The King of Speed - SR71 holds olds the flight airspeed record at 2193mph (3530kmh)
First read this short story.
Then read this comment.
It's not really "obscure", but most people - even airplane geeks - don't really appreciate how ingenious the Blackbird's engine is.
In most ways, the J58 engine is like a normal afterburning turbojet. It's got an intake/diffuser (with a neat spike that helps convert airspeed into pressure, but that's not substantially different from similar spikes in other airplanes like the MiG-21 and F-104, or from the sharp intake edges in airplanes like the XB-70 and almost every fighter jet out there since the F-4), then a compressor, then a combustor, then a turbine, then an afterburner, then a nozzle. All that is just like any fighter jet engine, nothing unusual yet.
But it ALSO has a bunch of big bypass pipes that go from the intake to the afterburner. And it is these unique pipes that allow the Blackbird to exceed MACH 3 with late-1950s engine technology. It's pure genius. The reason is as follows.
What the front half of a jet engine (the intake/diffuser, and the compressor blades, i.e. all the stuff that happens before fuel is burned) does is; it heats up the air until it's hot enough for fuel to ignite. First, the intake/diffuser slows the air down, which raises its pressure, which raises its temperature. The faster you're going, the more of a temperature rise you get just from slowing the air down as it enters the big hole in the front of the engine (because the air has more speed, and more energy, to convert to heat). Then the air goes through those spinning blades that compress it (and thus heat it) further, until it's hot enough to burn fuel. THEN, you burn fuel, which gets the air (now with fuel and exhaust mixed in) to the hottest temperature anywhere in the airplane. Now we enter the rear half of the engine. The air - at its peak temperature - goes through the turbine, which is a bunch of blades that act like a windmill and absorb some of that energy in order to spin the compressor. The amount of fuel you can burn in the combustor (or, rather, the rate at which you burn fuel) is therefore limited by your turbine's materials: The more fuel you burn (per unit time), the hotter the turbine air becomes, so you can only burn fuel so fast before you melt your turbine. Once your turbine temperature is as hot as it can sustain, the only way you could burn more fuel (to get more thrust) is if you had a bigger engine. (Or by burning fuel in the tailpipe - the afterburner - which does not have meltable spinny parts in the middle). So you make your turbine out of the highest-melting-point materials known to man, and that determines how much fuel you can burn and how much thrust you can get. (All this is true about every jet engine since the Nazis and Whittle started experimenting with jet engines in the 1930s). But remember that the faster you go, the hotter the air becomes just by going into the big hole at the front. That means that, if your turbine is at the hottest temperature it can sustain, then you're at your top speed: if you go any faster, you won't be able to burn as much fuel in the combustor before you exceed your turbine's critical temperature. By the time you get to MACH 3, the air in the engine intake is already hot enough to start melting turbomachinery. You can't burn almost ANY fuel in the combustor, or your engine melts. This is why a conventional jet engine (read: any jet in the world other than the Blackbird or ramjets like the D-21, X-43, X-51, etc) just can't get you past MACH 3.
What the J58 engine does is, it routes more and more air from the intake (the space just behind the spike, in front of the spinning compressor blades) into big bypass pipes that go around the engine's spinning parts and take the air straight to the afterburner. The air in the intake is already more than hot enough to burn fuel, so you don't need spinny parts at all at that speed. Even at subsonic speeds, a good intake can heat the air up enough to burn fuel without a compressor's help. That's called a ramjet. The problem is, a ramjet doesn't work at all until you get to that speed; until you're going fast enough that just slowing the air down in the intake gets the air hot enough to burn fuel. So you need a spinning compressor - and a turbine to power it - in order to take off and get up to speed.
So the Blackbird takes off with its engine working just like any fighter jet engine. But as it goes faster and faster, and the air in the intake gets hotter and hotter, so less and less of that air goes through the spinning "core" of the engine (and less fuel is burned in the combustor) and more and more of that air goes around the core and into the afterburner (where more and more fuel is burned). By the time you get to MACH 3, the spinning core of the engine is basically just sitting there and windmilling around, burning little or no fuel... and the afterburner is getting almost all the air and generating almost all the thrust.
