SR71 Blackbird

Another Ahab

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Inlet design is just as important, if not more so, than what comes out the back. Once jets started getting into the transonic region, managing the shock waves in the intakes became a major headache, and variable geometry inlets became a necessity, thus all those moving ramps and cones and auxiliary doors in the front. You had to manage getting enough air in, with not getting too much and pushing the shock wave back out of the inlet
I ran into this vid (not too long), which gives some explanation about all that:



https://youtu.be/F3ao5SCedIk
 

M813rc

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Now you understand why I didn't try to get too far into that, there is NO way I could have said all that in 5 minutes and 39 seconds! :)
Or made it as coherent in ten times as long.

Cheers
 

Another Ahab

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Yes, indeed.

That vid was pretty tight and clear.

The one thing I can't figure out is:

- Why isn't the "spear point" at the intake symmetrical (when everything else about the engine and the nacelle IS)?

It looks "off" by just the littlest bit. But, why?
 

pjwest03

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It's to keep the the cone pointed forward parallel to the air flow. The actual engine nacelles are canted inboard and droop with respect to the wing. This was done to maximize pressure recovery as it relates to the wings normal angle of attack.
 

USAFSS-ColdWarrior

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Yes, indeed.

That vid was pretty tight and clear.

The one thing I can't figure out is:

- Why isn't the "spear point" at the intake symmetrical (when everything else about the engine and the nacelle IS)?

It looks "off" by just the littlest bit. But, why?
It's to keep the the cone pointed forward parallel to the air flow. The actual engine nacelles are canted inboard and droop with respect to the wing. This was done to maximize pressure recovery as it relates to the wings normal angle of attack.
These pics show that AOA (Angle of Attack) a bit exaggerated due to the relatively low speed required for matching speeds with the tanker aircraft, but you get the idea. The axis of the cones is "tuned" to point "into the wind".

Lockheed-SR71-Blackbird-Refuel.jpg . sr71-big-tale-kc135-refueling-right-670x250.jpg
 

Guyfang

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Lockheed spent a ton of money on figuring this out. And still had problems with it up till the end. Several of the birds lost, were due to, I hope I remember right, Compressor stall. The engine would go into an "unstart", (I hope I get this right, I need to review this part of the document I got from the CIA again) and the bird would Yaw to one side or the other. The pilots came up with a method to correct it, and restart the engine.
 

Another Ahab

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Lockheed spent a ton of money on figuring this out. And still had problems with it up till the end. Several of the birds lost, were due to, I hope I remember right, Compressor stall. The engine would go into an "unstart", (I hope I get this right, I need to review this part of the document I got from the CIA again) and the bird would Yaw to one side or the other. The pilots came up with a method to correct it, and restart the engine.
Are you saying that the engines would shut down in flight?
 

pjwest03

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Yep, the P-80, F-86 and some other early jets were prone to compressor stalls / flameouts.
Most if not all early engines were susceptible to compressor stalls. There's a point were the rotation speed of the compressor blades causes the airfoils of the the blades to stall just like an airplane wing. It's dependent on a lot of factors but a big one is the amount of air flowing into the inlet. Anything that disrupts that flow can cause a compressor stall. Generally the engine will surge as the air flow disruptions pulse through the engine. In some cases that will "blow the candle out" and it can cause considerable damage to the engine from the vibration and shock waves. In early jet aircraft, that had to managed carefully by the pilots. They had to keep their flight maneuvers within the operating envelope of the engine. Avoiding sudden turns, side slips, ingesting exhaust from another jet or a missile; basically anything that disrupts the airflow into the engine inlet. The other big one was fast application of the throttle, trying suck more air in faster than the increase in airspeed can supply it. It was all totally manual before electronic digital controls.

It was particularly bad for a plane such as the SR-71. That complex inlet made it quite easy to cause a compressor stall. The other problem is that the SR-71 didn't have a lot of yaw authority from the tail, worst at low speeds. That meant that keeping the engine thrust balanced between the two engines was critical and entirely manual. The relatively large distance between the engines added to that problem. If one engine was failing, the other engine exerted a lot of leverage making it very difficult to keep the plane pointed forward. The main result being a flat spin and bad day for all involved.
 

Tracer

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B-58 1.jpgB-58 2.jpgB-58 3.jpg The B-58 Hustler used a little less sophisticated type of Variable Geometry Inlets. The inlets moved forward and aft to help prevent air flow disruption from shock waves that formed when the aircraft was operating at supersonic speeds. Top speed of the B-58 was about 1320mph, the high speed and advanced weapons pod required the B-58 to have computers operate the majority of the aircrafts flight operations. The B-58 was a hot airplane especially when landing. Over 20 B-58s out of the 120+ built were lost to accidents. The B-58 had a short service life 1960 thru 1970, this was mainly due to advancements in Soviet surface to air missiles. The B-58 was replaced by the F-111B.
 

