NOTED NZGS - AI vanish, *poof*, after landing or getting taxi clearance

[freddy]

The grass runways at Gisborne (NZGS) have no linked taxi nodes in the AFCAD.

As such, any time the grass runways are landed on by AI, or assigned to AI for takeoff, the AI aircraft simply just disappear in to thin air, *poof* because they have nowhere to taxi to. This is extremely unrealistic.

Paved runway 16/32 is the only runway that works at Gisborne because it is the only runway which has connected taxi nodes in the AFCAD linking it to the gates and parking spots.

To stop AI aircraft from simply vanishing in to thin air at Gisborne, the fix would be either to provide connected/linked taxi nodes to the respective grass runways in the AFCAD ... or, to mark the grass runways as "closed" (no takeoffs, no landings) in the AFCAD.

[normandean]

Your ai aircraft should not be assigned to the grass runways. MSFS always uses the longest runway unless two are almost the same length and the runway is long enough for the weight of the aircraft. In this case 14/22 is 1310M whilst the longest grass runway is only 1173M. For the same reason they should not land on the grass runways either. You can get multiple runway operation, but that requires further input into the AFD file. The only exception to this is very extreme weather with strong cross winds.

Norman

[freddy]

Hmmm. Well, the bad news is that the AI planes ARE indeed using the grass runways. Specifically, the AI were using runway 3/21 when I noticed the issue. ATC was vectoring landing AI aircraft to that runway, and they were happily landing on it.

I get what you're saying about FSX using the longest runway. From my understanding, I agree that forms part of the the FSX decision making process. However, don't the prevailing winds also form part of FSX's runway choice decision as long as the runways are marked as "usable" in the AFCAD (ie, they are set to allow Takeoff and Landing for the Primary end or the Secondary end [or both ends] in the AFCAD)? For example, due to a significant wind direction change, you would notice ATC does change the selected runway at large International airports which have multiple paved runways (I'm not talking about changing from one end to the other, I'm talking about changing to a different runway altogether).

Here is a screenshot from the AFCAD confirming that grass runway 3/21 at NZGS is indeed set to allow Takeoff and Landing, in both directions (primary and secondary). The other grass runways are similarly set the same way. So, therefore, FSX happily uses those grass runways, if the wind direction favours that runway.

Unless I am missing something or there is something I am yet to learn about FSX, or unless my AI is set up incorrectly (in the aircraft.cfg files?), then that has always been my understanding. And, when I edit my own AFCADs, that is always how runway usage has worked for me. By the way, I am familiar with cross runway operation in AFCADs using the star method (or whatever it is called), although I've never done one myself.

As a test, and to check and determine what I wrote in my original post above, I manualy set the winds in FSX to 320 degrees and the AI happily taxied to and used the paved runway (no magic vanishing act). But when I set the winds to 30 degrees, the AI did the magic vanishing trick, *poof*, as they had no way of getting to grass runway 03 to face in to the wind for their takeoff. Similary, AI aircraft landing on grass runway 03, vanished too as they had no way to taxi to the ramp.

[normandean]

Obviously it is happening in your situation, and I don't know why. I did say above that extreme weather conditions could cause the sim to ignore normal procedures and I don't know what wind strength you are setting up. There is a factor to determine when the runways are of similar length to allow use of either, but for the life of me I can't remember the equation. However, I would have thought that a difference of 120M with a runway length of 1148M would not come within this category.

However, if it is happening then, as you say, the cure is easy and takes a couple of minutes to implement.

Norman

[freddy]

I'm only setting moderate winds. Wind speed: Moderate (16kts).

I gather from what you're saying that what I am describing isn't happening for you? The AI at NZGS is working fine for you and is always taking off from the paved runway? Even if you experiment with the wind direction? Can anyone else confirm that this is the case for them too?

If that is true, then that's quite interesting, and I would have no idea what would be unique about my setup such that it only happens for me.

(For the record, in case it matters, I am using Traffic X AI and not the ORBX freeware AI.)

I've used, tweaked and done enough work with Flight Simulator over the years that I've built up a certain experience and understanding about how it works and what makes it do what it does. That would include how FSX chooses runway selection for AI. I've also done my fair share of AFCAD editing. I'm not suggesting I am an expert ... far from it ... but I believe I have good enough experience with Flight Simulator, and AFCADs, to know when something isn't quite right.

Runway selection for AI is based on various factors. Runway length is one of them. Wind direction is a major factor. Apparently there's also runway surface type, aircraft weight, aircraft type, engine type and even the proximity from the parking spot to the runway start point. According to Google searches and forum posts, the algorithm for runway selection is buggy in some aspects ... but works well enough for the most part. Interestingly, a buggy algorithm may explain why a twin engine Beech 1900D turbo prop or a twin engine Dash 8 turbo prop get selected to use a GRASS runway as opposed to a PAVED runway. At least, they do in my FSX. That is annoying and unrealistic enough. But certainly grass runway use for smaller light aircraft such as Cessna 172s or Piper Cherokees does make sense and I would be happy for those runways to be in use for that purpose.

The AFCAD editing and tweaking that I have done in the past has taught me enough about how AI taxiing works, how to set taxi vectors and hold-short nodes, and generally how to create/edit an airport so that AI will get to and use the runways correctly. Based on my observations at NZGS, and my understanding of how FSX handles AI taxiing and runway choice, as well as my AFCAD experience, it occurs to me that something isn't right with the NZGS AFCAD. If it is working for others, then that is great. But it certainly isn't working correctly for me. Therefore, it's possible that it may not be working correctly for others.

I could of course do my own AFCAD changes and tweaks for NZGS and get it to work the way I want it to work. But it makes more sense for ORBX to look in to it and make changes if they deem them to be necessary, for the benefit of all. On the other hand, if the AFCAD is determined to be OK and the issue I'm experiencing turns out to be something unique in my own setup, then that will be yet another learning curve for me that I look forward to.

I'll leave it up to the experts at ORBX, and then go from there.

[DaveH-UK]

The problem I have found in FSX is that the file NZGS_ADEX_FHK.bgl allocates Rwy 14/32 correctly as Bitumen and Rwy 03/21 as Grass; but Rwy 14L/32R and Rwy 09/27 as Asphalt instead of Grass.

 Maybe this is why twin engine AI aircraft are able to land on the 'Grass' runways as the loading will be correct for heavier GAs.

Just a thought.

Dave