Hello,

 

I've been having a problem with VNAV descents and thought I would check here for some help. At T/D with VNAV engaged the aircraft will start its descent as it should. After a few thousand feet the A/T applies full power and blows right through the target airspeed putting the aircraft in an overspeed situation resulting in a climb not a descent. What is happening here? What am I doing wrong? I did not have this problem in the tutorial.

 

Thanks,

James

The tutorial likely had you pull your hardware's throttle back to IDLE. Remember that in certain A/T modes, the throttle is not clamped. If your hardware throttles had servos in them, the A/T would move them back to idle, and then I believe it would unclamp so that you can move them at your discretion (you're in pitch for speed mode). Since your hardware doesn't have servos in it, your throttles never got placed on the idle stops, and since your throttles are still probably at the forward stops from takeoff, it's firewalling your throttles as soon as they're unclamped.

Yeah as Kyle mentioned the A/T often goes into ARM during descent when in VNAV path, this pulls back the throttles to idle and unclamps them if you need to make adjustments. If your physical throttles remain forward of idle if may command that thrust setting when in ARM mode. There is a PMDG option in the FMS to disable manual override control of your [physical] throttles during ARM or any other A/T mode.

 

Either that for remember to pull your throttles back on descent to match the virtuals ones in the virtual cockpit, assuming this is the problem however.

Yep, that's probably the problem. I will test it tonight and report back. Thanks guys.

 

James

Welcome. Let us know if it works or not.

Pulling the throttles back to idle worked. Thanks again guys.

Awesome! Glad we were able to get it sorted!

Good to hear.