This makes total sense! So what's the deal with AC 91-67 (brought up
by Tony V above)? AC 91-67 seems to be a total red herring - it
contradicts the sensible interpretation of a MEL and seemingly permits
a pilot to do something stupid.

-John

On Jan 25, 9:36 am, Tony wrote:
no, if an instrument is on the required instrument list for a certain
type of operation then it must be installed and working. if it is not
on the required instrument list then it can be non-working and
placarded inoperative.