F-15 still pulling 14G with two bags and no damage

[GGTharos]

I didn't do it at 600kts myself, but I supposed I'd find it useless - you wont't see any damage on the real thing either, but it'll be there. If you're hauling bags it should break apart, everyone's on-board with that :)

 

My question is, where here are you pulling some kind of 12g tracking shot?

 

There are reasonably well known 12g events on f15 airframes. One lasting several seconds (dive pull-out at 12.5g), one a transient similar (but don't know if the same) to yours, the pilot got excited and made a hard pull to enter combat. In the first one, the airframe was written off, in the second, returned to service.

 

I go by the g-meter in the F2 view. Tacview will show a little less G because it averages over a relatively long period of time.

[Esac_mirmidon]

If the real F-15 can sustain 12G repeatedly like in my ACMI, at 100% fuel with 8 missiles i dont have anything more to say. Im not arguing about shoots. Only aircraft resistance.

 

So in conclusion Su-27 is breaking in pieces always the very first time you push more than 8 G. Like the real aircraft limits.

 

The F-15 can sustain 12 G repeatedly without breaking in pieces because in real life the aircraft is like that.

 

Over.

[GGTharos]

If the real F-15 can sustain 12G repeatedly like in my ACMI, at 100% fuel with 8 missiles i dont have anything more to say. Im not arguing about shoots. Only aircraft resistance.

 

Who knows, the 12.5g F-15 was lighter almost for certain, the other as well. And in any case, it would have to take a trip to the depot at that level of over-g.

 

So in conclusion Su-27 is breaking in pieces always the very first time you push more than 8 G. Like the real aircraft limits.

It shouldn't with a light flanker, you should be able to exceed 9g.

 

The F-15 can sustain 12 G repeatedly without breaking in pieces because in real life the aircraft is like that.

 

Over.

Sustain, no, and no one sustains that. An F-15 full of fuel and with bags should break up, and there's a real incident of that, too.

Also realize that the F-15's official 9g design limit is at a weight that's just a few hundred KG heavier than an empty flanker. They're just very, very different airframes.

Edited April 2, 2017 by GGTharos

[Esac_mirmidon]

So its safe to say that the F-15 in DCS has a higher tolerance to overstress at high G, than the real frame and ideally It must be tunned down?.

 

And the Su-27 is closer modelled to the real airframe limits?

[GGTharos]

Actually it doesn't have any tolerance ... since the DM just doesn't exist. And didn't we say that we all agree that one should be applied?

 

The disagreement is on whether it causes a tangible advantage. All of the scenarios where this could be a (minor) issue are artificial.

 

Scenarios where it should be catastrophic are even more artificial.

 

I don't know about the Su-27, Yo-Yo knows better and as stated, the SU-27 conforms to limits from the manual - ie. breaking after 150% over-g.

 

 

So its safe to say that the F-15 in DCS has a higher tolerance to overstress at high G, than the real frame and ideally It must be tunned down?.

 

And the Su-27 is closer modelled to the real airframe limits?

[esb77]

Really this all argument boils down to, "which plane misbehaves less when I try to rip my stick out of it's base?"

 

 

The crankiness is based on the premise that in DCS the F-15 is excessively idiot friendly while the Su-27 is a bitch that will kill you if you don't court it with champagne, caviar, and fine chocolate.

 

There's a grain of truth to this. American engineers are a bit more inclined to pamper the end user (and also to assume that the end user is an incurable idiot).

 

 

Mostly though, this is a matter of how the idiot resistant features in the respective planes work.

 

In the F-15, it's largely based on the idea that if you try to tell the plane to do something excessively stupid, the plane is either strong enough to take it or just ignores your stupid inputs. This translates very well into a computer game.

 

In the Su-27, if you start being excessively stupid in similar ways, the plane starts trying to swing a stick around pretty hard to get the pilot's attention. Specifically, the control stick. There is some limiting of execution of control inputs, but mostly it's a matter of alerting the pilot through the flight controls rather than overriding the pilot's control of the flight. This does not translate well into a purely software based representation. It would work much better as output for a force feedback stick coupled with a force feedback stick that has some pretty strong actuators.

 

ED isn't being unfair to Flanker users, the Flanker users are just failing to upgrade their input hardware to be fully compatible with a Flanker simulation.

 

I'm saying that from a position of the Flanker being my favorite plane (at least until the Hornet comes out).

 

If everyone built and flew from a full fidelity pit with a properly calibrated FFB stick, I don't think there would be much griping about the Flanker being unruly around the edges of its envelope.

 

 

The flight models are a continuous WIP for ALL the modules, and probably everyone posting in this thread knows that.

