# AI research

#### johnor999

Hello!

I'm currently doing a lot of research on AI-behaviors in MSFS. One thing I'm a bit stuck on is the infamous 37-minute problem.
This has been discussed to death and is covered in the AIFP manual but my question is:

Given a flight with user defined departure time 12:00Z and arrival time 14:00Z, does the 37 minute problem mean that if the calculated arrival time is 37 minutes earlier than the user defined arrival time - the aircraft will spawn at the parking?
In other words, if the calculated arrival time is 13:23Z, will the aircraft spawn at the parking?

#### johnor999

I did some experimentation in FSX.

Aircraft:
AC#390,436,"Boeing 737-800 Paint1"

Flightplan:
AC#390,SE-390,1%,Week,IFR,1/11:00,1/12:00,300,R,0000,ESGG,1/13:00,1/14:00,300,R,0000,ESSA

I focused on the leg ESSA-ESGG. And the entry time into the furthermost sector from ESGG that's within the 9 closest sectors is about 1/11:35:12.
If I spawn at 1/11:35:11, the inbound flight doesn't spawn at all which is expected given that it's too early.
If I spawn at 1/11:35:12 and the cruise speed in the bgl is set to 435 kts, the aircraft spawns enroute.
If I spawn at 1/11:35:12 and the cruise speed in the bgl is set to 436 kts, the aircraft spawns at a parking at ESGG.

The distance between ESSA and ESGG is approx 213.11 thus:
213.11 / 435 equals an estimated arrival time of around 1/11:29:24
213.11 / 436 equals an estimated arrival time of around 1/11:29:20

There's no way I can make any sense of 37 minutes given the above observations...

#### tgibson

Resource contributor
I think the relevant part of the AIFP manual are these sentences:

"In particular, if an AI is
scheduled to be activated (i.e., enter the sector occupied by the user aircraft or
one of the surrounding eight sectors) more than about twenty minutes later than
as calculated by the AI/ATC engine using the distance travelled from departure to
destination at the cruise speed specified for the aircraft in the traffic file, that AI
will not materialize for landing. Instead, it will spawn in a parking spot at the
destination airport some time later in preparation for the next leg. "

So the relevant time is "about 20 minutes", not 37 minutes. Your 25 minutes is "about 20 minutes".

Hope this helps,

#### johnor999

In other words, the "37-minute rule" is a bad name for it. Thank you for your help!

#### robystar

It is much more complicated than that but in essence, it is what jpfil said.
And a wise advice that has been given is to always use GMT!
As a matter of fact, your flight plan from Stockholm to Gothenburg is not really realistic. Your altitude is too high (for fs at least) to make it for AI possible to reach the flightplan altitude and then descent to approach altitude. Check the real world flight plans!

#### johnor999

The flight plan is irrelevant in terms of altitude since the purpose was to determine the time at which the aircraft would no longer spawn.

Next step might be to check if the cruise altitude has any effect on the deadline or not.

#### johnor999

It is much more complicated than that but in essence, it is what jpfil said.
And a wise advice that has been given is to always use GMT!
As a matter of fact, your flight plan from Stockholm to Gothenburg is not really realistic. Your altitude is too high (for fs at least) to make it for AI possible to reach the flightplan altitude and then descent to approach altitude. Check the real world flight plans!
12:00Z means Zulu time or UTC which is the same as GMT. They are not the same zones but practically they mean the same.