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SR-71
The SR-71, unofficially known as the “Blackbird,” was a long-range, Mach 3+, 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.
The Blackbird was in a different category from anything that had come before. “Everything had to be invented. Everything,” Skunk Works legendary aircraft designer Kelly Johnson recalled in an interesting article appeared on Lockheed Martin website.
No need for a traditional starter
To save on weight, the Skunk Works eliminated a traditional starter for the Blackbird. So, they figured out another way to start the SR-71.
Former Blackbird pilot Richard H. Graham explains in his book SR-71 Revealed The Inside Story;
‘The high flashpoint brings up another problem. Most jet engines use igniter plugs, nothing more than a very hot spark plug, if you will. Using these igniter plugs they used with the JP-7 and just drowns it out, it won’t ignite. Kelly [Johnson] put his engineers to work, and he said, ‘OK, gentlemen, how are we going to start this?’ They came up with a very unique way. Triethylborane – TEB for short. Each engine has a one-and-a-quarter pint. If I had it in a squirt gun and I squirted it into the atmosphere, it would go Kaboom! – it explodes with contact with the atmosphere. And that’s how we started the engines. As the engines rotate, at the right time, it sprays this amount of TEB into the turbine section, which goes kaboom, which in turn lights the engine. When you take the throttles up into the afterburner, it puts this metered amount of TEB in that lights up the JP-7. You get 16 shots for each engine.’
How to light SR-71 Blackbird afterburners without TEB
I was recently asked what was the plan if you run out of the 16 shots of TEB? TEB was required every time you started the engine or the afterburners, kick the tires and light up the engines.
In the 24 years the SR 71 flew, it never ran out of TEB, but there was a plan just in case.
John Olp, an SR-71 Mechanic from 1975-1985 at Beale AFB, explains;
‘The J58 engine had a unique way of lighting the afterburners if TEB wasn’t available for whatever reason.
‘Inserted into three rings of the flame holders were six catalytic ignitors. If TEB wasn’t available, the engines could be manually over-trimmed to increase the exhaust temperature and superheat the ignitors. When the throttles were advanced into afterburner, the glowing catalytic ignitors would light off the fuel, albeit somewhat harshly!
‘The catalytic ignitors were in place as a backup if TEB wasn’t available. There was a manual up-trim switch in the cockpit to control engine EGT. It was a hard light off if used, but was an option!’
Olp concludes;
‘Overtemping the engine would only be momentary to allow the afterburner light, probably not enough to cause any damage to the engines. That’s why the manual up-trim switches were available.’
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, Instagram Page SR71Habubrats and Facebook Page Born into the Wilde Blue Yonder Habubrats for awesome Blackbird’s photos and stories.
Photo credit: U.S. Air Force and Lockheed Martin
