Originally Posted by
threemiles
You should not be bothered. Language in aviation in general, SBs and ADs in particular, is safety critical and should be clear, not contradictory and unambigious. This sentence MAY mean what you say, but it needs interpretation and twice thinking about it. This is bad and typical for lawyers. Boeing should know how to do better.
We should keep in mind that this is an
Emergency Airworthiness Directive. The point here is to get what is perceived to be critical information out to the operators as fast as possible. In the course of doing so they make sure that the contents are correct and pertinent, but it may err on the side of caution. There may not have been time to verify that it is
always true that the autopilot disconnects in all conditions leading to the autotrim continuing to trim nose-down, so it says that it
may disengage or cannot be engaged, and "autopilot off" is part of the procedure. There is nothing very unusual about this E-AD.
And to those complaing that they are trying to fix the human to conform to the defective machine, again this is a temporary measure, it contains some element of CYA, but it is also probably the best that can be done on a few days' notice.
After a thorough investigation, a technical fix may follow, but this takes a long time in the aviation industry to make sure that the fix actually improves
overall safety, and not just fixes this particular instance of a problem, while exacerbating other problems (such as weakening the stall-"prevention" function of the nose-down trim when air data is accurate or when the higher-reading AoA input is actually correct and stall is impending.)
What worries me a bit more is the sentence
[...] set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.
I'm not that closely familiar with 737MAX systems, but how can the trim still run away if the switches have been set to "CUTOUT"? Aren't they mechanical circuit breakers?
Bernd