Su-27. Extreme G-loads... G=?

[Ironhand]

...I don't see how you can determine that based on the translation.

You're right. :)

[DarkFire]

It would be as you say, but in the event that the airframe is actually warped, they'd just write it off.

 

That would make sense. Short of X-raying the entire airframe to determine the level of micro stress fracturing present in structural members, the entire thing would probably be written off as un-certifiable as safe for use. Even if for some reason you did want to X-ray the entire thing this wouldn't help with any mono-crystalline parts, but at that point it probably becomes cheaper to buy a new airframe than it does to test & repair the old one.

[SinusoidDelta]

Inspection for micro fractures would be used to verify a lack of fatigue damage. Once a structural member has yielded, it's compromised.

[Svend_Dellepude]

Wait until guidance is fixed.

 

You know something..? :)

[GGTharos]

.... I have a dream? :D:pilotfly:

 

You know something..? :)

[mvsgas]

There more I think about it the more I am impress by the design of the SU-27. For it size it can withstand 171000kg of g force, 171tons! That is more than this truck can hold.

 

Google tells me is 376990.468lbs (I trust and believe Google) that is more than 6 F-16 or 3 F-111F or 2 C-130 ( strictly speaking on weight term, not capabilities of the aircraft mention).

 

I know is not the only aircraft that can do it and is not like you can mount 4 fully loaded Semi-trucks on it. But it is a impressive feat for all big agile fighters like the F-15, Su-27, etc.

 

:D

[Stuge]

Wait until guidance is fixed.

 

I'm looking forward to this GG! Any idea when? 1 year? 3? 5?

[RvETito]

On every real aircraft exceeding the g-limit in flight or during hard landing is calling an un-scheduled maintenance and if deformations are found on primary structure it's very likely the airframe to be considered BER and hence written off, as someone mentioned.

 

That was something I've always wanted to see in a flight sim. You overstress your bird - boy, you're now grounded for a month :D Of course, for commercial product like DCS would be nonsense for example as penalty to limit you somehow of accessing certain parts you've paid for. But having something that will force you to fly the aircraft in the most realistic manner (as much as the modeling allows) is a great feature in my eyes. So watch out how pull-happy you are with the stick and enjoy flying the Flanker :)

[Esac_mirmidon]

+1

[Stuge]

On every real aircraft exceeding the g-limit in flight or during hard landing is calling an un-scheduled maintenance and if deformations are found on primary structure it's very likely the airframe to be considered BER and hence written off, as someone mentioned.

 

That was something I've always wanted to see in a flight sim. You overstress your bird - boy, you're now grounded for a month :D Of course, for commercial product like DCS would be nonsense for example as penalty to limit you somehow of accessing certain parts you've paid for. But having something that will force you to fly the aircraft in the most realistic manner (as much as the modeling allows) is a great feature in my eyes. So watch out how pull-happy you are with the stick and enjoy flying the Flanker :)

 

This would be nice yes. A simple way would be to have the game give feedback in debriefing.

 

Speaking of that the mission structure in DCS is really too simple. Voice acted briefings and debriefings should be standard, and the missions and campaigns themselves be much more thought through and polished and bug-free and also with more interesting plots than country A goes to war with country B.

[SinusoidDelta]

It would be awesome to model some type of OWS like in the F-15:

https://www.google.com/patents/US4302745

[jejsus]

Not above G limit and not over-speeding and the plane just fall apart... Huge disappointment having to deal with problems update after update... I thought updates were to fix things not to break them. And just don't try to explain me that it's beta, cause I'd stay in stable if servers were to stay in stable too... In fact I'd restricted servers to stable versions immediately if I were ED and stop using people as test bunnies. Do you guys even try the thing before release? We have statistics running at pro servers and you guys are ruining it for us BIGTIME. Thanks. In hope to not get banned again, Sincerely Yours.

[Ironhand]

Not above G limit and not over-speeding and the plane just fall apart..... Sincerely Yours.

:)

[Esac_mirmidon]

Post your speed, G´s, weight and maneuver when you fall apart.

 

Maybe we could help you.

 

Sincerely yours...

[jejsus]

Nice one Ironhand :). On this occasion let me thank you for all the tutorials you've made for us! Big respect and I'm happy that you had some fun on my account :)

 

I've attached the track of two flights I've done the first one I got shot down, the second one I went down by a structural damage. In second flight I launched two missiles. I think I went somewhere around 1100km/h true airspeed and it seems to have broken apart at 6.4Gs. There were some negative Gs before I went into a pull, maybe that is the reason but don't know how realistic that is. At that point I'm probably having 6000l of fuel and I started the sortie with 2x27ER, 2x27R, 2x27ET, 2x73R, 2xECM.

Tacview-20160415-223308-DCS.txt.rar

[GGTharos]

So, you're flying a fully fueled and armed tanker; you've pulled positive g up to or past the structural limit at supersonic speed (M1.2), and negative g past the structural limit (why -ve g's anyway?)

 

You weakened the airframe to the point where it came apart at faily low g.

 

You've exceeded the realistic limitations of the aircraft; no one ruined anything for you ... you just failed to respect the aircraft's g-loading limits.

