Military Aviation

SR-71 Pilot explains why even though the Blackbird could attain Mach 3.5, at that speed serious damage to the aircraft might occur

‘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,’ Bredette BC Thomas, high-time SR-71 Blackbird pilot.

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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.

No reconnaissance aircraft in history has operated in more hostile airspace or with such complete impunity than the SR-71 Blackbird. It is the fastest aircraft propelled by air-breathing engines. The Blackbird’s performance and operational achievements placed it at the pinnacle of aviation technology developments during the Cold War.

The Blackbird was 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.

‘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.

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‘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.’

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 SR-71 and Born into the Wilde Blue Yonder for awesome Blackbird’s photos and stories.

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Photo credit: U.S. Air Force

Linda Sheffield Miller

Grew up at Beale Air Force Base, California. I am a Habubrat. Graduated from North Dakota State University. Former Public School Substitute Teacher, (all subjects all grades). Member of the DAR (Daughters of the Revolutionary War). I am interested in History, especially the history of SR-71. Married, Mother of three wonderful daughters and four extremely handsome grandsons. I live near Washington, DC.

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