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keyscapt

747 Autothrottle Problem

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I'm having a little problem with the autothrottles in the 747 ... I've searched here and through the docs, but haven't found a solution.During cruise flight, with either ECON or LRC settings, A/T armed and engaged, the aircraft will constantly slow into the yellow and eventually the red regimes. The only solution I have is to disengage the A/T, manually control the power levers to regain speed, and try to find a setting that will hold the target speed. I've tried all the options: speed, VNAV, FL CH, but no matter which is engaged, the aircraft will behave as above, even though the A/T is being controlled by either the MCP or the FMC. The altitude is as selected by the FMC for the load, in this case FL300.Just to reiterate, as soon as any A/T regime is activated, the power levers will move toward flight idle and the aircraft will slow into the stall range. N1's are at 96% or thereabouts. The FMC is commanding M.832. I've checked fuel loads and weight limits, all are in range. I'm a little stumped here. Oh yeah ... this is FSX on a Vista machine, with all the necessary ingredients.Thanks.Tom S

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Did you take a look at the PFD when this happens? Is there any indication of the autothrottles actually commanding the aircraft? SPD or THR REF should be indicated. If the annunciator is blank then the autothrottles are not engaged.Karsten

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They are engaged ... I made sure of that before I posted. I know that the indicators will light even when they're not being commanded by the system, but I verify by moving the power levers myself.Just to add, I observe them move towards flight idle under command regardless of which autothrottle regime is active.Thanks.

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A/T problem only during cruise? So takeoff and climb are okay but in cruise the speed decreases.... try it without any weather see if symptoms change.

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Although I did mess with the settings in FSUIPC when trying to troubleshoot this (in flight) and selected real world weather as well, with no difference noted, I will try another flight and eliminate weather as you suggest.Thank you for the input.

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Have you tried to repair the installation? This has cured other problems for me. Don't know what it is in Vista, but XP it's control panel, add/remove programs, then select the change button under PMDG and repair the installation.Jeff P.

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I'll give that a shot also. Thanks for the suggestion. I'll let you guys know the results.Edit: Well, no repair option in Vista. It's either remove completely or pound sand. :(

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