 

You can compute the safe limit as follows:

 

At GW < 0.85M Gmax = 171000kg/GW

At 0.85M < GW < 1.25M Gmax = 139000kg/GW

At GW > 1.25M Gmax = 150000/GW

 

Once you exceed Gmax the airframe starts taking damage, and Gmax becomes less.

Gmax can also be smaller if you are creating an asymmetric g-load, ie. pulling and rolling at the same time.

If you exceed Gmax * 1.5 the aircraft will disintegrate (though as Ironhand has pointed out, this is not always the case)

 

 

A fully fueled flanker with weapons is 30000kg or so. When you make your first supersonic turn - let's be generous and say you are at 27000kg.

At that time ( +22:46) tacview indicates a maximum g or 6.6 (it's probably more since tacview records an average) at M1.18.

Your Gmax at that time is 139000/27000=5.1g

Gmax * 1.5 = 7.7g

 

You are over-stressing the airframe.

Edited April 16, 2016 by GGTharos

[jejsus]

The blame goes on me then :(. I failed, that's it. Thank you very much for a detailed explanation. A question follows - Do su-27 in real life has (did had) indicator that calculates max G at a different loads - if yes, then I hope it will be implemented, if not then - oh my :S, I mean I'm not getting any younger :D

[GGTharos]

It's tuned only to the 21500kg GW aircraft (52% fuel and 2xR-27, 2xR-73) for the Su-27S. You need a more modern Su-27 to have a full-up OWS like the F-15 for example.

 

My advice is ... plan your fuel use and think very carefully about how much those R-27's weigh in at - always be aware of your GW :)

 

If I don't forget, I'll create a quick chart for people to be aware of the limitations. I didn't see what the -g limitations are, but I can sort of guess from the +g ones.

[Ironhand]

The blame goes on me then :(. I failed, that's it. Thank you very much for a detailed explanation. A question follows - Do su-27 in real life has (did had) indicator that calculates max G at a different loads - if yes, then I hope it will be implemented, if not then - oh my :S, I mean I'm not getting any younger :D

This might help. I posted it earlier in this thread:

 

 

The Max OP(erational) Gs column lists the Gs for the 3 speed "classes" and 5 gross weights I used. Exceeding the Gs in that column can lead to problems... Ignore everything in the columns to the right of Max OP G.

 

As a matter of practice, I've found you don't have to worry about it--as long as the limiters are on-- until you pass the 25,000 kg weight (EDIT: at < M 1.0). After that, things become more problematic.

Edited April 16, 2016 by Ironhand

[DarkFire]

It's tuned only to the 21500kg GW aircraft (52% fuel and 2xR-27, 2xR-73) for the Su-27S. You need a more modern Su-27 to have a full-up OWS like the F-15 for example.

 

My advice is ... plan your fuel use and think very carefully about how much those R-27's weigh in at - always be aware of your GW :)

 

If I don't forget, I'll create a quick chart for people to be aware of the limitations. I didn't see what the -g limitations are, but I can sort of guess from the +g ones.

 

I've seen the -G limit listed as -3.5, which would place the absolute 150% airframe limit at -5.25G which empirically appears to be close to what we see in the game.

[Esac_mirmidon]

According to manual maximum -G are, for 21.400 Kg:

 

-2G at <0.85

-1G at >0.85

-0.5G at < 310 Km/h

[SinusoidDelta]

I posted that earlier:

 

Translated straight from the real flight manual for reference.

 

Note the limitations through the transonic region (0.85 < M ≤1.25)

 

Maximum operational overload at design

gross weight of 21,400 kg :

- Pu max = 8.0 at M≤0,85

- Pu max = 6.5 at 0.85 < M≤1,25

- Pu max = 7.0 for M > 1.25

For instruments that are different from the calculated gross weight ,

Overload is set at the rate of :

- M • Pu max = Const = 171,000 kg at M < 0.85 , but not

more than 9.0 =pu

- M • Pu max = Const = 139,000 kg at 0.85 < M≤1,25 but

not more than =7.0 pu

- M • Pu max = Const = 150,000 kg at M > 1.25 , but not

more than =7.5 pu

 

[DarkFire]

Ah, of course. Derp on my part. So the maximum -G value at which airframe failure should occur would be -3G.

[Oceandar]

As a matter of practice, I've found you don't have to worry about it--as long as the limiters are on-- until you pass the 25,000 kg weight (EDIT: at < M 1.0). After that, things become more problematic.

 

Very true. Especially when Aim-120 heading towards me, its quite difficult to do maneuver and at the same time watching the g meter. It was easy dodging it before....need more practices I guess

 

 

 

Gam Zeh Ya'avor - King Salomon

[pewbeef]

As Bushmanni previously stated, bending moments is the cause of wings falling off at high load factors. This means that weapons hanging off the 6 wing pylons actually reduces the bending moments at the root, allowing for higher load factors (if we assume that failures occur at the wing root). This means that the increased gross weight might actually work in favor of higher load factors, depending on where it is located.

 

Has anyone seen that this would be the case in the sim (only carrying missiles/bombs on wing pylons to increase load factor before failure)?

 

P.S.

One note on this is that while bending moments are reduced, shear stresses in the wing might be increased and could probably also be a cause of failure. And then also the case of the weapon attachments failure as happens with the MiG-21, but I guess this is not implemented on the SU-27?

Edited April 18, 2016 by pewbeef