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 The engine of the A-12, YF-12, SR-71 - The JT11D aka The J58 Turbojet
KA3B  [Life Member]
6/11/2008 5:57:57 PM EST
The J58 is a turbojet engine.

The propulsion system of the SR-71 aircraft has three primary components.

These components are axisymmetric mixed compression inlets, Pratt & Whitney J58 turbojet engines, and airframe-mounted, convergent-divergent blow-in door ejector nozzles.

The entire engine system of the Blackbird family consists of:

The J58 Turbojet engine

The inlet assembly, consisting of:
The air inlet computer (AIC) or the digital automatic flight and inlet control system (DAFICS)
The aerospike (or translating spike) assembly
The DAFICS controlled forward bypass doors
The aerodynamicly positioned blow-in doors and ejector flaps

The J58 engine (and not the inlet assembly) is a turbojet engine.
It does not need the inlet assembly in order to operate the engine in the test stand.

The J58 is not a bypass engine, it does not bypass any internaly compressed air.

The engine assembly is considered to be a turbojet assisted ramjet.

At speed about 80% of the thrust is created by the inlet assembly and 20% of the thrust is created by the J58 turbojet engine.






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Chokey  [Life Member]
6/11/2008 5:58:52 PM EST
Merrell  [Team Member]
6/11/2008 6:03:58 PM EST

Originally Posted By KA3B:
The J58 is a turbojet engine.

The propulsion system of the SR-71 aircraft has three primary components.

These components are axisymmetric mixed compression inlets, Pratt & Whitney J58 turbojet engines, and airframe-mounted, convergent-divergent blow-in door ejector nozzles.

The entire engine system of the Blackbird family consists of:

The J58 Turbojet engine

The inlet assembly, consisting of:
The air inlet computer (AIC) or the digital automatic flight and inlet control system (DAFICS)
The aerospike (or translating spike) assembly
The DAFICS controlled forward bypass doors
The aerodynamicly positioned blow-in doors and ejector flaps

The J58 engine (and not the inlet assembly) is a turbojet engine.
It does not need the inlet assembly in order to operate the engine in the test stand.

The J58 is not a bypass engine, it does not bypass any internaly compressed air.

The engine assembly is considered to be a turbojet assisted ramjet.

At speed about 80% of the thrust is created by the inlet assembly and 20% of the thrust is created by the J58 turbojet engine.

www.enginehistory.org/P&W/J58/J58_AB_stand.jpg


farm2.static.flickr.com/1298/975833148_80b0d8d6f5.jpg?v=0



Bypass Turbojet.

Silence  [Member]
6/11/2008 6:04:52 PM EST
Oh boy.

Incoming Geek Fight

WarWeapon762  [Team Member]
6/11/2008 6:06:47 PM EST
not even gonna touch this topic with a 30ft pole
DnPRK  [Team Member]
6/11/2008 6:09:22 PM EST
Turbojet with air bypass ducts. You can see the bypass ducts running from fore to aft in the linked pic.
www.hill.af.mil/library/factsheets/factsheet_media.asp?fsID=5786
Merrell  [Team Member]
6/11/2008 6:11:11 PM EST

Pratt & Whitney J58 Turbojet

The Pratt & Whitney J58 engine was a nine-stage, axial-flow, bypass turbojet originally developed in the late 1950s to meet U.S. Navy requirements. It was the first jet engine designed to operate for extended periods using its afterburner. The J58 generated a maximum thrust of 32,500 pounds -- more than 160,000 shaft horsepower -- and was the most powerful air-breathing aircraft engine yet devised.

The J58 was specifically tailored for operation at extreme speeds, altitudes, and temperatures, and was the first aircraft engine to be flight qualified for the Air Force at Mach 3. At maximum output the fuel flow rate in the J58 is about 8,000 gallons per hour and the exhaust-gas temperature is around 3,400 degrees. The J58 was only used on the Lockheed YF-12 interceptor and its descendents, the A-12 and SR-71.

The J58 required the use of a special AG330 engine starter cart to spool the engines up to the proper rotational speed for starting. The cart was powered by two unmuffled Buick Wildcat V-8 racing car engines which delivered a combined 600 horsepower through a common gear box to the starter drive shaft of the aircraft engines. The J58s had to be spun up to about 3,200 RPM for starting.

