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MV-JimStewart avatar image
MV-JimStewart asked B21 commented

Configuring damage & overstress?

I'm having some issues trying to configure reliable over-stress and damage airspeeds in my aircraft when the relevant options are turned on in the assistance settings.

First of all, it would be very handy to have a page covering this topic in the SDK docs; unless I've missed something, there is currently nothing that addresses this in a concrete manner. Could we have a list of all the areas where we can configure values that will cause overstress and/or damage?

First of all - flaps. There are two lines in the [FLAPS.x] section of the flight_model.cfg file, 'damaging-speed' and 'blowout-speed' that seem to do very little. While I can indeed blow the flaps out if I build up an excess of airspeed, it doesn't seem to be linked to the value I specify here; it's significantly higher, with seemingly no effect if I lower the values.

Second - overstress due to exceeding Vne. I can't at all see where this is configured in a manner that actually causes overstress to occur. In an extreme pitch down profile, I can get well above red line. And while the aircraft will shake about a ton, I have yet to be able to make it cause an overstress at all. Is there something I'm missing here?

Third, gear damage. Am I correct in thinking that fixed gear ignores a specified airspeed limit for damage?

aircraftflightmodel
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B21 avatar image B21 commented ·
@MV-JimStewart Did you find the asnswer or can I bump this? I am following EXACTLY the same search you will have been doing and so far no luck. SDK menu "Options" "Disable Crashes" set to off (default always resets to on) was indeed the first important tip.


But my plane is triggering the overstress warning at 158 knots (in zero flaps) and I cannot find where in which settings file this is actually controlled.

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FlyingRaccoon avatar image FlyingRaccoon ♦♦ B21 commented ·
Hello.

This is in my todo list and I will investigate this subject when I find some time.

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MV-JimStewart avatar image
MV-JimStewart answered FlyingRaccoon commented

I should also mention something in regards to testing this, that would save someone else headaches in the future: Having developer mode turned on prevents the flaps from blowing out, regardless of airspeed or assistance settings.

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FlyingRaccoon avatar image FlyingRaccoon ♦♦ commented ·

Hello.

I'm really surprised by this. I did all my flaps blowout tests with the DevMode enabled and Aircraft Editor opened.
However, notice that any change to the "Disable Crash" option will not be saved if the game is not closed properly. That can cause some confusion.

Regards,
Sylvain

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B21 avatar image
B21 answered

I *think* the correct answer is flight_model.cfg / max_indicated_speed

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FlyingRaccoon avatar image
FlyingRaccoon answered B21 commented

Hello @MV-JimStewart @B21

Here's the information I could gather from the simulation:

Preliminary note: make sure you have all assistances turned off and that the Disable Crash option of the Devmode is disabled.

Flaps damage and blowout:
Flap damage is just used to trigger pilot assistance warning. There's no efficiency degradation.
Flap blowout doesn't happen at the provided speed. A dynamic pressure is computed from that speed (0.5*sea_level_density*speed²). When that pressure is reached, we trigger that same assistance warning but the actual blowout will occur when we reach 2 times that pressure threshold.

Overspeed:
The overspeed crash will occur when you fly above the Vne for more than 6 seconds

Overstress:
The overstress crash will occur when you fly beyond the negative or positive g limit for more that 1 second.
The g limit is computed as an interpolation of the negative/positive_g_limit_flaps_up/down parameter values you provided in the AIRPLANE_GEOMETRY section (interpolation based on flaps position).

Landing gear:
The landing gear damage will not trigger crash, it will prevent the gear from extending or retracting.
So this is only applicable to retractable landing gear.

@Nocturne for documentation

I hope this helps.

Regards,
Sylvain

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B21 avatar image B21 commented ·

Thanks Sylvain that's a huge help. I see yesterday's Asobo 26th Jan dev update notice is using an image of one of our gliders overspeeding into "flutter" so this is particularly timely.

https://www.flightsimulator.com/january-26th-2023-development-update/

For the docs it may be worth noting if the Vne for overspeed is IAS (testing suggests that is the case). TAS would be more accurate but I expect it's only gliders that would notice the difference and if it is "max_indicated_speed" then IAS is pretty explicit there.

All works great - 50-seconds into this video it's the MSFS overspeed damage kicking in when the screen goes black -it actually made me jump when I first saw it even though I'd just spent several hours developing the behaviour:

https://www.youtube.com/watch?v=Lpq05RJc5sM

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donstim avatar image donstim commented ·

Following along this interesting discussion. Note that the speed Vne is only defined for piston-engined airplanes. For the rest, the maximum operating speed would be Vmo in the speed regime and Mmo in the Mach regime. But regardless of the speed being referenced, be it Vne or Vmo, this is not a structural limit speed. Flying above Vne (or Vmo) for 6, of for that matter, 600 seconds, should not result in a structural failure (crash) due to overspeed.

The structure must be good out to to the design dive speed, Vd, which is above Vne or Vmo.

Regarding the overstress crash, you are applying the safety factors to the g-limit parameters and not just using the g-limit parameters directly, right?

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FlyingRaccoon avatar image FlyingRaccoon ♦♦ donstim commented ·

Hello @donstim


From what I can see, the safety factor is not considered here. (documentation seems to be wrong about this)
And I get your point regarding design speeds.
I'll add this topic to my next review with our core sim engineers.

Regards,
Sylvain

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donstim avatar image donstim FlyingRaccoon ♦♦ commented ·
Thanks! I hope including the safety factor will also be a topic for your discussion (or just included) since that is what it is there for - to provide a safety margin beyond the design limits.
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