On occassion, I am unable to engage the A/T Arm switch (Auto Throttle). I flip it on, but it immediately switches itself off! All other sections of the autopilot work well, LNAV AND VNAV,despite the fact the A/T is not engaging. This does not happen all the time, only on occassion.What causes this? How can I correct it while in flight?Thanks.Stanner

Hm, hard to tell without more details but:(1) Does your A/T go off when your throttle control is manually moved? If that is the case, then this could be a noisy joystick.(2) Something tells me that the AFCS somehow does not know what the speed should be -> do you have the weights enteredin the FMC?Hope this helps ...- Neeraj

Stanner,I'll bet my next paycheck you don't have your ENG GEN engaged when you can't engage the A/T. ;-)Hope it helps,