 

For the simulation improvement, sure the F-15 model might be able to use a more realistic damage model for g overstress, but not nearly as much as the cranky Su-27 users need to get better input hardware.

 

The Flanker communicates to the pilot by swinging a stick at them, if your stick doesn't do that then if you want a better Flanker simulation then you need a more lively stick.

[Falcon_S]

http://www.f-16.net/forum/viewtopic.php?t=10663

Real-life is not a video game or a oversimplified textbook. G limits are not a constant. The G. limit of an aircraft can vary widely depending on the (payload) load out, amount of fuel, etc…

ATFS is 100% correct. You can over "G" a 16 with 4 g's .....it's depends on how it is configured and where the fuel is. If you have 370 tanks full and pull 7 G's you would be lucky to still have wings..........

After having failed miserably with the engine fan blade discussion, I’m going to take this on anyway. The G limit question is both complex and simple at the same.

 

If you are talking aircraft “performance”, then G limits are a function of many of the previously described factors, primarily configuration and weight. But generally, the aircraft wing will be capable of a specific maximum G available at or above a particular calibrated airspeed. The more speed you’ve got, the more G available. Basically, it doesn’t matter what’s hanging on the airplane, if you have the speed, you’ve got the G available. It may not be a good idea to use it, because it is possible for things to come off of the airplane, including the wings.

 

“Performance” for a particular amount of structural G allowable is a function of how low a speed you can attain the G and Boyd’s “P sub s”, i.e., in what geometric plane you can or can't sustain it.

 

But on the simple side, there is only one “maximum” G limit under whatever the optimum conditions for that aircraft to achieve this limit happen to be (air-show config?). Clean configuration, lower gross weights, symmetrical application of control inputs, etc., all contribute to the “biggest” number.

 

U.S. aircraft prior to the F-15 (with one exception) were generally limited to 7.33 G, which is 2/3’s of 11 G which is the structural fatigue limit that was spec’d and tested for those aircraft. After the F-15, they advertised them as 9 G aircraft. I don’t know if they raised the structural fatigue spec to 13.5 G or lowered the buffer to 9/11’s of 11 G.

 

I’m not familiar with the European aircraft, but I suspect structural limits for a particular manufacturing process are probably global.

 

I don’t know the later models, but the F-16A used to have a switch in the cockpit with two positions: Cat 1 & Cat 3. For a given side-stick input, Cat 1 would give you a full up 9 G airplane regardless of weight or configuration. Cat 3 was to be selected in certain configurations that had more restrictive G limitations and the FCC would prevent the pilot from over-stressing the aircraft. It also, evidently, prevented a particular pilot from being able to pull out prior to impact on the Wildcat Range in Utah, because he was following the recommended procedures. I never flew in anything but Cat 1.

 

I always wondered what happened to Cat 2.

 

In the operational world, and according to the booklets, the F-16A will allow up to 9.5 for a short while. If it ever happens I don't know, but the FLCC is not cosidered to have failed if it allows 9.5G. If the HUD indicates that 9.8G has been pulled a structural check must be performed. I saw 9.9G, so the rest of the day was ruined. It later turned out that this was an indication fault on the HUD.

 

From video description:

 

The fact the F-15 held together and was able to land safely is a testament of its durability. I can't remember exactly but it sustained like 15-20 Gs for about 2-3 seconds. For a fraction of a second it pulled something like 30-40 Gs. It held together but the wing skin had crinkled (technical term j/k) because the airframe was bent so badly. Unfortunately I have no external views. It pulled so many Gs that the tape pulled off the recorder head and lost sync for a bit, so the tape misses the highest G.

 

So, yes it is possible but there are always consequences that are not in DCS F-15C. That`s why we all talk here about how ppl use F-15C in DCS without any of consequences.

Edited April 2, 2017 by Falcon_S

[OnlyforDCS]

 

If everyone built and flew from a full fidelity pit with a properly calibrated FFB stick, I don't think there would be much griping about the Flanker being unruly around the edges of its envelope.

 

 

 

I just wanted to chime in on this. The Flanker has a really enjoyable flight model, and I believe this is partly because I own a FFB stick. You get cues through it that you just can't get in a spring loaded stick.

[GGTharos]

The video description is and wrong. This is the video of the 12.5g incident, but you have to dig a bit to find the pilot's description of it.

 

And the reason we talk about how people use the F-15C is because one aircraft breaks, and one doesn't.

 

No one is arguing that the DM shouldn't be there, and no one is saying that lack of consequences is correct.

But no one want to account for the fact that real F-15s have transitioned through 12g and gone back into service, either.

