Flight envelope issue when using Full G Effects

[nannosk]

sorry Phil_c6, if i understand you mean that at low speed the F15 simulated in lomac lose 10° of aoa confronted to the real F15C????

[Pilotasso]

Isnt that affirmation a litle off any context? I mean less 10º AOA in wich circunstances? People I fly with say the f-15 in lomac can turn with exagerated AOA already so whats the deal here?

[Cobra360]

Unless you ask a RL F-15 pilot to go and test the flight model for us. Anybody know one?

[D-Scythe]

The AoA limit of the F-15C is 30 degrees. And I don't think AoA deviates as much as other aspects of the FM like g-limit, ITR and STR in different portions of the flight envelope...it might, but I'm not sure.

[GGTharos]

Isnt that affirmation a litle off any context? I mean less 10º AOA in wich circunstances? People I fly with say the f-15 in lomac can turn with exagerated AOA already so whats the deal here?

 

 

The F-15C is supposed to have excellent low-speed AoA performance. Not quite lik the Su-27, but more than enough to make F-16 drivers dislike fighting the 15 in that regime.

[169th_Crusty]

Hi

The low AOA of the F15 in Lo (it seems about 10° of less than the real) is the second reason ;-)

 

Have a good day @+

 

Are we talking degrees or units? ;)

[LiquidFuse]

The F-15C is supposed to have excellent low-speed AoA performance. Not quite lik the Su-27, but more than enough to make F-16 drivers dislike fighting the 15 in that regime.

 

Hi GGTharos,

 

I'm sorry, could you provide a source I can read that would support that statement?

 

Nearly every source I have says otherwise, with the Eagle lacking in low speed / high AoA maneuverability due to the absence of automatic flap lowering like in the Super Hornet. Also, if you take notice on the Eagle's design, you can come to the conclusion that its shape is not for a high lift/drag scenario, but completely the opposite. The Eagle was aparently designed to reach Mach 2+ sacrificing wingspan, thus sacrificing low speed maneuverability. The Eagle's wingspan as FAR shorter than that of the Flanker.

 

I cannot produce where I found the following, but I remember hearing (or reading) that USAF pilots train exceptionally hard to withstand high G's for very prolonged periods of time since it is critical to extract the last ounce of turning performance out of their fighters. Most USAF fighters turn at the 350-450 KIAS range - definitely not a slow speed realm.

[GGTharos]

No, you'll have to go look for someone who's seen'em fight or one who has been in such a fight - that's what I did, basically.

 

 

And no, your assumption about the design is wrong - the F-15 has a lifting body, which gives it better AoA handling at low speeds than the F-16. Wing SPAN has nothing to do with it. Lifting AREA is what it's all about, specifically, wing loading, which is weight/lifting area, which should explain why the flanker's wings HAVE to be as large as they are (and incidentally, it also has a lifting body)

 

The Flanker has slightly lower wing loading than the F-15, which is why it has better AoA performance and better instantaneous turn rate at speed.

[Weta43]

According to Leafers link from a pilot transfered from F18-s to F16-s (good link - worth reading if you haven't) the F16 is electronically limited to a 25 degree maximum angle of attack clean, & 15 degrees with a full loadout. It's not a slow dogfighter.

[britgliderpilot]

(flicks through thread, slowly)

 

 

So Fuse thinks the advanced G-model blacks out too soon?

 

9 pages to establish that . . . . christ :p

 

It's not a flight envelope issue at all, is it?

[Pilotasso]

whats your personal experience in G sufference?

[britgliderpilot]

whats your personal experience in G sufference?

 

Rather limited - and I don't wear a G-suit. Bit complicated for a glider :p

 

 

I do know that while flying aerobatics with an instructor, I greyed out at an indicated 5 and a half G . . . . . that was sustained for only a few seconds.

With a G-suit plus training in how to deal with heavy G's, should be able to deal with it much better.

 

 

There may indeed be issues with the G-model (in fact I think it's likely), but what we have here appears to be a lot of pomposity and chart-fapping more often found on Ubi's Il-2 forums . . . . . .

[mikoyan]

take a look of the eagle wings they use the <wascout> design

[LiquidFuse]

There may indeed be issues with the G-model (in fact I think it's likely), but what we have here appears to be a lot of pomposity and chart-fapping more often found on Ubi's Il-2 forums . . . . . .

 

You're absolutely right. LOL

 

The only reason I began to do my own research was to prove some of my arguments once they were being disregarded simply as "bad flying".

 

A track was posted afterwards that proved otherwise.

 

The flight envelope issue is with the F-15C's inability to sustain a turn at its turning speed of 350 KIAS. I'm sure I don't need to explain further for you to realize that the current G-model does not allow for a sustained turn at this speed for more than a few seconds.

 

Hence, the result is always a slow speed fight for all aircraft with A-LOC occuring at as little as 5 G's...F-15C forced to fight at 280-250 KIAS, where its turn rate is slower when compared to the flanker.

 

The length of this thread is due the continued debate after ED "representatives" felt it was more prudent to defend the model at all costs before accepting the possibility that it was overdone in some areas.

 

Cheers.

