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Lightning inlet cone


Max89
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I've come to learn that the inlet cone was actually movable on many cold war aircraft, and that it'd move forward or backward depending on the airspeed.

 

Did any of the Lighting variants have a movable cone? Or was it fixed/immovable?

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This was a superior feature on the SR-71 but I am unsure if any other aircraft used it (to the extent of the blackbird at least, there may have been test aircraft built with a similar feature?)  Interested to learn more. 

 

Edited by phat trev
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IIRC the Lightning nose cone was fixed, that makes the type unusual since others aircraft with the same intake configuration had moving cones to optimize the intake area when speed varies: the MiG-21 and the Su-7/9/17 all featured moving cones (with the exception of the latest Su-17 variants).

A similar concept was used on all Mirages, where the half-cones moved to change the intake section.

 

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It is indeed really odd that the EE Lightning had a fixed/immovable cone. I would've thought that this was a necessity for any aircraft that exceeded mach 1.

 

Was this the case for all variants?

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To the best of my knowledge the Lightning shock body was immovable on all variants and I don't think the geometry was changed for any of the operational marks. The original English Electric PI had no inlet body, but much lower power engines, The P1B did have a central shock body and higher power engines, I think. Presumably the necessary trials were done to attain the optimum compromise during P1B flight trials?

 

Given the low fuel capacity of the original Lightning, possibly the thinking was that a movable body would add much complexity for very little return. Short duration dashes only.

 

Edited by John B (Sc)
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Hallo

But somehow the speed of sucked air  must have been controled anyway. No matter how. Each turbine gets immediatly a stall and flame our if she sucks supersonic air. No matter if the cone was this or that.

Happy modelling 

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1 minute ago, dov said:

Hallo

But somehow the speed of sucked air  must have been controled anyway. No matter how. Each turbine gets immediatly a stall and flame our if she sucks supersonic air. No matter if the cone was this or that.

Happy modelling 

Id imagine that each engine had inlet guide vanes ....im ex AV but im sure a grubber(dirty stinkin')can elaborate further😆but seriously IGVs ensure the air enters the the compression stages and the combustion chamber nice and smooth 

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The Lightning didn't have a movable inlet cone, nor (to the best of my knowledge) did any of it's unbuilt derivatives. For that matter there are plenty of contemporaries that also didn't bother, another good example being the Bristol 188. I suspect that in the Lightning's case, the cone was simply fixed far enough forwards that at all the expected inlet speeds the air would have formed sufficient shocks to become subsonic. It's probably slightly less efficient on paper than a movable one, but unlikely to be a significant issue across the kind of speed ranges the Lightning sees.

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Quote

But somehow the speed of sucked air  must have been controled anyway. No matter how. Each turbine gets immediatly a stall and flame our if she sucks supersonic air. No matter if the cone was this or that.

Happy modelling 

The item your referring to as a "shock cone" was actually called the Radar Bullet it was fixed and only removed when the radar was in need of attention. The intake shape aft of the bullet reduced under the cockpit and then opened out slowing the air down, a couple of feet in front of the No1 (Lower Engine) were around 8-10 (4-5 each side) Vortex Generators these gave a rotation to the air mass allowing the No2 (upper) engine an air flow.

 

I was always told the intake design and the fact the engine has IGV's (inlet guide vanes) allowed the air to enter the engine at an acceptable speed. from my time on type I don't recall many engine surges unlike tornado and Jaguar.  

Edited by tweeky
typo
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2 minutes ago, tweeky said:

 

1the item your referring to as a "shock cone" was actually called the Radar Bullet it was fixed and only removed when the radar was in need of attention. The intake shape aft of the bullet reduced under the cockpit and then opened out slowing the air down, a couple of feet in front of the No1 (Lower Engine) were around 8-10 (4-5 each side) Vortex Generators these gave a rotation to the air mass allowing the No2 (upper) engine an air flow.

 

I was always told the intake design and the fact the engine has IGV's (inlet guide vanes) allowed the air to enter the engine at an acceptable speed. from my time on type I don't recall many engine surges unlike tornado and Jaguar.  

See....told it like an AV 🤣🤣🤣

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4 hours ago, Max89 said:

It is indeed really odd that the EE Lightning had a fixed/immovable cone. I would've thought that this was a necessity for any aircraft that exceeded mach 1.

 

Was this the case for all variants?

 

A lot of supersonic aircraft feature fixed intakes. Really variable geometry intakes are needed to improve the efficiency of the system and become important over M2. For example the F-15 features variable geometry intakes while on the F-16 it was decided to save the cost and weight of such a system and limit the speed to M2

 

4 hours ago, dov said:

Hallo

But somehow the speed of sucked air  must have been controled anyway. No matter how. Each turbine gets immediatly a stall and flame our if she sucks supersonic air. No matter if the cone was this or that.

