correct as-is Concerns about G-Onset and Damage to wings

[Flappie]

I did a few instantaneous G load tests with a filled internal tank and an empty payload :

• F-5 : wings snap when G > 10.2 (seems correct)
• MiG-15bis : wings are OK at 10.3G (I couldn't reach higher Gs) (seems too much)
• F-86 : wings are OK at 13G (I couldn't reach higher Gs) (seems too much)
• F-15C : wings snap when G > 12 (seems correct)
• L-39C : wings snap when G > 14 (seems too much)
• MiG-29 : wings snap when G > 15 (seems too much)

Do we have some official documentation claiming the F-5E could withstand more than 10G, especially as an instanenous load ?  (manuals often only mention sutstained Gs)

Aside from the wings being ripped off at 10G, I'm puzzled by the pilot not getting gLOC while I pull to 10G. Maybe the real problem is here? How could we know we're pulling 10G when the pilot doesn't seem to be under heavy G?

[Cab]

15 minutes ago, Flappie said:

I did a few instantaneous G load tests with a filled internal tank and an empty payload :

• F-5 : wings snap when G > 10.2 (seems correct)
• MiG-15bis : wings are OK at 10.3G (I couldn't reach higher Gs) (seems too much)
• F-86 : wings are OK at 13G (I couldn't reach higher Gs) (seems too much)
• F-15C : wings snap when G > 12 (seems correct)
• L-39C : wings snap when G > 14 (seems too much)
• MiG-29 : wings snap when G > 15 (seems too much)

Do we have some official documentation claiming the F-5E could withstand more than 10G, especially as an instanenous load ?  (manuals often only mention sutstained Gs)

Aside from the wings being ripped off at 10G, I'm puzzled by the pilot not getting gLOC while I pull to 10G. Maybe the real problem is here? How could we know we're pulling 10G when the pilot doesn't seem to be under heavy G?

Even accepting the 10.2g-load (which I don’t, but have no evidence), it is still far too easy to break the wings. I have had the smallest stick movement at 500+kts result in them snapping off. This simply does not happen in real life.

So maybe the problem is with the default curve coded to stick movement at high speed. 

[Flappie]

11 minutes ago, Cab said:

I have had the smallest stick movement at 500+kts result in them snapping off. This simply does not happen in real life.

I'll test your track and be back shortly.

Edited July 22, 2023 by Flappie

[Flappie]

On 5/25/2023 at 5:45 PM, Cab said:

F-5 wing demo.trk 271.12 kB · 6 downloads

You pulled 9.7G.

Maybe the F-5E G calculations are wrong, for some reason.

[GGTharos]

47 minutes ago, Flappie said:

• F-15C : wings snap when G > 12 (seems correct)

You shouldn't really be able to reach a g at which you can snap the wings unless you're loaded.  There is an additional (maybe minor, maybe not?) issue here where the elevators have no resistance due to air pressure, achieving deflection and thus g that they shouldn't be able to - basically the highest recorded G on an eagle, ever, is 12.5 which ended up with bent wings, fuselage etc.  But it didn't break apart.

47 minutes ago, Flappie said:

Do we have some official documentation claiming the F-5E could withstand more than 10G, especially as an instanenous load ?  (manuals often only mention sutstained Gs)

Not really surprising, but you'd bend the wings depending on how long you kept that g going (maybe you'd bend them no matter how long at that g).  The issue in DCS is asymmetric g, so you need to put in a bit of roll with aileron or especially rudder.  Another possible issue is that the wings are being broken instead of being permanently bent and affecting the FM.  This is a bit of a compromise between realism and gaming - making the wings break is relatively quick and easy, making them bend and screw up the FM is less so.

47 minutes ago, Flappie said:

Aside from the wings being ripped off at 10G, I'm puzzled by the pilot not getting gLOC while I pull to 10G. Maybe the real problem is here? How could we know we're pulling 10G when the pilot doesn't seem to be under heavy G?

Not an issue - do a bit of research on the STOHL curve for g tolerance.   Basically the brain has a few seconds of oxygen available even if you mess up your AGSM.  The higher the g, the less that available consciousness time.

Edited July 22, 2023 by GGTharos

[=475FG= Dawger]

Catastrophic wing failure rarely, if ever, occurs at the initial over-G, especially if it is short duration. The catastrophic failure normally occurs at a later loading of the wing. 

