Strange MD-83 taxy pic

[Biggles Flies Undone]

Very strange... (http://www.airliners.net/open.file?id=599959&WxsIERv=TWNEb25uZWxsIERvdWdsYXMgTUQtODMgKERDLTktODMp&WdsYXMg=QWVyb21leGljbw%3D%3D&QtODMg=TWV4aWNvIENpdHkgKC0gTGljZW5jaWFkbyBCZW5pdG8gSnVhcmV6I EludGVybmF0aW9uYWwpIChNRVggLyBNTU1YKQ%3D%3D&ERDLTkt=TWV4aWNv&ktODMp=TWF5IDE0LCAyMDA0&BP=0&WNEb25u=UmljYXJkbyBNb3JhbGVzIEF2aWF0aW9uIFBob3RvZ3JhcGh5IG9m IE1leGljbw%3D%3D&xsIERvdWdsY=Tjk0NkFT&MgTUQtODMgKE=QU0gZG9taW5hdGluZyB0aGUgc2NlbmUhIDQgdGF4aWluZyB vdXQsIDEgZGVwYXJ0aW5nIDIzUiwgb25lIG1vcmUgaG9sZGluZyBiZWZvcmU gMjNSIGFuZCBhbiBpbnRydWRlciBpbiB0aGUgcGljIQ%3D%3D&YXMgTUQtODMgKERD=MzI1Ng%3D%3D&NEb25uZWxs=MjAwNC0wNi0xNg%3D%3D&ODJ9dvCE=&O89Dcjdg=NDk2NTgvMTQ2MQ%3D%3D&static=yes&size=M)

Looks like the port elevator on each aircraft is a max deflection - what's going on?

[HEATHROW DIRECTOR]

Nothing unusual - seen it a million times. Hopefully an aircrew member will explain why..

[airborne_artist]

The taxiway is wet, and it's the reflection of the fuselage of the a/c behind, I think!

[square leg]

Those elevators are of the servo tab/trim tab type. They flip/flop in the wind (especially tailwind). Once you've got speed they're rigid and work with the airflow, being directed by the servo tab (opposite direction... etc).

The Avro RJ (BAe146) has them too, so quite British as well.

The last option is that they all might be taxying to the maintenance hanger to get those elevators bent "straight" again (at least the first few).

[Flightmech]

As somebody has already said the MD-80 srs elevator system is normally non-powered, it is a non-servo control with a tab. From memory of working on the Airtours MD-83's their flight manual said the pre-take-off elevator range of movement check must be done with a minimum taxi speed of 10-15kts to allow for sufficient airflow over the tab/surface. I remember this because once had an MD-83 come back to the gate for "stiff elevators" on taxi-out. It transpired that due to frozen snow on the taxiway and freezing fog the check was done at a much slower taxi speed and therefore more resistant was felt than normal as controls were heavier to lack of assisting airflow.

The elevator was powered in the full nose down direction as part of the stall recovery requirement, and indicated when in use (hopefully hardly ever!) by an "elevator power on" annunciator on the overhead panel.

flightmech

[chiglet]

The old Bristol Britannia [sp] when reverse thust was selected, the elevators would "dance", ground "unlocks" in AFAIK.
Mind you, the "gout" of flame on a wet start was quite exiting
watp,iktch