The variable-geometry inlets for the engines were quite complex and intricate. The most prominent feature was a hydraulically-actuated conical spike which was automatically moved forward or aft by the Air Inlet Computer as required to keep the supersonic shockwave properly positioned in relation to the inlet throat. Working in conjunction with a series of bypass ducts and doors, the spike prevented supersonic air from entering the inlet and maintained a steady flow of subsonic air for the engine. At Mach 3.2 cruise the inlet system itself actually provided 80 percent of the thrust and the engine only 20 percent, making the J58 in reality a turbo-ramjet engine.

At the speeds the SR-71 operated, surface temperatures were extremely high due to aerodynamic heating: 800 degrees at the nose, 1,200 degrees on the engine cowlings, 620 degrees on the cockpit windshield. Because of the operating altitudes, speeds, and temperatures, Lockheed designers were forced to work at the cutting edge of existing aerospace technology, and well beyond in many cases. Many features and systems simply had to be invented as they were needed, since conventional technology was inadequate to the task. New oils, hydraulic fluids, sealants, and insulations were created to cope with the ultra-high temperatures the craft would encounter. A new type of aviation fuel, JP-7, was invented that would not "cook off" at high operating temperatures, having such a low volatility and high flash point that it required the use of triethylborane as a chemical ignitor in order for combustion to take place. The fuel itself was rendered inert by the infusion of nitrogen and then circulated around various components within the airframe as a coolant before being routed into the J58 engines for burning.


http://www.hill.af.mil/library/factsheets/factsheet.asp?id=5786

KA3B  [Life Member]
6/11/2008 6:11:56 PM EST

Originally Posted By Merrell:
Bypass Turbojet.


USAF says....TURBOJET!
www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=880

The Manufacturer says....TURBOJET!
www.pw.utc.com/vgn-ext-templating/v/index.jsp?vgnextoid=f245912bc27fb010VgnVCM1000000881000aRCRD
Pita_146  [Team Member]
6/11/2008 6:12:36 PM EST
What did I miss?
KA3B  [Life Member]
6/11/2008 6:14:25 PM EST

Originally Posted By Merrell:
[ bypass turbojet


Can't be, a turbojet engine does not bypass any air, it all goes down the tube and out the back.
Tolip  [Team Member]
6/11/2008 6:16:05 PM EST
The separate J58 engine itself is a turbojet.

The system that powered the blackbird was a turbo/ramjet (J58 + surrounding components).
Merrell  [Team Member]
6/11/2008 6:18:49 PM EST

Originally Posted By KA3B:

Originally Posted By Merrell:
Bypass Turbojet.


USAF says....TURBOJET!
www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=880

The Manufacturer says....TURBOJET!
www.pw.utc.com/vgn-ext-templating/v/index.jsp?vgnextoid=f245912bc27fb010VgnVCM1000000881000aRCRD


The guy who holds the patent on the J58 is my old Weibull instructor, Dr. Bob Abernethy.

www.bobabernethy.com/bios_bob.htm


Dr. Bob holds the patent on a feature of the J58 Pratt & Whitney engine that powers the world’s fastest aircraft. His invention converts the afterburning turbojet into a partial ram jet at high Mach number.


It is NOT a straight turbojet.



KA3B  [Life Member]
6/11/2008 6:19:06 PM EST

Originally Posted By Tolip:
The separate J58 engine itself is a turbojet.

The system that powered the blackbird was a turbo/ramjet (J58 + surrounding components).


Didn't I say that.
the-fly  [Team Member]
6/11/2008 6:22:39 PM EST
I dont care what they call it, i want one on my car
KA3B  [Life Member]
6/11/2008 6:26:25 PM EST

Originally Posted By Merrell:
The guy who holds the patent on the J58 is my old Weibull instructor, Dr. Bob Abernethy.

www.bobabernethy.com/bios_bob.htm


Dr. Bob holds the patent on a feature of the J58 Pratt & Whitney engine that powers the world’s fastest aircraft. His invention converts the afterburning turbojet into a partial ram jet at high Mach number.


It is NOT a straight turbojet.


Dr. Bob does not hold the patent on the J58 engine.
He did not invent or develop it.

Your post even states that fact.

"His invention converts the ***afterburning turbojet*** into a partial ram jet..."

KA3B  [Life Member]
6/11/2008 6:27:20 PM EST

Originally Posted By the-fly:
I dont care what they call it, i want one on my car


You own a 64 Chevy Impalla?
danpass  [Team Member]
6/11/2008 6:27:39 PM EST
I'LL TAKE IT!

