SR-71 blackbird cockpit

[PlonioFludrasco]

I've found this while surfing the net, I'm sure you will appreciate it!

[Red Iron Crown]

Nice find, one of my favorite planes.

[Vanamonde]

Cruise: 10.5 tons of fuel per hour. TONS!

[Aghanim]

That is one seriously inefficient plane...

[MaxxQ]

That is one seriously inefficient plane...

Especially considering it was *designed* to leak fuel all over the place until it was moving fast enough that friction heating cause the skin to expand, finally sealing the tanks. They didn't have the materials needed to seal them that could withstand the heat, as well as be flexible enough to keep the tanks sealed while on the ground. That's why they always refueled almost immediately after takeoff.

[TwoHedWlf]

Especially considering it was *designed* to leak fuel all over the place until it was moving fast enough that friction heating cause the skin to expand, finally sealing the tanks. They didn't have the materials needed to seal them that could withstand the heat, as well as be flexible enough to keep the tanks sealed while on the ground. That's why they always refueled almost immediately after takeoff.

It's not so much that they had to refuel because all the fuel leaked out. The actual amount lost was relatively small. But they usually took off with significantly less than a full tank. The wear and strain on the landing gear at a full load of 80,000 lbs of fuel was much more than at the normal 45-60,000 lbs. And with a full tank the minimum controllable speed with an engine out was around 300 knots. So at speeds less than that if an engine failed they would have to cut the throttle on the remaining engine to avoid uncontrollable yaw. And at that point it would not have enough thrust to stay in the air. Meaning crash and burn. Lower take off weight means lower minimum controllable speed means less time in the crash and burn zone if the engine failed.

[Red Iron Crown]

That is one seriously inefficient plane...

Depends on how you look at it. It's a very efficient way to go Mach 3+.

[Deadpangod3]

Is that the navball?

[rdfox]

Actually, the SR-71 was insanely efficient in both specific fuel consumption and miles per gallon, compared to most jet aircraft, almost entirely due to its raw speed. Yes, it burned 21,000 pounds per hour in cruise, while the 737-800 (comparable in maximum takeoff weight and fuel capacity) burns about 6000 pph in cruise. However, this works out to about 0.094 miles per pound (or 0.63 miles per gallon) for the SR-71, and 0.085 miles per pound (0.57 miles per gallon) for the 737-800, which has literally forty years of Boeing and CFM spending a fortune to try and improve fuel efficiency that the Blackbird didn't have. So in terms of miles per gallon, the Blackbird was about 11% more fuel-efficient than the 737-800.

Going by specific fuel consumption (pounds of fuel burned per hour per pound of thrust) and correcting for speed as per Wikipedia's recommendations, I get a result for the Blackbird of 0.309 pounds per hour per pound thrust, and 0.220 pounds per hour per pound thrust for the 737; correcting for speed by the method they recommend (dividing by speed), I get 1.572*10^-4 as the SFC for the Blackbird, and 4.305*10^-4 for the 737. (The units are pounds of fuel per (pounds thrust times miles), which is a hideous thing to write out.) So in terms of specific fuel consumption, the Blackbird was about 2.75 times as efficient as the 737!

The reason for this is simple--the Blackbird's engine was actually designed to do some very unique tricks at full speed. The J-58 turbojet was actually a unique engine; it operated as a straight turbojet at subsonic speeds, then it started to add more and more bypass air as it got faster, akin to a modern high-bypass turbofan, except that instead of using the engine fan section to move the bypass air, it simply used ram air pressure and inlet shaping to compress it instead. Above about Mach 2, most of the thrust was coming from the afterburner, fed by bypass air, and the engine control system actually started reducing power on the gas turbine section of the engine, since it was no longer needed to compress the air. By Mach 2.5, the engine had transitioned over to being essentially a straight ramjet, with the turbine merely running at low idle power to keep the alternators and hydraulic pumps running, and to avoid trying to windmill-start it during deceleration/descent. In fact, by that speed, the inlet alone was generating a significant amount of thrust; the Air Force has stated that at cruise, 60% of the Blackbird's thrust came from the intake, 35% from the afterburner, and only 5% from the turbine itself. With the gas turbine just idling and not spending much of its energy output compressing air to make thrust, this translates to a significant reduction in fuel flow and, even with the afterburner running at all times, the net is surprisingly low fuel flow for the thrust generated...

