SR-71 Top Speed

‘The SR-71 could attain Mach 3.5 but at that speed serious damage to the aircraft might occur,’ former Blackbird Pilot says

When talking about SR-71 probably the most frequently asked Blackbird question is-how fast does it really fly?

The SR-71, the most advanced member of the Blackbird family that included the A-12 and YF-12, was designed by team of Lockheed personnel led by Clarence “Kelly” Johnson, then vice president of Lockheed’s Advanced Development Company Projects, commonly known as the “Skunk Works” and now a part of Lockheed Martin Corp.

The Blackbirds were designed to cruise at “Mach 3+,” just over three times the speed of sound or more than 2,200 miles per hour and at altitudes up to 85,000 feet.

Now when talking about SR-71 probably the most frequently asked Blackbird question is-how fast does it really fly?

‘Our maximum speed limit, directed by the Flight Manual, was Mach 3.3, but the SR-71 was not power-limited, so it could fly faster,’ Bredette BC Thomas, high-time SR-71 Blackbird pilot, says on Quora.

‘However, doing so would exceed the compressor inlet temperature limit, as well as other limits both heat related and structural. I am certain that no pilot ever put both throttles in maximum afterburner and let the aircraft accelerate to see how fast it would go. That would be a violation of military orders, the flight manual restrictions, and common sense. I, and most probably all other pilots, never purposely violated any published limits while flying the SR-71.

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‘The SR-71 could attain Mach 3.5, but the aircraft would be in an untested and prohibited area outside of its flight envelope, and serious damage to the aircraft might occur. The SR-71 was point-designed to cruise continuously at Mach 3.2, which is quite an achievement, but it was not intended to have a lot of margin above that speed.

‘I know of no time when the SR-71 was flown above Mach 3.33, and I doubt that one was flown faster, except by accidental error.’

Thomas went on explaining why the SR-71 Blackbird’s throttle was never pushed to the limit, even during the aircraft final flight;

‘There may be a misunderstanding concerning the role of a test pilot. His/her job is to consult with flight test engineers, fly a test mission according to an agreed-upon plan, and terminate a test point when something unpredicted and/or dangerous is found. Land, then determine what to test next.

‘That is how the flight envelope is established. After the limits are published, they cannot, under normal operations, be exceeded intentionally. No serious, professional pilot will defy the published limits of an aircraft.’

Thomas concludes;

‘For military pilots, intentionally exceeding aircraft limits also violates military orders and the pilot would be subject to disciplinary punishment. Military flying is not meant to be experimentation, except for well-planned test projects.’

Photo credit: U.S. Air Force

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Dario Leone

Dario Leone is an aviation, defense and military writer. He is the Founder and Editor of “The Aviation Geek Club” one of the world’s most read military aviation blogs. His writing has appeared in The National Interest and other news media. He has reported from Europe and flown Super Puma and Cougar helicopters with the Swiss Air Force.

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