IM SENT!










oh wait ....
KA3B  [Life Member]
6/11/2008 6:28:27 PM EST

Originally Posted By danpass:
I'LL TAKE IT!

IM SENT!

oh wait ....


Paypal not accepted.
Matt_The_Hokie  [Team Member]
6/11/2008 6:30:08 PM EST
i say its a piston powered radial engine. with a 4 bladed prop.
KA3B  [Life Member]
6/11/2008 6:32:06 PM EST

Originally Posted By Matt_The_Hokie:
i say its a piston powered radial engine. with a 4 bladed prop.


Turbocharged, supercharged or turbo-supercharged?
Blue_Monkey  [Team Member]
6/11/2008 6:33:13 PM EST
Can i hook that up to my Weber Grill ?
ExParatrooper  [Member]
6/11/2008 6:35:57 PM EST
If you were to put a J58 on a treadmill, and wind it up to military power, and at the same time, speed the treadmill up to the equivalent velocity, would the engine.............
Merrell  [Team Member]
6/11/2008 6:36:14 PM EST

Originally Posted By KA3B:

Originally Posted By Merrell:
The guy who holds the patent on the J58 is my old Weibull instructor, Dr. Bob Abernethy.

www.bobabernethy.com/bios_bob.htm


Dr. Bob holds the patent on a feature of the J58 Pratt & Whitney engine that powers the world’s fastest aircraft. His invention converts the afterburning turbojet into a partial ram jet at high Mach number.


It is NOT a straight turbojet.


Dr. Bob does not hold the patent on the J58 engine.
He did not invent or develop it.

Your post even states that fact.

"His invention converts the ***afterburning turbojet*** into a partial ram jet..."



RIF:

Dr. Bob holds the patent on a feature of the J58 Pratt & Whitney engine


Not a feature of the A12/YF12/etc that converts a J58 into something else.

He was working for P&W at the time.


Your picture from your first post is from http://www.enginehistory.org/P&W/p&w_j58.htm

That is the very same page that the plaque is from:



The two links you posted might as well say "jet engine" which is correct, but hardly as detailed as the links I have cited.


Find a J58 without Abernethy's patent. (Yes and there are plenty of other patents on the engine)

Tolip  [Team Member]
6/11/2008 6:42:14 PM EST

Originally Posted By KA3B:

Originally Posted By Matt_The_Hokie:
i say its a piston powered radial engine. with a 4 bladed prop.


Turbocharged, supercharged or turbo-supercharged?


* Aren't those the same thing?
Merrell  [Team Member]
6/11/2008 6:52:10 PM EST
I sent Dr. Abernethy an email, we'll see what he says.

OP is welcome to send emails to all the people he knows who worked on the J58.
Armed_Scientist  [Member]
6/11/2008 6:56:34 PM EST
The J58 itself is a turbojet, the bypass duct, intake spike and ejector nozzle it is mounted in compose the ramjet. Want proof, look at the picture of the J58 on the ground test, if the J58 were a ramjet there is no way it could operate while static.
junker46  [Team Member]
6/11/2008 7:04:09 PM EST
I know that pic: last run of a J-58. Used to burn off all the remaining JP8 JP7.
I used to run J-52s, and I was amazed at the glowing tail section; how oil lines running through it didn't boil (the inside oil) away or the back end self-destruct.


ETA for the question: the whole QEC is designated as a J-58, so I'll say 'compound ramjet.'

ETA2 Thanks Armed_Scientist for correcting my rookie mistake.
KA3B  [Life Member]
6/11/2008 7:05:58 PM EST

Originally Posted By Armed_Scientist:
The J58 itself is a turbojet, the bypass duct, intake spike and ejector nozzle it is mounted in compose the ramjet. Want proof, look at the picture of the J58 on the ground test, if the J58 were a ramjet there is no way it could operate while static.


Shhhhhh, don't add facts......
Armed_Scientist  [Member]
6/11/2008 7:16:27 PM EST
While we are discussing air breathing high mach flight behold the future, the Lockheed-Martin HTV-3 Blackswift


It's a demonstrator roughly the size of a F-16 and uses two turbine based combine cycle engines. It will be the first (in the white world) vehicle to demonstrate zero velocity to above mach 6 flight in a reusable platform.
Merrell  [Team Member]
6/11/2008 7:17:24 PM EST

Originally Posted By junker46:
I know that pic: last run of a J-58. Used to burn off all the remaining JP8. I used to run J-52s, and I was amazed at the glowing tail section; how oil lines running through it didn't boil (the inside oil) away or the back end self-destruct.


