Other planes bounce sharply during takeoff

[AntonKuf]

after updating to beta 44, other planes bounce abruptly during takeoff

[justinshannon]

Can you provide a video evidence of this? What version of X-Plane?

[AntonKuf]

Can you provide a video evidence of this? What version of X-Plane?

I will make a video tomorrow. Xplane 12.03

[AntonKuf]

Can you provide a video evidence of this? What version of X-Plane?

https://youtu.be/_2jDc1YT6LM show video of this problem

[justinshannon]

Does this happen with every aircraft at any airport?

[AntonKuf]

Does this happen with every aircraft at any airport?

Yes

[ogruetzmann]

Can also confirm this. Also, saw a plane with a sharp nose down attitude during push, another one bouncing back/forward during taxi (think these two might be related).

[ogruetzmann]

The opposite happens during landing

[justinshannon]

Are you using real weather in X-Plane? I can only reproduce the altitude anomaly if I use manual weather, specifically if the temperature and altimeter settings are different than what they are in real life.

[ogruetzmann]

I'm using real weather.

[justinshannon]

What airport are you seeing this at? I observed at KBOS for about an hour and had no issues.

[ogruetzmann]

I've been seeing it (I think) everywhere. EDDM for sure.
I'll go for a second install of x-plane to see what happens with a clean sim. I'm also still seeing planes at some odd levels (like 600 feet above/below) that should be x000 ft apart, so it might also be on my end.

[ogruetzmann]

Unfortunately, the same thing happens with vanilla X-Plane (12.03 r01) with only xPilot and BB CSL installed. Used real weather and the values I got from X-Plane were the same I was expecting from the METAR.

For testing, I switched back to xPilot beta.43 and take offs/landings look normal again.

[justinshannon]

After further testing last night, it does seem to only happen in areas with high altimeters (above 29.92” Hg). This is because X-Plane’s pressure altitude dataref returns a negative value if you’re sitting on the ground, which as a result makes xPilot overcompensate for the altitude correction, causing these weird altitude anomalies you’re seeing.

Can you try observing at an airport with a low altimeter (below 29.92) and let me know if things look normal?

I’ll try to get a fix out later today.

[ogruetzmann]

Indeed, this is the case and also keeps aircraft on the ground when low pressure is present.
I manually set the pressure to 975 hPa / 28.79 inHg and watched aircraft staying on ground during take off or touch down way too early, so this effect works in both directions.

[justinshannon]

I just released beta 45 that should hopefully fix this. Let me know if you're still seeing weirdness after updating.

[ogruetzmann]

Still happening. I was spotting at VNKT this time, QNH 1021 and landing aircraft dropped onto the runway out of ~200-300 feet, which looks like the offset between QNH 1013 and 1021.
When playing with the local pressure, aircraft will be either high (high pressure) or low (low pressure) on the approach/departure.

It seems like this is the offset present in upper airspace as well, I was seeing similar values up there (like 700 feet above/below for traffic on levels 1000 feet above/below me). It more or less seems like the altitude correction is not applied at all, no matter if the traffic is within 6000 feet, but that observation might be wrong.

[justinshannon]

Thanks to @ogruetzmann, this should be fixed in beta 46.