[Red Iron Crown]

I'm not sure that is a fair comparison, you need to compare payload, too. The SR-71 carried 2 pilots and a couple hundred pounds of surveillance gear, the 737-800 carries 160-190 passengers and thousands of pounds of cargo. A plane with the SR-71's payload and the 737's performance would be much smaller and consume far less fuel; a plane with the 737's payload and the SR-71's performance would be gigantic and consume far more fuel.

Basically, the 737 is carrying a lot more dead weight, so its specific fuel consumption is lower.

[PlonioFludrasco]

Also remember for what the SR-71 and the 737 are built: the first to take pics of strategic targets inside reds' territories, without being spotted or intercepted: that means high speed and low radar cross section.

The second is buily to carry passengers with competitive operational costs, that means low specific fuel consumption and low maintenance costs. Speed is limeted to the subsonic regime due to international regulation and by the two factors I've already mentioned.

So I don't think we should compare the payloads of the two planes...

PS: Anyone noticed the CoG indicator and the procedure to keep it in the right position?

[JetjockJim]

On 3/9/2014 at 10:57 AM, rdfox said:

"Actually, the SR-71 was insanely efficient in both specific fuel consumption and miles per gallon, compared to most jet aircraft, almost entirely due to its raw speed. Yes, it burned 21,000 pounds per hour in cruise, while the 737-800 (comparable in maximum takeoff weight and fuel capacity) burns about 6000 pph in cruise. However, this works out to about 0.094 miles per pound (or 0.63 miles per gallon) for the SR-71, and 0.085 miles per pound (0.57 miles per gallon) for the 737-800, which has literally forty years of Boeing and CFM spending a fortune to try and improve fuel efficiency that the Blackbird didn't have. So in terms of miles per gallon, the Blackbird was about 11% more fuel-efficient than the 737-800......"

Actually this is inaccurate.   You're off by a factor of roughly 2.   The SR burns 21,000 lbs/hr per side.    As a former FA-18 SuperHornet pilot and a current airline pilot - I can provide a little context.

To do an apples to apples comparison you need not only speed and fuel flow but also weight.   At 0.85M and at mid fuel weight of 42K - a FA-18E will burn about 5600 lbs per hour total fuel flow.   A mid weight SR-71 weighs about 105K - or 2.5x a much.  If we were able to scale up the Super Hornet to the Blackbirds weight - all other things being the same - it would be burning about 14,000lbs/hr.  at 510KTAS or 27.5lbs per NM.    A SR-71 is burning 42,000lbs/hr at 1850KTA = 22.7lbs per NM.   Therefor a SR-71 at cruise in afterburner is 17% more efficient than our scaled up Hornet flying in non AB.  That in itself is pretty amazing.   By Comparison, a Boeing 777 (what I fly) - at a mid cruise of .83M and weight of 550,000lbs is doing about 500KTAS and is burning about 13,500lbs fuel.   If we scaled it down to the size of a SR - that would equate to a fuel flow of 2600lbs/hr or 5.2lbs/NM.   This would make the scaled down B777 burning only 19% of what a Hornet or 5x more efficient - and only 23% of what a SR-71 or 4.3x more efficient in apples to apples comparison.   Without doing the math - my guess is that a B737-800 would be somewhere about 25-26% or 3.9x more efficient of the fuel burn of the SR71.

I will share a different tidbit.  I once flew with the commander of the last HABU squadron at Beal.  This was a 3 day trip we did together where I got to share the cockpit with a guy who knew everything about the SR.  As a buff I got to pick his brain - here are a few things he told me:

 - Very temperature sensitive.   A temperature forecast that was 5 degrees off - could mean a difference in 10K fuel. 

-  Would take off - maintain 450KIAS in the climb until getting to critical Mach and EAS.  Passing about about 60K feet - the airspeed would bleed off until it was in the in the 410-420KIAS range which in the high 70's/low80's works out to be be 3.2M.   

