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Chairman

747 fs9 more VNAV problems ...

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It's my turn for the VNAV issues ...The 747 is basically unflyable for me at the moment :-( After I take off I begin a climb to cruise altitude and the VNAV goes all to heck. The climb rate varies from plus 7000fpm to minus whatever it takes to recover from the inevitable stall, and the max speed I ever see while this is going on is around 240 because as soon as the stall stops the nose comes up again.I've had what feels like a thorough search/read through here and everything seems to point to the weather, so on the latest attempt I killed activesky and loaded the "clear skies" weather theme which claims to clear all the weather, no improvement. Another issue I have which may be connected is that the autothrottle doesn't seem to want to control anything, it can suggest whatever it wants with the white lines across the bars on the N1 gauges but what the engines actually do is whatever my throttle lever tells them to. Cycling the AT off and on a couple of times often solves this.The trim is within the green band, the fuel seems correctly set up, the plane wasn't overloaded - max payload and ~88000 lbs of fuel.Here's a screenshot showing the main panel and all the bits that normally get asked for, if you want to see the overhead there's another copy here that shows that as wellhttp://www.pbase.com/garylowndes/image/102854052Any suggestions ?ThanksGaryps yes I know I haven't updated the heading :-)http://www.pbase.com/garylowndes/image/102...17/original.jpg


Gary Lowndes

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What is your TOW? If you are experiencing high climb rates try D-Rating the climb to climb 1 or 2. This can be done in the Thrust Ref page.Also try lowering the CI to about 70.You mentioned cycling the A/T on and off solves this, are you engaging TO/GA on the ground by clicking on the screw next to the A/T?PS: When youre in LNAV you don't need to worry about the Heading. That should be in the FMC.


Kevin Hester,

 

Indianapolis, Indiana

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Okay, you've ruled out weather. Next, let's figure out why VNAV isn't controlling pitch. I'm not expert but your panel shot looks okay except for the obvious speed/attitude problem.At what point after takeoff and engaging A/P does she start loosing pitch control? Does she accelerate through the flap retractions schedule alright and hold the initial climb speed below 10,000?I think we gotta start looking for the problem well before you make it to FL330, maybe there are some clues where it starts misbehaving.


Dan Downs KCRP

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>>ps yes I know I haven't updated the heading :-)>And you haven't set standard pressure passing 18000... But none of those is the problem here.Being at 33620 ft, you are climbing with excessive pitch (10


signed: José Luis

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Despite weather being ruled out I am leaning towards the famous OAT problem. It seems the TAT on the EICAS shows +32 which is IIRC high for FL320. Gary, can you recollect the outside air at the time of the erratic behaviour and possibly confirm the TAT temperature shown? Maybe the Clear Weather doesn't reset the temperatures?Hope it helps,


Mats Johansson
PMDG Flight Test Dept
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I'm forming the conclusion that it is something to do with weather after all. Unfortunately it takes about 15 mins per test flight so it's a slow process :-(I've done a whole bunch more takeoffs all from the same saved flight and I think what's happening is that if I load FS9 and load the flight and go everything is fine - I can use any of the weather themes and it's all good, departure and climb are by the numbers.As soon as I load Activesky (6.5) it all turns to custard. If I then close AS and go back to any of the built in weather themes such as clear weather it's still custard - once AS is loaded I have to exit FS9 to unload it and get back to proper vnav behaviour.I haven't tried it with FS9 live weather, and I haven't tried it using AS's themes instead of live updates, I'll give that a shot tonight.I think the temp shown is actually -32 not +32. Yes I'm clicking the screw for TOGA, often I don't even bother moving the throttles, I just click the screw and away we go :) That actually seems to be behaving now so it was probably pilot error.If it's going to turn to custard it will do so almost immediately after takeoff. I'll do a couple more tests tonight and give a running commentary on exactly what's going on.ThanksGary


Gary Lowndes

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Well ..........I've tried a few different things, and a lot of different attempts at this saved flight. There doesn't seem to be any rhyme or reason to it. Loading ActiveSky did turn it to custard, but so did trying with the clear skies theme which worked fine 5 times in a row last night. The only 'textbook' result I got tonight was with the 'stormy weather' theme.One thing that does occur to me looking at my screenshot, isn't it a bit odd that the autothrottle is showing "THR REF" ? I'd have accepted THR or even SPD but if I'm RTFMing correctly THR REF makes the engines sit on their thrust limits which is probably not the best possible way to control anything. The whole thing is actually probably down to pilot incompetence :-zhelp (-: CheersGary