Each J58 engine in a Blackbird are like a turbojet sitting inside a ramjet. At first, the turbojet does almost all the work. As the Blackbird accelerates, the turbojet is fed less and less fuel, until it's basically just dead weight, a useless lump of spinning metal sitting in the middle of a ramjet. You needed the turbomachinery in order to get to supersonic speeds, but once you're at MACH 3, you route your air around it.
Then check this picture.
I will admit, I always loved this jet but now I love it more.
True story? Dunno, but it sounds plausible.
- - -
There were a lot of things we couldn't do in an SR-71, but we were the fastest guys on the block and loved reminding our fellow aviators of this fact. People often asked us if, because of this fact, it was fun to fly the jet. Fun would not be the first word I would use to describe flying this plane. Intense, maybe. Even cerebral. But there was one day in our Sled experience when we would have to say that it was pure fun to be the fastest guys out there, at least for a moment.
It occurred when Walt and I were flying our final training sortie. We needed 100 hours in the jet to complete our training and attain Mission Ready status. Somewhere over Colorado we had passed the century mark. We had made the turn in Arizona and the jet was performing flawlessly. My gauges were wired in the front seat and we were starting to feel pretty good about ourselves, not only because we would soon be flying real missions but because we had gained a great deal of confidence in the plane in the past ten months. Ripping across the barren deserts 80,000 feet below us, I could already see the coast of California from the Arizona border. I was, finally, after many humbling months of simulators and study, ahead of the jet.
I was beginning to feel a bit sorry for Walter in the back seat. There he was, with no really good view of the incredible sights before us, tasked with monitoring four different radios. This was good practice for him for when we began flying real missions, when a priority transmission from headquarters could be vital. It had been difficult, too, for me to relinquish control of the radios, as during my entire flying career I had controlled my own transmissions. But it was part of the division of duties in this plane and I had adjusted to it. I still insisted on talking on the radio while we were on the ground, however. Walt was so good at many things, but he couldn't match my expertise at sounding smooth on the radios, a skill that had been honed sharply with years in fighter squadrons where the slightest radio miscue was grounds for beheading. He understood that and allowed me that luxury. Just to get a sense of what Walt had to contend with, I pulled the radio toggle switches and monitored the frequencies along with him. The predominant radio chatter was from Los Angeles Center, far below us, controlling daily traffic in their sector. While they had us on their scope (albeit briefly), we were in uncontrolled airspace and normally would not talk to them unless we needed to descend into their airspace.
We listened as the shaky voice of a lone Cessna pilot asked Center for a readout of his ground speed.
Center replied: "November Charlie 175, I'm showing you at ninety knots on the ground."
Now the thing to understand about Center controllers, was that whether they were talking to a rookie pilot in a Cessna, or to Air Force One, they always spoke in the exact same, calm, deep, professional, tone that made one feel important. I referred to it as the "HoustonCenterVoice." I have always felt that after years of seeing documentaries on this country's space program and listening to the calm and distinct voice of the HoustonCenterControllers, that all other controllers since then wanted to sound like that... and that they basically did. And it didn't matter what sector of the country we would be flying in, it always seemed like the same guy was talking. Over the years that tone of voice had become somewhat of a comforting sound to pilots everywhere. Conversely, over the years, pilots always wanted to ensure that, when transmitting, they sounded like Chuck Yeager, or at least like John Wayne. Better to die than sound bad on the radios.
Just moments after the Cessna's inquiry, a Twin Beech piped up on frequency, in a rather superior tone, asking for his ground speed.
"Ah, Twin Beach: I have you at one hundred and twenty-five knots of ground speed."
Boy, I thought, the Beechcraft really must think he is dazzling his Cessna brethren.
