Do fighter jets have a Vne?

[bunk22]

btw,

Thanks to all you pros who put up with people like me.


I read your replies and get humbled very quickly.

thanks so much.

The pro's respond to you because we just like seeing your avatar over and over....well...I do

 

[BobDDuck]

From your post (and others), it seems that Vne is a bit of a dumbing down of the factors involved in general aviation (I never got a c-172 up to Mach 2--tried--but the best I could do with a 40 knot tailwind was 170 kph).

Behind Vne is our beloved Load Factor and I am thinking that is the key point; or am I missing something?

Awesome post, btw

Kind of...

Vne is simply a test speed at which bad things could start happening. You could theoretically hit Vdive at 1 g and not be worried about load limits at all. Same thing with Vne (as it is just a percentage of Vdive) so while load limits certainly play a factor, the bigger concerns related to Vne are probably related to stuff just getting ripped off the side of the plane and maybe potential harmonic damage from vibration.

As far as the OWS, my understanding is that it simply provides an load envelope to operate in based on the aircraft load out. Your speed doesn't play a factor into any of that until you start loading and unload Gs on to the airframe and even then, the only relationship is that at a higher airspeed a set maneuver (such as a pitch change or turn) may be at a higher G level.

 

[Roger, Roger]

True, and situation dependant. In my former business, the times it would help you were far outweighed by the times it could kill you if your mind was spending any brain bytes on it.

You don't have time to think. You think, you're dead.

 

[Hacker15e]

As far as the OWS, my understanding is that it simply provides an load envelope to operate in based on the aircraft load out. Your speed doesn't play a factor into any of that until you start loading and unload Gs on to the airframe and even then, the only relationship is that at a higher airspeed a set maneuver (such as a pitch change or turn) may be at a higher G level.

The OWS actually does factor in speed -- at a higher speed, there is less G available because of other airframe stresses (and the G onset rate will be faster, imparting greater stress on the various parts of the aircraft). There is an area of the operating envelope that we call "the thumbprint" (because of how it looks in the chart in the manual -- shaded with crosshatched lines that sorta look like a thumb-print) where allowable G is reduced due to airspeed.

The F-15E displays max G allowable in the HUD as calculated by the OWS. This is 9.0G for the vast majority of the time you're flying around, but when you get fast - somewhere in the neighborhood of 500 KCAS and above - that displayed max allowable G begins to reduce.

 

[TUCKnTRUCK]

Again, I've had the Eagle running all out, full burner, unloaded acceleration....starting over the Mach up in the 30s, and pushing the nose over to accelerate as fast as I can get it....and still not gotten close to max Mach or KCAS.

Just wondering, are you guys running de-rated right now? or are you still at max. rated thrust? I "thought" I remembered reading that you guys derate during non conflict to save mx etc. (when have we not been in conflict right?)

 

[Hacker15e]

What Ive been trying to tell people in the CFI Forum here for a long time. There's "need to know" information, and there's "nice to know" information.

To be fair, there is a huge segment of the pilot population that has never had to fly an airplane AND use it as a weapon. They don't know what kind of knowledge and mental intensity it takes in and of itself to employ an aircraft as a weapon, so it's simply outside their sphere of understanding why a pilot wouldn't need/want to know that ultra-techy "I read it in the Aerodynamics For Naval Aviators book" stuff.

I found this to be one of the biggest stumbling blocks for new students in IFF. They were nearly always quite able to handle the demands of jockeying the T-38 safely from point A to B, perhaps in formation, and perhaps at low level. Once you started throwing in having to do all that, AND:

- know your own tactics
- know the bandit tactics
- know how your own weapons work and are employed
- know how the bandit's weapons work and are employed,

...and then having to actually EXECUTE your own tactics and weapons employment while dynamically responding in real time to bandit weapons and tactics (and all under the physiological strains of G forces)....well, that was an entirely new level of mental concentration that they'd never had demanded of them before.

I've seen some incredibly smart and talented young aviators come through that program as students and not be able to hang with all those demands. My bet is that many of the civilian pilots on this board would be surprised at the knowledge level required on the ground (like having to know how the AMRAAM works at the very same detail level that you have to know how your own airplane works), plus the difficulty intensity of applying that knowledge in flight. I also bet that those same folks might think differently if they experienced some of that.

I've rather enjoyed (in a somewhat sadistic way) teaching people to both fly and fight with the T-38 for exactly these reasons. The T-38 is a fantastic trainer in that regard -- an equal-opportunity embarrasser!

 

[Hacker15e]

Just wondering, are you guys running de-rated right now? or are you still at max. rated thrust? I "thought" I remembered reading that you guys derate during non conflict to save mx etc. (when have we not been in conflict right?)

