FMS Questions

[zachlog 18]

A couple of questions:I am able to couple the FMS to the AP so the programmed route is followed, however, during th flight I do something which disconnects the FMS from the AP. Once NAV mode has been captured, what disconnects the FMS from the AP ? I know I did not hit NAV nor did I disengage the AP.After loading a previously saved flight, the FMS always loads dark....as if it were never programmed ? Doesn't saving a flight also save FMS data ?Thanks,Zach

[falcon999 24]

A couple of questions:I am able to couple the FMS to the AP so the programmed route is followed, however, during th flight I do something which disconnects the FMS from the AP. Once NAV mode has been captured, what disconnects the FMS from the AP ? I know I did not hit NAV nor did I disengage the AP.After loading a previously saved flight, the FMS always loads dark....as if it were never programmed ? Doesn't saving a flight also save FMS data ?Thanks,Zach

Could you describe further what you mean by FMS disconnects from the AP? Is the issue the nav is not following your way points?Loading previous flights will reset the FMS.

[zachlog 18]

Could you describe further what you mean by FMS disconnects from the AP? Is the issue the nav is not following your way points?Loading previous flights will reset the FMS.

In other words, NAV follows my waypoints initially and then it stops following them, i.e., it continues on the last/current heading. It is probably something I am doing (I am new to the JS4100) but other than pressing the NAV or disengaging the AP, I don't know another way to stop NAV from following the waypoits programmed in the FMS so if you know what else "disengages NAV", please let me know so I will stop doing it !Are you saying that FMS data cannot be saved and the FMS must be re-programmed after loading a flight that was saved to be completed at a al ater time ?Thanks,Zach

[downscc 1,327]

The FMS will 'disconnect' if the sidstar file has a vectors statement. This is pretty common in both non-RNAV sids and all STARs in the US.The FMS state is not saved. The implementation does not include the full featured panel states of the bigger/more expensive 747/MD11.

[Guest BlueRidgeDx]

Hi Zach,The AP/FD could stop following the LNAV route if you accidentally change the lateral mode of the FD. Make sure you don't press the HDG, APR, BC or SBY mode buttons, as this could override the NAV mode (SBY mode will remove the FD entirely).Also, make sure you don't press the V/L switch on the EFIS Display Controller more than once. Doing so will cause the AP/FD to couple to the VHF radios for VOR-based navigation, again resulting in the loss of LNAV.Also check that the YD is engaged along with the AP on the center console.When the problem occurs, can you verify what is displayed in the FMA on the EADI? You should see a green AP and a green NAV in addition to any captured vertical mode. Also verify that you see LNAV down the left side of the EHSI (I think it's cyan)...if you see VOR1 or VOR2, then something is wrong.

[MatzeH84 81]

The FMS will 'disconnect' if the sidstar file has a vectors statement. This is pretty common in both non-RNAV sids and all STARs in the US.

Also in europe. Personally I check the SID/STAR for vectors after activating and delete them; this works for me.What also disconnects the AP is pushing the warning lights test button (but I guess this won't be the issue in your case :( )

[zachlog 18]

When the problem occurs, can you verify what is displayed in the FMA on the EADI? You should see a green AP and a green NAV in addition to any captured vertical mode. Also verify that you see LNAV down the left side of the EHSI (I think it's cyan)...if you see VOR1 or VOR2, then something is wrong.

Nick,Thus far I have not been able to recreate the problem. However, I do remember that when I lost LNAV when I did whatever it is I was not supposed to do, the following happened:1. On the EADI, the LNV that is between the AP and ALT changed to GA.2. ALT disengaged (the selection switch on the FD became dark) and altitude started changing almost immediately.3. NAV on the FD went from CAP to dark.If the above rings a bell, please let me know what to avoid, otherwise I will just put this one under the "startup pains" column !Thanks again,Zach

[Guest BlueRidgeDx]

Nick,Thus far I have not been able to recreate the problem. However, I do remember that when I lost LNAV when I did whatever it is I was not supposed to do, the following happened:1. On the EADI, the LNV that is between the AP and ALT changed to GA.2. ALT disengaged (the selection switch on the FD became dark) and altitude started changing almost immediately.3. NAV on the FD went from CAP to dark.If the above rings a bell, please let me know what to avoid, otherwise I will just put this one under the "startup pains" column !Thanks again,Zach

Hi Zach,Sounds like you pressed the Go Around button on the power levers. I'm not sure if you've setup any of the key commands that were added in SP1 or not, but that could be it. Or possibly you were manipulating the power levers with the mouse, and accidentally clicked the button?There are some other behaviors to look for if you want to confirm that this is the issue:The AP will disconnect (with aural alert)The FD bars should rise to approx 8 degreesThe FD bars should command wings levelTry pressing the GA button and see if these symptoms match what you saw in the past.