How fast was the SR-71? Let’s answer the question with someone who actually knows.
Tim Yarrow an aviation Research and Analysis expert was an Electrical Engineer at Lockheed Martin’s secretive “Skunk Works” team from 1974-1994….here’s his answer:
Faster than widely published. Blackbird’s cruise speed was officially Mach 3.2…but there’s MORE.
Blackbird pilot Brian Shul described a surveillance mission over Tripoli, Libya, in April 1986.
Photographic evidence was required for bomb damage assessment (BDA) following a U.S. bombing run in retaliation for the Qaddafi-sponsored terrorist attack on a Berlin disco.
Satellites were not available to immediately task over Tripoli for BDA. This was a surveillance mission for which the SR-71 was designed, albeit a quarter-century ago.
The difference was that by 1986 missile capability had significantly improved. And Libya had them.
As the Blackbird crossed the “Line of Death” into Libyan territory, Shul’s co-pilot warned of ground-based missile launches, Russian SAMs they guessed, capable of Mach 5 flight.
Those scary little f***ers were probably the only thing a Blackbird pilot feared.
Remember: the only defenses a Blackbird had was speed and altitude.
Still, flying at Mach 3.2 at 80,000 feet is a significant head-start.
Shul relates that he and his co-“However, on this day the jet performed flawlessly and delivered the speed asked of it.” calculated they could *just* make their turn over Libya to accomplish their surveillance objectives, but only if they increased speed.
Because the Blackbird surveillance missions are planned to the second with regard to speed, altitude, and fuel load, a speed excursion above Mach 3.2 was a pilot safety decision completely outside of pre-flight planning.
However, on this day the jet performed flawlessly and delivered the speed asked of it.
The plane responded with smooth, confident power, delivering speed that was previously the subject of much theory and conjecture.
Shul narrates that as more missile launches were detected with:
The MACH easing to 3.5’, he pushed the throttles full forward against the stops.
Shul continued a 500-Feet per Minute climb (one-sixth of one degree pitch-up…do the math) while accelerating, to the turn-point. The engines ran ‘relatively cool’.
Quote from Major Brian Shul:
After several agonizingly long seconds, Co-pilot Walter suggested, ‘You might want to pull it back’. It was then that I noticed……I still had the throttles full forward.
The plane was flying a mile every 1.6 seconds, well above our Mach 3.2 limit. It was the fastest we would ever fly.” -Major Brian Shul
Tim Yarrow continued:
They took the photos, made the turn, and only when the blue Mediterranean was safely outside their window, he backed off the throttle.
To be sure, this was no hopped-up model of the SR-71. This was the standard Blackbird, maintained and flown in top form.
So, I presume there will continue much discussion of just how fast the plane could fly……and if it was much faster than Mach 3.5, it is a well-kept secret, possibly for the national security reasons.”
Shul’s narrative of flight at or above Mach 3.5 is so far the most detailed evidence available of SR-71 top speeds.”
Mach 3.2 at 80,000-ft Altitude = 2,133 MPH
Real Top Speed of Blackbird:
Shul “easing to 3.5” at 80,000-ft Altitude = 2,333 MPH
If you want a little more, Tim Yarrow explains how the SR-71 works…
“At speed, the J-58 engines operate more like a RAM jet than a turbo jet. It operates more efficiently the faster it flies.”
“The catch is that inlet and exhaust temperatures must be monitored closely to stay within engine design limits. In this mode, the engine was gulping more than 100,000 cubic feet of air every second.”
(“Spikes = round cone air enters)
“The engine spikes retract 26 inches into the nacelles, and all engine inlets doors are closed except for the main inlet and exhaust.”
“J-58 engine inlet and nacelle, showing the shock spike extended fully forward, the position for engine start, take-off, and cruise up to mach 1.5. At speeds above mach 1.5, the spike was incrementally pulled back into the nacelle 1.6″ per 0.1 mach increase until retracted a full 26 inches at mach 3.2.
This was done to capture the “normal” shock wave in the engine nacelle inlet and slow the air for subsonic delivery into the engine compressor stages.”
The mighty J-58 powerhouse under a Blackbird’s left nacelle.
Those six large pipes (ABOVE-three visible here, three on the other side of the engine) bled air stacking up at the fifth compressor stage and dumped it into the afterburner.”
“This is the much-storied ram effect achieved at and above mach 3.2. And consider that this is 1950s technology!”