I was thinking of those cases where the trainers have decided wings level or skid ball central is an easier option than trying to determine the required bank angle and those steam driven attitude indicators which try to erect to a "false" vertical at small bank angles (as you mentioned).
When manoeuvres are required it is very difficult to maintain zero sideslip even with beta indicator - constant rudder force seems ok (at constant CAS). I know this wasn't part of the original thread subject but may be part of an escape flight path.
When I did my Canberra training (nearly 50 years ago) the RAAF was firmly skid ball central at all times. I clearly recall turning base, asymmetric, with almost full left rudder and the aileron hand wheel bumping the right stop in turbulence! I suspect this technique may have contributed to at least one loss of control incident. The fix was back off half the rudder deflection, and the ailerons returned to about neutral - who cares where the skid ball was!
Later at ETPS an instrumented Canberra was available to clearly demonstrate the folly of the RAAF technique.
I believe the RAF lost a Hunter which had an asymmetric external fuel tank jettison, the pilot was told "simple, just keep the ball centered", I think it was in manual reversion with limited aileron authority. Anyway it departed rolling rapidly in the direction of the applied rudder.
Last edited by zzuf; 26th Feb 2017 at 10:33.
Reason: typo