What causes the AP bug in the caravan, cub, tbm where it just plunges into the ground?

Discussion Hub General Discussion
1

I am not a flight sim expert by any means but i would like to know how they AP bug is cause and how to avoid it. I have an example that happened yesterday where AP was working fine for a bush trip. Some time about 3/4 into the trip i had to make an adjustment and move off the flight path to avoid hitting something. This turned off the AP as it should. I navigate around the obstacle and from then on if i hit AP it backs hard left with 100% up trim and spirals towards the ground.

I have tried. Turning AP off making sure no AP functions are there (nav , vs alt hold etc etc). I have tried flying back into the gps line and making sure i am on the right path again and soon as hit AP it just does the same thing.

I also cleared the flight path and did a direct to and that seems to make it work again but I lose the rest of the flight plan. I had to fly manual mode the rest of the flight which was not too bad as it was only 10 minutes left.

Any tips appreciated.

2

I’ve a couple ideas:

You might go over rather than around.

Otherwise, to avoid an obstacle while leaving the AP on, I temporarily go to HDG mode and use the DG bug to adjust the course slightly left or right. I then go back to NAV mode and let the AP put me back on course.

FWIW, I don’t trust the HDG mode when there’s a considerable difference between its random initial setting and the desired/current course. I always ensure that it’s close before turning the AP on, especially if I’m intending to use HDG mode. Not doing so ~may~ be what combines with ALT not being set to precipitate a problem (a theory, not a fact).

Note too that NOT setting the altimeter or DG frequently enough can result is some sudden AP activity when you do remember to update them.

3

Increase the deadzone on your controller a bit. That seemed to help for some people who had this issue.

4

WIll try it’s bizarre it works then all of the sudden when I switch AP on it goes insane. But will try the deadzone setup.

5

I’ve noticed that the plunge usually happens when the set altimeter numbers are in yellow (whatever that means… deviation warning maybe?) Syncing the alt so that the numbers are in blue usually removes this problem for me.

6

Thanks. This is not the case for me at this time. The Alt indicator was synced to current height and was blue but I will keep an eye on it.

I will make a video of it when it happens again.

7

There’s a real life autopilot failure that can act like this… If you’re pulling back on the yoke as you disengage, the trim might not disengage properly, or it might think it needs to correct using trim and it’ll send you into the ground.

I don’t know that this is happening, but you asked what might cause it…

2 Likes
8

I used to have this AP issue until I increased my deadzones on all controller axes. Since then I haven’t had any AP issues. I still have alignement issues with some planes when performing autoland though.

Another issue I suspect is that there is a bug in the game with keys or controls getting “stuck”. I noticed when looking around the cockpit or from external view, sometimes the directional keys get stuck until I hit the windows key to momentarily show the desktop and back to the game. I think the control axes sometimes gets stuck like those directional keys causing the AP issue.

1 Like
9

@FlyingsCool5650 thanks for that info. I’ll read that and make sure I don’t do that :slight_smile:

Next time It happens I will record it. So we know we are all on the same page.

1 Like
10

I should have included, as somebody else pointed out above, it could be deadzone related. Given it’s an electrical signal, anything non-zero may indicate pressure on the yoke to the AP, and could cause issues as well when disconnecting. Not to mention the springs in joysticks/yokes are not perfect, and friction may exist in the joint, so when lettnig it go, it may not return to zero as well.

1 Like