Hi guys,
this issue has been around since FSX was first released (and P3D as well), it just becomes more common/obvious when using detailed landclass add-ons with dense urban or suburban autogen.
If you slew quickly across a (mountainous) landscape you can see how the building autogen in the distance gets loaded in blocks/batches and then, occasionally, one block spawns much higher than it should be. I don't really know what specifically triggers those incorrect data points but suspect it has to do with the sim reading the various LODs of the terrain data. I've noticed that the likelihood of floating houses seems higher with terrain-mesh add-ons installed, which points to perhaps occasional confusion between loading different terrain file sets for the same location. Still, even mesh files generated from different sources wouldn't normally have elevation differences that would cause a batch of buildings to get spawned a couple hundred feet above the surface so something else must be at play as well. Perhaps an occasional hiccup in data interpolation along QMID cell boundaries?
One can usually return the floating buildings back to the ground during a flight. Either select World > Scenery Library and then click on "OK" or assign a key combination to the "Refresh scenery" event in the Options > Settings > Controls menu (Buttons/Keys tab); I use Ctrl-Shift-S but any unassigned combination will work. Of course, if one continues flying or slewing at high speed then it won't be long until the next block pops up...
FYI, one item of the list of "Fixes and Improvements" in P3D v3.2 reads
- Reduced cases of autogen buildings floating above ground
but I haven't read any specific comments whether that is, in fact, the case. Assuming that Clutch Cargo is using v3.2 or higher then, I suppose, it hasn't been fully eliminated yet. Then again, he writes of "a few feet" and "when loading a flight" so perhaps, it's not the same issue as those blocks of houses high up in the air.
Cheers, Holger