JP7.

Former client made special gas (vapor) detectors for them (and this was in the late 80's)
Matt_The_Hokie  [Team Member]
6/11/2008 7:20:17 PM EST

Originally Posted By KA3B:

Originally Posted By Matt_The_Hokie:
i say its a piston powered radial engine. with a 4 bladed prop.


Turbocharged, supercharged or turbo-supercharged?


Im gonna go with... supercharger. and it has quad .50s in each wing...and a 20mm cannon in the nose cowling.
JB69  [Team Member]
6/11/2008 7:22:58 PM EST

Originally Posted By Tolip:

Originally Posted By KA3B:

Originally Posted By Matt_The_Hokie:
i say its a piston powered radial engine. with a 4 bladed prop.


Turbocharged, supercharged or turbo-supercharged?


* Aren't those the same thing?


No, a turbosupercharger is a system that used BOTH types of compressors, in series...

Link here clicky about halfway down the page.

It takes advantage of the strengths of both individual types of forced intake air compression to give a much more substantial and flexible power adding effect to an engine that normally runs at very high altitudes.

Fletchette  [Member]
6/11/2008 7:26:18 PM EST

Originally Posted By Matt_The_Hokie:

Originally Posted By KA3B:

Originally Posted By Matt_The_Hokie:
i say its a piston powered radial engine. with a 4 bladed prop.


Turbocharged, supercharged or turbo-supercharged?


Im gonna go with... supercharger. and it has quad .50s in each wing...and a 20mm cannon in the nose cowling.


What are you talking about! It is a diesel with a 30mm!
Matt_The_Hokie  [Team Member]
6/11/2008 7:30:20 PM EST

Originally Posted By Fletchette:

Originally Posted By Matt_The_Hokie:

Originally Posted By KA3B:

Originally Posted By Matt_The_Hokie:
i say its a piston powered radial engine. with a 4 bladed prop.


Turbocharged, supercharged or turbo-supercharged?


Im gonna go with... supercharger. and it has quad .50s in each wing...and a 20mm cannon in the nose cowling.


What are you talking about! It is a diesel with a 30mm!


NOO silly. thats the U2. the SR71 runs on Kerosene. and has a maximum height of 1200000ft. and a max speed of mach6. but you were had the right idea though.
JoseCuervo  [Member]
6/11/2008 7:32:00 PM EST

Originally Posted By the-fly:
I dont care what they call it, i want one on my car


You must have missed this part:


the fuel flow rate in the J58 is about 8,000 gallons per hour


At who knows how much for jet fuel, fuck that!

Rob
KA3B  [Life Member]
6/11/2008 7:32:42 PM EST

Originally Posted By Matt_The_Hokie:

Originally Posted By KA3B:

Originally Posted By Matt_The_Hokie:
i say its a piston powered radial engine. with a 4 bladed prop.


Turbocharged, supercharged or turbo-supercharged?


Im gonna go with... supercharger. and it has quad .50s in each wing...and a 20mm cannon in the nose cowling.


FTW
Merrell  [Team Member]
6/11/2008 7:52:34 PM EST

Originally Posted By Armed_Scientist:
The J58 itself is a turbojet, the bypass duct, intake spike and ejector nozzle it is mounted in compose the ramjet. Want proof, look at the picture of the J58 on the ground test, if the J58 were a ramjet there is no way it could operate while static.


That's on a ground test. Nobody is claiming a ramjet will operate on the ground (without forced air input). Furthermore, nobody is claiming the J58 is a pure ramjet.
Here's what went in the plane:



That's a J58-P4

See those pipes on the side? The big ones? There are six of them. They are BYPASS ducts.

Care to guess which compressor stage they are extracting air from?
KA3B  [Life Member]
6/11/2008 8:07:23 PM EST

Originally Posted By Merrell:
See those pipes on the side? The big ones? There are six of them. They are BYPASS ducts.
Care to guess which compressor stage they are extracting air from?



Those are bleed air ducts that only open up above Mach 2.2.

At mach 2.2 some of the airflow is bled from the fourth stage of the compressor and dumped into the augmentor inlet through six bleed-bypass tubes.

