An excessive rate of descent that would trigger Modes 1 and 2 of the GPWS system and eventually Mode 5 as you descend below the glide slope.
Actually we did it in the airplane above 10,000' as a demonstration maneuver during maintenance acceptance flights. As I recall, it was in excess of 3,500 fpm. During maintenance acceptance flights, we would extend the flaps to 40 degrees via the alternate flap extension system, while the normal extension was limited to 30 degrees. Again, that was at a pretty light weight as we burned off most up to the point we got to the alternate flap extension portion of the flight.