PMDG 744 alt. hold \ VNAV crz oscillations.

[Guest NGdriver]

Greetings all.I`ve been having some problems with the 744, when on cruise altitude the plane never seem to capture the assigned alt. properly and keeps chasing it by up to +- 1000fpm. I`ve only used the PMDG fuelpax loader, deactivated VAS in ASV and even tried to deactivate the joystick axes to see if that could help but to no avail. The problem occur on all cruise altitudes, any speeds and in any weight conditions.Anyone else experiencing this?BrgdsKevin

[Mats_J 2]

Kevin,This was never reported as a problem during beta. Have you tried to uninstall and then reinstall the 747? I seem to remember that sometimes the A/P in the NG showed the same behaviour and that a reinstall could solve it.Hope it helps,

[WAD3 0]

I am having the same problem currently from PAE-SFO.

[Guest NGdriver]

Hi Mats, yes three times already but it`s the same every time.

[jordanal 70]

Yup, saw this same thing last night. Oscillates by about 500ft. But this didn't happen on my first flight the night before. Could it be load manager related? That's the only thing I can think of that I may have changed b/w filghts.Al

[Guest bofficer]

I too am experiencing this same problem. I haven't made a definate connection, and this could be purely coincidental, but when I went into SPOT view and back to the cockpit is when it seemed to happen with me.Brian Officer

[Guest NGdriver]

Might be it! On the first install everything worked fine the first flight. I hadn`t used the load manager there but on the next flight after using it the AP went crazy. On the second install i used the loadmanager before the first flight and the same occurred. On the third (phew!) i did the first flight without using the load manager and the AP was steady as rock but now on the second flight (also without using the loadmanager) the AP is constantly overcorrecting the altitude. Oh, BTW! Thanks for the pogostick! :D

[WAD3 0]

What I worry about is how many validations do you get. With my luck I will do a reinstall have a problem and then need to try it again and not be able to validate. I guess though if it didnt correct the problem for others probably wouldnt help me out either.

[Guest Ray CYYZ]

could be weights are off ... also ... what about frame rates? are you trying to run it quicker then your machine can handle? I remember this kind of oscillation with time compression when you overrun your machines ability to crunch numbers.Smooth as silk here with fs9 locked at 25 fps.Ray

[Guest NGdriver]

Same as you Ray, i was thinking it might be a FPS related problem but it can`t be.

[Guest Ulf Karscht]

I think this babe has got problems on slower computers.My AP works fine, but my thrust levers have a #### of a roller coaster when going on 4 times acceleration!

[Tabs 2,790]

Had a friend seeing this issue and it was because he was trying to climb to an altitude that was too high for the plane at that weight/fuel load. What kind of flight are you seeing this on?The real 747 has to step climb on a long flight where the plane is heavy - don't take off with a full load expecting to zoom up to FL410.If you look at the FMC CRZ page, it shows you an optimal altitude based on current gross weight. Don't try to climb above that altitude - climb to it or slightly below it and the plane will tell you when it's time to step climb up another 2000 feet.

[shortspecialbus 13]

I can vouch for this. I was in a stable cruise at 37000 and for no apparent reason the plane started climbing and descending at around 3600fpm up to about 40000 and back down to 35000 without ever stabilizing again. Speed basically would go to overspeed during descents and 50kts low during climbs.My fix at the time was to disable the autopilot and autothrottles, manually level the thing out at 37000 and manually adjust my speed. I then turned the AP back on in VNAV mode with the A/T on as well, and it worked itself out.I've also noticed some strange behavior on approach - it got itself stuck in a 1800fpm descent and drove itself into the ground (i let it, just to see what would happen) on a different flight. Never gave a terrain warning or any callouts. This was going into LAX from the Ocean side - not really any terrain there... It didn't even try to hold the glideslope.Along with that, I've noticed sometimes my #1 engine gets stuck about 40% N1 Higher than the rest of the engines - My last approach into KORD was too crazy with that engine basically doing whatever it wanted, so I disabled A/T and did the throttles myself. Not really a big deal, since I don't mind using the Throttle Quadrant that my girlfriend got me recently, but it is a bug nonetheless.Maybe I shouldn't lump this all into one post, but they all seem vaguely related to the Original Poster's problem.-stefanedit: oops, forgot to sign...

[NunTsuKao 0]

Hi.I have a big problem...i dont now why, but my B747 appears whit the start up completed and after a few seconds (about 20 sec) all my displays get off...buf and i cant reed any information. Im lookimg for this in the manual but i dont find any procedure....Please help.Thx.

[Guest NGdriver]

The oscillations occur regardless of altitude, on my last flight they started at FL320 (the CDU suggested 330 as optimal FL but i had to take 320 due to RVSM).To NunTsuKao, please don`t hijack this thread.