Again, it's not a bypass engine, it's a turbojet.

Those are bleed air ducts that are taking 4th stage bleed air and dumping it into the afterburner section.

A bypass turbine engine has a seperate fan section that ducts fan compressed air around the core (thereby BYPASSING the core), hence the name "bypass engine" (with the exception of a high-bypass external fan engine).
Tanker06  [Team Member]
6/11/2008 8:12:40 PM EST

Originally Posted By Pita_146:
What did I miss?

Not sure. This ground-pounder is trying to make sense of the postings, but the common
theme seems to be that the tech/nerd-fu is strong in this thread!
danno-in-michigan  [Team Member]
6/11/2008 8:19:11 PM EST

Originally Posted By KA3B:
At speed about 80% of the thrust is created by the inlet assembly and 20% of the thrust is created by the J58 turbojet engine.




Inlets don't create thrust. I think what you meant to say is that, at speed, 80% of the thrust is created by the bypass system that dumps air from the 4th stage of the compressor directly into the afterburner. It's nitpicking but I don't want folks claiming the SR-71 is sucked through the air by its inlets.
Merrell  [Team Member]
6/11/2008 8:36:14 PM EST

Originally Posted By KA3B:

Originally Posted By Merrell:
See those pipes on the side? The big ones? There are six of them. They are BYPASS ducts.
Care to guess which compressor stage they are extracting air from?



Those are bleed air ducts that only open up above Mach 2.2.

At mach 2.2 some of the airflow is bled from the fourth stage of the compressor and dumped into the augmentor inlet through six bleed-bypass tubes.

Again, it's not a bypass engine, it's a turbojet.

Those are bleed air ducts that are taking 4th stage bleed air and dumping it into the afterburner section.

A bypass turbine engine has a seperate fan section that ducts fan compressed air around the core (thereby BYPASSING the core), hence the name "bypass engine" (with the exception of a high-bypass external fan engine).


What the Sam Hill do you think extracting air before it is fully compressed is?

You can call it 'bleeding' but in fact it is BYPASSING the complete compression available. That it was used to cool the afterburners (and enrich the mixture and increase thrust) instead of to reduce exhaust velocity to more efficiently match that of aircraft speed is irrelevant. It is BYPASSING the core of the engine. As do both high-bypass and low-bypass turbofans. For differing reasons but bypassing nonetheless. And it is an INTEGRAL part of EVERY J58-P4. Not just stuff ahead of and after the engine.

Pure Turbojets do not have this. The J58-P4 is a BYPASS variable cycle engine.

Kelly Johnson's successor at Lockheed, Ben Rich calls it a "Bypass jet engine by air withdrawal".

Merrell  [Team Member]
6/11/2008 8:44:52 PM EST

Originally Posted By KA3B:
The J58 is not a bypass engine, it does not bypass any internaly compressed air.




YES IT DOES
KA3B  [Life Member]
6/11/2008 9:49:55 PM EST

Originally Posted By danno-in-michigan:

Originally Posted By KA3B:
At speed about 80% of the thrust is created by the inlet assembly and 20% of the thrust is created by the J58 turbojet engine.




Inlets don't create thrust. I think what you meant to say is that, at speed, 80% of the thrust is created by the bypass system that dumps air from the 4th stage of the compressor directly into the afterburner. It's nitpicking but I don't want folks claiming the SR-71 is sucked through the air by its inlets.


The inlet assembly, assembly being the key word.
2A373  [Team Member]
6/11/2008 9:55:00 PM EST

Originally Posted By Pita_146:
What did I miss?


www.ar15.com/forums/topic.html?b=1&f=5&t=718842&page=2
METT-T  [Team Member]
6/11/2008 10:07:25 PM EST

Originally Posted By Tanker06:

Originally Posted By Pita_146:
What did I miss?

Not sure. This ground-pounder is trying to make sense of the postings, but the common
theme seems to be that the tech/nerd-fu is strong in this thread!


And these are some catty technerds to boot!
KA3B  [Life Member]
6/11/2008 10:12:38 PM EST

Originally Posted By Merrell:

Originally Posted By KA3B:

Originally Posted By Merrell:
See those pipes on the side? The big ones? There are six of them. They are BYPASS ducts.
Care to guess which compressor stage they are extracting air from?



Those are bleed air ducts that only open up above Mach 2.2.

At mach 2.2 some of the airflow is bled from the fourth stage of the compressor and dumped into the augmentor inlet through six bleed-bypass tubes.