Happy modelling 

There's no need for a variable geometry intake to slow down the air to subsonic, this is achieved mainly through the shock wave (or waves) generated by whatever surface is used for the purpose and through the design of the intake duct (like in convergent divergent duct). In the case of the Lightning there would likely be at least 2 shock waves, one generated by the tip of the radome and the other by the intake lip. From then down air would enter a convergent-divergent duct. A variable geometry intake is of course more efficient as can better control the flow and also avoid that a shock wave enters the intake if the duct is not designed for such an event.

 

3 hours ago, ChocolateCrisps said:

The Lightning didn't have a movable inlet cone, nor (to the best of my knowledge) did any of it's unbuilt derivatives. For that matter there are plenty of contemporaries that also didn't bother, another good example being the Bristol 188. I suspect that in the Lightning's case, the cone was simply fixed far enough forwards that at all the expected inlet speeds the air would have formed sufficient shocks to become subsonic. It's probably slightly less efficient on paper than a movable one, but unlikely to be a significant issue across the kind of speed ranges the Lightning sees.

 

Not an expert on the Lightning itself but I suspect that a compromise was made with an intake capable of serving well enough through the various speed ranges. I'd expect such an intake to be optimised for a certain speed accepting lower efficienty at all others.

We should also keep in mind that some of the effects of a variable geometry intake can be achieved through other systems capable of altering the flow in the duct

 

2 hours ago, tweeky said:

 

The item your referring to as a "shock cone" was actually called the Radar Bullet it was fixed and only removed when the radar was in need of attention. The intake shape aft of the bullet reduced under the cockpit and then opened out slowing the air down, a couple of feet in front of the No1 (Lower Engine) were around 8-10 (4-5 each side) Vortex Generators these gave a rotation to the air mass allowing the No2 (upper) engine an air flow.

 

I was always told the intake design and the fact the engine has IGV's (inlet guide vanes) allowed the air to enter the engine at an acceptable speed. from my time on type I don't recall many engine surges unlike tornado and Jaguar.  

That would be the convergent-divergent duct: a supersonic fluid will decelerate whenever the section in a duct decreases, contrary to what happens to a subsonic fluid. Ideally the air would reach M1 at the point of minimum section (known as throat), from then on the now subsonic fluid will decelerate further as the section increases.

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Hallo

If you have a geometricaly constant air intake, the air speed reduction is done by clever arranging the shock waves. By whatever means.

At each time, the first compressor stage MUST get at about 0.8 Mach or lower. Otherwise it is a flame out.

That is life.

The flying envelope is more restricted than.

Happy modelling 

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6 minutes ago, exdraken said:

Talking about efficiency: the Lightning is not known for fuel efficiency at all... maybe also the intake compromise is to blame for that...

Not so much an efficiency issue, more a lack of space for fuel, but given its intended role as a point defense aircraft range was never really a big consideration. 

John

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3 hours ago, canberra kid said:

Not so much an efficiency issue, more a lack of space for fuel, but given its intended role as a point defense aircraft range was never really a big consideration. 

John

hmm .. I might have had it wrong here!

 

but fuel quantity/ fuel burn definitely was an issue with all Lightnings... 

 

thinking a second time, an inefficient air-intake will limit airflow... and therefore limit engine power/ aircraft speed... in the high power settings..

but on the other hand, an inefficient air intake also has more losses when converting the air's speed in the intake into pressure before the actual engine compressor... therefore being less efficient engine intake combintion leading to a higher fuel consumtion, no?  

 

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The Lightning as a whole was designed to wring maximum efficiency from the available engines, initially the Armstrong Siddeley Sapphire, in order to achieve a fully supersonic performance, ultimately Mach 2 plus.  To achieve this intake duct design was crucial and it was optimised for the top end of the performance envelope.  

 

As a moveable shock cone was impractical on the grounds of weight, complexity and/or cost the relationship between the tip of the radome and the lip of the intake ring was vital as these created the initial shock waves which begin slowing the supersonic air flow to a speed acceptable to the engine compressors.  Further shock waves were created by the nosewheel bay and radome support structures and by the convergent/divergent form of the intake duct.  A final shock wave was created by the leading edge of the wing centre section where the duct splits to serve each engine independently.  Immediately aft of the bottom trailing edge of the nosewheel bay are a set of vortex generators (not inlet guide vanes) to energise the airflow along the lower surface of the intake duct .

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Immediately aft of the bottom trailing edge of the nosewheel bay are a set of vortex generators (not inlet guide vanes) to energise the airflow along the lower surface of the intake duct .

Each Avon 302 engine was equipped with IGV's. As for the Vortex Generators the slightly further back then you quote.

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12 minutes ago, Bozothenutter said:

The Coremans book has a close-up, the caption calls  it kevlar, certainly looks like it to me.

 Kevlar wasn't invented until 1965 and Wikipedia states the first commercial use as early 1970's. Given that the Lightning had entered service in 1960, it seems unlikely.

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