Then out of the blue, a Navy F-18 pilot out of NAS Lemoore came up on frequency. You knew right away it was a Navy jock because he sounded very cool on the radios.
"Center, Dusty 52 ground speed check."
Before Center could reply, I'm thinking to myself, hey, Dusty 52 has a ground speed indicator in that million dollar cockpit, so why is he asking Center for a readout? Then I got it -- ol' Dusty here is making sure that every bug smasher from Mount Whitney to the Mojave knows what true speed is. He's the fastest dude in the valley today, and he just wants everyone to know how much fun he is having in his new Hornet.
And the reply, always with that same, calm, voice, with more distinct alliteration than emotion:
"Dusty 52, Center, we have you at 620 on the ground."
And I thought to myself, is this a ripe situation, or what? As my hand instinctively reached for the mic button, I had to remind myself that Walt was in control of the radios. Still, I thought, it must be done -- in mere seconds we'll be out of the sector and the opportunity will be lost. That Hornet must die, and die now.
I thought about all of our Sim training and how important it was that we developed well as a crew and knew that to jump in on the radios now would destroy the integrity of all that we had worked toward becoming. I was torn. Somewhere, 13 miles above Arizona, there was a pilot screaming inside his space helmet.
Then, I heard it. The click of the mic button from the back seat. That was the very moment that I knew Walter and I had become a crew. Very professionally, and with no emotion, Walter spoke:
"Los Angeles Center, Aspen 20, can you give us a ground speed check?"
There was no hesitation, and the reply came as if was an everyday request:
"Aspen 20, I show you at one thousand eight hundred and forty-two knots, across the ground."
I think it was the forty-two knots that I liked the best, so accurate and proud was Center to deliver that information without hesitation, and you just knew he was smiling. But the precise point at which I knew that Walt and I were going to be really good friends for a long time was when he keyed the mic once again to say, in his most fighter-pilot-like voice:
"Ah, Center, much thanks. We're showing closer to nineteen hundred on the money."
For a moment Walter was a god. And we finally heard a little crack in the armor of the HoustonCentervoice, when L.A. came back with,
"Roger that Aspen, Your equipment is probably more accurate than ours. You boys have a good one."
It all had lasted for just moments, but in that short, memorable sprint across the southwest, the Navy had been flamed, all mortal airplanes on freq were forced to bow before the King of Speed, and more importantly, Walter and I had crossed the threshold of being a crew. A fine day's work.
We never heard another transmission on that frequency all the way to the coast. For just one day, it truly was fun being the fastest guys out there.
Then read this comment.
It's not really "obscure", but most people - even airplane geeks - don't really appreciate how ingenious the Blackbird's engine is.
In most ways, the J58 engine is like a normal afterburning turbojet. It's got an intake/diffuser (with a neat spike that helps convert airspeed into pressure, but that's not substantially different from similar spikes in other airplanes like the MiG-21 and F-104, or from the sharp intake edges in airplanes like the XB-70 and almost every fighter jet out there since the F-4), then a compressor, then a combustor, then a turbine, then an afterburner, then a nozzle. All that is just like any fighter jet engine, nothing unusual yet.
But it ALSO has a bunch of big bypass pipes that go from the intake to the afterburner. And it is these unique pipes that allow the Blackbird to exceed MACH 3 with late-1950s engine technology. It's pure genius. The reason is as follows.
