Runways for aircraft types

Hi,

Despite having done a lot of AI Flight plans, as well as airport designs, over the years, I've just come across a puzzling feature for which there may be an answer out there.

I've modified Duxford EGSU (it could be any airport, I suppose) so that lighter (historic) aircraft park on the grass and can only take off on 6L/24R (grass), while larger/heavier aircraft parked on the tarmac aprons are taxiway'ed to the asphalt runway 6R/24L. But if aircraft such as DH Dragon Rapide, or Beaufighter, are parked on the grass they don't take off, just vanish when their time comes for taxi to runway. If I alter the airport design to give them access to the asphalt runway from the grass parking spots, they taxi and take off on the hard runway. Lighter aircraft such as Bristol Fighter, Spitfire, Texan, are quite happy to taxi to the grass runway and take off.

So the question is, what 'property' (in aircraft.cfg or elsewhere) of any particular aircraft determines whether or not it will take off on grass? The two runways are more or less the same length and width. Is it just engine numbers ie only single-engined aircraft can take off on grass? Is there anything I can do to force take off on grass, rather than just vanishing?

Brian

Beats me but I found this 5-year-old post on the net, see if you can pick up any clues-

"In FSX you need to have an airport background to flatten and exclude autogen (runways do not do that as in FS9). I usually do that after I lay out the runway and basic aprons. You are using closed taxiways that are not connected to anything to make visuals that are better done with aprons and polygons.

I think ATC makes the lowest # runway the default for take off, which could explain why AI take off from 7 even though you have in marked as secondary. In any event, ATC has 7 as the active runway"

FULL THREAD here, but double-check that some people are not talking about a different flight sim than FSX- http://www.fsdeveloper.com/forum/threads/ai-aircraft-wont-take-off.22266/

Thanks for that. Interesting stuff though not quite addressing my problem. The essence of my query is that different aircraft seem to behave differently even though starting from the same grass parking area and having access to a valid runway.

Just to confuse the issue, I programmed the Dragon Rapide to fly from a different airfield, grass taxiway and runway, but no alternative runway, and it took off fine. Back at Duxford, it will only taxi and take off if it has access to 6R/24L. If I change the grass runway to being asphalt, it makes no difference. Maybe there's a critical size difference between the two runways. BTW the scenery is UK2000.

I shall keep calm and investigate further.

Brian

I googled '"ai aircraft takeoff fsx" and a bunch of hits came up, but you have to sift through them to make sure other flight sims haven't crept in there.

And even if they don't address your specific problem, they might indirectly give you some clues etc.

For examp-

https://www.flightsim.com/vbfs/showthread.php?261269-ai-wont-take-off

Yes, thanks, I will look through those.

But another interesting development, that I'm in progress of investigating by trial and error, is that if I increase the grass runway to the same length as the asphalt, it works fine. I'm gradually reducing the grass runway length to find the point at which twin-engined AI refuse to taxi and take off, just disappear instead.

FlyerDoc

Has nothing to do with grass.

What you see is the aircraft size/weight restriction runway in use.

You have 2 runways that are parallel meaning they are within 7.9 degrees of each other. The multi engine plane is parked closest to the center line of the short runway. Because the 2 runways are parallel the twin engine must have access to a parallel runway that is longer then 4000 ft.

If there is no taxiway path network to the longer runway the multi engine plane will vanish when its time to taxi.

Jvile,

Yes, I think I agree with you so far. I've found that if the grass runway (to distinguish it from the asphalt, though I understand the surface is irrelevant here) is greater than 4000ft it allows multi-engines to take off. But what I've also found is that once the grass runway is long enough, then the asphalt, which is actually longer, becomes inactive, and aircraft linked only to it, and unable to access the grass runway, will vanish when it's take-off time. So, when the grass runway is too short for multis, atc allows both runways to be used, though only by appropriately-sized aircraft. Once the grass runway is lengthened to accept multis, atc closes down the other, even though it's longer, and is exactly the same heading, and now won't allow take-off. Weird.

Perhaps the only way to force the issue is to create two superimposed airports. Sounds like it could be fraught with snags.

I wonder, too, if it's possible to modify aircraft.cfg to make the aircraft seem smaller/lighter, settings that don't affect the flight characteristics. I might experiment there.

Once the grass runway is lengthened to accept multis, atc closes down the other, even though it's longer, and is exactly the same heading, and now won't allow take-off.

Once the grass runway is 4000 ft. the runway rule changes. The asphalt runway is still active but not needed for the multi engine prop plane parked closest to the grass runway. Any planes that have parking spots closest to the asphalt runway will use it for departure as long as the taxiway network is attached to both runways.

Perhaps the only way to force the issue is to create two superimposed airports. Sounds like it could be fraught with snags.

That's called overlaying 2 or more airports with different ICAO codes and works with no ill effects. FSX has airports where each has a different ICAO code but share the same scenery.

OK with both those points. In my case, because the basic layout of the airport is fixed, I can't park the multis closer to the asphalt runway than the grass. If I give them access to the grass runway they use it. If no access, they disappear.

I'm now working on overlaying two airports; should do the trick. Many thanks for your help and suggestions.