Yes, the engines do run slightly de-rated, but in the F-15E there is a switch you can throw in the cockpit (the 'V-MAX' switch with the PW-220 engine) that cranks up the FTIT and allows that extra thrust.

 

[TUCKnTRUCK]

Yes, the engines do run slightly de-rated, but in the F-15E there is a switch you can throw in the cockpit (the 'V-MAX' switch with the PW-220 engine) that cranks up the FTIT and allows that extra thrust.

Interesting... we have an over travel region which runs the engines up to max rated (133%?) but... we also have a system that tells on us seeing how fast it would go just isn't worth the carpet dance. (especially because it still isn't that fast. It would be like drag racing a prius)

Do you have thermal heating concerns? or do you run out of gas before you would suffer any heat damage from prolonged runs at high speed?

 

[Springer]

Do you have thermal heating concerns? or do you run out of gas before you would suffer any heat damage from prolonged runs at high speed?

The F-4 had a 750KIAS or Duct HI Temp light whichever came first limitation. No Mach limits.

 

[beasly]

To be fair, there is a huge segment of the pilot population that has never had to fly an airplane AND use it as a weapon. They don't know what kind of knowledge and mental intensity it takes in and of itself to employ an aircraft as a weapon, so it's simply outside their sphere of understanding why a pilot wouldn't need/want to know that ultra-techy "I read it in the Aerodynamics For Naval Aviators book" stuff.

I found this to be one of the biggest stumbling blocks for new students in IFF. They were nearly always quite able to handle the demands of jockeying the T-38 safely from point A to B, perhaps in formation, and perhaps at low level. Once you started throwing in having to do all that, AND:

- know your own tactics
- know the bandit tactics
- know how your own weapons work and are employed
- know how the bandit's weapons work and are employed,

...and then having to actually EXECUTE your own tactics and weapons employment while dynamically responding in real time to bandit weapons and tactics (and all under the physiological strains of G forces)....well, that was an entirely new level of mental concentration that they'd never had demanded of them before.

I've seen some incredibly smart and talented young aviators come through that program as students and not be able to hang with all those demands. My bet is that many of the civilian pilots on this board would be surprised at the knowledge level required on the ground (like having to know how the AMRAAM works at the very same detail level that you have to know how your own airplane works), plus the difficulty intensity of applying that knowledge in flight. I also bet that those same folks might think differently if they experienced some of that.

I've rather enjoyed (in a somewhat sadistic way) teaching people to both fly and fight with the T-38 for exactly these reasons. The T-38 is a fantastic trainer in that regard -- an equal-opportunity embarrasser!

fwiw, I just downloaded that Aerodynamics for Naval Aviators in pdf format here: http://www.askacfi.com/3219/aerodynamics-for-naval-aviators-pdf.htm (now to get it on my Kindle....)

On the rest of your post...man, I am jealous and a bit mad at myself! Misdirected youth and all that.

 

[MikeD]

To be fair, there is a huge segment of the pilot population that has never had to fly an airplane AND use it as a weapon. They don't know what kind of knowledge and mental intensity it takes in and of itself to employ an aircraft as a weapon, so it's simply outside their sphere of understanding why a pilot wouldn't need/want to know that ultra-techy "I read it in the Aerodynamics For Naval Aviators book" stuff.

I found this to be one of the biggest stumbling blocks for new students in IFF. They were nearly always quite able to handle the demands of jockeying the T-38 safely from point A to B, perhaps in formation, and perhaps at low level. Once you started throwing in having to do all that, AND:

- know your own tactics
- know the bandit tactics
- know how your own weapons work and are employed
- know how the bandit's weapons work and are employed,

...and then having to actually EXECUTE your own tactics and weapons employment while dynamically responding in real time to bandit weapons and tactics (and all under the physiological strains of G forces)....well, that was an entirely new level of mental concentration that they'd never had demanded of them before.

I've seen some incredibly smart and talented young aviators come through that program as students and not be able to hang with all those demands. My bet is that many of the civilian pilots on this board would be surprised at the knowledge level required on the ground (like having to know how the AMRAAM works at the very same detail level that you have to know how your own airplane works), plus the difficulty intensity of applying that knowledge in flight. I also bet that those same folks might think differently if they experienced some of that.

I've rather enjoyed (in a somewhat sadistic way) teaching people to both fly and fight with the T-38 for exactly these reasons. The T-38 is a fantastic trainer in that regard -- an equal-opportunity embarrasser!

+2 on IFF. And on the T-38; although I only flew the A-model in UPT as well as at HMN. Don't know if the C-model makes anything easier.

 

[TUCKnTRUCK]

The F-4 had a 750KIAS or Duct HI Temp light whichever came first limitation. No Mach limits.

oops.. I meant thermal heating of the plane/structure not so much the engine I guess, are there any adverse effects on the plane from prolonged flight at maximum speed, aside from burning out a motor.