What the front half of a jet engine (the intake/diffuser, and the compressor blades, i.e. all the stuff that happens before fuel is burned) does is; it heats up the air until it's hot enough for fuel to ignite. First, the intake/diffuser slows the air down, which raises its pressure, which raises its temperature. The faster you're going, the more of a temperature rise you get just from slowing the air down as it enters the big hole in the front of the engine (because the air has more speed, and more energy, to convert to heat). Then the air goes through those spinning blades that compress it (and thus heat it) further, until it's hot enough to burn fuel. THEN, you burn fuel, which gets the air (now with fuel and exhaust mixed in) to the hottest temperature anywhere in the airplane. Now we enter the rear half of the engine. The air - at its peak temperature - goes through the turbine, which is a bunch of blades that act like a windmill and absorb some of that energy in order to spin the compressor. The amount of fuel you can burn in the combustor (or, rather, the rate at which you burn fuel) is therefore limited by your turbine's materials: The more fuel you burn (per unit time), the hotter the turbine air becomes, so you can only burn fuel so fast before you melt your turbine. Once your turbine temperature is as hot as it can sustain, the only way you could burn more fuel (to get more thrust) is if you had a bigger engine. (Or by burning fuel in the tailpipe - the afterburner - which does not have meltable spinny parts in the middle). So you make your turbine out of the highest-melting-point materials known to man, and that determines how much fuel you can burn and how much thrust you can get. (All this is true about every jet engine since the Nazis and Whittle started experimenting with jet engines in the 1930s). But remember that the faster you go, the hotter the air becomes just by going into the big hole at the front. That means that, if your turbine is at the hottest temperature it can sustain, then you're at your top speed: if you go any faster, you won't be able to burn as much fuel in the combustor before you exceed your turbine's critical temperature. By the time you get to MACH 3, the air in the engine intake is already hot enough to start melting turbomachinery. You can't burn almost ANY fuel in the combustor, or your engine melts. This is why a conventional jet engine (read: any jet in the world other than the Blackbird or ramjets like the D-21, X-43, X-51, etc) just can't get you past MACH 3.
What the J58 engine does is, it routes more and more air from the intake (the space just behind the spike, in front of the spinning compressor blades) into big bypass pipes that go around the engine's spinning parts and take the air straight to the afterburner. The air in the intake is already more than hot enough to burn fuel, so you don't need spinny parts at all at that speed. Even at subsonic speeds, a good intake can heat the air up enough to burn fuel without a compressor's help. That's called a ramjet. The problem is, a ramjet doesn't work at all until you get to that speed; until you're going fast enough that just slowing the air down in the intake gets the air hot enough to burn fuel. So you need a spinning compressor - and a turbine to power it - in order to take off and get up to speed.
So the Blackbird takes off with its engine working just like any fighter jet engine. But as it goes faster and faster, and the air in the intake gets hotter and hotter, so less and less of that air goes through the spinning "core" of the engine (and less fuel is burned in the combustor) and more and more of that air goes around the core and into the afterburner (where more and more fuel is burned). By the time you get to MACH 3, the spinning core of the engine is basically just sitting there and windmilling around, burning little or no fuel... and the afterburner is getting almost all the air and generating almost all the thrust.
Each J58 engine in a Blackbird are like a turbojet sitting inside a ramjet. At first, the turbojet does almost all the work. As the Blackbird accelerates, the turbojet is fed less and less fuel, until it's basically just dead weight, a useless lump of spinning metal sitting in the middle of a ramjet. You needed the turbomachinery in order to get to supersonic speeds, but once you're at MACH 3, you route your air around it.
Then check this picture.
I will admit, I always loved this jet but now I love it more.
Comments
[h=3]
SR-71 in flight
Among professional aviators, there's a well-worn saying: Flying is simply hours of boredom punctuated by moments of stark terror. But I don't recall too many periods of boredom during my 30-year career with Lockheed, most of which was spent as a test pilot. By far, the most memorable flight occurred on Jan. 25, 1966.
Jim Zwayer, a Lockheed flight-test specialist, and I were evaluating systems on an SR-71 Blackbird test from Edwards. We also were investigating procedures designed to reduce trim drag and improve high-Mach cruise performance. The latter involved flying with the center-of-gravity (CG) located further aft than normal, reducing the Blackbird's longitudinal stability.
