Hi,

I've owned PMDG 747 and the other titles for years. All the other aircraft run without any problems (737, MD-11) I also have LevelD 767-300 / 777 and Feelthere A320 so I am extremely experienced simmer.

 

However now and then the PMDG 747-400 sometimes does not allow the master Autopilot to engage. Via the CMD switch on the MCP Panel. It doesn't always not work I'd say about 1 in 10 flights I'll take off all FMC is setup and I'll engage the A/P, the light comes on and all is well, I then engage VNAV / LNAV etc etc. As I said all is well.

 

But sometimes the Master A/P refuses to swich on and illuminate, even by pressing the "Z" key it ignores my request. However the VNAV button will switch on and LNAV but the aircraft will not fly automatically. The Flight director follows the VNAV / LNAV mode but I have to fly manually, which ain't gonna work on a 8 hour flight !! So I have to abort the flight and return to my departure airport.

 

I thought it may be something I was doing wrong, but it doesn't happen on any other aircraft (even the PMDG 737) and I have performed checklists etc to make sure I haven't missed anything, as I said it doesn't always happen. I've also tried loading the default Cesna 172 before loading the 747. But this doens't prevent it.

 

Anyone have any ideas? Getting the same problem?? I can't find a thread which describes this issue...

 

Help appreciated !

 

Thanks

Tom.

I do not think that the Z command will work with the B747-400. If you want to use a keyboard shortcut with the B747, I believe you have to set it through PMDG's own menu.

Thanks for your reply.

 

But no it's not to do with using the Z key. The A/P will not engage through the CMD button on the cockpit. My point was the A/P will not engage at all, even using a dedicated key via PMDG options as well.

 

Again appreciate you trying to help but I don't think I'll get anywhere with this as nobody seems to have the same problem.

 

Cheers

T.

Did you trim the aircraft before trying?

 

Lee

Hi Lee,

Thanks for your reply. Yes I trim the aircraft as part of the pre-flight checklists and it's weird because when it happens it doesn't come on at all, no light on the CMD L comes on when I click on it i.e. if it was not trimmed properly at least it comes on then disconnects, so good thinking but unfortunately not the resolution, it's almost as if there is a systems failure, but I've checked the failures I reset them etc....

 

Funnily enough I just took off and the a/p worked totally fine, as I said before it seems totally random, which is really annoying because you can plan a flight get everything setup then have to abort your flight or fly the whole journey manually hmmmm.....

 

Cheers

T

Do you use the 2-D cockpit or the virtual cockpit? When you attempt engaging the autopilot through pressing any of the three switches, do they animate at all, or is it only the lights that do not light up?

 

Have you tried arming LNAV or VNAV before taking off? Have you made sure that all obvious errors have been addressed (autopilot disconnect tab has been pushed in, etc.)? Do you use any other add-ons involving views (e.g., EZCA) that might interfere with the operation of the virtual cockpit?

 

If you still have not determined the solution, perhaps screen shots of the controls, instruments, or panels would be helpful. Of course, you could try reinstalling the aircraft, too.

my cmd do the same thing when i turn on my aline. what to do? if you guy have answer thankyou.

Please provide better descriptions and screen shots in order for us to determine the cause of your issue. There are too many possibilities ranging from operator error to program malfunctions.

 

Welcome to AVSIM! If you experience further issues with flight simulation, consider opening your own thread.

I came across to this info in another forum written down by daveygurm10;

 

Both of your YAW damper switches are INOP which means they are not working.

Your havent aligned your IRS correctly either which is the cause.You can tell this from the yellow TRK on you nav display.

This is how to align properly.
 

1)First, press ALT and go to PMDG options. Find IRS alignment and change it to instant for this test.

2)load cold and dark - ONCE LOADED TURN YOUR IRS SWITCH TO OFF!!
3)standby BAT AUTO, BATTERY ON, APU START
4)APU will begin to run and click APU ENGINE BLEED ON -WAIT 30 SECS OR SO AND THEN YOU CAN CLICK APU AVAIL LIGHTS BY THE APU SWITCH.
5)This is the important bit - IRS  - ONE Right Click L,C & R IRS from OFF to NAV and then go straight back to L and LEFT click back to ALIGN, do this for C and R too.
6)Open FMC - Wait for the MSG saying POS INIT or similar.
7)go to POS page and where it says GPS position CLICK THIS and enter the digits intot he boxed filed below.
8)go back to overhead panel and RIGHT CLICK L,C,R IRS back to NAV. all you displys should become alive.