Having trouble downloading the report there but I'll take a stab at it.
Unless you really know or are give written instructions as to which CB's to pull , you can end up doing more harm than good.
I refer you to the Atlantic Glider thread. In the report the A330 F/O pulled the CB marked CVR. Unfortunately it was the one for the protection circuit and not the power circuit. Thus the CVR which would have been preserved automatically was in the majority erased.
Edited to add, just got the report.
Nasty incident, but the report says they did de-power the CVR, just not quickly enough.
Last edited by Daysleeper; 24th Oct 2004 at 14:46.