autopilot question pmdg 747

[pkofman 4]

Today i encountered an intereesting scenario wherein I programmed the fms fully in the 747 and took off. I did engage the FD and AT , but decided to fly to the first fix using Heading Hold and Alt hold and that worked out well, I then engaged lnav and vnav, and that worked as well and I proceeded on course. BUT, when i pressed the cmd buttons on the autopilot it did not light up or engage. I would have thought it should be lit when the lnav and vnav is engaged. Is there is some reason the cmd button does not light up if the autopilot is engaged and the aircraft is following the programmed fms.Peter

[lostmoon 0]

this what comes to mind:1. i've noticed with my experience, that when i fly the NG, then fly the 744 thereafter, CMD bottons become INOP. I learned the hard way with this when flying on VATSIM on one occasion (KLAX-KSFO)and upon rotation, at 1400', CMD buttons did not work. Dissengage bar was up, and no matter what I did, she wouldn't kick in! So, I hand flew her to KSFO. My yoke had a good workout that night.2. from what you are telling us, you flew "the first fix using Heading Hold and Alt hold and that worked out well..." weird, because i am not certain you can fly those particular modes without AP. Something is gone awry. GL, matey!

[pkofman 4]

>this what comes to mind:>>1. i've noticed with my experience, that when i fly the NG,>then fly the 744 thereafter, CMD bottons become INOP. I>learned the hard way with this when flying on VATSIM on one>occasion (KLAX-KSFO)and upon rotation, at 1400', CMD buttons>did not work. Dissengage bar was up, and no matter what I did,>she wouldn't kick in! So, I hand flew her to KSFO. My yoke had>a good workout that night.>>2. from what you are telling us, you flew "the first fix using>Heading Hold and Alt hold and that worked out well..." weird,>because i am not certain you can fly those particular modes>without AP. Something is gone awry. >>GL, matey!Well you are more patient than I, I would not have hand flown for the whole flight although it keeps up the IFR coordination.I dont really understand the situation either, because as in the 737ng the ap A needs to be engaged to use the HH or ALT Hold., The disengage bar was in the proper position, So I will try it again and report back. Normal procedure indicate that the cmd light should be on for autopilot use. Two more questions since we are at this1. Where is the TO/GA button,,on the 737ng it is a thing that looks like a rivet.. 2. Will the 747 autoland if the cmd a and b are engaged and both nav radios are on the same ils freq.Thanks for your help..Peter

[downscc 1,327]

You problem might be that the next fix as far as the FMC is concerned is the one you just passed flying heading and alt modes. If there is nothing else preventing AP to engage, then try moving the next fix up to the top line of the legs page. (use the LSBs, press the button left of the fix you want on the top line then press the top button). The FMC doesn't autosequence the fixes if they are flown by in any other mode but LNAV.

[pkofman 4]

>You problem might be that the next fix as far as the FMC is>concerned is the one you just passed flying heading and alt>modes. If there is nothing else preventing AP to engage, then>try moving the next fix up to the top line of the legs page.>(use the LSBs, press the button left of the fix you want on>the top line then press the top button). The FMC doesn't>autosequence the fixes if they are flown by in any other mode>but LNAV. Honestly, I will try it again tonight because it seemed like a glitch.I really think it should have worked. Perhaps there is a power switch for the AP i missed. There is no doubt that if I had 1-lsk the next waypoint the fms would have taken me there directly, Still no real answer as to why none of the cmd switches were not working.

[Guest Maxybo]

I have the same problem with the 747's autopilot, everything else is set up and sometimes the autopilot cmd button will just not engage.Hope somone finds a fix for this one :)Cheer