Autopilot problem

[ofentress 0]

I'm still learning the operation of the Boeing 747-400x and have only had minor difficulties until now. For some reason, after powering up and taking off I cannot get the autopilot switch to operate. It doesn't light nor does it show anywhere that it is active. All other systems seem to be in order. Is there something in the set up I've overlooked?I could sure use help on this one since I crashed a couple of times shortly after take off.Jack Fentress

[downscc 1,327]

Screenshot might be nice.Do you have LNAV/VNAV armed? Is the preflight complete and the flight plan loaded?Basically, the A/P won't engage if any number of things are wrong just to make sure the black box doesn't add to your troubles.It's worth the time to go through a complete checklist while learning how to take care of her.

[mburkhard 23]

Jack,this may sound strange... but if you say you crashed shortly after take-off because you couldn't engage the autopilot then there might be a fundamental thing in your flying that's wrong and thus prevents the autopilot from engaging.What SHOULD happen after lift-off if the autopilot is not coming on... the plane should just initially follow the flight director and then along the steering commands you give. No reason for a crash.So yeah screenshots would be a big help here, with those we'll certainly be able to help you.Regards,Markus

[ofentress 0]

Markus......When I say I crashed, what happened is that after engaging GPS and other required items (the exception being the autopilot at that stage) the aircraft climbs at a rate that causes a stall and then...... bango. I'll try to recreate with screenshots although I've never tried to use screen shots before. From the replies so far it looks to me as if I have not setup something correctly.Jack Fentress

[Guest jumbojock]

This used to happen to me. Found out I hadn't set the trim correctly and the ac was over-rotating. Once you've set up the take-off page in the FMS and hardened up the C of G, it will give you a trim setting which needs to be selected on the THR screen of PMDG. Might help, might not.David "jumbojock" Robertson

[craig_read 43]

GPS? I don't know what you mean by that.. I mean the 747-400 has a GPS system installed but I don't know what you mean by "engaging" it.. it's just a nav aid and won't control the aircraft.Really we need to see screenshots for this. But before you take off check your MCP, PFD and FMC.. to make sure everything is setup correctly.1 - PFD should be showing TO/GA and TO/GA as roll and pitch modes before takeoff. As you start your take off role and engage the autothrottle via the TO/GA switch the throttle mode should become THR REF.. If you see no mode within the throttle indication on the PFD then you're autothrottle is not in control.2 - Check the MCP has autothrottle switched ON, both flight directors are ON.. that you haven altitude set for your assigned altitude on the SID, that LNAV and VNAV are armed (lit) assuming you're not going to be vectored (steered by ATC) shortly after takeoff..3 - Check the FMC preformance data is accurate, check there is an active route if you're using VNAV and LNAV.. check that there are sensible altitudes programmed. Check that your de-rates within the thrust page are set correctly, if you're unsure leave it unrated, CLB, TO...This should all be the case at the GATE, apart from the autothrottle switch, that's turned on (in my case at least) as I cross the hold to line up.. the same time as I put my strobes and landing lights on.. FLAPS go down after I've finished the push normally, or shortly after I've begun my taxi to the hold.. But your PFD at the GATE should show the flight director indicating the initial nose up to climb and the TO/GA roll and pitch modes..If you're crashing shortly after takeoff.. something is very very wrong.. Not sure if what I've said there helps.. above post is absolutely right, screenshots would make it a lot easier to diagnose..CheersCraig

[ofentress 0]

To all who replied with help-I'll try to recreate the scenario this weekend and also try to get screen shots. Thanks to everyone who replied. I'm sure I'll get the problem solved because of your varied responses.Jack Fentress

[ofentress 0]

Marcus (and Dan Downs, David Robinson, Craig).......Thank you all for your replies and suggestions which were finally successful. It looks as if I was overlooking some items in setting up a flight but when I went back (a few times I admit) and redid things it all worked out as it is supposed to. Now, it's a pleasure to fly this bird.Thank you all again. What a great forum this is.Jack Fentress