AI aircraft making a 180 deg turn on the runway

[Guest Stamatis]

Has anyone found a way to make AI aircraft execute a 180 degrees turn on the runway and stay on it, as opposed to ending up alongside the runway?This is for when the AI aircraft have to backtrack a runway in order to reach its threshold due to lack of taxiways.Stamatis

[Holger 0]

Hi Stamatis:Look at Section 44 "Problems and Q & A" in the AFCAD Manual (Version 1.3.2) under "Aircraft make a U turn and take off from the edge of the runway". What you need is a (simulated) turn-around bay.Cheers, Holger

[Guest Captain Barfbag]

I've just been playing with this, but only in the situation where the back-taxi is short. The problem is that AI aircraft start a fixed distance from the end of the runway, NOT at the AFCAD "Start Position," which is only for your aircraft.I just made the runway shorter in AFCAD, and then moved it back towards the other end since just changing the length will chop an equal amount off each end. The AI aircraft entering a taxiway not exactly at the end of the runway no longer go back. Of course, the AI's coming in from the other side taxi a bit further up before taking off, but they always have plenty of room so it's not a problem.This really only works when the problem taxiway is only a short distance from the end. I've got no solution for the odd runway with a center-only entry, but have you tried creating a loop? Might work.Be careful about the hold-short nodes, though. If you shorten the runway too much, you will no longer be close enough to the old hold-short node. The Fault-Finder option in AFCAD will spot this for you.

[Guest Stamatis]

Holger,I have played with it but I must be doing something wrong because it doesn't seem to work.In the example illustrated, which way is the aircraft supposed to execute the loop? Is it supposed to reach the last node on the runway and then execute the loop turning right, or is it supposed to leave the runway to the right at the penultimate node and execute the loop turning left?Stamatis

[Holger 0]

Hi Stamatis:have a look at what I wrote in the London City thread in this forum: http://ftp.avsim.com/dcforum/DCForumID13/1296.htmlI'm not sure that I agree with Captain Barfbag that the Start Position doesn't have any relevance to AI traffic but he's beginning to convince me ;-) I usually place the Start Position in the middle between the two nodes where the turnaround loop meets the runway and also make sure that the loop is not too close to the end of the runway; that should cover your bases in either case.Cheers, Holger

[Guest Stamatis]

Hi Holger,Thank you for the reply, but you did not answer my question in my second message. Is the aircraft entering the loop after it reaches the runway end node, or before?RegardsStamatis

[Holger 0]

oops! sorry, missed that one.The aircraft will leave the runway at the first node of the loop and follow it to turn back onto the runway at the RW's end node, or wherever it meets the runway. That's why it's important to help the aircraft turn back towards the runway with the second node of the loop itself being closer to the runway than the first. Note that you can have more than 2 nodes in the loop and, if the distance between the node in the loop and the runway is large enough, even just one node. Go ahead and experiment with the way that affects the aircraft's movements. In general, placing more points does only lead to more "jitter" in aircraft movement, whereas a single point leads to rather abrupt turns.Another point: as far as I know, the loop does not have to be at the end of the runway; in other words, if the runway continues on beyond the turnaround loop, an aircraft coming out of the loop will not turn towards the RW end but complete the turn as we want it to, i.e. faciong takeoff direction. However, if the AI knows the distance to the end of the runway, as Captain Barfbag's tests seem to indicate, there might be a distance threshold at which the aircraft will turn towards the RW end coming out of a turnaround loop. Who knows?Hope that helps.Cheers, Holger

[Guest Stamatis]

Hello Holger,Thanks for the explanation.However, if the AI knows the distance to the end of the runway, as Captain Barfbag's tests seem to indicate, there might be a distance threshold at which the aircraft will turn towards the RW end coming out of a turnaround loop. Who knows?If you look at the appropriate SDK you will notice that each AI aircraft has a dataset where the minimum runway length is specified.If the runway length is sufficient for the type, an AI aircraft will turn and takeoff before the end of a long runway.I have noticed this when a taxiway meets the runway halfway to the runway end. The bigger aircraft will backtrack all the way to the end of the runway, turn around and takeoff. Smaller aircraft will not backtrack at all and simply takeoff from the place where the taxiway intersects the runway.Stamatis

[Holger 0]

Hi Stamatis:nice detective work - hey, you cheater, are you reading manuals and SDKs? ;-)Could you tell me which "appropriate" SDK manual provides that information?Cheers, Holger

[Guest Stamatis]

Hello Holger,I think it is called the AI Traffic SDK?Stamatis

[Guest]

It's also worth mentioning that increasing AI taxi speed has an effect on the way AI use loops.I've just spent some time creating a loop at EGLC, which the AI studiously ignored. For a while I thought I wasn't getting the angles right. Then, on a hunch, I lowered the Taxi Speed using TaxiSpeed.exe. I had previously set this to 23. Initially I reduced it to 15 and all worked fine - the AI traffic followed the loop perfectly! I then nudged up the AI speed to 18 and all is well! It seems that if the AI speed is too high, then the AI traffic can't negotiate the loops properly! Microsoft obviously tested AI taxiing behaviour at default AI taxi speed, so increasing it may cause some odd effects!Just something to bear in mind!

[betelgeuse 41]

Clever thinking! I've had the same problem but solved it a different way. Seems to me that if the first node is too far away from the runway the aircraft never finds its way back again. I've found this several times, especially if the runway is narrow, like at a small landing strip. Keeping the first node as near to the runway as possible but far enough out to allow an inwards angle to the penultimate node worked for me. The distances and angles for loops seem especially critical. BTW, for general interest, if you put hold short nodes on loops they won't work.