MCP error (IAS and HDG knobs stop working) on 747-400X

[RPRIEVER 52]

Greetings all,Here's a weird situation that's occurred twice in a row. After starting with a "cold and dark" scenario, I went thru the normal operating checklist. After I got to the fuel panel, I loaded the fuel (using the PMDG menu). After that, I was unable to rotate the IAD/MACH and HDG knobs on the MCP panel. The numbers wouldn't change. The ALT knob, however, worked fine. Because this had happened previously, I had checked the knobs after I booted up the sim, and they worked ok. Any idea what's happening here? It could be something unrelated to adding the fuel, including any items from the beginning of the checklist. Appreciate your help,Ron

[Mats_J 2]

Ron,Never seen anything like this reported on the forum. Confirm you not using a panel state file saved with an older version of the 744. And just to rule out the obvious confirm you tried both right and left button click.Hope it helps,

[Guest glenlee]

Hi, do you have the power on?On mine if there is no external power at the time you try to turn the IAS and HDG knobs they dont turn. Connect either the APU or External power to the bus and off they go!Glen Lee

[RPRIEVER 52]

Hi Glen and Mats,Sorry for the delay in responding, it was a busy weekend. I just booted up the system to recreate the problem. I went to a saved "cold and dark" scenario. I had to go to the PMDG options page and click on the "Ground air/power available" option. This of course allowed me to turn on the ground power in order to do the checklist. I had the APU off. Starting from page 1 of the official checklist, I was able to turn the IAS and HDG knobs normally. I proceded thru the list, checking every so often to see if the knobs were disabled, which they weren't.....until I got to the "fuel panel" section. I added some fuel (using the PMDG menu, not the MSFS one) and sure enough, the knobs stopped working. That's when I checked to see if the power was still on, and lo and behold, the "external power" seems to have shut down after I added the fuel. This corresponds to what Glen had said. I had to go back to the PMDG options, again click on "Ground air/power available", press the ground power button on the overhead panel, and the knobs worked properly at that point. Now, the obvious questions is....why is the EXT power shutting down after I add the fuel? This applies not only to the overhead button, but also in the options menu. Is this by design, or is there a glich in the system? I'm perplexed.Many thanks,Ron

[downscc 1,327]

That's interesting.I've always started up the APU early where first mentioned in the checklist. This gives it time to run for a couple of minutes before putting a load on it's electrical or bleed air supply.If you wait until the second time APU is mentioned in the checklist, that is just before engine start and you're going to have to wait a minute before pushback.I'm waiting to hear from an expert if this is normal behavior.