...you use MEL or operation manual
Ops manual and common sense.
However, I've noticed otherwise, by some sideways thinking individuals/companies.
Lets look at an example.
Three engine widebody airplane.
#1 IDG trips offline, and cannot be reset, whilst taxiing for takeoff.
Abnormal checklist completed, APU started, and left operating until 10,000 feet, as per procedures.
What
not should be done, is returning to the stand, so engineering can put an 'inop' sticker on the panel and the defect recorded in the DD log.
And yet, I've seen pilots do just that...
