LNAV is messed up (I think)

Hey guys

This is why we pack extra fuel 😂

I’m currently flying EHAM to KMSP in the KLM 772. This plane is amazing. I departed three hours ago. Guess where I am?

Been flying for three hours and barely left the SID 😂

I think LNAV has an issue. The waypoints were close, but they were mostly in a straight line. There have been a few community members that I know this has happened to (in different aircraft types; not just the 772). I’m pretty sure it didn’t happen before 20.1.

I’ve activated a leg farther down the flight plan and it’s going smoothly now.

If you’re wondering, this post serves two purposes:

1). LNAV (might) have an issue and (may) need to be looked into.

2). If you have a SID with a bunch of waypoints close together, activate a leg farther down. Fly the SID without LNAV and activate LNAV once your waypoints start getting farther apart.


How to activate a specific leg

You can do this by going to the map, clicking “MAP” at the bottom until it shows your flight plan. Click the desired waypoint and click “ACT LEG” at the bottom. Your aircraft will start flying toward that waypoint. This comes very handy in a lot of situations actually.


I hope that this gets looked into if necessary or that my post helped you to not have to circle for hours.

Thank you!

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Even the smallest of turns can still be a problem if your waypoints are too close, especially with the plane the size of a 777. Speed also has an influence on that. If you are too fast, the turns are going to be way wider. The way LNAV works is that your aircraft needs to be at or very close to the waypoint in order for the next leg to be activated. If you miss it, your plane will try it’s best to get to that point which may result in a bunch of circles

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some SIDs may have speed restrictions and they are few and far between. I say keep an eye on it as people had issues before LNAV. From my experience LNAV isn’t new it is just the A/P we are used to but separated so that VNAV can act regardless of it.

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I realize that. I also followed the speed restrictions for my particular SID 🙂

I would suppose hand fly it then some aircraft don’t rotate fast enough and remember restrictions on speed is the maximum allowed not the speed you have to fly at.

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That sucks. I hope you brought enough fuel

I did hand fly until nearly cruise (I like doing that, lol). I was already cruising once I started having problems. The waypoints I was circling were rather far apart.

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I have 10 hours of fuel left :)

I realize that, but also, it should just work properly. The waypoints were rather far apart. Far enough to have plenty of room to turn just a little bit.

The waypoints weren’t part of the SID.

I was under the impression that you were still on the SID. It very well may be that your way points may be duplicates or overlapping. If you put in a SID and the last way point of the SID was lets say BAMMA and you then put in VXV BAMMA the LNAV might start freaking out.

I made sure that everything was a good copy (no duplicates or anything at all)

no clue as that is all the trial and error I have.

Thanks anyway for the help :)

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Is your NAV set to GPS?

Yes, it is

Hmmm, no clue then. Can you go to your device and send a pic of your flight plan and the track?

I don’t know how to show the track, but I do have my LiveFlight pic above. I’ll show the FPL in a few minutes.

Hold on, let me grab a screenshot of what I’m talking about.

@Thunderbolt Here’s my flight plan

Here’s my track (from earlier but still)

Hold on, let me spawn in and check out what’s going on. It may just be an issue with LiveFlight (I doubt it), but I want to see if the tracks are similar.