We took off from Edwards at 11:20 a.m. and completed the mission's first leg without incident. After refueling from a KC-135 tanker, we turned eastbound, accelerated to a Mach 3.2-cruise speed and climbed to 78,000 ft., our initial cruise-climb altitude. Several minutes into cruise, the right engine inlet's automatic control system malfunctioned, requiring a switch to manual control. The SR-71's inlet configuration was automatically adjusted during supersonic flight to decelerate airflow in the duct, slowing it to subsonic speed before reaching the engine's face. This was accomplished by the inlet's center-body spike translating aft, and by modulating the inlet's forward bypass doors.
Normally, these actions were scheduled automatically as a function of Mach number, positioning the normal shock wave (where air flow becomes subsonic) inside the inlet to ensure optimum engine performance. Without proper scheduling, disturbances inside the inlet could result in the shock wave being expelled forward - a phenomenon known as an "inlet unstart."
That causes an instantaneous loss of engine thrust, explosive banging noises and violent yawing of the aircraft--like being in a train wreck. Unstarts were not uncommon at that time in the SR-71's development, but a properly functioning system would recapture the shock wave and restore normal operation.
On the planned test profile, we entered a programmed 35-deg. bank turn to the right. An immediate unstart occurred on the right engine, forcing the aircraft to roll further right and start to pitch up. I jammed the control stick as far left and forward as it would go. No response. I instantly knew we were in for a wild ride. I attempted to tell Jim what was happening and to stay with the airplane until we reached a lower speed and altitude. I didn't think the chances of surviving an ejection at Mach 3.18 and 78,800 ft. were very good. However, g-forces built up so rapidly that my words came out garbled and unintelligible, as confirmed later by the cockpit voice recorder.
The cumulative effects of system malfunctions, reduced longitudinal stability, increased angle-of-attack in the turn, supersonic speed, high altitude and other factors imposed forces on the airframe that exceeded flight control authority and the Stability Augmentation System's ability to restore control. Everything seemed to unfold in slow motion. I learned later the time from event onset to catastrophic departure from controlled flight was only 2-3 seconds. Still trying to communicate with Jim, I blacked out, succumbing to extremely high g-forces. Then the SR-71 . . literally . . disintegrated around us. From that point, I was just along for the ride. And my next recollection was a hazy thought that I was having a bad dream. Maybe I'll wake up and get out of this mess, I mused. Gradually regaining consciousness, I realized this was no dream; it had really happened. That also was disturbing, because I COULD NOT HAVE SURVIVED what had just happened.
I must be dead. Since I didn't feel bad - just a detached sense of euphoria. I decided being dead wasn't so bad after all. As full awareness took hold, I realized I was not dead. But somehow I had separated from the airplane. I had no idea how this could have happened. I hadn't initiated an ejection. The sound of rushing air and what sounded like straps flapping in the wind confirmed I was falling, but I couldn't see anything. My pressure suit's face plate had frozen over and I was staring at a layer of ice.
The pressure suit was inflated, so I knew an emergency oxygen cylinder in the seat kit attached to my parachute harness was functioning. It not only supplied breathing oxygen, but also pressurized the suit, preventing my blood from boiling at extremely high altitudes. I didn't appreciate it at the time, but the suit's pressurization had also provided physical protection from intense buffeting and g-forces. That inflated suit had become my own escape capsule.
My next concern was about stability and tumbling. Air density at high altitude is insufficient to resist a body's tumbling motions, and centrifugal forces high enough to cause physical injury could develop quickly. For that reason, the SR-71's parachute system was designed to automatically deploy a small-diameter stabilizing chute shortly after ejection and seat separation. Since I had not intentionally activated the ejection system, and assuming all automatic functions depended on a proper ejection sequence, it occurred to me the stabilizing chute may not have deployed.
