Originally Posted by
ph-sbe
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.
Oh but there is a reason to declare an emergency and even more importantly squawk 7700. You may be happy that the controller you are speaking to understands the problem but you have just gone into a crash descent into another controller's sector perhaps crossing through several. Squawk 7700 takes no time to select and EVERYONE in ATC for several hundred miles definitely all the controllers in New York and DC centers and associated TRACONs know about it as a 7700 squawk does not get filtered by the system. That will mean that aircraft that you WILL be conflicting with will be turned out of your way by their controllers without the controller you are speaking to -
who does not have authority for the airspace you have descended into - having to add multiple ground line calls to her/his workload. It will also mean that before even being contacted PHL will have seen a 7700 aircraft coming their way. It really smooths the path for you in the ground systems.
Sure follow the mantra Aviate Navigate - but you are in one of the busiest airspaces in the CONUS - if you do not communicate you may add TCAS RAs and worst case a collision to your bad day. A simple 7700 solves all of that and tells everyone that you have a problem.
For those of you that care, current ATC systems will maintain your identity but add symbology that shows you have an emergency on controller displays.
7700 is the same for MAYDAY or PAN so it removes the dialectic nuances of is it really a MAYDAY or only a PAN and with modern surveillance systems is far more effective than an R/T call.