Erratic VNAV control

[Guest chrisdb]

HiHaving read the excellent flight guide published in this forum I have now managed a couple of successful flights. There is, however, still one problem that I encounter quite a lot (most times in fact) whereby the plane does not follow the VNAV flight path. Worst still, the speed keeps varying between 145 - 160 knots while the vertical speed oscillates from anything between +/-4000fpm.I also find that sometimes HOLD does not come on during the take-off rollout, and sometimes auto throttle does not come on at all despite having FD and Auto throttle turned on.LNAV is always followed perfectly and I wondered if my problem is glaringly obvious from the symptoms.Alas I am not near the computer so I can't be any more precise at the moment.ThanksChris

[Guest D17S]

[Guest chrisdb]

Thanks very much for your time Sam. I will get all the information together this evening. Would it be useful for me to attach the saved flight so that you can also see the exact state of everything? If so, what file(s) would be required?ThanksChris

[Guest D17S]

The MSFS "saved flights" function means 'start here.' That'd work fine . . . except I pulled up one of my old saved flights and found that the airplane was where I left it, but the panel was blank. It seems a saved PMDG "panel state" might also be required This panel state could be saved with the PMDG drop-down menu item > Panel State > Save/Load Panel State.For the files involved in a flight that you saved with the MSFS 'Save Flight' function, look in the MSFS Help Index under "Categories (of flights)." That will tell you where the MSFS files are and which files are involved.One way, or some other way there will be a PMDG 'Panel State' file involved. Either MSFS saved it with your saved flight file or you will have to save it yourself when you save the flight with the MSFS save function (PMDG drop-down menu item > Panel State > Save/Load Panel State). These files are typically stored in FS9 > PMDG > 747400 > Panelstate. There are .sav and .rte files in there . . . and this file structure-flight rebuilding stuff is getting way beyond me real fast now! Help. Anyone? But I think we're on the right track. Great idea. This would be a great 'help' tool if folks could send an actual flight for the community to look at. If you could round up all those files, it would be worth a try to rebuild the flight on a remote machine.Now how to make them available? Once again, Help. Anyone? I'm not aware of how (or if it's even possible) to attach files to a post. Got a little, personal web site we can download them from? Other than the picture, a thousand words may have to do.

[Guest chrisdb]

Hi SamFirst the bad news. I meticulously played out the scenario making a note of everything that I did from loading the saved flight until take off, and it went perfectly with no problems at all. So I feel very silly indeed.But, the good news is that I have created a public shared folder on my company's web server that everyone can use to upload files as they wish. To access the share :-Go to "Network Places" in windows and create a new network place. The url is http://public.linchetta-software.co.uk/FlightSim. No logon is required. The folder will open just as in Windows Explorer and you may copy files in and out just by the usual drag/drop or copy & paste.I though the best scheme to use for putting files up is to create a folder with your forum alias (right click and choose New Folder), and then create the folder tree as it is under flight sim so that it will be obvious where files need to go, so for example, chrisdbPMDGSIDSTARSchrisdbPMDG747400PanelStateetc... and put the relevant files in thir respective folders.I have not put any restrictions in terms of permissions or file sizes etc., so you can create and delete folders and files as you wish.If you or anyone has any more ideas to improve or refine this then plase say.Best regardsChris

[Guest D17S]

Woah. . . I was just dreamin' out loud. This sounds very, very good. I'll gather up a set and upload em, then see if I can transfer a flight across the room to my laptop . . . via the other side of the world. Is this fun or what?

[Guest chrisdb]

Hi SamAlas, I spoke too soon. I do still get the same behaviour. I have now uploaded all the files for this flight so you can try it. If you go into the chrisdb folder all the files are in the structure as on my machine. The flight is at the threshold of 27L heathrow, flying to Amsterdam. You will have to open the FMC and on the Per Init screen use LSK R4 to set the trim, as this setting is not persisted. The autobrake setting is not saved either.If you take off, everything should be alright for a minute or two, but the speed will then be very erratic! Try it and let me know what you think.CheersChris

[Guest D17S]

