Just a minor correction.
The AD is actually CASA AD/Gen/39 amdt 3 of 9/2000.
What is interesting also is the comment that the previous revision, Amend 2, was issued in Nov 1967... and the reasons and changes from the original are unknown.
That is very much what I expected.
Many of these AD's are historic... based on an event so far back that no-one is even too sure what brought it all on at that time.
It takes even more input now to go and research everything for the AD to be cancelled or otherwise amended.
It all goes back to an FAA Advisory Circular, dated 1965.
AC20.40
At that time many pilots were possibly used to self exciting generators. These days it is the exact opposite, as we have already mentioned the alternator is commonplace. Commonsense and training will tell us that the alternator will not come online with a flat battery.
http://rgl.faa.gov/Regulatory_and_Gu...LE/ac20-40.pdf
BACKGROUND: Since an alternator is but one class of generator, approval
of alternator installation in light aircraft have been made by the
Agency under those rules in FAR 23 and 27 which deal with generator
systems. It has been found, however, that certain types of alternators
(which are apparently used in a number of automotive applications)
obtain their field excitation from the battery. When field excitation
is obtained in this way, there is the danger that, if the alternator
is turned off in flight, subsequent loss or discharge of the battery
would result in Loss of the alternator as well. This unusual design
feature invokes the provisions in @23.1541(a)(2) and 27.1541(a)(2).
ACCEPTABLE MEANS OF COMPLIANCE: With respect to battery-excited
alternator instarlations, an acceptable method of complying with
6823.l.S41(a)(2) and 27.1541(a)(2) is to provide a placard advising
the pilot not to turn off the alternators in flight, except in case
of emergency