[Pilotasso]

Liquid I realy understand what your saying and I agree. G modeling seems a bit too pessimistic IMHO. But lets wait for the patch, the DEV's read our posts and hopefully our virtual endurance wont be as bad as our own IRL (felt unconfortable at 4 G's already) ;)

 

I would like to try full amniotic fluid G-suits. The problem would be you cant speak with them, but I'de like to know how a 20 G turn feels like. :D

[KILSEK]

Hi all.

 

Liquid I realy understand what your saying and I agree. G modeling seems a bit too pessimistic IMHO. But lets wait for the patch, the DEV's read our posts and hopefully our virtual endurance wont be as bad as our own IRL (felt unconfortable at 4 G's already) ;)

 

I would like to try full amniotic fluid G-suits. The problem would be you cant speak with them, but I'de like to know how a 20 G turn feels like. :D

 

Maybe it's the heat and humidity but I just had the scene from Dr. Strangelove go through my head. :D -KILSEK

[britgliderpilot]

The flight envelope issue is with the F-15C's inability to sustain a turn at its turning speed of 350 KIAS. I'm sure I don't need to explain further for you to realize that the current G-model does not allow for a sustained turn at this speed for more than a few seconds.

 

I'd need to check, but it seems you're complaining that the pilot can't sustain the G-loadings induced by that turn, not that the aircraft can't sustain the turn. Right?

 

As such, it's a G-model issue - not a flight envelope issue. Not being able to sustain a 7G turn without blacking out has jack to do with flight envelopes :p

 

 

 

What kind of turn are you trying to get, anyway? A sustained turn at almost any speed is possible - the G-loading you'll get depends on how tight you're trying to turn . . . . .

[GGTharos]

He's trying to get a sustained corner speed turn.

[Pilotasso]

...without G-lock at 6 G's

[Kula66]

According to what I've heard (and this is 3rd and 4th hand info, but I had no reason to think it false yet) a pilot will recover within about 30 sec completely when unloaded because of the brain being fed oxygen again.

 

Have a search for "MirageCloseCall.mpg" ... I don't know what the G rating he pulled ... but he certainly wasn't with it even by the end of the video!

[LiquidFuse]

I'd need to check, but it seems you're complaining that the pilot can't sustain the G-loadings induced by that turn, not that the aircraft can't sustain the turn. Right?

 

As such, it's a G-model issue - not a flight envelope issue. Not being able to sustain a 7G turn without blacking out has jack to do with flight envelopes :p

 

 

 

What kind of turn are you trying to get, anyway? A sustained turn at almost any speed is possible - the G-loading you'll get depends on how tight you're trying to turn . . . . .

 

The reason I labeled it a flight envelope issue was because the F-15C could not hold a turn at its RL turning speed of 350 KIAS for more than a few seconds. This I stated on numerous previous posts.

 

I can understand why you say it is not a flight envelope issue, but further thought on the subject will prove that the relativity between turning speed and back pressure required to hold that specified speed on the turn will create an almost constant G-load as long as this speed is held constant on a level circle turn.

 

In real life, "turning speed" assumes that the pilot can hold the speed in question for prolonged periods of time, making it possible for him/her to perform a fight in that speed envelope. If the pilot cannot hold the speed, this speed would not be classified as "turning speed". What good is a "turning speed" if you cannot turn in it? :icon_roll

 

The overall flight envelope is based on this.

 

Hence the problem, if the F-15C's turning speed is 350 KIAS, then the pilot MUST be able to hold that turn for prolonged periods of time in order to fight in it.

 

Finally, in real life, USAF pilots who cannot hold 7 G turns are classified with "low G tolerance". Regardless of what some may believe, USAF fighters are speed fighters pulling turns in the 7 - 9 G realm.

 

They train for this, plain and simple.

[britgliderpilot]

The reason I labeled it a flight envelope issue was because the F-15C could not hold a turn at its RL turning speed of 350 KIAS for more than a few seconds. This I stated on numerous previous posts.

 

I can understand why you say it is not a flight envelope issue, but further thought on the subject will prove that the relativity between turning speed and back pressure required to hold that specified speed on the turn will create an almost constant G-load as long as this speed is held constant on a level circle turn.

 

In real life, "turning speed" assumes that the pilot can hold the speed in question for prolonged periods of time, making it possible for him/her to perform a fight in that speed envelope. If the pilot cannot hold the speed, this speed would not be classified as "turning speed". What good is a "turning speed" if you cannot turn in it? :icon_roll

 

The overall flight envelope is based on this.

 

Hence the problem, if the F-15C's turning speed is 350 KIAS, then the pilot MUST be able to hold that turn for prolonged periods of time in order to fight in it.

 

Finally, in real life, USAF pilots who cannot hold 7 G turns are classified with "low G tolerance". Regardless of what some may believe, USAF fighters are speed fighters pulling turns in the 7 - 9 G realm.

 

They train for this, plain and simple.

 

 

I still don't think it's a flight envelope issue. The aircraft *CAN* sustain that turn, and as such seems to be modelled correctly.

 

If the pilot is unable to sustain 7Gs, then the G-model doesn't coincide with the flight envelope of the F15 - but it's the G-model that's wrong, not the F15 flight envelope.

[LiquidFuse]

I agree, under that reasoning.