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Topper80,
When your aircraft was certified it met the regulatory requirements to fit into Category C under normal operating conditions.
Airports, their runways, and approaches are built to include protected airspace. It is understood that a Category C aircraft will remain within a fixed distance from the approach end of the runway. Minimums are set with respect to obstacles within that protected airspace.
If the aircraft's ground speed is such that it is unable to remain within the protected airspace and that aircraft flies outside the physically protected airspace then no protection from obstacles or terrain is provided by the published minimums. So your Cetegory C jet at max takeoff weight returning for a landing with no flaps or slats is not going to be able to slow down enough with its clean wing to fit into Category C speeds. In that case one would use Category D minimums to reflect the actual operational speeds. Flying to Category C minims while maneuvering at Category D speeds will take you out of protected airspace.
As an emergency aircraft the regulations allow you to what is necessary to bring your flight to a safe conclusion. Declare the emergency, use all your resources to come up with the best plan fly to whatever minimums you can safely fly to and land. The approach categories, minimums, and speeds were designed for routine operations. With a crippled jet you are no longer in the normal operations regime.
Some companies require operations at the next higher Category minimums under certain conditions as a matter of policy. An example would be requiring crews to use Category D minimums to circle, even though the jet is a Category C aircraft.
Last edited by Northbeach; 24th September 2012 at 23:40.