Hoover Dam and other objects provide magic lift

I really didn't know how to call that... anyway.

When passing beneath the bridge at Hoover Dam, the aircraft experiences some sort of ground effect/lift/fake ground, which disrupts its flight dynamics. This is most easily noticeable if you do so slowly with a helicopter (Huey in my case).

You can watch the track I provided to see that if you "land" between the road and the arch, you can even shut the engine down, and the aircraft will stay in the air, drifting slowly and eventually fall down.

I must add though, that this is not exclusive to the dam's bridge, as I had that happen with oil rigs and some hangars in DCS 1.2.16 and 1.5 as well (one such hangar can be found right next to Batumi airport).

Hoover_Dam_bug_01.trk

Potentially related:

Odd Transient When Flying Under Bridge

Landing flare at Nellis

Here's another track with the Huey, this time I shut the engine down while flying under the bridge (not between the arch and the road).

A wild guess would be that it has to do with the collision model of concave objects, or with flying below objects when everything is supposed to be flying over objects.

Hoover_Dam_Huey.trk