However, I quickly determined I was falling vertically and not tumbling. The little chute must have deployed and was doing its job. Next concern: the main parachute, which was designed to open automatically at 15,000 ft. Again I had no assurance the automatic-opening function would work. I couldn't ascertain my altitude because I still couldn't see through the iced-up faceplate. There was no way to know how long I had been blacked-out or how far I had fallen. I felt for the manual-activation D-ring on my chute harness, but with the suit inflated and my hands numbed by cold, I couldn't locate it. I decided I'd better open the faceplate, try to estimate my height above the ground, then locate that "D" ring. Just as I reached for the faceplate, I felt the reassuring sudden deceleration of main-chute deployment. I raised the frozen faceplate and discovered its uplatch was broken. Using one hand to hold that plate up, I saw I was descending through a clear, winter sky with unlimited visibility. I was greatly relieved to see Jim's parachute coming down about a quarter of a mile away. I didn't think either of us could have survived the aircraft's breakup, so seeing Jim had also escaped lifted my spirits incredibly. I could also see burning wreckage on the ground a few miles from where we would land. The terrain didn't look at all inviting, a desolate, high plateau dotted with patches of snow and no signs of habitation.
I tried to rotate the parachute and look in other directions. But with one hand devoted to keeping the face plate up and both hands numb from high-altitude, subfreezing temperatures, I couldn't manipulate the risers enough to turn. Before the breakup, we'd started a turn in the New Mexico-Colorado-Oklahoma-Texas border region. The SR-71 had a turning radius of about 100 mi. at that speed and altitude, so I wasn't even sure what state we were going to land in. But, because it was about 3:00 p.m., I was certain we would be spending the night out here.
At about 300 ft. above the ground, I yanked the seat kit's release handle and made sure it was still tied to me by a long lanyard. Releasing the heavy kit ensured I wouldn't land with it attached to my derriere, which could break a leg or cause other injuries. I then tried to recall what survival items were in that kit, as well as techniques I had been taught in survival training. Looking down, I was startled to see a fairly large animal, perhaps an antelope, directly under me. Evidently, it was just as startled as I was because it literally took off in a cloud of dust.
My first-ever parachute landing was pretty smooth. I landed on fairly soft ground, managing to avoid rocks, cacti and antelopes. My chute was still billowing in the wind, though. I struggled to collapse it with one hand, holding the still-frozen faceplate up with the other.
"Can I help you? " a voice said. Was I hearing things? I must be hallucinating. Then I looked up and saw a guy walking toward me, wearing a cowboy hat. A helicopter was idling a short distance behind him. If I had been at Edwards and told the search-and-rescue unit that I was going to bail out over the Rogers Dry Lake at a particular time of day, a crew couldn't have gotten to me as fast as that cowboy-pilot had. The gentleman was Albert Mitchell, Jr., owner of a huge cattle ranch in northeastern New Mexico. I had landed about 1.5 mi. from his ranch house, and from a hangar for his two-place Hughes helicopter. Amazed to see him, I replied I was having a little trouble with my chute. He walked over and collapsed the canopy, anchoring it with several rocks. He had seen Jim and me floating down and had radioed the New Mexico Highway Patrol, the Air Force, and the nearest hospital.
Extracting myself from the parachute harness, I discovered the source of those flapping-strap noises heard on the way down. My seat belt and shoulder harness were still draped around me, attached and latched. The lap belt had been shredded on each side of my hips, where the straps had fed through knurled adjustment rollers. The shoulder harness had shredded in a similar manner across my back. The ejection seat had never left the airplane. I had been ripped out of it by the extreme forces, with the seat belt and shoulder harness still fastened.
I also noted that one of the two lines that supplied oxygen to my pressure suit had come loose, and the other was barely hanging on. If that second line had become detached at high altitude, the deflated pressure suit wouldn't have provided any protection. I knew an oxygen supply was critical for breathing and suit-pressurization, but didn't appreciate how much physical protection an inflated pressure suit could provide. That the suit could withstand forces sufficient to disintegrate an airplane and shred heavy nylon seat belts, yet leave me with only a few bruises and minor whiplash was impressive. I truly appreciated having my own little escape capsule.