Normally, one would see indications of the over-G such as fuel streaming from the wing tanks, unusual control inputs for straight and level flight, etc. More significantly, other parts of the airframe break before the wing does.

 

The structural testing program report I posted in another thread clearly indicates that there was NO structural failure at ULTIMATE LOAD. There is direct evidence against catastrophic failure yet we have catastrophic failure at ultimate load. 

Why the F-5 was chosen for this draconian treatment remains a mystery, especially with direct written evidence contradicting the modeling and 5 plus decades of hard aircraft service with no anecdotal examples of wing structural issues.

[Bucic]

18 hours ago, GGTharos said:

You shouldn't really be able to reach a g at which you can snap the wings unless you're loaded.  There is an additional (maybe minor, maybe not?) issue here where the elevators have no resistance due to air pressure, achieving deflection and thus g that they shouldn't be able to - basically the highest recorded G on an eagle, ever, is 12.5 which ended up with bent wings, fuselage etc.  But it didn't break apart.

Not really surprising, but you'd bend the wings depending on how long you kept that g going (maybe you'd bend them no matter how long at that g).  The issue in DCS is asymmetric g, so you need to put in a bit of roll with aileron or especially rudder.  Another possible issue is that the wings are being broken instead of being permanently bent and affecting the FM.  This is a bit of a compromise between realism and gaming - making the wings break is relatively quick and easy, making them bend and screw up the FM is less so.

Not an issue - do a bit of research on the STOHL curve for g tolerance.   Basically the brain has a few seconds of oxygen available even if you mess up your AGSM.  The higher the g, the less that available consciousness time.

 

This got me thinking... It there a way to get a graph of X and Y stick input a DCS module actually accepts in-flight? I mean for a user. I'm sure ED testers do have a tool that extracts the data from the submitted track files.

It could be that failed (either the general implementation or a momentary occurence) RAW input filtering combines with incomplete implementation of control surface deflection limitations and results in hard to mitigate airframe disintegration. Could you guys remind me where airframe FM properties and stress properties reside in DCS? I recall I've seen such data in plain text during one of my LUA lurking sessions.

[=475FG= Dawger]

On 7/22/2023 at 9:34 AM, Flappie said:

 

Do we have some official documentation claiming the F-5E could withstand more than 10G, especially as an instanenous load ?  (manuals often only mention sutstained Gs)

 

https://apps.dtic.mil/sti/pdfs/ADA032403.pdf
 

We do, although the language may not be as direct as one might desire. 

A careful read will determine that the F-5 was static tested to ultimate load of 1.5 times 7.33 G with NO STRUCTURAL FAILURE. 

Also, the F-5 was subjected to 4 lifetimes of expected real world loads (4000 hours, 3244 flights per lifetime) with two additional, more severe lifetimes underway when the report was published. 
 

There is a chart that clearly indicates that 9 G was expected to be exceeded approximately 40 times per 1000 hours or 160 times per lifetime. The chart ends at 9 G so there is no clear extrapolation of the number of 10+ G excursions but its pretty clear that more than one 10G+ excursion was to be expected during a normal lifetime. 
 

Also, you state that the the F-15 suffering catastrophic failure at >12 G seems correct yet we know for a fact that exceeding 12 G in the Eagle resulted in bent wings, not snapping off. 
 

Cheers!

Edited August 6, 2023 by =475FG= Dawger

[Grumman86l]

Starting about 2 beta updates back Ive been having an issue where both wings rip in nearly straight and level flight. Most recently I was only doing about 400 and beginning a gentle climb and without warning both wings were just gone. No previous damage or contact with the enemy. The normal wing rip is annoying but this is something else.

[Flappie]

Please attach a track the next time it happens to you. The shorter the better.

[Bucic]

On 8/3/2023 at 4:09 AM, Grumman86l said:

Starting about 2 beta updates back Ive been having an issue where both wings rip in nearly straight and level flight. Most recently I was only doing about 400 and beginning a gentle climb and without warning both wings were just gone. No previous damage or contact with the enemy. The normal wing rip is annoying but this is something else.

What is your joystick model? I'm starting to get convinced it is caused by either the rate of aileron deflection or controller signal spikes. I flew for hours using keyboard. In that time I made sure most of my dive recoveries were at 9+ G, often close to 10 G. I did not avoid aileron corrections. I only managed to snap the wings at 10 G.

