I seem to finally have found the issue: It's a bug introduced with P3D 4.5 HF2. Before I noticed that I tried to reinstall Amsterdam using the old installers from 2016 and 2017 because I was unable to locate the rumored EHAM-compatible new universal installer anywhere (it may be a myth or just too well hidden).
Reinstallation fixed the elevation issue at first with EHAM sitting at the very top of my scenery library. I started P3D with the 737 NGXu on H1 as in the screenshots above to reproduce the exact same scenario. Everything stayed stable for a few restarts until I decided to move FSAerodata's BGLs back on top of EHAM. Guess what? The old issue reappeared.
I searched Google again and this time a post from the FSDeveloper forums showed up: https://www.fsdeveloper.com/forum/threa ... ed.446186/
The issue comes from LM having introduced a new bug in 4.5 HF2 by altering the way P3D determines airport elevations.
To quickly summarize the linked threads: If multiple 3rd party addons redefine an airport, "incomplete airports" (such as FSAerodata's updates to approaches, navaids and comms) no longer just add their data to sceneries below but instead terrain elevation is read from them as well. BGLs strictly require an elevation to be specified which means FSAerodata BGLs are in fact specifying some previously ignored airport elevations. Due to the P3D bug they are now modifying terrain all over the place (not limited to FlyTampa EHAM).
The issue cannot be fixed by scenery developers/FlyTampa
but there are some options to solve the issue:
- Move conflicting scenery below FlyTampa EHAM. I tried that before and it obviously did not work for me but maybe something else was broken at that time. The effect, if it works, is that FSAerodata cannot update EHAM to latest AIRAC.
- Disable conflicting scenery. For FSAerodata that obviously means FSAerodata no longer applies anywhere.
- For FSAerodata: Run a correction tool and keep FSAerodata scenery on top of everything else. Download link and details are provided on the FSAerodata forum. It only takes a few minutes to run the correction but it has to be repeated after each AIRAC cycle and after every scenery update/installation which changes elevations.
It appears that running FSAerodata's correction tool did the job for me (if more testing shows that it did not, I will reply to this thread again).
Note about the correction tool: If you only see -1M for every airport something has gone wrong. Check again that FSAerodata sceneries are really disabled before running Makerwys.exe, Makerwys has finished and generated text files no longer contain any FSAerodata entries. Then rerun the tool.