 

So, given that such transients are not only possible, but may also not cause as much damage as some people think (and perhaps more than what some others think) depending on the actual G and amount of time spent with this amount of oveload,

 

The question people consistently fail to answer is:

 

"Does that high-g transient cost you the fight? When, where, and how many times - what GW for the eagle?"

 

Because in reality, the game data to quantify this not only exists, but can be generated through experiment in the game. And I very strongly believe that if it is quantified, you will find that this complaint amounts to mostly nothing.

 

And I will reiterate what is mentioned over and over in this thread, but people want to pretend like the opposite is happening:

 

No one is arguing that the DM shouldn't be there, and no one is saying that lack of consequences is correct.

 

So, yes it is possible but there are always consequences that are not in DCS F-15C. That`s why we all talk here about how ppl use F-15C in DCS without any of consequences.

[GGTharos]

I think we can actually code a poor man's DM with lua just for testing. Since you can read aircraft G in lua and the slope of the over-g is known, it would be simple enough to implement for destroying the aircraft. I don't know if you could implement accumulating damage this way.

 

For pure research purposes you can use tacview to measure g's used and it's possible that GW will be available also (without GW you only get part of the needed data. Not a disaster but less accurate).

 

You can quite literally quantify the effect this has on gameplay to justify fixing this ... or realizing that the effect is none-to-mininal.

 

Me, I'd like to see some other things fixed first, like the control issue, visibility, etc - yes, because I believe that people aren't losing fights because of this so I believe that it is low priority.

[Esac_mirmidon]

But you will agree that carefree handling with the F-15C makes combat much more easier. If you know that it doesnt matter how hard you pull or manouver with the Eagle that gives you much extra time and SA to focus only in combat.

 

Su-27 pilots must combat and take care at the same time about his airframe, G, speed and handling.

[GGTharos]

No, I don't.

I don't fly in a way that this is an issue. In other words, I will always have care-free handing and so will anyone who flies in a half-way reasonable manner.

 

But having said that, this is just speculation on my part, and I'll try to work on this 'poor man's DM' script to try and prove or disprove my theory :)

 

But you will agree that carefree handling with the F-15C makes combat much more easier. If you know that it doesnt matter how hard you pull or manouver with the Eagle that gives you much extra time and SA to focus only in combat.

 

Su-27 pilots must combat and take care at the same time about his airframe, G, speed and handling.

[Esac_mirmidon]

You dont fly that way, but others could do so....

 

Anyway thanks for testing that. Interesting.

[GGTharos]

You are right, but my point is that we're talking about a relatively narrow set of parameters, specifically:

 

- High GW (so lots of fuel, never mind missiles)

- High speed (600kts) to get the g you want

- Full aft stick pull

 

This is my very very basic criteria for breaking the airframe very quickly. Damaging it is another story and IF possible I will implement this also - or rather, I'll replace the whole thing with just damage (the more over-g, the faster damage accumulates - pull enough g and damage accumulates so fast that your aircraft will break right away). I'm only assuming that the LUA environment can provide all this ... so my attempt at making this happen might fail. We'll see :)

 

The above is a bit vague and that's why I want to build the DM, so that we see some real results instead of speculation on everyone's part.1

[Esac_mirmidon]

Thanks again GG, sounds promising.

[captain_dalan]

The crankiness is based on the premise that in DCS the F-15 is excessively idiot friendly while the Su-27 is a bitch that will kill you if you don't court it with champagne, caviar, and fine chocolate.

 

There's a grain of truth to this. American engineers are a bit more inclined to pamper the end user (and also to assume that the end user is an incurable idiot).

 

 

Just wait until the F-14 comes around , and people start crying "foul game" when the jet kills them for trying snap rolls at 250 knots! :joystick::megalol:

Not all birds made in the US are as friendly and docile as the Eagle is. That plane was/is really hard to depart, or do something stupid in it.

 

If everyone built and flew from a full fidelity pit with a properly calibrated FFB stick, I don't think there would be much griping about the Flanker being unruly around the edges of its envelope.

 

........

The Flanker communicates to the pilot by swinging a stick at them, if your stick doesn't do that then if you want a better Flanker simulation then you need a more lively stick.

 

Alas, i lament the day when upgrading to win10 killed the force feedback on my stick. No i have no indication of buffeting and incoming stalls when i fly departable planes in any sim. It's also much harder to "hold" a g in a dynamic and aggressive environment. I have to be mindful of how much i pull on the handle and every now and then peak at the accellerometer just to be safe. If no FFB is available, then at least vibrations would provide so warning.

 

It's time for a new stick i guess, but that's not going to be that easy.....

[GGTharos]

It looks like what I'm trying to do is not possible, at least not without the addition of some functions by ED.