Then I switched to Xbox controller and wing snaps started occuring more often. Of note, still *very* rarely.

On 7/22/2023 at 6:22 PM, GGTharos said:

You shouldn't really be able to reach a g at which you can snap the wings unless you're loaded.  There is an additional (maybe minor, maybe not?) issue here where the elevators have no resistance due to air pressure, achieving deflection and thus g that they shouldn't be able to - basically the highest recorded G on an eagle, ever, is 12.5 which ended up with bent wings, fuselage etc.  But it didn't break apart.

Not really surprising, but you'd bend the wings depending on how long you kept that g going (maybe you'd bend them no matter how long at that g).  The issue in DCS is asymmetric g, so you need to put in a bit of roll with aileron or especially rudder.  Another possible issue is that the wings are being broken instead of being permanently bent and affecting the FM.  This is a bit of a compromise between realism and gaming - making the wings break is relatively quick and easy, making them bend and screw up the FM is less so.

Not an issue - do a bit of research on the STOHL curve for g tolerance.   Basically the brain has a few seconds of oxygen available even if you mess up your AGSM.  The higher the g, the less that available consciousness time.

 

Is aeroelasticity accounted for in DCS F-5E to any degree. What I mean is, could Sidewinder loadout be a factor in all this. I'd gladly learn that we don't have to double test runs to with/without Sidewinders

Edited August 14, 2023 by Bucic

[MAXsenna]

2 hours ago, Bucic said:

What is your joystick model? I'm starting to get convinced it is caused by either the rate of aileron deflection or controller signal spikes. I flew for hours using keyboard. In that time I made sure most of my dive recoveries were at 9+ G, often close to 10 G. I did not avoid aileron corrections. I only managed to snap the wings at 10 G.

Interesting. You might be on to something. I have ripped the wings off once or twice by yanking the stick in emergencies. I use an FFB stick, so it's kind of easy to know the load. 

Cheers! 

[GGTharos]

10 hours ago, Bucic said:

Is aeroelasticity accounted for in DCS F-5E to any degree. What I mean is, could Sidewinder loadout be a factor in all this. I'd gladly learn that we don't have to double test runs to with/without Sidewinders

 

Unfortunately I have no idea.  I haven't flown the F-5E for a while now

[Schmidtfire]

The issue is really that we have no sense of forces in game. It’s very easy to over G fast and snap the wings. Not something that happens on a regular basis IRL.

Edited August 18, 2023 by Schmidtfire

[Cab]

41 minutes ago, Schmidtfire said:

The issue is really that we have no sense of forces in game. It’s very easy to over G fast and snap the wings. Not something that happens on a regular basis IRL.

 

That issue exists for all modules. It doesn't explain why the F-5's wings are so much easier to break than the others.

[VZ_342]

I've tried to snap the wings in several other modules, never did it. Get in the F-5, and it's remarkable how quick they snap. Must be made out of graham crackers or something...

[SparrowLT]

17 hours ago, VZ_342 said:

I've tried to snap the wings in several other modules, never did it. Get in the F-5, and it's remarkable how quick they snap. Must be made out of graham crackers or something...

I can with the F-15C , Flankers and the F-14.. but in the F-15 for example you need to have tanks hanging from the wings and if not you need like over 12Gs (still unrealistic as the 15C wings will take 12Gs irl  , with damage certainly but wont snap off clean, one even pulled 12Gs in a dogfight with a MIG-25 in Irak and kept flying the mission without issues, tought maintenance probably wouldnt be happy after he returned) . The F-14 it wil also snap the wins if doing a pull hard enought at high speed.

The Flankers need to deactivate the angle of attack limiter and do a hard pull at high speeds

 

Again.. i had my F-5 wings broke off even doing supersonic merges with bandits without turning much.. like if the wake broke them or something

Edited August 19, 2023 by SparrowLT

[GGTharos]

Did you roll while pulling?

The transonic zone is the most vulnerable zone for g tolerance, coupled with the loss of several g when applying asymmetric g.

Edited August 19, 2023 by GGTharos

[FoxAlfa]

12 hours ago, SparrowLT said:

(still unrealistic as the 15C wings will take 12Gs irl  , with damage certainly but wont snap off clean, one even pulled 12Gs in a dogfight with a MIG-25 in Irak and kept flying the mission without issues, tought maintenance probably wouldn't be happy after he returned)

Its like saying you can survive a car crash cause a people survived it ... yes, you can, but there are way more other determining factors that don't allow for making such a blanket statement.  

