LNAV of the 744

[Guest Raptor]

Hi guys,I took a long flight. At the final altitude (FL370) the Queen goes well ,but after while, the Queen turned to the right out of the routeand continued to go that direction until I got back to my computer and corrected the direction,(it gave me lots of wrong messages since the LNAV has been disconnected and cannot be connected till you get back in the line of the route).what causes the Queen to behave like that? what is the reason ?is it LNAV problem ? But I have the latest update!!I don't think it's because of the 60 knots cross winds, the Queen is bigger than to be played by winds.Do I have to be in front of my computer for 6 hours ?Abraham

[Chris from Angle of Attack 7]

Hey Abe,Not sure what I can add to this, but it does seem like quite an odd situation. Sometimes it'll take a bump of the controls or something else simple to knock it off. I leave the thing on for 13+ hours at times, so that shouldn't be the issue.All I can say is always watch your Flight Mode Annunciator to make sure that you are in fact in LNAV as your lateral AFDS mode.

[cavaricooper 2,615]

I too fly for hours at a time- and have not experienced this. Would you check your PMDG menu and see if the control inputs override boxes are checked? Then read the post about spurious inputs cancelling the AP. I do not check these boxes- seems to work best for me (except for throttle).There had to be something that disconnected VNAV.....might have clicked a heading select? Boeing pilots are forced to constantly align the heading knob with the actual heading. Forgetting about this and then clicking on the heading select will turn the a/c to the last selected course which could be dramatically different than the FMC legs.....Also- VNAV will not re-engage unless the a/c is on an intercept course to the current leg. Simply down selecting and up selecting the first (L1SK) waypoint will recalculate if you don't want to manually select an intercept course. Once on that course you can enable VNAV again.Always check your FMAs- if VNAV is not green it is not active- may be armed- but not active. This becomes particularly useful when deciding if the A/T is providing speed protection.Let us know if you figure out what did it......Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png

[Guest Raptor]

Thank you Mr.Carl. I'll check 'em now then try a long flight later.I'll reply if things go well or not.Regards

[Guest Raptor]

Thank you very much,,, it works

[cavaricooper 2,615]

Glad to hear of your success- sorry if there was some confusion in my initial reply- I obviously meant LNAV.Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png

[Guest Raptor]

It succeeded, but today I faced such problem.. The queen should pass over the air points, ok.but if there were cross winds, the aircraft won't pass over it 100% for sure. It partly will pass over it, our Queen behaved stupidly over one point on Italy. It started to circle and circle and circle. Orbited the point trying to pass over it ! .. ain't that stupid !?... Fortunately, I wasn't out of my home yet, I corrected it to the right path.. thanks god I've arrived LIRF safety ;)regards

[cavaricooper 2,615]

Hello-Not overflying waypoints is not incorrect- the FMC will plot the best intercept course for leg routes (heading changes). As far as the circles, I'm betting your leg had a hold programmed in it somewhere and you did not delete the hold before EXECUTING. There had to be SOMETHING that caused the "circle and a racetrac hold seems the most plausible..... As far as your crosswind theory- again the FMC will plot and fly best course for corrections- look at the heading and track difference on your ND.As far as the aircraft's stupidity- I often find myself less smart than the airplane (of course in my case, I'mnot too sure that speaks very highly for the Queen :). )BTW- you should sign your postings with your NAME (per forum rules)- thanks!Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png