-  The aircraft was temperature limited not airspeed limited.   The aircraft got stronger and more efficient as speed increased - but the aircraft structure and engine inlets could not handle the heat.  It would still be accelerating strong and they would have to pull it back at 3.2.   I asked him how fast it would go if there were no temp limit - he said "Don't know - definitely 3.5 - maybe 4 - but they plane would melt before you got there".  He did say - that during the Lybia raid - they got shot at by a large SAM - pushed it up - and he guessed they were doing over 3.3M when they pulled it back after defeating the missile.

- Stable airplane - flew nice - but you had to plan everything so as not to overshoot - or get down early and burn too much gas.

-  He used to heat his Lean Cuisine by putting it on the glare shield under the window.   Said that was about 450F.  Perfect oven.

- Biggest emergency would be an "Unstart".   If it happened at altitude would be an automatic ejection and probable death.

- Overall said it was a fantastic experience.  Best part was the quality of the guys in the program.

 

 

 

 

[StrandedonEarth]

Blackbird cockpit? Okay, here ya go, trainer version....

(California Science Center, L.A.)

[XB-70A]

53 minutes ago, StrandedonEarth said:

Blackbird cockpit? Okay, here ya go, trainer version....

 

Woah, Titanium Goose! How lucky you were to catch her! I was already happy when I saw my first Oxcart on the Independence some years ago, but I don't know what I would give to see that sole and only trainer variant.

[YNM]

On 19/02/2018 at 2:53 AM, JetjockJim said:

The SR burns 21,000 lbs/hr per side.

Assuming ~300 m/s for the speed of sound, a speed of mach 3.5 (I've seen how the machmeter rolls on it - it definitely isn't a precision device), and two engines, that equates to 5 kg of fuel per km - around 6 litres per km with density of kerosene.

That is like cutting a 2*2 mm hole in the tank and letting the fuel comes out.

Rather efficient I'd say.

 

 

Although, considering that the Space Shuttle gives 2 ft/gal when only the vertical distance and the SSME is taken into account, and that equates to cutting a hole 7*7 mm in the ET and leave it leaking, it's... not that terribly efficient...

Edited February 22, 2018 by YNM

[JetjockJim]

Actually when you do the math you find that the Shuttle at lift off is about 6x more efficient than the SR at takeoff on a lb for lb basis.   This has mainly to do with the incredible heat and pressure generated by the SSME In "cruise" of course, the Shuttle it is infinitely more efficient.

 

 

 

 

 

[YNM]

3 hours ago, JetjockJim said:

This has mainly to do with the incredible heat and pressure generated by the SSME In "cruise" of course, the Shuttle it is infinitely more efficient.

Yeah.

But it's not too fair that Shuttle had two big thermite on it's side and not counting that into account tbh.

Oh, anyway :

 

[StrandedonEarth]

I know this has been posted on this forum at least twice before, but you can't have a Blackbird thread without this excerpt from "Sled Driver":

Spoiler

This is an expanded excerpt from Brian Schul's book Sled Driver : Flying the World's Fastest Jet. (which happens to be out of print and ludicrously expensive now, I wish I had bought a copy when I could have afforded it).

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 " Houston Center voice." 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 Houston controllers, 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. "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 replay 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 Houston Center voice, 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.

 

[Bill Phil]

Reminds me of the Cessna(?) that reported a flight level of 3000. In terms of distance, that's 300000 feet, or, very near to the edge of space. Of course a Cessna can't fly that high, the pilot just reported altitude instead of flight level.

[Hotel26]

1 hour ago, Bill Phil said:

reported a flight level of 3000.

Sounds like he erroneously used the words "Flight Level" in reporting.  Technically, flight levels start from FL018 (18K' and higher).  So GA (general aviation) aircraft would usually be reporting altitude in feet.

[YNM]

11 minutes ago, Hotel26 said:

Technically, flight levels start from FL018 (18K' and higher)

Depends I guess, I've heard that in Europe FL goes lower than in the US (so you would have FL100 or so I thought, whereas in the US that's just 10,000). Also for 18,000 ft that would be FL180, FL018 would be only 1,800 ft.

