Originally Posted by
RodH
Why did the Capt. not simply give a mayday call as it was most appropriate.
Because she felt it was not needed. If you listen to the ATC recordings, she stayed exactly within the limits of her authority without getting "trigger happy".
She initiated her descent and subsequently informed the controller (aviate, navigate, communicate). By doing that she used her authority provided by 14 CFR 91.3b, and exactly by that rule: she only deviated from her previous clearance to the extent necessary (emergency descent).
She then asked for directions to the nearest suitable airport. At that point, the controller was perfectly aware of the situation and there really was no need to explicitly declare an emergency.
But, even so: if needed a controller can "declare an emergency" for you. In reality it was not needed, since no rules needed to be breached. If, for example, she had to fly through restricted airspace to get to the runway, then explicitly declaring an emergency may have made sense. But even in that case: no FAA official is going to question her actions.
You declare an emergency to get the attention you need. If you already have the attention, it's just a waste of brain cycles and precious communication time.