 

The other option, for anyone who wishes to do so, is pure research: Grab ACMIs from say the 104 and Blue Flag servers, extract all of the F-15 g performance and flag it automatically, then have a human check it to determine if it's a lag spike or something else.

 

Thanks again GG, sounds promising.

[esb77]

But you will agree that carefree handling with the F-15C makes combat much more easier. If you know that it doesnt matter how hard you pull or manouver with the Eagle that gives you much extra time and SA to focus only in combat.

 

Su-27 pilots must combat and take care at the same time about his airframe, G, speed and handling.

 

 

Well, if you had a pilot with a neurological disorder such that they couldn't feel acceleration or the pressure of the stick in different flight regimes then that pilot would be medically disqualified.

 

What people really want for the Su-27 is an accelerometer warning of some sort that doesn't glue your eyes in the pit when they really need to be outside the pit.

 

 

Really, this is a feature that both planes are missing, substitutes for the kinesthetic feedbacks a real plane would give.

 

To max perform the plane this is just as much a problem for the Eagle as it is for the Flanker.

 

 

The only difference is that for the Flanker if you get it wrong due to lack of kinesthetic feedback the worst case scenario is catastrophic airframe failure due to acceleration forces, whereas for the Eagle it's catastrophic airframe failure because you pissed away all your energy and took a R-73 up the tailpipe.

[Basher54321]

ATFS is 100% correct. You can over "G" a 16 with 4 g's .....it's depends on how it is configured and where the fuel is. If you have 370 tanks full and pull 7 G's you would be lucky to still have wings..........

 

 

This statement you have posted was actually false - JohnWill was structural engineer on the F-16 program and he replies to that further down:

 

Purplehaze - there is no loading on the F-16 which is over-g at 4g (symmetric maneuver). The limit with full 370s is 6.5g. Considering that all g limits have a 150% design factor, 7g would not cause any structural failure. Plus the only time you have full 370s is just as you drop off of a tanker.

 

So even if you could pull 9G with the full tanks all you might do is induce fatigue all being well.

 

Don't know about the F-15 etc but the in the F-16 case every part of the airplane is tested to 150% of its highest expected load ever encountered with nothing breaking.

It is also durability tested and must withstand two lifetimes of the "design usage" without failing. Note the design usage is not at constant 150% max load obviously.

[DarkFire]

The only difference is that for the Flanker if you get it wrong due to lack of kinesthetic feedback the worst case scenario is catastrophic airframe failure due to acceleration forces, whereas for the Eagle it's catastrophic airframe failure because you pissed away all your energy and took a R-73 up the tailpipe.

 

That's probably a pretty good summary :thumbup:

[Falcon_S]

...

 

No one is arguing that the DM shouldn't be there, and no one is saying that lack of consequences is correct.

 

:thumbup: That's why we're talking here and draws attention on DCS F15C especially now that his main opponent DCS Su-27 certainly has serious consequences if we violate restrictions.

[Breakshot]

Any idea if this will be corrected with either a limiter, or an actual damage model? Belsimtek I suppose dont give a cent about the F15 these days...

 

Also the instantaneous AOA spike at low speed is pretty overmodeled, IMO.

[Nerd1000]

Well, if you had a pilot with a neurological disorder such that they couldn't feel acceleration or the pressure of the stick in different flight regimes then that pilot would be medically disqualified.

 

What people really want for the Su-27 is an accelerometer warning of some sort that doesn't glue your eyes in the pit when they really need to be outside the pit.

 

 

Really, this is a feature that both planes are missing, substitutes for the kinesthetic feedbacks a real plane would give.

 

To max perform the plane this is just as much a problem for the Eagle as it is for the Flanker.

 

 

The only difference is that for the Flanker if you get it wrong due to lack of kinesthetic feedback the worst case scenario is catastrophic airframe failure due to acceleration forces, whereas for the Eagle it's catastrophic airframe failure because you pissed away all your energy and took a R-73 up the tailpipe.

 

Microsoft CFS3 had airframe creaking noises that started up when you pulled high G. They got louder the more G was pulled. Of course being able to hear the airframe flexing (or anything else, really) over the unmuffled 27 litre V-12 positioned a metre and a bit in front of your toes is highly unrealistic... but it certainly gave you that feedback that's often lacking in sims.

[NineLine]

Microsoft CFS3 had airframe creaking noises that started up when you pulled high G. They got louder the more G was pulled. Of course being able to hear the airframe flexing (or anything else, really) over the unmuffled 27 litre V-12 positioned a metre and a bit in front of your toes is highly unrealistic... but it certainly gave you that feedback that's often lacking in sims.

 

It is unrealistic for the most part, but this is already available with all theDCS WWII aircraft currently. I think it would be even more unrealistic with modern fighters though.