Got the files. This really works well. I loaded up the files and did an initial test flight. Are you a pilot? The cockpit and FMC are setup very nicely. I'm seeing the airspeed oscillations too. At first blush, this appears to be weather. Notice the ND is showing a 29 knot wind (I'd say nose/cross/whatever, but by the time got a handle on it, the airplane was 'weathervainings.' Even heading hold was having a tough time.So, let's troubleshoot. I want to stabilize the airplane as much as possible and keep it stable so I can isolate what's doing what. How about this for a setup? Go into the TO page and set the Flaps (LSK 1L) to 20/9999. The /9999 is the altitude that FMC will finally let the airplane accelerate beyond your initial V2 settings. I don't want this acceleration to happen because I want the airplane to just "stay put" long enough for me to see what else is going on. Also on the TO page set the THR Reduction (LSK 3L) to oh, say 8000 ft. This is where the AT will reduce thrust to climb power. I want this 'up out of the way' for now too (if/when we finally engage Vnav).Disarm Vnav and Lnav and set the MCP to V2+10 for this TO. This is because your initial goal will be to handfly directly to a V speed on a runway heading. You're very light here and you'll probably sail right on by your V2 of 146 kts. You are going to be handing the airplane off to the Autopilot ASAP. The AP is going to initially try to capture the MCP speed (if it's below the FMC's V2+10) and you don't want to be hunting around for this speed. You want a smooth, stable hand-off to the AP. An initial capture speed of V2+10 will just work better here.Ready for a test flight? Disarm Vnav and Lnav for the TO. Engage the AT with the secret screw. Roll. VR. Positive rate. Gear up. Stabilize at V2+10. Get your deck angle nice and stable. No wobbling. Engage the AP and heading hold. Check the pitch window. Make sure you are still in TOGA pitch mode. You will be right at the suggested flaps 20 retraction speed. Leave the flaps at 20. We want the airplane to just hang there at V2+10 with nothing else going on. What's happening? Wind?I'm going to go try again now. What do you get?

[Guest chrisdb]

Thnaks Sam!I'm not a pilot, though I used to fly the 737 simulator at Knaresborough a couple of times a year, and I once flew a 747 simulator at Cranebrook - but 911's put a stop to that now:( Are you a pilot? You certainly seem to know your stuff!I have learnt so much from your last email. I did not realise that you could set the THR Reduction. I spent all morning practicing the takeoff and controling the speed using the pitch. I also realised that the flight director displays the pitch to follow from the settings in the MCP. Everything went much better and I was able to follow the ATC directions by using the MCP panel to change altitude and direction. I got none of the erratic symptoms from before, but I did hit a couple of turbulent patches where the pane was reaaly thrown about.Having got to grips with the MCP I was able to follow the instructions from ATC when arriving at Amsterdam, but alas, they gave me runway 1L which is not in the FMC and I was not able to find the ILS frequency. I flew around for ages at 180knots but have now given up. Bit of a shame because I'm doing that route for real next week - I just hope the captain's FMC has these details! - lolI'm going to set up another flight - maybe Heathrow to Barcelona, and see how I get on. I've ordered a copy of the real FMC guide - If it comes soon enough I'll be able to read it on my way to EHAM :)You did say that the plane was a bit light, and I think that is because I missed one file. Normally, before setting up the flight I go into the PDMG Load Manager, and set the number of passengers to nearly full. This seems to save the information into the following two files:-PMDG747400gauges.iniAircraftPMDG747-400Aircraft.cfgThe way I found these was to use the Search in windows ecplorer to find files under the Flight Simulator folder that were modified today, and then look at the timestamp.I'm going to leave the public folder set up on the web for everyone to use as they like. If you have any problems then just let me know.CheersChris

[BoHappy 12]

>Hi Sam>>First the bad news. I meticulously played out the scenario>making a note of everything that I did from loading the saved>flight until take off, and it went perfectly with no problems>at all. So I feel very silly indeed.>>But, the good news is that I have created a public shared>folder on my company's web server that everyone can use to>upload files as they wish. To access the share :->>Go to "Network Places" in windows and create a new network>place. The url is>http://public.linchetta-software.co.uk/FlightSim. No logon is>required. The folder will open just as in Windows Explorer and>you may copy files in and out just by the usual drag/drop or>copy & paste.>>I though the best scheme to use for putting files up is to>create a folder with your forum alias (right click and choose>New Folder), and then create the folder tree as it is under>flight sim so that it will be obvious where files need to go,>so for example, >>chrisdbPMDGSIDSTARS>chrisdbPMDG747400PanelState>>etc... and put the relevant files in thir respective folders.>>I have not put any restrictions in terms of permissions or>file sizes etc., so you can create and delete folders and>files as you wish.>>If you or anyone has any more ideas to improve or refine this>then plase say.>>Best regards>Chris>Chrisyour ebsite does not workis it downBo

[Guest D17S]

Just ran a check. Look again and see if my "test file.txt" is there. Should be. There's a bit of a delay when you try to do stuff so give if 10-15 seconds for everything. Works just like any ordinary folder. Cut-paste // drag drop. Very Nice setup.

[Guest chrisdb]

Hi Bo, it is up - Sam uploaded a test file which is there now. You need to sure that you access the folder through the "My Network Places" otherwise it does not seem to work... Let me know if you still have problems :)

[Guest chrisdb]

Thanks Sam, just checked and the file is there. It may tke a while to copy things back and forth - it will depend on the size of the file(s) and if they are large then there might be an amount of time when nothing seems to be happening, but once you know this and let it continue it should work fine. You can also right click to create/delet folders and files etc. :)

[Guest D17S]

Nah, I just fix