Gary Lowndes

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VNAV SPD THR REF is entirely apporpriate for a VNAV climb- I am not entirely familiar with the 400X but have hundreds of hours in the FS9 version- VNAV is not an issue. I would urge you explore the temp issue, weights and FLs and encourage you to spend some time with the manual, it is entirely worth reading.For Kevin- despite not "needing" the heading in LNAV, I would urge you constantly align it with the a/c heading, that way should you need to go into HED SEL immediately (ATC or otherwise) its simply a matter of pressing the switch- the other way you could end up having to turn the knob at a furious pace, or worse commanding an unintentional turn.Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png| XP Pro SP3 with FS-GS System Unification | 2 x APC UPS | Coolermaster Stacker 830 SE | Asus P5E-Deluxe (X48) | e8500 @ 4gHz | Tuniq Tower 120 | EVGA 8800GT 512MB | Sony 40" Bravia XBR | 2 x 1 GB Corsair XMS2 | 500GB Seagate Barracuda 32MB SATA2 | Corsair HX620W PS | CH Products Yoke-Pedals-Throttle Quadrant | Aerosoft 747MCP-EFIS-EICAS |


Best-

Carl Avari-Cooper

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I know that I've posted this suggestion many times, but since you've tried everything else, here goes. In the PMDG 'Options' menu, try unchecking the two boxes next to 'Controls' and 'Throttle' overrides in the AFDS section. If you have electrical noise spikes with your controllers or you don't have a good sized 'null zone' set in the FSUIPC joystick calibration menu, these 'spikes' will disconnect the autothrottle with no warnings and other really bizarre VNAV behaviors similar to what you are experiencing.Kim


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>VNAV SPD THR REF is entirely apporpriate for a VNAV climb- I>am not entirely familiar with the 400X but have hundreds of>hours in the FS9 version- VNAV is not an issue.That's the version I'm using, and I'd have to say now that I agree with you. I just finished a short (~1 hour) flight from NZAA to NZCH using Activesky for weather, and I followed the normal procedures checklists religiously, and the plane performed flawlessly.No idea what I was getting wrong before but I'm happy not to still be doing it :-)I spent a while reading about autoflight too and I see now that yes THR REF is quite normal for a VNAV climb, provided the vertical navigation is in a mode that use pitch to control airspeed.Thanks,Gary


Gary Lowndes

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>I spent a while reading about autoflight too and I see now>that yes THR REF is quite normal for a VNAV climb, provided>the vertical navigation is in a mode that use pitch to control>airspeed.>....thats the VNAV SPD bit ;)She's a lovely girl- but she takes a bit of getting used to- enjoy!Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png| XP Pro SP3 with FS-GS System Unification | 2 x APC UPS | Coolermaster Stacker 830 SE | Asus P5E-Deluxe (X48) | e8500 @ 4gHz | Tuniq Tower 120 | EVGA 8800GT 512MB | Sony 40" Bravia XBR | 2 x 1 GB Corsair XMS2 | 500GB Seagate Barracuda 32MB SATA2 | Corsair HX620W PS | CH Products Yoke-Pedals-Throttle Quadrant | Aerosoft 747MCP-EFIS-EICAS |


Best-

Carl Avari-Cooper

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Guest D17S

The two main things I learned about the APFD/Vnav and the TO sequence was:1) That airplane is a rocketship. Even now, I rotate a bit early to control airspeed on the initial climb. My initial focus is on the airspeed tape. That's your whole world until airspeed is stable. I often have to pull - Agressive - pitch to control runaway airspeed. Speed - on - pitch. However, once airspeed it stable, do Not continue to use pitch to slow to some previously calculated V2. That FMC's calculated V2 is about clearing an obstacle from V1 with only 3 engines running. If you're that far along with 4 still running, that obstacle is no longer a factor. Never give back airspeed unless you are about to hit a bridge. Keep it "in the bank."2) Never hand Otto (the autopilot) an unstable airplane. The ol' boy is just not up to it. Once airspeed is stable, I'll poke da button, but not before. Otto will give you quite a ride if you leave it to him to capture a (still undefined) V2 in the case of an (still aggressively) accelerating airplane. Quite a ride!

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>2) Never hand Otto (the autopilot) an unstable airplane. The>ol' boy is just not up to it. Once airspeed is stable, I'll>poke da button, but not before. Otto will give you quite a>ride if you leave it to him to capture a (still undefined) V2>in the case of an (still aggressively) accelerating airplane.>Quite a ride! I'll drink to that ! The test flight I've been using for all this had me lined up on a runway facing almost exactly away from where I wanted to go. A couple of times I tried putting on LNAV and VNAV as soon as the plane was off the ground. Watching Otto try to do a steeply climbing 180 degree turn from ~v2+10 at the same time as controlling the pitch to bring the airspeed under control, yes, quite a ride. Gary


Gary Lowndes

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