Skin (Beta-120 / Ti-13V-11Cr-3Al):
The SR-71 was the first aircraft in history to be constructed almost entirely (93%) of titanium. At Mach 3.2, air friction heated the leading edges of the aircraft to over 600°F (315°C) and the engine nacelles to over 1,000°F (537°C). Standard aluminum would have melted or turned into 'putty' at these temperatures.
Turbo Ramjet:
A Turbo Ramjet is a hybrid engine designed to perform efficiently across a huge speed range, from a standstill on the runway to over 2,000 mph at the edge of space. It combines two different types of engines into one single housing. The Turbojet (Low Speed): At takeoff up to low supersonic speeds, the engine uses compressor, ignition chambers and turbine to produce thrust. At higher supersonic speeds, the air is moving so fast, that the 'ram' effect of the air hitting the engine at high Mach speed does the compression. At this point, the engine 'morphs' into a Ram-Jet mode. It diverts the majority of the incoming air through bypass tubes, skipping the compressor/turbine core and sending it straight to the afterburner. At Mach 3+, the engine functions effectively as a Ramjet, using the incredible pressure of its own forward speed to compress the air, making the aircraft more fuel-efficient the faster it flies.
The SR-71 was the first aircraft in history to be constructed almost entirely (93%) of titanium. At Mach 3.2, air friction heated the leading edges of the aircraft to over 600°F (315°C) and the engine nacelles to over 1,000°F (537°C). Standard aluminum would have melted or turned into 'putty' at these temperatures.
Turbo Ramjet:
A Turbo Ramjet is a hybrid engine designed to perform efficiently across a huge speed range, from a standstill on the runway to over 2,000 mph at the edge of space. It combines two different types of engines into one single housing. The Turbojet (Low Speed): At takeoff up to low supersonic speeds, the engine uses compressor, ignition chambers and turbine to produce thrust. At higher supersonic speeds, the air is moving so fast, that the 'ram' effect of the air hitting the engine at high Mach speed does the compression. At this point, the engine 'morphs' into a Ram-Jet mode. It diverts the majority of the incoming air through bypass tubes, skipping the compressor/turbine core and sending it straight to the afterburner. At Mach 3+, the engine functions effectively as a Ramjet, using the incredible pressure of its own forward speed to compress the air, making the aircraft more fuel-efficient the faster it flies.
Unstart:
A violent aerodynamic phenomenon where the supersonic shockwave is 'spilled' out of the engine inlet. This caused a massive, sudden loss of thrust on one side, often slamming the pilot’s helmet against the canopy as the aircraft yawed violently. The consequences at Mach-3 were dramatic: Instant asymmetric thrust, extensive loss of altitude and violent physical on the crew. Often, the violent yaw of an unstart on the left engine (for example) would cause the right engine to unstart as well. While terrifying, this was actually 'safer' in some aspects because it balanced the thrust, stopped the violent yaw.
Unstart Recovery:
To recover from an unstart, the pilot (or DAFICS) had to 'recapture' the shockwave by moving the spikes fully forward to their mechanical stop, for resetting the airflow. Additionally the forward and aft bypass doors were managed to spill excess air and reduce inlet pressure. In the meantime the aircraft lost altitude and speed until the unstart was recoverable.
YF-12 (Interceptor):
While the SR-71 was a spy, the YF-12 was built as a fighter. It featured a huge radar in a 'cut-back' nose and carried three massive AIM-47 Falcon missiles in internal bays. It holds the record as the largest, heaviest, and fastest interceptor ever built. If you see a 'Blackbird' with a chine-less, rounded nose and a second cockpit, it’s likely the YF-12.
Yo-Yo Ground Ops:
A ground refueling procedure where the aircraft was fueled to its maximum 80,000 lb capacity to purge air (thus - oxygen) from the fuel tanks. Then, ground crew de-fueled the aircraft to lighter take-off weight while pressurizing the tanks with inter nitrogen. This process eliminated the need for an air-refuel (which vented the pressurized air from the tanks), allowing the SR-71 to take-off straight into the Mach-3 climb!
A violent aerodynamic phenomenon where the supersonic shockwave is 'spilled' out of the engine inlet. This caused a massive, sudden loss of thrust on one side, often slamming the pilot’s helmet against the canopy as the aircraft yawed violently. The consequences at Mach-3 were dramatic: Instant asymmetric thrust, extensive loss of altitude and violent physical on the crew. Often, the violent yaw of an unstart on the left engine (for example) would cause the right engine to unstart as well. While terrifying, this was actually 'safer' in some aspects because it balanced the thrust, stopped the violent yaw.
Unstart Recovery:
To recover from an unstart, the pilot (or DAFICS) had to 'recapture' the shockwave by moving the spikes fully forward to their mechanical stop, for resetting the airflow. Additionally the forward and aft bypass doors were managed to spill excess air and reduce inlet pressure. In the meantime the aircraft lost altitude and speed until the unstart was recoverable.
YF-12 (Interceptor):
While the SR-71 was a spy, the YF-12 was built as a fighter. It featured a huge radar in a 'cut-back' nose and carried three massive AIM-47 Falcon missiles in internal bays. It holds the record as the largest, heaviest, and fastest interceptor ever built. If you see a 'Blackbird' with a chine-less, rounded nose and a second cockpit, it’s likely the YF-12.
Yo-Yo Ground Ops:
A ground refueling procedure where the aircraft was fueled to its maximum 80,000 lb capacity to purge air (thus - oxygen) from the fuel tanks. Then, ground crew de-fueled the aircraft to lighter take-off weight while pressurizing the tanks with inter nitrogen. This process eliminated the need for an air-refuel (which vented the pressurized air from the tanks), allowing the SR-71 to take-off straight into the Mach-3 climb!
Work In Progress
List evolves on a daily basis
