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?
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.
@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.
I think the correct answer is flight_model.cfg / max_indicated_speed
Hello. This is in my todo list and I will investigate this subject when I find
some time.
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
(0.5sea_level_densityspeed²). 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
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
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
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?
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
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.
It will 
For GLIDERS we’ve agreed to program the wing flutter to start at “published
Vne, converted to TAS at 1000m” + 10 percent, and build up over a range of 10
knots (i.e. at Vne+10% the flutter is zero). Vne for gliders is normally True
Air Speed above 1000m altitude e.g. a 145knot Vne will be more like 130 knots
IAS at (guess) 15,000 feet. We don’t have a good source of published data of
when each glider might go into flutter, just some very old tests typically in
special circumstances and since then glider wings have got longer, thinner,
and more flexible. So in practice for MSFS we need to set the critical damage
threshold from max_indicated_speed to be near the end of the flutter range at
1000m, and then accept that the MSFS damage threshold will become less
relevant at higher altitudes because in MSFS it’s the IAS rather than the TAS
which gliders need. Counter-intuitively flutter can be more of a problem at
altitude because the thinner air provides less damping. I understand the norm
for powered aircraft is the IAS Vne might apply for the entire operating
envelope of the plane, i.e. if the plane has a ceiling of 15,000 feet then the
IAS Vne still applies at that altitude. Presumably this gives a greater safety
margin at lower altitudes. Not sure about this though.