Again, it's not a bypass engine, it's a turbojet.

Those are bleed air ducts that are taking 4th stage bleed air and dumping it into the afterburner section.

A bypass turbine engine has a seperate fan section that ducts fan compressed air around the core (thereby BYPASSING the core), hence the name "bypass engine" (with the exception of a high-bypass external fan engine).


What the Sam Hill do you think extracting air before it is fully compressed is?

You can call it 'bleeding' but in fact it is BYPASSING the complete compression available. That it was used to cool the afterburners (and enrich the mixture and increase thrust) instead of to reduce exhaust velocity to more efficiently match that of aircraft speed is irrelevant. It is BYPASSING the core of the engine. As do both high-bypass and low-bypass turbofans. For differing reasons but bypassing nonetheless. And it is an INTEGRAL part of EVERY J58-P4. Not just stuff ahead of and after the engine.

Pure Turbojets do not have this. The J58-P4 is a BYPASS variable cycle engine.

Kelly Johnson's successor at Lockheed, Ben Rich calls it a "Bypass jet engine by air withdrawal".




Just because a turbojet, turboshaft or turboprop engine takes compressor bleed air and uses it to cool the core does not make it a bypass engine, even though it "bypasses' (some) compressor and power turbines.

Just because a turbojet, turboshaft or turboprop engine has bleed air ducts that take compressor bleed air and dumps it overboard does not make it a bypass engine, even though it "bypasses" (some) compressor and power turbines.

Again, the J58 is a turbojet engine.

A turbofan (a bypass engine) uses a SEPERATE fan section to compress the bypass air.
It does not tap off the compressor section to create the bypass air.

If you tap compressed air out of the compressor section it is called "bleed air", not bypass air.

Further, bypass air is always being bypassed since the fan section is always turning and creating bypass air.

The bleed air that is ducted by the 6 tubes is only bleed off when the aircraft is operating above mach 2.2.
AngeredKabar  [Team Member]
6/11/2008 10:16:12 PM EST
It's obviously using alien technology as no one can get a correct description.
KA3B  [Life Member]
6/11/2008 10:17:05 PM EST

Originally Posted By METT-T:
And these are some catty technerds to boot!


Meow.
Cypher15  [Team Member]
6/11/2008 10:18:52 PM EST

Originally Posted By Tolip:

Originally Posted By KA3B:

Originally Posted By Matt_The_Hokie:
i say its a piston powered radial engine. with a 4 bladed prop.


Turbocharged, supercharged or turbo-supercharged?


* Aren't those the same thing?

the correct term for turbo-supercharged is twin charged. this means a turbo and a supercharger.
KA3B  [Life Member]
6/11/2008 10:24:57 PM EST



The result of the tests carried out in conjunction with Lockheed evidenced, from the start, that at the intended higher Mach numbers the new engine would be unable to cope with the volume of air coming through the air-intakes.

This would result in compressor stalling with accompanying loss of efficiency and thrust at high speeds.

Pratt & Whitney therefore modified their JT-11 by installing a series of fixed flow-vanes downstream of the 4th compressor stage, which directed the surplus airflow along six longitudinal jet pipes running along the engine casing.

The surplus was then carried straight to the afterburner chamber serving to cool the burners, whilst enriching the mixture; so enabling higher combustion temperatures or increased thrust.

This principle, innovative at that time, figured largely in the future development of other engines called "bypass jets.

The J-58 cannot be properly referred to as being bypass jet, an unknown principle at that time, as that did not derive from flow-vanes with an irregular cooling affect, so serving to relieve the compressor at certain stages of flight, which was obtained by a bypass flow constantly shifting air from within the compressor towards the turbine outlet.



Nevertheless the chosen formula allowed an effective limitation of the phenomenon of unstarts and compressor fall-off due to variations in inlet temperature, on top reducing specific consumption from 10 to 15%.

This is the system which Ben R Rich (Kelly Johnson's successor as head of the "Skunk Works") qualified as being a "bypass jet engine by air withdrawal".


Rich did not work for Pratt and Whitney who made the engine and who call the J58 a turbojet engine.

Further, Rich does not refer to the J58 core, he refers to the system as a "bypass jet engine by air withdrawal".


KA3B  [Life Member]
6/11/2008 10:27:10 PM EST
aerostories.free.fr/technique/J58/J58_01/page10.html
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