Edited August 19, 2023 by FoxAlfa

[Braunn]

After I made the wingless supersonic and then landing video I haven't touched the F5. 

Is it still breakey wingy? 

 

[=475FG= Dawger]

59 minutes ago, FoxAlfa said:

Its like saying you can survive a car crash cause a people survived it ... yes, you can, but there are way more other determining factors that don't allow for making such a blanket statement.  

 

Except you have no examples where the people died in the car crash, only instances where they didn’t. 

[FoxAlfa]

1 hour ago, =475FG= Dawger said:

Except you have no examples where the people died in the car crash, only instances where they didn’t. 

I can clear mind say people die in car crashes, and it is exactly and equally correct as statement people survive car crashes until later you factor in all other factors and conditions, and that was exact point.

Eagle C in DCS can do 12.5G all day if you don't try it with stupid weights.

Weights like of 100% fuel and 4 120 4 aim7 have no issue at 13g in DCS.

Also you can't make a DM model based on one time events with lot of pulp and apply it to ALL scenarios.

But you can guesstimate based on the aircraft manual and limitations... and DCS F-15c can do 12.5g on any weight it is rated at 9g in the manual. On higher weights were its rated, lower, per exemple 7.5g or so, it can't and I find that quite fair.

 

 

 

 

Edited August 19, 2023 by FoxAlfa

[=475FG= Dawger]

37 minutes ago, FoxAlfa said:

I can clear mind say people die in car crashes, and it is exactly and equally correct as statement people survive car crashes until later you factor in all other factors and conditions, and that was exact point.

Eagle C in DCS can do 12.5G all day if you don't try it with stupid weights.

Weights like of 100% fuel and 4 120 4 aim7 have no issue at 13g in DCS.

Also you can't make a DM model based on one time events with lot of pulp and apply it to ALL scenarios.

But you can guesstimate based on the aircraft manual and limitations... and DCS F-15c can do 12.5g on any weight it is rated at 9g in the manual. On higher weights were its rated, lower, per exemple 7.5g or so, it can't and I find that quite fair.

 

 

 

 

 

I suspect you are being purposely dense so I will be clear. 
 

There are NO examples of the F-15 shedding its wings at 12+ G ( Car crashes causing death of occupants) while there are multiple instances of the F-15 sustaining 12+ G without catastrophic wing failure. ( car crashes with no dead people)

“Guesstimating” that a brand new fighter aircraft will shed its wings the very first time it achieves 1.5 its published G limit is a ridiculous standard. To add insult to injury, this ridiculous standard is arbitrarily applied to the F-5 while others suffer from no such adverse application.  

Edited August 19, 2023 by =475FG= Dawger

[Cab]

2 hours ago, Braunn said:

After I made the wingless supersonic and then landing video I haven't touched the F5. 

Is it still breakey wingy? 

 

Yes

[FoxAlfa]

26 minutes ago, =475FG= Dawger said:

I suspect you are being purposely dense so I will be clear. 
 

There are NO examples of the F-15 shedding its wings at 12+ G ( Car crashes causing death of occupants) while there are multiple instances of the F-15 sustaining 12+ G without catastrophic wing failure. ( car crashes with no dead people)

“Guesstimating” that a brand new fighter aircraft will shed its wings the very first time it achieves 1.5 its published G limit is a ridiculous standard. To add insult to injury, this ridiculous standard is arbitrarily applied to the F-5 while others suffer from no such adverse application.  

 

Have ALL F-15 or large amount done 12.5g and survived?

No, because Good pilots Don't do that because people who actually DESIGNED the plane told them not to do that since it will DAMAGE the plane! And there are plenty exemples of planes being damaged from over G.

Pushing any aircraft beyond its design limits that far no matter the reason, is BAD airmanship and having surived is just as much luck as anything else.

As such represent a very small set of case that can't be used as rule. 

All in all in DCS you CAN do 12G, under almost all circumstances.

You literally have to full Drop tanks and go very fast, and pull 10-11+ G to brake your wings in Eagle C, and sorry but that is on 100% on the pilot.

 

Edited August 20, 2023 by FoxAlfa