The plane that never flew America's first Jet fighter

[Larry Wong]

This is a must see, a lot of knowledge   Hope all will enjoy this..

[Douglas Ames]

Neat video, but those British Historians are truely clueless.

[John Stiles]

Best 49minutes I ever spent right there! Historic video; thanx for digging that up and sharing it.

[Larry Renger]

Douglas, why do you make your comment about cluelessness.  I have no knowledge on the subject and would like to hear more.  having worked for aerospace, i know they do a lot of "what if" studies that go nowhere, sometimes in advancing stages for a couple of decades before th concept dies.

Now aerodynamically, from a more current look at what really works, the aircraft does have an incredibly tiny intake duct, tiny exhausts and total lack of sweep.  Supersonic flight would have encountered a total lack of power to get there and ridiculous drag once you got close!  As far as I know, inline jet turbines didn't exsist then.  Look at the profile of the Panther and Cougar jets from a decade later to see what an annular compressor requires for spac.

Thanks, Larry

[Douglas Ames]

Two things.
Air doesn't burn as stated by one historian, fuel does. The oxygen in the air is part of the combustion process.

The air going thru a jet engine's compressor is not supersonic, hence the variable inlets on supersonic planes to slow it to sub-sonic.
The combustor is what generates the thrust by creating pressure and accelerating the gasses back thru the turbine wheel and nozzle.

[Brian Hampton]

Historians aren't necessarily engineers so any minor details such as "burning air" can be overlooked because that's a common mistake. However it's been known since Frank Whittle that a gas turbine can't "burn" all the oxygen. If it did, the engine would melt. I forget the exact figure now but only about 10% of the air coming from the compressor is used for combustion. The remainder is fed through holes in the walls of the combustion chamber for cooling purposes and to be heated to increase pressure. The remaining ~90% of the air (oxygen) can then be made use of with an afterburner which brings its own problems. The AB liner itself needs an exterior cooling airflow so it's riddled with small holes (and usually called a screech liner) but the pressure in the exhaust has to be kept within strict limits or you'll get either a compressor stall (too much back pressure) or catastrophic overspeed (too little back pressure) with an AB turbofan. The pressure is regulated using a variable exhaust nozzle.  Just for interest's sake, if there was a fault in the variable nozzle which allowed it to snap fully open when AB is first selected, the low speed turbine/fan assembly would accelerate at the rate of roughly 100,000 revs per second! A fault similar to that, but no where near as extreme, gave me the biggest fright of my life when doing an engine run on an afterburning turbo fan.

On the inlet side of things, at full power (military or AB) airflow is held at ~500mph at the compressor face. Non variable intakes are good up to a max of around Mach 2 because they're a divergent duct which slows the airflow. Above Mach 2 you need far more complex variable intakes which can close off the intake area but also positions a shock wave at the very front of the duct regardless of the angle of the shock wave at varying airspeed. Air passing through the shockwave slows to subsonic but also increases in pressure.

That's probably too much information to pass on in a historic video of an aircraft design .

[De Hill]

Hi Brian,

Are you a turbine engine mechanic?

[Bill Heher]

Brian,
Nicely done, airflow / pressures / combustion cooling in turbo-fan engines can be baffling to some who are used to re-cip engine power. you wrote a nice concise description.

the program did say he was planning on a axial flow multi-stage compressor, one picture showed what appeared to be "can - annular" combustors, so he was basically headed down the same path we ended up on 'ala JT-3, Early GE's , JT-8, etc. Add the afterburner( if they could make one that could handle the heat/stress) and you have the early military jets, fast, loud, and sucking gas!

I think if he had gotten funding for the engine - the metal and processes available would have taken a lot of advancement and research to make it servicable- same issue the Germans had- shot time on wing and numerous failures. still an enjoyable show- anything with Kelly Johnson involved is worth looking at.

[John Stiles]

That's probably too much information to pass on in a historic video of an aircraft design .

Thanks Brian, That was a very interesting and understandable explanation of the complexities one could expect to encounter in jet engine technology. I especially appreciated the part that "gave you a fright", and might point to why the first jet never got off the ground. Too bad, though!   P/S ya absolutely gotta love afterburners! 

[Brian Hampton]

Are you a turbine engine mechanic?

I was an aircraft engine fitter in the RAAF and did my last 8 years of service working on the F-111's and a lot of that work involved doing what was called a trim, essentially a tune-up, after an engine change or major repair. One thing that may be of some interest is that there's a gadget fitted to the engine called a Mach Trim Actuator. When the aircraft reaches Mach 1.7 (obviously in full AB ) it begins to cut down the fuel supply to the core engine so it starts to act as a partial ram jet.

One side benefit of being an engine fitter and changing an engine was that the aircraft had to do a test flight to check performance. The nav wasn't needed for that but someone had to be in the right hand seat to balance the module in case of an ejection. I got to be ballast a couple of times. Well, except when I took the controls. I'm not sure how fast we went although it was still accelerating significantly when the pilot throttled back but after I thought to look at the Mach speed indicator the needle was just coming back through Mach 2.3

[Douglas Ames]

<snip>
On the inlet side of things, at full power (military or AB) airflow is held at ~500mph at the compressor face. Non variable intakes are good up to a max of around Mach 2 because they're a divergent duct which slows the airflow. Above Mach 2 you need far more complex variable intakes which can close off the intake area but also positions a shock wave at the very front of the duct regardless of the angle of the shock wave at varying airspeed. Air passing through the shockwave slows to subsonic but also increases in pressure.

That's probably too much information to pass on in a historic video of an aircraft design .

That large conical nose cone on a SR-71 moves fore/aft for just that reason.
If you noticed, the Engineers presented the techncal info very well.
I still run into people who think Airliners dump their lavs at altitude.

[De Hill]

I was an aircraft engine fitter in the RAAF and did my last 8 years of service working on the F-111's and a lot of that work involved doing what was called a trim, essentially a tune-up, after an engine change or major repair. One thing that may be of some interest is that there's a gadget fitted to the engine called a Mach Trim Actuator. When the aircraft reaches Mach 1.7 (obviously in full AB ) it begins to cut down the fuel supply to the core engine so it starts to act as a partial ram jet.

One side benefit of being an engine fitter and changing an engine was that the aircraft had to do a test flight to check performance. The nav wasn't needed for that but someone had to be in the right hand seat to balance the module in case of an ejection. I got to be ballast a couple of times. Well, except when I took the controls. I'm not sure how fast we went although it was still accelerating significantly when the pilot throttled back but after I thought to look at the Mach speed indicator the needle was just coming back through Mach 2.3

I spent a few years working on the General Electric CF-6 family of engines. The variants were the CF6-6, -6K, -50 and -80. They were used on DC-10's ,767's and A-300's.
Airliners do not use afterburners. (the SSt is retired) They commonly use a large fan which is turned by a long driveshaft which is powered by the low pressure turbine. The fan provides 75 to 78% of the total engine thrust.

[ChrisSarnowski]

Good video, thanks for sharing!!!

-Chris

[Chris McMillin]

That large conical nose cone on a SR-71 moves fore/aft for just that reason.
If you noticed, the Engineers presented the techncal info very well.
I still run into people who think Airliners dump their lavs at altitude.

And the chemtrails.
Chris...

[John Sunderland]

Love the profile of the fuselage. From a stunt perspective, there are ideas to be taken advantage of here. To bad the canard configuration wont work.