All of a sudden my JS41 won't follow its LNAV plan, even though all the indications on the AP, FMS and EHSI are OK. Even though NAV shows CAP, the plane just tracks parallel or past the waypoints and seems to follow a default northerly heading.Does anyone know of a bug or issue that would cause this?With thanks as always!Best wishes,David

I occasionally find the same issue and would also like to know what causes it. I find it happens usually either after I fly initially for a period using HDG on AP and then switch to NAV, or if I have reloaded the J41 a few times in succession to try different liveries etc. It really annoying if you don't catch it quickly, especially online when departing on a SID and ATC ask what you are doing.... Usually a reload of FSX fixes the issue for the next flight.The J41 is a great aircraft, but its 'lightweight' status can be a pain, ie the FMC can't interpret many of the Navigraph SID/STARS like its big brothers and I fly it just as often using just VOR navigation. Be nice to see some improvements as part of the expected SP2, but who knows what that will bring or when.

The JS41 FMS is nothing like its big brothers. So there is nothing to "improve" in SP2...I quote Capt Randazzo from an earlier post:

The FMS on this airplane is effectively a glorified first generation GPS device.

Use "Direct To" to your next waypoint, then engage NAV.

Thanks to you both borgfan and Melkor..Yes, maybe the problem has arisen because I was doing quite a bit of relocation and JS41 aircraft exchanging before using the FMS etc. in flight. Pity.I already (and repeatedly) tried using DIRECT TO as Melkor suggests, but without joy. Neither does intercept using HDG with NAV on ARM work either, once this problem starts. Next flight I'll just try being less ambitious with relocations at FSX launch and hope the JS41 navigation systems can perform correctly as before. When they work they seem to follow my humble SIDs and STARs pretty well ...Best wishes,David

All of a sudden my JS41 won't follow its LNAV plan, even though all the indications on the AP, FMS and EHSI are OK. Even though NAV shows CAP, the plane just tracks parallel or past the waypoints and seems to follow a default northerly heading.Does anyone know of a bug or issue that would cause this?With thanks as always!Best wishes,David

Hi,You have to load a fsx flightplan. Never mind where to or where from. After loading the fs flightplan the plane is following the route normally.I think it is a little bug. but if you always loads a fllightplan (default) than you don't have this problem.Hope this helps.Eric

Hi,You have to load a fsx flightplan. Never mind where to or where from. After loading the fs flightplan the plane is following the route normally.I think it is a little bug. but if you always loads a fllightplan (default) than you don't have this problem.Hope this helps.Eric

Thanks for the thought, Eric.I will give it a try!Best wishes,David

I've had the same problem several times. I think the problem persists if you start your next flight from a saved flight during which the problem occurred. A reload of the aircraft seems to solve the problem. Just pretend the LNAV failed for real and you have to navigate the old fashioned way.

Just did another flight and had the same issue. Kind of annoying. Hope we can find a solution.

Hi,You have to load a fsx flightplan. Never mind where to or where from. After loading the fs flightplan the plane is following the route normally.I think it is a little bug. but if you always loads a fllightplan (default) than you don't have this problem.Hope this helps.Eric

I'm not sure what you mean. I've loaded a flight plan...

Just did another flight and had the same issue. Kind of annoying. Hope we can find a solution.I'm not sure what you mean. I've loaded a flight plan...

I'll try to explain in my best English....I have the same issue if I don't load a default fsx flightplan. (in the fsx flightplanner). I don't use it, because I use the PMDG flightplan to make a flight.Here is how I do it: I made a route in fsbuild, like EHAM-EGKK, export in to PMDG flightplans. I load this flightplan in the fmc of the J41. This is the flightplan I use for my flight.Then I load a flightplan in the default fsx , in the Menu : flightplanner.(it doesn't matter what kind of flightplan). But this flightplan I don't use. I just load it.If I do it like this, my plane always use the nav or heading it should use and don't go to the north.Even if I forget to load a fsx flightplan and the plane keeps heading north, I load a fsx flightplan (during flight) and after loading the JS41 turns normally tot the desired heading.Hope this helps.Eric

Just did another flight and had the same issue. Kind of annoying. Hope we can find a solution.I'm not sure what you mean. I've loaded a flight plan...

APOLOGIES TO ERIC FOR POSTING THIS JUST ONE MINUTE AFTER HE HAD ALREADY REPLIED. I AM SUITABLY EMBARRASSED :( Hi Steve,I believe what Eric means is that you need to go to Flight Planner in the FSX menu, create any old route there (if you haven't got one saved already), save it and then load it as if you weren't flying a PMDG aircraft. Reverting to the J41 environment, you won't find any disruption to your .rte inputs, but hopefully the problem will have gone away. I tried it - and so far, so good! Thanks Eric!Best wishes,David

APOLOGIES TO ERIC FOR POSTING THIS JUST ONE MINUTE AFTER HE HAD ALREADY REPLIED. I AM SUITABLY EMBARRASSED :( Hi Steve,I believe what Eric means is that you need to go to Flight Planner in the FSX menu, create any old route there (if you haven't got one saved already), save it and then load it as if you weren't flying a PMDG aircraft. Reverting to the J41 environment, you won't find any disruption to your .rte inputs, but hopefully the problem will have gone away. I tried it - and so far, so good! Thanks Eric!Best wishes,David

That's what I tried to explain. No problem for helping and a double post here.Eric

Thank you!! I understand now. I'll give it a try. I did try to load one last flight and I got a fatal error...seems to happen a lot if I try to do anything major while flying...

Thank you!! I understand now. I'll give it a try. I did try to load one last flight and I got a fatal error...seems to happen a lot if I try to do anything major while flying...

Steve,Maybe no need to mention, but don't forget to start FSX with a default plane. (ultra light is perfect)Eric

Yes, thank you, I've been trying to get back to doing that. Did a little searching and found that this issue is not new, and not launching from a default scenario can contribute to this and other problems.Appreciate all the help! Thank God for the forums!!

I had the same problem today.I followed the advice here and loaded my flightplan into the default FSX planner while in mid-flight, chose "no" when it asked me to move the aircraft and then pressed the NAV button.Viola. It started following my LNAV route.Thanks for the tips guys.What a weird bug.