Brian Shul, Retired SR-71 Pilot via Plane and Pilot Magazine, provides an answer.
As a former SR-71 pilot, and a professional keynote speaker, the question I'm most often asked is "How fast would that SR-71 fly?" I can be assured of hearing that question several times at any event I attend. It's an interesting question, given the aircraft's proclivity for speed, but there really isn't one number to give, as the jet would always give you a little more speed if you wanted it to. It was common to see 35 miles a minute.
Because we flew a programmed Mach number on most missions, and never wanted to harm the plane in any way, we never let it run out to any limits of temperature or speed.. Thus, each SR-71 pilot had his own individual "high" speed that he saw at some point on some mission. I saw mine over Libya when Khadafy fired two missiles my way, and max power was in order. Let's just say that the plane truly loved speed and effortlessly took us to Mach numbers we hadn't previously seen.
So it was with great surprise, when at the end of one of my presentations, someone asked, "What was the slowest you ever flew the Blackbird?" This was a first. After giving it some thought, I was reminded of a story that I had never shared before, and I relayed the following.
I was flying the SR-71 out of RAF Mildenhall, England, with my back-seater, Walt Watson; we were returning from a mission over Europe and the Iron Curtain when we received a radio transmission from home base. As we scooted across Denmark in three minutes, we learned that a small RAF base in the English countryside had requested an SR-71 fly-past. The air cadet commander there was a former Blackbird pilot, and thought it would be a motivating moment for the young lads to see the mighty SR-71 perform a low approach. No problem, we were happy to do it. After a quick aerial refuelling over the North Sea, we proceeded to find the small airfield.
Walter had a myriad of sophisticated navigation equipment in the back seat, and began to vector me toward the field. Descending to subsonic speeds, we found ourselves over a densely wooded area in a slight haze. Like most former WWII British airfields, the one we were looking for had a small tower and little surrounding infrastructure. Walter told me we were close and that I should be able to see the field, but I saw nothing. Nothing but trees as far as I could see in the haze. We got a little lower, and I pulled the throttles back from 325 knots we were at. With the gear up, anything under 275 was just uncomfortable. Walt said we were practically over the field-yet; there was nothing in my windscreen. I banked the jet and started a gentle circling maneuver in hopes of picking up anything that looked like a field. Meanwhile, below, the cadet commander had taken the cadets up on the catwalk of the tower in order to get a prime view of the fly-past. It was a quiet, still day with no wind and partial gray overcast. Walter continued to give me indications that the field should be below us but in the overcast and haze, I couldn't see it. The longer we continued to peer out the window and circle, the slower we got. With our power back, the awaiting cadets heard nothing. I must have had good instructors in my flying career, as something told me I better cross-check the gauges. As I noticed the airspeed indicator slide below 160 knots, my heart stopped and my adrenalin-filled left hand pushed two throttles full forward. At this point we weren't really flying, but were falling in a slight bank. Just at the moment that both afterburners lit with a thunderous roar of flame (and what a joyous feeling that was) the aircraft fell into full view of the shocked observers on the tower. Shattering the still quiet of that morning, they now had 107 feet of fire-breathing titanium in their face as the plane levelled and accelerated, in full burner, on the tower side of the infield, closer than expected, maintaining what could only be described as some sort of ultimate knife-edge pass.
Quickly reaching the field boundary, we proceeded back to Mildenhall without incident. We didn't say a word for those next 14 minutes. After landing, our commander greeted us, and we were both certain he was reaching for our wings. Instead, he heartily shook our hands and said the commander had told him it was the greatest SR-71 fly-past he had ever seen, especially how we had surprised them with such a precise maneuver that could only be described as breathtaking. He said that some of the cadet's hats were blown off and the sight of the plan form of the plane in full afterburner dropping right in front of them was unbelievable. Walt and I both understood the concept of "breathtaking" very well that morning and sheepishly replied that they were just excited to see our low approach.
