‘To ignite the JP-7 for engine start, and to light the afterburner section, a liquid chemical ignition system was used. The liquid chemical, triethylborane (TEB), had the physical property of exploding when exposed to air,” Richard H. Graham SR-71 Blackbird pilot.
The SR-71, unofficially known as the “Blackbird,” is a long-range, advanced, strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft. The first flight of an SR-71 took place on Dec. 22, 1964, and the first SR-71 to enter service was delivered to the 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base, Calif., in January 1966.
Throughout its nearly 24-year career, the SR-71 remained the world’s fastest and highest-flying operational aircraft. From 80,000 feet, it could survey 100,000 square miles of Earth’s surface per hour. On Jul. 28, 1976, an SR-71 set two world records for its class — an absolute speed record of 2,193.167 mph and an absolute altitude record of 85,068.997 feet.
The US Air Force (USAF) retired its fleet of SR-71s on Jan. 26, 1990.
The SR-71 burned JP-7 fuel. A one-of-a-kind fuel that used an additive to raise its flash point so the fuel would not break down at extreme temperatures.
Former Blackbird pilot Richard H. Graham explains in his book SR-71 Revealed The Inside Story:
‘To ignite the JP-7 for engine start, and to light the afterburner section, a liquid chemical ignition system was used. Talk about “unique!” The liquid chemical, triethylborane (TEB), had the physical property of exploding when exposed to air. Mounted on each engine was a sealed tank, inerted with nitrogen gas and filled by maintenance with 600cc of TEB prior to each flight. During engine start, rising fuel pressure in the fuel control signaled the ignition system that a metered amount of TEB could be injected into the engine combustion section, after the pilot moved the throttle from cut-off to the idle position. Preceded slightly by fuel, the TEB exploded and ignited the JP-7. Anyone watching an engine start from behind the aircraft could see the tell-tale green flash of the TEB exploding, igniting the engine.
‘Each time a throttle was lifted up and moved forward into the afterburner range, another metered shot of TEB would light the AB fuel. Each engine’s tank contained enough TEB for at least 16 metered shots to light either the engine or afterburners. Located on the throttle quadrant were TEB remaining counters for each throttle, reset to 16 by maintenance or crews, and mechanically clicked down a number every time the throttle was moved to start the engine or the AB was lit. The AB’s lit hard and rarely together. In the event you ran out of TEB, or had a leaking tank, the afterburner could be lit by a catalytic ignitor. The catalytic ignitors are made up of a ceramic disk and two sets of pure platinum screening disks. When the turbine gets hot, the platinum glows and allows afterburner fuel to light off. Since the SR-71 cruised in AB, its AB throttle range was relatively large, allowing for vernier control at all speeds.
‘The aircraft performance charts provided data for “minimum,” “mid-range,” and “maximum” afterburner throttle positions.’
The famous, cool photos and video featured in this post were taken at RAF Mildenhall in 1986 and show SR-71 Blackbird #960 creating a spectacular ball of flames while performing at Air Fete Air Show.
Former Blackbird Reconnaissance Systems Officer (RSO), Lt. Col. Doug Soifer, tells about the accidental making of these unique SR-71 pictures to Graham.
‘On our very first TDY to Mildenhall, Mike Smith [the pilot] and I were lucky enough to be there for Air Fete—the big annual air show at Mildenhall. We got to fly the first day and thought we did a good job. During the 20-minute sortie we had a real hard kick during one pass when we went to afterburner and pulled up tight. We didn’t think much about it until we landed and were overwhelmed by people as we stepped off the jet and asked us what we did. We had no idea what they were talking about until someone brought over his camcorder and showed us the tape.
‘During that pass we had “13 fireballs” come out of the plane’s exhaust. It looked beautiful, and people wanted to know if it could be done again. They used the picture of us with the flames coming out for the next year’s Air Fete poster. Mike and I became known as the “Fireball Twins.” The maintenance people figured it was the TEB [triethylborane] shooting out of its container and igniting the JP-7. With that start, we had an exciting six weeks in England.’
As told above the Blackbird featured in the photos and video of this post was SR-71 #960. This is the same SR-71 Kelly Johnson told my father, Blackbird RSO Butch Sheffield, that was structurally unsound.
This very same airframe came very close to crashing previous times.
Once in the 70s when my Dad, Butch Sheffield, and Ben Bowles were flying it and then once in the 80s when Dave Peters and Ed Bethart were flying it.
Then in 1984, it experienced another mishap yet again… Happy to report like the old expression “a cat that has nine lives.” This SR-71 escaped demise three times that I know of.
Today you can see the 960 at Castle Air Force Base, California, as it sits outside.
Be sure to check out Linda Sheffield Miller (Col Richard (Butch) Sheffield’s daughter, Col. Sheffield was an SR-71 Reconnaissance Systems Officer) Facebook Pages Habubrats and Born into the Wilde Blue Yonder for awesome Blackbird’s photos and stories.
Photo credit: Stuart Freer and US Gov Employee via Wikipedia