Another Ahab

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Top speed of the B-58 was about 1320mph, the high speed and advanced weapons pod required the B-58 to have computers operate the majority of the aircrafts flight operations. The B-58 was a hot airplane especially when landing.
Relying on 1960-era computers must have been presented some real challenges all of its own.




191661650972-0.jpg
 

Guyfang

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Are you saying that the engines would shut down in flight?

I took a look through my write ups on the SR-71. I found at least one bird, Tail number 64-17952 that was lost due to "An inlet scheduling malfunction, followed by an Unstart, on the right engine while in a 30 degree bank at 80,000 feet, and at Mach 3+". The aircraft broke up. Both pilot and RSO escaped the aircraft, but the RSO was found dead after parachuting to the ground.

The accident happened on 25 Jan.-1966, near Tucumcari, New Mexico. Pilot was Bill Weaver, the RSO was Jim Zwayer. For a detailed description of the event, read Lockheed SR-71, The Secret Missions Exposed, by Paul F. Crickmore. If you want to find out more about what an unstart is, and how the Lockheed company managed to fix the problem, Creekmore's book is the last word. Detailed description of who, how, what and pictures to go with it. My copy is dated, there has been at least one update.

What many people don't know, is that the SR-71 is the descendant of the A-12. The A-12 was a single seater. Had an incredible camera in it, that was designed by Eastman Kodak, just for the A-11 project. At first look, the planes are very similar. But upon closer inspection, there are some differences. Again, if you want to read about it, there are 15-20 good books to chose from, but Creekmore's book has to be the best. And yet, the documents I got from the CIA, through the FOI request I made, still had a thing or two that wasn't in the book! Very interesting!!

Some fun facts. Titanium, the material used to produce these fantastic birds. The world's largest producers are Russia, and South Africa. The United States had to acquire almost the entire amount of this metal, from those two countries, without letting anyone know what it was for. I bet the Russians could still scream about that.

During both projects, A-12 and SR-71 development, a problem developed with metal fatigue. BUT, strangely enough, it seemed to be caused by different location of part manufacturing. Many parts were made in California, and other parts on the East Coast. The manufacturing prosses was the same, in both facilities. So what could it be? Some people even suggested sabotage. After much studying of failed, and non failed parts, a smart guy decided he knew the answer. Fluoride. Yep, like in toothpaste. It seems that California was one of the first states to put fluoride in the drinking water. Water was used in the machining process to clear away metal filings and other debris. Titanium reacts with fluoride, and it weakens the metal! So all the machine shops in California had to use non fluoridated water, to correct the problem.

The tensile strength of titanium on the A-12's and SR-71's got higher, due to repeated heating, from high Mach flights.
 

swbradley1

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View attachment 687093View attachment 687094View attachment 687095 The B-58 Hustler used a little less sophisticated type of Variable Geometry Inlets. The inlets moved forward and aft to help prevent air flow disruption from shock waves that formed when the aircraft was operating at supersonic speeds. Top speed of the B-58 was about 1320mph, the high speed and advanced weapons pod required the B-58 to have computers operate the majority of the aircrafts flight operations. The B-58 was a hot airplane especially when landing. Over 20 B-58s out of the 120+ built were lost to accidents. The B-58 had a short service life 1960 thru 1970, this was mainly due to advancements in Soviet surface to air missiles. The B-58 was replaced by the F-111B.
For the F-14 it was this:

f14-detail-airintake-01.gif

For the F-4 it was:

220px-Royal_Military_Museum_Brussels_2007_230.JPG

The panel on the right side of the inlet in this picture would move out and reduce the opening to the engine.

One of the computer systems I supported at Ohio State ran the wind tunnel. Interesting how they test all this stuff to figure out what's going and then fix it.
 

Another Ahab

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During both projects, A-12 and SR-71 development, a problem developed with metal fatigue. BUT, strangely enough, it seemed to be caused by different location of part manufacturing. Many parts were made in California, and other parts on the East Coast. The manufacturing prosses was the same, in both facilities. So what could it be? Some people even suggested sabotage. After much studying of failed, and non failed parts, a smart guy decided he knew the answer. Fluoride. Yep, like in toothpaste. It seems that California was one of the first states to put fluoride in the drinking water. Water was used in the machining process to clear away metal filings and other debris. Titanium reacts with fluoride, and it weakens the metal! So all the machine shops in California had to use non fluoridated water, to correct the problem.
The whole story here is remarkable, and this little fluoride component is really engaging.

