PMDG 777 LNAV ACCURACY

[Georg Franz 2]

Hello everyone!

I have not found any similar threads to this, so I am starting a new one right here.

It seems like that the PMDG 777 is not 100% accurate when flying in LNAV mode. I know that there are inaccuracies sometimes, but when I am flying in the real Boeing 777 Cockpit the airplane keeps 0.0 NM even when performing an 80 degree turn in China. Also, having talked to numerous 777 pilots, they are all telling me that the aircraft hardly ever gets "off track" more than 0.1 NM L/R.

However, in the PMDG I usually get about 0.1 NM to even 0.7 NM L/R on sharp turns. (like overshooting). Wind data is inserted and all weights in the PERF page are all correctly inserted.

Am I the only one experiencing this problem?

Thanks in advance!

 

[MatthewS 761]

Apart from the LNAV issue, how do you find the accuracy of the PMDG 777 simulation otherwise?

Edited June 2, 2018 by MatthewS

[Driverab330 74]

Yes you are right. Real 777 hardly gets any off track with AP on. Even with 150kts tail wind in a turn over 80 degree over China at high altitude. Because the track will be adjusted with GS and AOB limit.

Except when the waypoint is a flyover waypoint, then the airplane will overshoot the magenta line drawn after the waypoint. 

The other cases of unintention off track will happen during an RNP / RNP AR approach when the speed restriction on approach is exceeded by the pilots. In that case the airplane will not the able to follow and RF leg accurately because the AP usually won’t command more than 30 deg AOB.

I never fly in in cruise using PMDG 777 so I cant really comment on whether your situation is normal or not, I guess sometimes you just have to live with the constraint that flightsim has. For example the RNP AR APPROACH in FSX is never like the real airplane either. 

[VHOJT 172]

The LNAV tracking on all the PMDG planes leaves a little to be desired - if I recall correctly I think it was some sort of compromise between the way it is and something involving a whole lot more work/time?  Happy to be corrected, I am sure Kyle will...

Hopefully in the future we might see some better LNAV tracking/updated flight models.

Cheers,

 

[downscc 1,327]

16 hours ago, VHOJT said:

if I recall correctly I think it was some sort of compromise between the way it is and something involving a whole lot more work/time?

This is basically what was explained to me during beta.  The physics of the turn are not calculated outside of the simulator platform as are many of the other flight dynamics, and it is something that I was told they want to do but the development time required to do it hasn't been set aside yet....so the sloppy turns is due to using default flight dynamics in this case.  The QOTSII does a better job than the 777 but they still need to elevate it above the underlying code and do it their way in my opinion.

Another major improvement in the QOTSII that should make its way into the 777/NGv3 would be VNAV performance,  both the 777 and NGX suffer from vertical path discontinuities that seem to be fixed in the Queen.

[VHOJT 172]

9 hours ago, downscc said:

This is basically what was explained to me during beta.  The physics of the turn are not calculated outside of the simulator platform as are many of the other flight dynamics, and it is something that I was told they want to do but the development time required to do it hasn't been set aside yet....so the sloppy turns is due to using default flight dynamics in this case.  The QOTSII does a better job than the 777 but they still need to elevate it above the underlying code and do it their way in my opinion.

Another major improvement in the QOTSII that should make its way into the 777/NGv3 would be VNAV performance,  both the 777 and NGX suffer from vertical path discontinuities that seem to be fixed in the Queen.

I agree with everything you said there.

Edited June 3, 2018 by VHOJT

[Wanthuyr Filho 83]

Not only the track is subpar at times, but also the magenta line drawing occasionally has glitches.

[scandinavian13 5,192]

This is something that will be revisited when we revisit our overall navdata handling.

[VHOJT 172]

On 6/5/2018 at 10:17 PM, scandinavian13 said:

This is something that will be revisited when we revisit our overall navdata handling.

Didn't see this, awesome!  I'm glad it's on the to-do list.  I have been spoilt by the FSL Airbus nav tracking/drawing.  Don't tell them, but I like my PMDG 744 better in every other way...

[Kevin Handl 1]

Hello, I have a Question, will this be a Problem you will have a look into in the near Future or will this Problem persist for longer ?

Greetings,