High G damage

[Stuge]

From old Flanker simulator manual:

"The FCS of the Su-27 limits positive and ��negative Gs to +8.5 and -2.5, respectively. However, the aircraft can be flown to +9 and -3 Gs and has structural design limitations of +15 and -5 Gs."

 

So the load factor limit of the design is 15G.. which is quite nice I have to say :)

 

This means it can take at least 15G without getting damaged. So I would guess the real limit is more than that, possibly even over 20G? Maybe an aircraft engineer could shed some light on this...

[BronzeBuddha]

So the load factor limit of the design is 15G.. which is quite nice I have to say :)

 

This means it can take at least 15G without getting damaged. So I would guess the real limit is more than that, possibly even over 20G? Maybe an aircraft engineer could shed some light on this...

 

No, 15 g is probably the ultimate structural limit, and acts as the buffer for a design g limit of 9. Structure rated for 20 g would be unnecessarily heavy. From what I've read about the F-16, its design g limit is 9, and structural limit is 13.5.

 

Side note regarding g, during flight testing an F-22 accidentally pulled negative 11 g during departure testing. After the plane landed they did a thorough inspection and found some warping. I think that aircraft is at a museum now.

[Ironhand]

...

This means it can take at least 15G without getting damaged...

I just want to mention something about these numbers. Even if this were not the ultimate structural load limit, you might be able to go there once. But if you continue going there, you will fatigue the airframe to the point where something will break--and, most probably, at a lower stress level. DCS might not ever model airframe fatigue over time but it's something to consider when we start talking about any of these numbers.

 

I, for one, am looking forward to the day when more than landing gear and tire damage are modeled. :)

[amazingme]

Good point.

[85th_Maverick]

On 12/11/2014 at 12:28 AM, pyromaniac4002 said:

I'm sure they'll get around to it. As much as anyone might want to represent the Flanker as an all-powerful king of the airborne world, they can still recognize the fact that no fighter jet can pull more than twice the G limit of a missile designed to shoot it down and remain in one piece. Besides that, it's a relatively easy fix.

And so they did! Now the Flanker's wings rip off very rapidly at just 10G. I've had a discussion about the Over G of the F-18C in DCS which can be achieved by pulling full aft stick and the pressing the autopilot disconnect paddle once and after that the plane's AoA goes somewhat higher and the F-18 is now limited to some much higher vertical G than 7.5 or whatever it was initially, all until you release the stick and the original limitation kicks back in. There I have been actually reminded by someone that the wings won't break that easy even some good Gs above the operational limit (what the aircraft's flight control system automatically limits it to) but eventually bend and remain remain unrepairable for good.

In order to break, you must really pull some very serious Gs for many seconds, not just some 1.5 x the operational limit (1.5 x 9G = 13.5G). Maybe nobody has access to this sensitive data from the aircraft's design period but with some initial minimal knowledge and data we can estimate it with acceptable error. Knowing that the Su-27 prototype, the T-10 had at some exercise been subjected to some vertical G loads that broke one of the wings closer to the tip and the plane landed safely and was investigated, the Sukhoi Design Bureau had redesigned the wing reinforcing it.

It's common sense that the Su-27/33 in DCS must have their wings breaking G-load some higher than just 10. If the F-18 in DCS which is a naval aircraft having folding wings (the hinge is a weaker structural element) reaches and holds over 10G (hard but doable at the right speed and height), how come that the more robust Su-33 breaks immediately there, not to mention the Su-27 which should be among the most structurally tough in this area. Someone must revise and rise the wings breaking G-load of the Su-27/33 by some amount. I'd guess it for at least 14G on the Su-27 and some 12G on the Su-33 with full internal fuel and no fuselage loadout (the internal fuel and fuselage loadout is the weight that breaks the wings..., what's on the wings matters only for their pylons)

[85th_Maverick]

On 1/10/2015 at 1:50 PM, BronzeBuddha said:

 

No, 15 g is probably the ultimate structural limit, and acts as the buffer for a design g limit of 9. Structure rated for 20 g would be unnecessarily heavy. From what I've read about the F-16, its design g limit is 9, and structural limit is 13.5.

