F-15 "Variable" Inlets

[pauldy]

I know the F-15 Inlets sort of droop down when on the ground and such and it is automatic...

 

I'm just interested to know what flight conditions would make the inlets droop down or go fully up..

 

Thanks ^

Edited September 6, 2010 by pauldy

[mvsgas]

http://www.f-15e.info/joomla/en/technology/engines/100-air-inlets

[pauldy]

Oh i see ^

 

So the Ramps go fully up or down depending on the Airspeed or AoA.

 

btw, are ramps designed to make the air going into the engine slow down into subsonic speeds when the aircraft is flying beyond mach 1?

[mvsgas]

Oh i see ^

 

So the Ramps go fully up or down depending on the Airspeed or AoA.

 

btw, are ramps designed to make the air going into the engine slow down into subsonic speeds when the aircraft is flying beyond mach 1?

 

Yes, notice than most aircraft that can achieve high speed flight (Mach 1.5+) have variable intakes. Come to think of it, I only know two modern aircraft that can reach those speed and do not have a variable intake, the F-18 and the F/A-18.

[pauldy]

I think the Super Hornet inlet seem to "curve" or some sort of "zig zaging" inside.. Judging from some pics i saw around the net..

I don't know about the Legacy Hornets though.

 

I also thought the F-16 has a simple inlet..

 

So it also has some variable ramps inside?

[mvsgas]

No, that is what I meant in my previous post. F-16 and F/A-18 do not have variable intake.

[Exorcet]

F-22, F-35, F-111 are not variable if I remember.

[Avilator]

You can add the F-22 and F-35 to that list as well, no?

EDIT: argh, beaten to it.

[mvsgas]

Not sure about 22 or 35 but the 111 had variable intake, at least some of them, look at 02:26

Edited July 27, 2018 by mvsgas

[EtherealN]

I think the Super Hornet inlet seem to "curve" or some sort of "zig zaging" inside.. Judging from some pics i saw around the net..

 

That is most likely primarily about hiding the turbine blades from enemy radars, since exposed turbines make up a surprisingly large fraction of the radar return. Ensuring that an enemy radar cannot get a direct echo from a turbine is an instant and massive radar cross section reduction.

 

You'll see the same feature with the russian PAK-FA.

[Exorcet]

The video says that moving cowl was deleted, also, I don't think it was for control of shockwaves, but I'm not sure. The inlet spike dealt with supersonic flow.

 

Also add to the list the B-1B and YF-23.

[Blaze1]

Not sure about 22 or 35 but the 111 had variable intake, at least some of them, look at 02:26

 

Nice post mvsgas. I've never actually seen any footage of the inlet spike in action. The actuation mechanics look quite complex and in motion its almost as if the device is breathing.

[mvsgas]

Yes, notice than most aircraft that can achieve high speed flight (Mach 1.5+) have variable intakes. Come to think of it, I only know two modern aircraft that can reach those speed and do not have a variable intake, the F-18 and the F/A-18.

Well I did not think that one through, did I? :doh: (Dam you Dos XX! :drunk::puke:) Does the JAS-39 have variable intakes?

How bout the Tornado, Rafale and Typhoon?

Edited September 8, 2010 by mvsgas

[Avilator]

IDK about the first two, but the Typhoon has a movable lower lip that moves down at high AoA.

[GGTharos]

The F-22 has variable inlets ... they're not not 'traditionally variable', ie. there has been talk of using means other than physically moving ramps to shape the airflow.

[Exorcet]

Correct me if I'm wrong, but isn't that just an unconfirmed rumor at this point? And wouldn't non moving manipulation still be a fixed intake (semantics battles are always fun).

 

I think Avilator is right on the Typhoon.

 

The Tornado's intakes themselves don't move, but there is a ramp inside them I think, like the Concorde.

 

The Crusader III might have been another fixed intake plane. That's a guess though.

[GGTharos]

I'm not convinced it can be much an 'unconfirmed rumour' when the engines maintain the thrust to supercruise without afterburner at altitude and mach >1. I'd say there is DEFINITE pressure recovery happening.

[Avilator]

The F-22 has variable inlets ... they're not not 'traditionally variable', ie. there has been talk of using means other than physically moving ramps to shape the airflow.

 

Are you referring to something like shape-shifting materials without hinges?

[GGTharos]

No. I don't know -how- they do it, someone has theorized that they might be blasting air out to form a wall (of air) or using sound to accomplish the same thing.

 

Are you referring to something like shape-shifting materials without hinges?

[Avilator]

Ahh, OK. Using the streams of air sounds reasonable. Using sound seems interesting.

[pauldy]

What would happen if the air the hits the fan blades are supersonic anyway?

 

compressor stalls or so? Sorry for my poor aviation knowledge^

[mvsgas]

No. I don't know -how- they do it, someone has theorized that they might be blasting air out to form a wall (of air) or using sound to accomplish the same thing.

 

Sorry trying to understand this, What are you referring to?

[mvsgas]

What would happen if the air the hits the fan blades are supersonic anyway?

 

compressor stalls or so? Sorry for my poor aviation knowledge^

 

The way I understand it, the ramps help control the airflow to the engine to improve first stage compression (N1) and minimize possibility for a stagnation or stall ( stall is a nor recoverable stagnation, RPM will decrease, temperature will increases and can cause engine failure in many ways ) Look at the F-15, MIG-29, F-4 intakes for example, the airflow has very little obstruction which is good until you look at high speed flight and all the different effect it has on the engine. Some aircraft compensate this by having a specific shape on the intake. This is also desirable since it hides the engine ( to some degree) from radars. Keep in mind that newer engines also have a better control on the airflow by utilizing Inlet guide vanes or Compressor guide vanes and with better and more reliable "FADEC," engine can handle airflow, shock waves and other things better.

Edited September 9, 2010 by mvsgas

[mvsgas]

Some info on jet engines

N8BvtihvZaE

Edited July 27, 2018 by mvsgas

[Avilator]

What would happen if the air the hits the fan blades are supersonic anyway?

 

compressor stalls or so? Sorry for my poor aviation knowledge^

 

Would the vibrations from the shockwaves break blades off?