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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.
Throughout its nearly 24-year career, the SR-71 remained the world’s highest-flying and fastest operational aircraft. From 80,000 feet, it could survey 100,000 square miles of Earth’s surface per hour.
Today the Blackbirds remain the world’s fastest and highest-flying production aircraft ever built. The Blackbirds were designed to cruise at Mach 3.2, just over three times the speed of sound or more than 2,200 miles per hour and at altitudes up to 85,000 feet.
There are many rumors about just how fast the SR-71 could go. As we have explained in a recent article, the late former Blackbird pilot David Peters pointed out that the SR-71 limiting speed was Mach 3.55.
Former SR-71 pilot Raymond E. (“Ed”) Yeilding who, along with Lieutenant Colonel Joseph T. (“J.T.”) Vida as reconnaissance systems officer (RSO), on Mar. 6, 1990 established four National Aeronautic Association and three Fédération Aéronautique Internationale speed records during Lockheed SR-71A Blackbird serial number 61-7972 final flight from Air Force Plant 42 (PMD) at Palmdale, California to Washington Dulles International Airport (the aircraft was turned over to the Smithsonian Institution National Air and Space Museum), adds some interesting details on Blackbird limiting speed.
‘About Dave Peters flying Mach 3.4+ and a limit of Mach 3.55.
‘I’ll start by saying that I had great respect and admiration for Dave Peters and have no doubt that he flew Mach 3.4+ in an area of extreme cold. I certainly miss Dave!!!
‘On our speed record coast-to-coast flight, I allegedly said we didn’t exceed Mach 3.2 for fear of running out of fuel before landing at Dulles airport. I am certain that I have never said that to anyone. Our cruise speed was Mach 3.3 on that record flight. Fuel certainly was a limiting factor. We didn’t have enough fuel to cross the coast lines at top speed Mach 3.3, but most of the distance was at Mach 3.3.
‘I am very pleased with my narrative of that coast-to-coast speed record flight in Rich Graham’s SR-71 Blackbird Stories, Tales, and Legends published 2002, pages 221 – 227. I gave details about our speeds, fuel considerations, speed record times with average speeds, and conveyed the excitement that JT Vida and I experienced that special day.
‘In Graham’s book, I stated that our cruise speed was Mach 3.3, and at all my talks about our speed record flight, I always say that our cruise speed was Mach 3.3. Of our four records that day, our fastest average speed was 2,190 mph between St Louis and Cincinatti, only 3 mph slower than the absolute aircraft speed record set in 1976 and still stands.’
He continues;
‘Most of all our missions were in the stratosphere where the temperature is almost always minus 56.5 degrees centigrade. At that temperature, the speed of sound is 660 mph, so Mach 3.2 was usually 3.2 x 660 mph = 2,112 mph (not “more than 2200 mph” as in the article). However, as Dave said, big temperature deviations sometimes happened in the Arctic, Barent Sea, region. I personally never experienced extreme cold that required greater than Mach 3.2.
‘I have no doubt that Dave heard about a Mach 3.55 limit, but I never heard that. I checked with high time SR pilot and Test Pilot School graduate, BC Thomas, and he never heard that either. Our flight manual had no mention of speed above Mach 3.3.
‘When I asked the Skunk Works about their opinion of a one time last flight above Mach 3.3, three engineers lead by Von Wright drove up from Burbank to meet with me and JT in person. They said that the SR was not designed to go faster than Mach 3.3, it was never flight tested above Mach 3.3, and with an unstart above Mach 3.3, we might not be able to keep the pointed end forward. It might pitch up and break apart. They also said there is no fuel flow data above Mach 3.2 (not 3.3 as in the article).’
Yeilding concludes;
‘It turned out that fuel economy at Mach 3.3 and slightly higher altitude seemed exactly the same as at Mach 3.2 at best altitude for aircraft weight.’
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: Stuart Freer and U.S. Air Force