 

Side note regarding g, during flight testing an F-22 accidentally pulled negative 11 g during departure testing. After the plane landed they did a thorough inspection and found some warping. I think that aircraft is at a museum now.

Heh, the same ultimate load limit factor of 1.5!:D 13.5 / 9 = 1.5

Wow..., and that F-22 only had some warped skin (we don't know about the internal structure and may never know publicly) at negative 11G (for how many tents of seconds if not seconds)? Well..., as all fighters are having their structure designed to withstand better positive G-load limits at the expense of negative G-load limits, just think how well it could've went at positive without any damage at all.

On 1/10/2015 at 9:17 AM, Stuge said:

 

So the load factor limit of the design is 15G.. which is quite nice I have to say

 

This means it can take at least 15G without getting damaged. So I would guess the real limit is more than that, possibly even over 20G? Maybe an aircraft engineer could shed some light on this...

Wow! So, there you go..., 15G even if it's form the old manual, it's the same old aircraft anyway. I was close when guessing it at 14;) for the Su-27 and thinking that it should be at least 12 for the Su-33.

Now let's just ask the devs to take the time and tweak it a bit to about that before the wings break. Cheers to everyone!

Edited August 4, 2022 by 85th_Maverick

[Cmptohocah]

5 hours ago, 85th_Maverick said:

And so they did! Now the Flanker's wings rip off very rapidly at just 10G. I've had a discussion about the Over G of the F-18C in DCS which can be achieved by pulling full aft stick and the pressing the autopilot disconnect paddle once and after that the plane's AoA goes somewhat higher and the F-18 is now limited to some much higher vertical G than 7.5 or whatever it was initially, all until you release the stick and the original limitation kicks back in. There I have been actually reminded by someone that the wings won't break that easy even some good Gs above the operational limit (what the aircraft's flight control system automatically limits it to) but eventually bend and remain remain unrepairable for good.

In order to break, you must really pull some very serious Gs for many seconds, not just some 1.5 x the operational limit (1.5 x 9G = 13.5G). Maybe nobody has access to this sensitive data from the aircraft's design period but with some initial minimal knowledge and data we can estimate it with acceptable error. Knowing that the Su-27 prototype, the T-10 had at some exercise been subjected to some vertical G loads that broke one of the wings closer to the tip and the plane landed safely and was investigated, the Sukhoi Design Bureau had redesigned the wing reinforcing it.

It's common sense that the Su-27/33 in DCS must have their wings breaking G-load some higher than just 10. If the F-18 in DCS which is a naval aircraft having folding wings (the hinge is a weaker structural element) reaches and holds over 10G (hard but doable at the right speed and height), how come that the more robust Su-33 breaks immediately there, not to mention the Su-27 which should be among the most structurally tough in this area. Someone must revise and rise the wings breaking G-load of the Su-27/33 by some amount. I'd guess it for at least 14G on the Su-27 and some 12G on the Su-33 with full internal fuel and no fuselage loadout (the internal fuel and fuselage loadout is the weight that breaks the wings..., what's on the wings matters only for their pylons)

Su-27SK is limited to 8G - mind you this is only for M < .85. Higher speeds and different loadouts decrease this even further.

In 8+ years that I am flying the Flanker in DCS, I broke the wings once or twice and I yank that thing really hard.

If you are pulling 10 or more Gs, you need to revize your flying strategy.

Problem we have is that currently overstress damage is binary: all or nothing.

We should habe progressive systems failures, airframe bending , panels flyng off etc.

[85th_Maverick]

On 8/4/2022 at 11:00 PM, Cmptohocah said:

Su-27SK is limited to 8G - mind you this is only for M < .85. Higher speeds and different loadouts decrease this even further.

In 8+ years that I am flying the Flanker in DCS, I broke the wings once or twice and I yank that thing really hard.

If you are pulling 10 or more Gs, you need to revize your flying strategy.

Problem we have is that currently overstress damage is binary: all or nothing.

We should habe progressive systems failures, airframe bending , panels flyng off etc.

Ok, be it, 8G (although that guy said the manual tells something about 15G for ultimate load) operational will most certainly mean more than 12..13 constantly held for many seconds before the wings should rip off with full internal fuel and no belly loadout. The common sense brings a least average error when concrete data isn't available!

Edited August 6, 2022 by 85th_Maverick