Good point Mach 84, an MEL example for one of several combinations of Center System Pump failure -
Center System Demand Air Driven Pumps (ADP)
One may be selected OFF provided:
.1 Both center system Alternating Current Motor Pumps (ACMPs) operate normally,
.2 Associated ADP is verified not running when selected OFF,
.3 Remaining ADP heater operates normally,
.5 APU is used as ADP air source during takeoff, and
.6 Appropriate performance adjustments are applied.
Item .5. refers to APU operation during Takeoff. Fairly hefty (at least in the commercial sense) 1st segment weight corrections apply due to slower gear retraction, even with the APU back-up of the failed system.
Regards,
Old Smokey