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Crash detection anyone?

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Crash detection anyone?

Postby Sigmoid » Tue Mar 26, 2013 8:13 pm

I've noticed the marked absence of a crash detection in the simulator. I had planes smashing into the ground nose first, and nothing happened, it bounced like a ball, and started spinning like a top.

I mean, at least a dialog that says "you have crashed" would be in order, in my opinion. :) Maybe it's something I can toggle on or off, but I haven't seen anything similar. It would be good to have some detection that checks the angle of landing, speed, etc., to tell whether I landed or if this approach would have broken the wheels off and turned the plane into a fireball in real life. Maybe some speed checks on extending flaps, etc.

I'm entirely sure other people have had these ideas and thought it would be cool to implement them. At least I hope so. So how can I turn such features on?
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Re: Crash detection anyone?

Postby Philosopher » Tue Mar 26, 2013 8:21 pm

Hehe, we have already has some of these discussions before, let me dig up a link. Flightgear already supports warning messages when flaps or gear are lowered above a configurable speed (and one other condition that I'm forgetting at the moment), but those are just warnings. And the issue with bouncing/spinning is with JSBSim aircraft, not YASim ones. The former I've also seen sink into the ground and travel at an incredible speed. But a lot of crashing can be done from Nasal via the /sim/crashed property (I think?), I think David Culp's aircraft usually had an over-G detection, and one turboprop aircraft can simulate its engine overheating and failing. There are a lot of things here, let me dig up some links and I'll respond a bit later :), but bottom point: it can be done, but usually isn't (it's all up to the aircraft designer as usual ;)).
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Re: Crash detection anyone?

Postby Hooray » Tue Mar 26, 2013 8:40 pm

I've noticed the marked absence of a crash detection in the simulator. I had planes smashing into the ground nose first, and nothing happened, it bounced like a ball, and started spinning like a top.

I mean, at least a dialog that says "you have crashed" would be in order, in my opinion

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Re: Crash detection anyone?

Postby Philosopher » Tue Mar 26, 2013 9:07 pm

This is the discussion I kinda participated in :P : viewtopic.php?f=49&t=15188
And then the wiki article on the limits.nas system: http://wiki.flightgear.org/Howto:Define_limits
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Re: Crash detection anyone?

Postby Sigmoid » Wed Mar 27, 2013 1:37 am

So it should be implemented in the aircraft model itself?

Funny how the 172P doesn't have it. It is something like a default aircraft for the sim, isn't it? Which aircraft are considered the most "finished"?
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Re: Crash detection anyone?

Postby Philosopher » Wed Mar 27, 2013 1:53 am

Yes, it is up to the aircraft (designer) to implement it...

Sigmoid wrote in Wed Mar 27, 2013 1:37 am:Funny how the 172P doesn't have it. It is something like a default aircraft for the sim, isn't it? Which aircraft are considered the most "finished"?

Lol, that reminds me: you have to check out the Mig-15. Hands down is one of the most detailed models, ailerons get reversed at high speeds, you'll crash if you bring the nose down into the runway too quickly, you can't stray off of the runway on takeoff/landing (breaks the nose gear), you make a cup of hot chocolate or tea before the engines autostart, and it really is exceptional modeling without much performance cost on your GPU.

As for the C-172: yes, I suppose so, but I really haven't been a believer in that. It runs rather badly on my system (texture problem I think) and it is almost like the B-1900D performance-wise! But in general it works fine, JSBSim based so not many built-in crashing functions, but it hasn't been maintained in a while so it needs some care and some love... But if someone put some work into updating it, nothing major, it could have better support for crashing/warnings and could have a better reputation in my eyes :D.
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Re: Crash detection anyone?

Postby Hooray » Wed Mar 27, 2013 2:03 am

P: You could try the 2D panel instead, it should be more lightweight and have better performance. If not, the system monitor/OSG stats would be interesting to have a look at, to see what is eating up all that performance. Normally, I would expect the c172p to work on most/all systems reasonably well. And we should certainly work out ways to make it more portable if it doesn't - especially given the fact that it is rather well-developed and pretty mature overall, and our "reference" aircraft, too.
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Re: Crash detection anyone?

Postby Thorsten » Wed Mar 27, 2013 8:10 am

So it should be implemented in the aircraft model itself?


With YaSim it comes as part of the FDM package - someone just hard-coded certain behaviours into this. WIth JSBSim it doesn't, so it's up to the individual aircraft developer what he wants to do. As the MiG-15 shows, it can be done really well.