2 hours ago, StrandedonEarth said:

but you can't have a Blackbird thread without this excerpt from "Sled Driver":

Spoiler

with some illustration :

 

 

[Hotel26]

2 minutes ago, YNM said:

FL180, FL018

Thanks for the correction!

[XB-70A]

12 hours ago, YNM said:

Depends I guess, I've heard that in Europe FL goes lower than in the US (so you would have FL100 or so I thought, whereas in the US that's just 10,000). Also for 18,000 ft that would be FL180, FL018 would be only 1,800 ft.

Indeed, like a lot in aviation, it is dependent from the local regulation. I remember how messy it could be when we were flying in the Windward Islands: TJSJ still using the inHg, while nearly all the others were in hPa,  controls on the islands still part of the Commonwealth were giving distance in NM while the others were in Km, and the best, all of these were using actual pressure for the altitude... excepted TAPA (Antigua) which was using a constant pressure of 1013 to work in flight levels, whatever your altitude was. At least we didn't have to scroll the wheel here... 

[YNM]

4 hours ago, XB-70A said:

Indeed, like a lot in aviation, it is dependent from the local regulation. (*goes with one heck of an example*)

That sounds messed up XD

I know that they're partly due to the overseas control of those fine archipelago, but don't they agree to something when it comes to the nautical miles ? I know that hPa is used in Europe (so any european-controlled areas would go with one presumably), but I thought nmi was, you know, a bit universal (eAIP from Europe supplied in height based off ft and distance in nmi) ?

Edited February 25, 2018 by YNM

[XB-70A]

1 hour ago, YNM said:

That sounds messed up XD

I know that they're partly due to the overseas control of those fine archipelago, but don't they agree to something when it comes to the nautical miles ? I know that hPa is used in Europe (so any european-controlled areas would go with one presumably), but I thought nmi was, you know, a bit universal (eAIP from Europe supplied in height based off ft and distance in nmi) ?

Indeed, it was! Actually, Puerto Rico is a bit an exception today, as even on the U.S. mainland the pressure now is given in hPa (excepted the military of course).

About the distance it is still a bit "floating", despite all the forms and declarations made by the guys at Cologne. There is still some exceptions a bit everywhere, sometime I was wondering if it was not like some kind of a small revenge against the use of the imperial system units, while most of the European countries were using the metric system in aviation before the Second World War. As an example, when I was flying in the Brest area, the distance were given in Km, and the speed sometime in km/h instead of the NM/KTS, but the altitude/height has to be declared in feet at all time.

Here are some creepy pictures took by my father at this time:

Spoiler

 

In a Robin DR400-120, if you look closely at the airspeed you can see two arcs, the larger one in "KM/HR", and the smaller one in Knots, but the alti' is in feet (still, I flew one day in another DR400 which got a metric altimeter... totally illegal, even here!)

 

This one on the right seat MFD of the Aerospool WT9 (the best of all in the fleet ) with distance settled in Km. The airspeed indicator also was in km/h in this one, but as the MFDs were configurable on the ground as well as in the air, it was not a problem when we had to go to the British territories, such as Jersey and Guernsey.

 

 

The only one which was correct in the fleet, the Diamond DA40NG with the ASI in Kts, the alti in ft, and the sort-of-GPS in nm.

 

 

But honestly, I remember when I started to fly at 14 I was so proud of using the imperial system. As a kid who grew up in a total metric system I felt like it was making you different... and now, more than ten years later I don't know what I would give for them to stop using this system in aviation and switch to the metric one... Please dear controllers and traffic agents, no more in-flight conversion!  Sometimes I was feeling like the guys from the ATC were just some torturers who liked to ask us for wacky information requesting miles-to nm conversion for the DME, or mph to knots while we were flying in aircraft with old ASI, or the best: what is the time you are expecting to reach this point at this altitude while you're descending at this number of feet-per-minute, while travelling in mph, and the distance you are covering is in nm...

Edited February 26, 2018 by XB-70A