After helping me with the chute, Mitchell said he'd check on Jim. He climbed into his helicopter, flew a short distance away and returned about 10 minutes later with devastating news: Jim was dead. Apparently, he had suffered a broken neck during the aircraft's disintegration and was killed instantly. Mitchell said his ranch foreman would soon arrive to watch over Jim's body until the authorities arrived. I asked to see Jim and, after verifying there was nothing more that could be done, agreed to let Mitchell fly me to the Tucumcari hospital, about 60 mi. to the south.
I have vivid memories of that helicopter flight, as well. I didn't know much about rotorcraft, but I knew a lot about "red lines," and Mitchell kept the airspeed at or above red line all the way. The little helicopter vibrated and shook a lot more than I thought it should have. I tried to reassure the cowboy-pilot I was feeling OK; there was no need to rush. But since he'd notified the hospital staff that we were inbound, he insisted we get there as soon as possible. I couldn't help but think how ironic it would be to have survived one disaster only to be done in by the helicopter that had come to my rescue.
However, we made it to the hospital safely - and quickly. Soon, I was able to contact Lockheed's flight test office at Edwards. The test team there had been notified initially about the loss of radio and radar contact, then told the aircraft had been lost. They also knew what our flight conditions had been at the time, and assumed no one could have survived. I explained what had happened, describing in fairly accurate detail the flight conditions prior to breakup.
The next day, our flight profile was duplicated on the SR-71 flight simulator at Beale AFB, Calif. The outcome was identical. Steps were immediately taken to prevent a recurrence of our accident. Testing at a CG aft of normal limits was discontinued, and trim-drag issues were subsequently resolved via aerodynamic means. The inlet control system was continuously improved and, with subsequent development of the Digital Automatic Flight and Inlet Control System, inlet unstarts became rare. Investigation of our accident revealed that the nose section of the aircraft had broken off aft of the rear cockpit and crashed about 10 mi. from the main wreckage. Parts were scattered over an area approximately 15 mi. long and 10 mi. wide. Extremely high air loads and g-forces, both positive and negative, had literally ripped Jim and me from the airplane. Unbelievably good luck is the only explanation for my escaping relatively unscathed from that disintegrating aircraft.
Two weeks after the accident, I was back in an SR-71, flying the first sortie on a brand-new bird at Lockheed's Palmdale, Calif., assembly and test facility. It was my first flight since the accident, so a flight test engineer in the back seat was probably a little apprehensive about my state of mind and confidence. As we roared down the runway and lifted off, I heard an anxious voice over the intercom. "Bill! Bill! Are you there?" "Yeah, George. What's the matter?" "Thank God! I thought you might have left." The rear cockpit of the SR-71 has no forward visibility - only a small window on each side - and George couldn't see me. A big red light on the master-warning panel in the rear cockpit had illuminated just as we rotated, stating: "Pilot Ejected." Fortunately, the cause was a misadjusted micro switch; not my departure.
Bill Weaver flight-tested all models of the Mach-2 F-104 Starfighter and the entire family of Mach 3+ Blackbirds including the A-12, YF-12, and SR-71. He subsequently was assigned to Lockheed's L-1011 project as an engineering test pilot, and became the company's chief pilot. He later retired as Division Manager of Commercial Flying Operations, and continued to fly the Orbital Sciences Corp.'s L-1011, which was modified to carry the Pegasus satellite-launch vehicle. And as an FAA Designated Engineering Representative Flight Test Pilot, was involved in various aircraft-modification projects, conducting certification flight tests.
Links to additional SR-71 Articles:
SR-71 - Inflight Breakup
SR-71 - Ceiling
SR-71 - Landing at Buckley ANG Base
SR-71 - Cancellation
SR-71 - Flight over France
SR-71 - Landing at Grand Forks, ND AFB
SR-71 - History
SR-71 - Flight over Libya
SR-71 - Navy challenge
SR-71 - Fueling from KC-135 Tankers
SR-71 - Titanium construction[/h]
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.
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 refueling 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.
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.
http://aerostories.free.fr/technique/J58/J58_01/page8.html