Funny how the 172P doesn't have it. It is something like a default aircraft for the sim, isn't it?


There's a quite popular school of thought that maintains that Flightgear is a flight-simulation rather than a crash-simulation and that you sort of know anyway when you missed the runway that this wasn't done well even without the fireball graphics of the exploding airplane.

That is to say - the majority of aircraft developers simply seem to be interested in other aspects than crash visuals or realistic collision behaviour.
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Re: Crash detection anyone?

Postby Hooray » Wed Mar 27, 2013 10:52 am

Right, it takes a fair amount of time to develop even a semi-plausible crash animation that works in 1% of the cases likely to be encountered. Thus, it is pretty hard to come up with a generally plausible crash detection/animation scheme. That is time that could be spent developing features that are actually useful in-flight, rather than only being useful in a scenario that may take a fraction of a second and which isn't intended to be simulated by FG.
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Re: Crash detection anyone?

Postby Sigmoid » Wed Mar 27, 2013 11:57 am

Thorsten wrote in Wed Mar 27, 2013 8:10 am:There's a quite popular school of thought that maintains that Flightgear is a flight-simulation rather than a crash-simulation and that you sort of know anyway when you missed the runway that this wasn't done well even without the fireball graphics of the exploding airplane.

That is to say - the majority of aircraft developers simply seem to be interested in other aspects than crash visuals or realistic collision behaviour.


It really isn't about animation or special effects. As I said, a popup dialog would suffice perfectly.

Even in professional flight simulation, one of the most important tasks people run are emergency tests. You know the sort: lose three engines a hundred miles from the landing strip, will you make it?

Also, for beginners, telling apart a landing that would have torn the wheels off, and a proper landing may be harder than deciding whether you crashed into the ground or missed the runway or not.
I remember that in the early '90s, MS Flight Simulator 4 had some pretty good limits checks, it told you if you lost the wings in-flight by flying too fast, if you extended the flaps above allowed airspeed they would break off, etc. That was 20 years ago. :)

BTW, I tried a yasim model, the Cub, and it didn't have crash detection. It did pop a warning when falling faster than the airspeed limit though, which makes it the best one so far.
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Re: Crash detection anyone?

Postby Thorsten » Wed Mar 27, 2013 12:00 pm

With some knowledge of Nasal, it'd probably cost you 15 minutes to implement any limit check you'd like to see tested for the aircraft of your choice at the level of a popup-box message. Just write a loop which monitors various properties and pops a warning whenever you exceed a limit.
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Re: Crash detection anyone?

Postby Philosopher » Wed Mar 27, 2013 1:16 pm

Sigmoid wrote in Wed Mar 27, 2013 11:57 am:BTW, I tried a yasim model, the Cub, and it didn't have crash detection. It did pop a warning when falling faster than the airspeed limit though, which makes it the best one so far.


Well did you try flying into its wing like it was a skewer? ;) That usually gets them to crash. Another one that you could try is the AN-225, which is an example of a very simple YASim and 3D model, but its particularly hard to land since the gear don't have any compression length and you crash if you come down with any momentum at all, since its a hulking beast of an aircraft. And you should also try a (YASim) helicopter, run its blades into the ground and see what you get (I think the bo105 is the one I am thinking of, I think it ends up with bent blades).
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Re: Crash detection anyone?

Postby Sigmoid » Wed Mar 27, 2013 1:54 pm

:D

By the way, it's off on a tangent, but I'm a bit confused by all the aircraft models in various stages of completion. Even the install package comes with some below-par and alpha stage models.
Is there a compiled list of aircraft that are considered "well done"? :)
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Re: Crash detection anyone?

Postby Gijs » Wed Mar 27, 2013 1:55 pm

Take a look at the download page and adjust the filters to your liking.
http://www.flightgear.org/download/airc ... ilterable/
Airports: EHAM, EHLE, KSFO
Aircraft: 747-400
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Re: Crash detection anyone?

Postby Hooray » Wed Mar 27, 2013 2:18 pm

Thorsten wrote in Wed Mar 27, 2013 12:00 pm:With some knowledge of Nasal, it'd probably cost you 15 minutes to implement any limit check you'd like to see tested for the aircraft of your choice at the level of a popup-box message. Just write a loop which monitors various properties and pops a warning whenever you exceed a limit.


That's exactly what the "limits.nas" script is there for: it handles all the details, after all it IS implemented in Nasal :-)
The added advantage being that it is XML-configurable, so that lots of things can be implemented without even having to write any Nasal, just XML.
http://wiki.flightgear.org/Howto:Define_limits
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