i read the tutorial on the autothrottle and am still having problems with autothrottle spontaneously disarming when i try to arm it. it happens right after i attempt to arm it in the pmdg 737, i am probably missing something obvious. i would just like to know some suggestions as to what it could possibly be. it does work when i immediately arm the autothrottle after starting up my flight and as long as i keep the engines running on the ground. after i stop the engines, and restart them, i get the warning light of autothrottle disarmed when i attempt to arm it or if i wait too long after the fs session has begun. any suggestions for something i may have overlooked would be greatly appreciated.

From what I am reading, and I may be misinterpreting your, you are arming autothrottles after start up. You don't want to be doing this. Arm autothrottles when at the runway hold short line. Then disarm upon engine idle on landing.