First off, thanks in advance for the great product line and support that you guys put behind it!I am having an issue when descending in VNAV that I didn't have on the 744 before installing the F.Shortly after the aircraft has begun its descent and settled in on the path (by the way, nice transition from cruise, much smoother than before) the throttles decide to advance to near full power, rather than staying back and maintaining the descent speed. Then, once the plane reaches overspeed, the engines throttle down, and then back up again. This same problem happens when using FLCH for a descent as well, the engines never pull back to idle, instead they advance to max power.When I disconnect the autothrotle and set thrust manually it behaves itself. Haven't gone back to the pax version to see if the problem is there as well.I certainly hope that I'm overlooking something new in this update that I didn't have to do in the original B744.Any suggestions would be appreciated!

Check the PMDG options menu for A/T overide.................Randy J. Smith................A PROUD MEMBER OF THE PMDG BETA TEAM[h4]Evolution is a process that results in heritable changes in a population spread over many generations[/h4]

Randy,I have it checked. Pretty sure I've had it this way since is was added. Is this correct?

I don't get this logic. One of the most advanced airliners in the world and the A/T won't operate like they do in almost every other aircraft? What good is A/T?

>and the A/T won't operate like they do in almost>every other aircraft? Is it an appeal to Boeing to redesign their A/T in 747? Hmm.. ok.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg

No no, you missed my point. Why would the A/T not prevent overspeed like it seems to do in the 737. I know they're different, but it seems an Autothrottle should at least prevent going over the MCP or FMC calculated speed even it's it basically idle for descent. I find that logic odd.

I am running into a similar situation. I walk away from the aircraft in cruise and when I come back it is in overspeed. The only way to get the thing to slow down is to disconnect AT and retard the throttles manually. This also seems to happen if I leave it paused for a while. I've never run into this before and I'm very familiar with fms/at/ap opperaton so I'm a little confused. This never happened in the pax version.Scott

The path that VNAV PATH calculates is based on idle thrust at a specific airspeed. Therefore, at TOD, thrust should go to idle. Watch that left FMA like a hawk. That's your thrust mode. It should annunciate "IDLE" ("IDLE" then "HOLD" with the new version?). What's it annunciating when things go haywire? Also, what is your target airspeed (above the speed tape) before and after the thing goes nuts. An FMA __ left-thrust / right-pitch __ and target airspeed (magenta airspeed above the speed tape) 'blow by blow' might be helpful too. Are you using the DES NOW function? (Please, no!)Just for fun: . . . With the AT engaged, move your controller's throttle. Can you adjust thrust with your throttle? Keep checking and un-checking boxes till you CANNOT control thrust with your controller's throttle when the AT is engaged. That'd take one variable out of the troubleshoot.

Actually, in my problem mentioned above, the A/T did protect against overspeed. What was strange is that it would go to max power, accelerate to overspeed, and then throttle back, then repeat that cycle.Randy mentioned the Throttle Override option. Despite reading the manual and a number of related posts I'm not quite sure I understand what that option does.Can anyone please explain it for me? Why do I want to use it?

Sam,Getting late, but here's the play by play as I remember it:1) Frindly FMC warning to check MCP altitude. I do so.2) At TOD, the throttle reduces, IDLE is annunciated, target speed as determined by the FMC is 313 knots.3) Plane begins gentle descent, nice and smooth.4) Within 30-40 seconds, throttle goes to the wall, HOLD is annunciated. Still reads 313 for the target.5) I try changing the target by changing the speed on the MCP. No go, still full power.6) I switch to FLCH, now have IDLE back, but no change in throttle.7) Time to disengage the A/T, setting thrust manually works fine with FLCH. Too terrified to bring back VNAV.I'll try to grab some screenshots tomorrow to help tell the story. Thanks for your input!

4) Within 30-40 seconds, throttle goes to the wall, HOLD is annunciated. Still reads 313 for the target.That might be it. "HOLD" is now an active VNAV mode in the new model. "HOLD" will allow a thrust adjustment without disco-ing the AT. The HOLD mode may be allowing some external input to control the throttles. Do you have the reg'd FSUIPC? (See where I'm going?) Try the throttle override experiment with the left FMA annunciating anything BUT "HOLD". I'll bet you can override thrust with your controller. That would be good, because we probably found the problem . . . or not . . . that would be bad because we still haven't found it. 6) I switch to FLCH, now have IDLE back, but no change in throttle.If so, this is a glitch. "IDLE" should allow the AFS to retrieve throttle control from . . . whatever. However, maybe once you give control to a controlling controller, it may not want to give it back. You know how that goes.

He could also do a simple experiment - once he reaches TOD he could physically unplug his controller (with the throttle) and see what happens. I think he might be surprised at the results.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg

Guys,You're not understanding what HOLD and the A/T Override option do and I believe that's the source of the problem here:The real 744's throttles are connected to a mechanical servo that moves them when the A/T is in SPD or THR mode. When it goes into HOLD mode, that servo disconnects, allowing the throttles to be manually repositioned. VNAV PTH is exactly such a mode where this occurs - it's there so that the pilot can make slight adjustments to the A/T in order to compensate for slight under and overspeeding. Why couldn't it just stay in SPD mode all the time? Ask Mr. Boeing. HOLD is not, however, a "VNAV mode" as someone said above - it is an autothrust mode and doesn't happen only in VNAV.Anyhow, the issue here is that unless you're a crazy home cockpit builder with tons of cash, you don't have a servo in your throttle moving it under the AT's commands. If this is the case, you need to manually position your throttle to the setting that corresponds with the commanded N1 value. This is not easy to do with a small sensitive joystick and if you happen to have your throttle firewalled when the A/T goes to HOLD, it will go to the N1 limit and you'll overspeed. For that reason I recommend UNCHECKING A/T Override, which gives total control to the panel and does not allow your throttle to affect thrust in HOLD mode. You may under or overspeed slightly in descent, but it will be only by +/- 5 knots or so usually.

Thanks Ryan,I'm guessing that might explain the behavior I'm getting in cruise also. I firewall the throttle on departure and let AT take over. If it goes to hold, it would overspeed.Scott

>happen to have your throttle firewalled when the A/T goes to>HOLD, it will go to the N1 limit and you'll overspeed.That was my hunch from the beginning, therefore suggested that he unplugs it and see what happens.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg