737 A/T ARM mode
 

Why Boeing didn't recommend the A/T to be armed during landing (deselect the existing) rather disengage the A/T? Doing this will let the auothrottle advance automatically to go around thrust during a single go around.

Q 2. I understand the A/T ARM mode provide underspeed protection, but why during takeoff mode thrust goes to THR HLD instead of ARM? If the mode would be "ARM" will this make the thrust to advance again in case of a rejected takeoff? If so, why? where is the "underspeed" in this situation?

Q1: My understanding is if a/c slightly slow approaching flare A/T will engage in MCP SPD and then at 27' RA engage in RETARD. If unexpected it could lead to a tail strike.

Q2: Actively prevents unwanted A/T activity, whereas ARM allows other modes to engage. This would be undesirable during takeoff.

Here are a few threads about the issue. It is a recurring question , enjoy reading:

http://www.pprune.org/tech-log/50018...-deselect.html
http://www.pprune.org/tech-log/27954...ing-737-a.html
http://www.pprune.org/tech-log/27478...ttle-b737.html
http://www.pprune.org/tech-log/13788...de-select.html
http://www.pprune.org/tech-log/82487...-arm-b737.html
http://www.pprune.org/tech-log/10958...othrottle.html