The benefits of science.

It brings to mind the story of how the U.S. figured out during WWII where the Japanese were manufacturing their "floating" fire bombs. The U.S. sleuthing was the work of some on-the-ball geologists recruited by the War Department. One or two B-29 sorties later, the whole fire bomb problem went away.
 

M813rc

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The United States had to acquire almost the entire amount of this metal, from those two countries, without letting anyone know what it was for.
This brings up the $900 screwdrivers and toilet seats that Lockheed, and other DOD contractors used to "make".
Because of how we do things, budget-wise, the military has to show how much money they pay contractors each year. If you are doing secret projects, you can't just say "$xxxxxxxxx for secrets", because others can tell how a project is going just by to whom, and how much we are spending on it.
The ridiculous price items were a way of concealing payments being made to Lockheed to develop stealth technology, and the F-117. I suppose they didn't expect some reporter to diligently look line by line for something to bitch about.
Of course, they couldn't say "No, we're not that stupid, we're concealing secret projects", so they just rolled with it. The people who needed to know the truth, did.
And it worked! At the time the F-117 was finally revealed, the aviation media suspected it was an advancing test program, not an aircraft that had been in squadron service for years already. I was tickled pink that America had actually kept a military secret.

Cheers
 
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USAFSS-ColdWarrior

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This brings up the $900 screwdrivers and toilet seats that Lockheed, and other DOD contractors used to "make".
Because of how we do things, budget-wise, the military has to show how much money they pay contractors each year. If you are doing secret projects, you can't just say "$xxxxxxxxx for secrets", because others can tell how a project is going just by to whom, and how much we are spending on it.

The ridiculous price items were a way of concealing payments being made to Lockheed to develop stealth technology, and the F-117. I suppose they didn't expect some reporter to diligently look line by line for something to bitch about.
Of course, they couldn't say "No, we're not that stupid, we're concealing secret projects", so they just rolled with it. The people who needed to know the truth, did.
And it worked! At the time the F-117 was finally revealed, the aviation media suspected it was an advancing test program, not an aircraft that had been in squadron service for years already. I was tickled pink that America had actually kept a military secret.

Cheers
The volume on this video is low, but you'll get the message at the end.....

https://www.youtube.com/watch?v=QdmH47VNiS4
 

Guyfang

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This brings up the $900 screwdrivers and toilet seats that Lockheed, and other DOD contractors used to "make".
Because of how we do things, budget-wise, the military has to show how much money they pay contractors each year. If you are doing secret projects, you can't just say "$xxxxxxxxx for secrets", because others can tell how a project is going just by to whom, and how much we are spending on it.
The ridiculous price items were a way of concealing payments being made to Lockheed to develop stealth technology, and the F-117. I suppose they didn't expect some reporter to diligently look line by line for something to bitch about.
Of course, they couldn't say "No, we're not that stupid, we're concealing secret projects", so they just rolled with it. The people who needed to know the truth, did.
And it worked! At the time the F-117 was finally revealed, the aviation media suspected it was an advancing test program, not an aircraft that had been in squadron service for years already. I was tickled pink that America had actually kept a military secret.

Cheers
Part of the 300 dollar toilet seat problem, is the government itself. Everything is over engineered. Everything is special developed. The aforementioned toilet seats. They are not normal toilet seats like we sit our patooties down on. They are extremely fire resistant. The material is very tough. Its supposed to last forever. It's non static producing material. And on and on.

ALL electronic devices that we had in Patriot, launchers, radars, command centers, commo gear, everything you can imagine, and LOTS more you cant, were EMP resistant. All the armored vehicles that are in our inventory, are EMP resistant. Generators, some anyway, are EMP hardened. Go look at a civilian gen set, take note of all the bells and whistles. Then look at a comparable military gen set. they are not even close. Hands down, the military gen set has more saft devices then you can think of. Every aircraft is EMP resistent. There are a kazillion other requirements to also be figured in. It all cost extra money. While I have never seen a 900 dollar screwdriver, I have seen some that cost 40-50 dollars. Non magnetic, non sparking, handle non static producing. Yep, cost money. THEN to make it more expensive, when a manufacturer at last meets all the criteria, passes all the tests, the military changes something. Or tells the manufacturer that no, you cant use that sub vendor, the owner had a federal conviction for transporting bootleg whisky, 55 years ago. Or since the sub vendor is not employing enough left handed Austrians, you need to find another vender.

I will not say that some over payment, to compensate the big companies don't go on. But it's not all graft. And yes, the concealment of projects goes on, and lots bigger than we can imagine.
 
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