When ever I fly the PMDG 777, while descending, the engines always spool up like crazy out of no where. This forces me to disconnect the Autothrottle, control the engine power, then turn it back on, its very strange. Anyone know why?

What position are your physical throttles in when this happens?  The most likely cause is that you left the throttles in the full forward position at the beginning of your descent.  The next time your aircraft reaches the TOD (Top of Descent) point, watch the auto-throttle mode indication at the top center of the PFD.  Shortly after beginning the descent, you will temporarily see the word "IDLE" appear.  At this time, it is recommended that you should move your physical throttles (on your controller) to the idle position and leave them there until or unless you deliberately choose to manually control the power of the aircraft.  After a few seconds, you will see the mode change to "HOLD."  Once this happens, if you move the throttles at all, even if just the slightest nudge, the auto-throttle will assume that you are manually controlling the engines, and the power setting will automatically jump to wherever your physical throttles are set (and so if your throttles are pushed all the way to the firewall, then the engines will give you a mighty shock.  Remember that on the real aircraft, the physical throttles are driven by servo motors and automatically reposition themselves to whatever setting the auto-throttle calls for whenever it is engaged.  And so, even if you do accidentally nudge the throttles a little, the engine power would not change dramatically, since they are already in the physically appropriate position. "Hold" mode essentially means that the throttles can be overridden by physically moving them, as opposed to having to click press the "disengage" button.  The auto-throttle is designed to shift into this mode during phases of flight when the pilot might need to override the throttles quickly, such as during takeoff  before V1, and also during certain phases of descent.  When hold mode is not active, physical force on the throttles will not disengage the auto throttle, and the pilot must press the actual button.

 

If you do not like this effect, or if perhaps you suspect that your controller is spiking, you can turn the feature off entirely by going into PMDGs settings (in the FMC) and changing the throttle manual override settings to "NEVER."  Hope this helps.

 

Andrew Jones

When ever I fly the PMDG 777, while descending, the engines always spool up like crazy out of no where. This forces me to disconnect the Autothrottle, control the engine power, then turn it back on, its very strange. Anyone know why?

 

Ensure that your physical throttle levers are at idle, as Andrew mentioned. See his post for better detail.

 

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