Originally Posted by
DaveReidUK
It's hard to see how a system, the existence of which pilots were initially unaware of, could appear in the MEL/CDL.
Point of clarification needed here.
MEL = Minimum Equipment List
CDL = Configuration Deviation List
Both of these documents provide the operator the authority to dispatch an aircraft with certain systems or components that are inoperative, degraded or missing. There are usually some maintenance actions and operational limitations associated with a particular inoperative component.
If a system is not listed in either of these two documents, then that system must be fully operational for dispatch. There are many aircraft systems and components that are not in the MEL or CDL.
That said, Boeing considered MCAS to be a sub-function of the Speed Trim System (STS). In the original design, Speed Trim (and hence MCAS) used two independent controllers that alternated every flight. The MEL allows dispatch with one STS controller inoperative as long as the other was verified as operative. I assume this MEL item will be removed or substantially altered before the MAX returns to service.