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FS2004 AI Flight Leg paths-- still trying to make sense of them

Okay, so if I've been down this rocky road before, and am repeating the same question/ or mentioning the same issue I brought up about 6 months ago; please forgive me. I tend to forget with new scenarios, what's a similar situation and what's not.

I know for the most part AI aircraft are designed to be looked at from afar (in the background) while you're at your user aircraft parking/taxiing, landing, taking off, etc. They typically are not meant to be followed from point A to point B, and analyzed in meticulous detail. Yet, I do find it fascinating to follow them, because if you keep up, or slew and stay within 30 mile radius of them, you really can follow them from stem to stern. I know they will take very specific departure paths and approach paths in and out of airports, and these can vary depending upon wind direction, or what departure airport I came from, when I get to the arrival airport. I know this, because I've tested it in the past and I've seen it happen.

But there is something that I'm not sure they can do. Do they follow proper waypoints/VOR's/STARS/SIDS from airport A to airport B, or do they just approximate a straight line until they find the specified approach pattern, as outlined by the default airport.bgl?

And I ask this because back in June (in real life)-- I took a flight out from Oakland, CA to Salt Lake City, UT... and then back again a few days later. In the eastbound trip, the plane took a path north of Sacramento, Lake Tahoe, and Reno, and seemed to favor the northern part of Nevada before coming into Utah and setting up for approach at KSLC.

On the way back home, It was pretty much the same thing in reverse, only when setting up for landing in Oakland, it was a very different approach than I had ever seen before, compared to incoming flights from Kansas City I had taken years back in 2008 & 2010: Rather than approaching the Bay Area from Yosemite Valley, over Stockton, and the southeast part of the Bay Area and turning north to land in Oakland, this time we came in over what I think was Chico, Napa/Sonoma County and the North Bay. We proceeded southbound over Berkeley and the spine of the Oakland hills to the east of Oakland. Then made a u-turn over Hayward, met up with the path we would have taken if coming in from Kansas City, and took the usual final-approach northbound to land on runway 30.

Now my question is two fold:

1. Why in real life does the Oakland arrival from Salt Lake take such a decidedly different approach vs. the one from Kansas City, if both KC and SLC are to the east? Yes I know, SLC is slightly further north, but not exceeding further north where it should make that much of a difference on approach... wouldn't you think? I could understand an approach from the north southbound into the Bay Area over Napa and Sonoma counties if the flight was coming from say.... Seattle or Portland. That's a given. But SLC is still a bit of a mystery to me.

AND now that I set this up by referencing my real life experience.... let's turn to AIFP:

2. When I set up my AI flight via AIFP to fly from Salt Lake to Oakland (just like my real life flight), why didn't it follow the same northerly path outbound, and the same northerly approach inbound? I followed my AIFP flight from KOAK to KSLC, and it left the Bay Area due east, over Yosemite area, well south of Lake Tahoe and Walker Lake in Nevada. On the way back, it also flew back into California south of Lake Tahoe, over Yosemite Valley and took more of a direct path over Stockton to Hayward, turn north, and final approach from the south.

Is there a reason AIFP planes do not follow the same flight paths as do planes in real life-- despite the fact that there initial climb outs and final approaches (to and from the airports themselves) *DO* appear to be relatively accurate?


-- John


Resource contributor

Question 1: I'm not sure what you mean by "in real life"; I thought this was an FS question. In FS, the AI aircraft will follow a great circle route between the time they turn away from the runway heading during takeoff to when they get slotted into the approach at the arrival airport. No VORs, airways, etc. They will take different approaches for landing either when they are assigned to a different runway (or runway end), or when they are not first in line for landing - ATC will vector them further away to allow for spacing. This can be quite far away. Note this works only for the first three (or so) aircraft, then any additional aircraft will bunch up together (which will cause go arounds).

In real life, the path of a given city to city route is often "standardized" to keep traffic separated. For example, When I fly from Sacramento to San Diego, when southbound you often fly right next to the Sierra Nevada mountains, but when flying the other direction you often fly up the Central Valley. This can change with weather, etc. But the route in both directions will always be inland from Sacramento to LA, then they go directly over LA and out over the ocean for the route from LA to San Diego. But if you fly from *San Francisco* to LA, the path will often be right along the ocean all the way - thus separating the traffic from Sacramento from the traffic from SFO. These standard routes make the controller's job much easier. I'm sure it's the same thing on east/west routes. And I assume that airport towers will give aircraft coming from different locations different STARs to keep them separated too. This will allow a higher traffic density.

Question 2: Same answer - AI traffic will fly great circle routes. If you use the FS (or other) flight planner and choose a Direct - GPS route, you should see that the AI aircraft flew very close to that resulting great circle.

Hope this helps,
T Gibson,

Sorry to have confused you. You're right it was an FS question, but I was using my real life example of my OAK to SLC flight this past June, to help set up my question as to why my AI flight doesn't fly the same route as my real flight did-- between those two cities.

You answered it and hit the nail right on the head though. And your answer was what I had pretty much suspected, but I just wanted to confirm that I was correct. The AI planes will fly straight-line "great circle route" paths (as you said above), from whatever city pair I created for my leg. While this might be how a novice would think jetliners fly, or ideally how you might GPS a ptA to ptB path, in reality as you said not true. I just wasn't sure whether the AI aircraft were capable of respecting the same "highways in the sky" system as real aircraft, but you have now confirmed that the program is not smart enough (or at least in fall of 2003), was not smart enough at that time to anticipate such paths.

However, as I suspected, final approach paths can be a little more realistic and vary by condition, as one would expect in real life.

Thank you for your input and confirmation.

-- John