Too much FLI37 drift

[MYSE1234]

@IronMike

Due to as test I just did as I had a sneaking suspicion that this was the case. The rate at which drift happens in the FLI is too high.
As you can see in the video below in about 14 minutes it drifts about 5 degrees north, just standing still on the runway.

According to this TIFF (Teknisk Information För Flygmaterieltjänsten) magazine it says the drift rate in FLI37 is about 1 degree per hour. Not 20-ish as it seems to be now.

Worth noting is that it only drifts about 7 or so degrees until it stops doing so.

 

 

Edited November 4, 2021 by MYSE1234

[Machalot]

Earth rotation rate is 15 degrees per hour. Does that explain this drift? I'm not sure if it's actively compensated for this. Older INS packages sometimes weren't. 

[CaptCrash]

would this affect the HUD waypoint direction? I noticed if i stick the flight path vector on the indicator course it's pretty inaccurate but if i offset about one vertical line im more accurate.
edit: the compass rose after some time will disagree with the HUD as well. I'll try and get a photo later tonight.
edit II: Here are some numbers I computed based on the video
Delta Time: 1.20694hrs (Start: 08:00:00 -> End: 09:12:25)
Approx Drift: 6 degrees
Drift Rate: 4.971 degrees per hour which is ~5deg/hr or 0.083deg/min. so still about 5x higher than stated of 1 degree/hr
@MYSE1234 can you confirm the time stamps in the video are HH:MM:SS format?

Edited October 26, 2021 by CaptCrash

[MYSE1234]

@Machalot

I think that this is not what was seen in that clip. As far as I know FLI37 only works based of "gravity-down", and should as far as I understand not be affected by the earth's rotation.

 

@CaptCrash

That's the reason for this test I did, seeing the waypoint drift to the side as I was flying toward it.

You can see the in-game time in the bottom right corner in the time format you mentioned. Mission starts at the default 08:00:00.

Edited October 27, 2021 by MYSE1234

[CaptCrash]

9 hours ago, MYSE1234 said:

@CaptCrash

That's the reason for this test I did, seeing the waypoint drift to the side as I was flying toward it.

You can see the in-game time in the bottom right corner in the time format you mentioned. Mission starts at the default 08:00:00.

 

Ya it makes precision navigation very difficult especially when you need a precise line up for a target. Hopefully @IronMike can add this to the list to get resolved. 5 degrees/hour for this type of system would exceed the 2-sigma 1 degree/hr probability of heading drift. I was flying the second campaign where you do CAP in the second mission and the HUD/FLI37 disagreed by about 7 degrees by the time i was called off station, that would cause a gross navigational error and warrant replacement of the unit - if it happened irl.
Edit: To be clear this also affects the Central Indicator ring.

Edited October 27, 2021 by CaptCrash