The placard that is mentioned and queried in this thread is a result of CASA AD/Gen/37 amdt 3 of 9/2000.As a result of this the warning must be in place on all aircraft that fall within the AD scope.
It clearly states on page 2 of the AD that "The reason for this directive is to ensure that the aircraft battery does not become flat in flight resulting in a generator not being able to produce power when selected on."
The term generator in CASA speak also refers to any electrical producing unit and includes alternators.The lack of auto excitation on an alternator has already been referred to by a number of posters.
This is different and really has nothing to do with why an alternator would be selected off prior to start.The only bearing that this AD would have on the original question is that if the gen/alt is left on then the chance of flattening the battery accidentally is removed.
In many Cessnas at least, when ground power is applied a number of circuits are not powered by the GP, particularly avionics.
Wunwing
Last edited by Wunwing; 27th June 2012 at 07:55.