As we retired to the equipment room to change from space suits to flight suits, we just sat there-we hadn't spoken a word since "the pass." Finally, Walter looked at me and said, "One hundred fifty-six knots. What did you see?" Trying to find my voice, I stammered, "One hundred fifty-two." We sat in silence for a moment. Then Walt said, "Don't ever do that to me again!" And I never did.
A year later, Walter and I were having lunch in the Mildenhall Officer's club, and overheard an officer talking to some cadets about an SR-71
fly-past that he had seen one day. Of course, by now the story included kids falling off the tower and screaming as the heat of the jet singed their eyebrows. Noticing our HABU patches, as we stood there with lunch trays in our hands, he asked us to verify to the cadets that such a thing had occurred. Walt just shook his head and said, "It was probably just a routine low approach; they're pretty impressive in that plane." Impressive indeed.
Little did I realize after relaying this experience to my audience that day that it would become one of the most popular and most requested stories. It's ironic that people are interested in how slow the world's fastest jet can fly. Regardless of your speed, however, it's always a good idea to keep that cross-check up. and keep your Mach up, too.
Wednesday, August 17, 2011
How Slow can the SR-71 Fly?
Brian Shul, Retired SR-71 Pilot via Plane and Pilot Magazine, provides an answer.
So how slow and how fast can it fly?ReplyDelete
As stated in the story, "One hundred fifty-two" knots for the slowest(it was in a stall), which is 174.92 MPH as a nautical mile is 1.1508 what a statute mile is. 152 Knots = 174.92 MPH according to>>> http://www.readyforanythingnow.com/Explanation/knots%20to%20miles%20conversion%20chart.htm<<<Delete
The top speed is still classified. Brian said "It was common to see 35 miles a minute" which is 2100 MPH. According to Wikipedia info:"The SR-71 also holds the "Speed Over a Recognized Course" record for flying from New York to London distance 3,508 miles (5,646 km), 1,435.587 miles per hour (2,310.353 km/h), and an elapsed time of 1 hour 54 minutes and 56.4 seconds, set on 1 September 1974 while flown by U.S. Air Force Pilot Maj. James V. Sullivan and Maj. Noel F. Widdifield, reconnaissance systems officer (RSO). This equates to an average velocity of about Mach 2.68, including deceleration for in-flight refueling. Peak speeds during this flight were probably closer to the declassified top speed of Mach 3.2+. For comparison, the best commercial Concorde flight time was 2 hours 52 minutes, and the Boeing 747 averages 6 hours 15 minutes."
According to Blackbirds.net:: "So how fast does the SR-71 really go.......?
The fastest published speed of the SR is Mach 3.5. There are several factors that limit the speed of the SR, one is the shock waves generated by various parts of the plane, at around Mach 3.6- 3.8 the shock wave off the nose of the aircraft narrows enough to go into the engine, while there is the inlet spike (which slows the air to subsonic before it enters the engine), the shock wave bypasses the spike and causes the engine to unstart.
Second is the heat generated by the plane moving through the atmosphere, even titanium has it's limits, and the heat generated by the SR brings the fuselage to the brink. Just recently I found out that during a Lockheed Skunk Works study to see how much money and development it would take to get the SR to go faster than it's designed top speed 3.2- 3.5, the designers discovered (among other things) that the metal divider between the windshield was heating up so much above mach 3.5 that it was affecting the integrity of the windshield, and at that point they had stretched the glass technology to the max! So Mach 3.2 to a max of 3.5.
Now according to Richard Graham: "The design Mach number of the SR-71 is 3.2 Mach. When authorized by the Commander, speeds up to Mach 3.3 may be flown if the CIT limit of 427 degrees C. is not exceeded. I have heard of crews reaching 3.5 Mach inadvertently, but that is the absolute maximum I am aware of." >http://www.blackbirds.net/bbirdm&f.html<
Mach 1 is approximately 760 MPH (all depending on altitude) according to
which means Mach 3.5 is 2,660 MPH. The U.S. Government has never declassified the SR-71’s top speed