Sorry for asking, but your description is unclear (at least for me):
If you uncheck "autonomous", does the UAV takes off on its own?

Thanks for replying. You start with the UAV flying a holding pattern (created in the editor). As the player you decide you're finished using the UAV and want to send it to the airport. You uncheck 'autonomous' and select auto-land. The plane lands. You shut down the engine. You release the controls to go do something else, but the plane starts up its engines and takes off again without your permission.

This situation is reproducible with a UAV starting in the air. If you put a UAV on the ground at the airfield (without waypoints) it won't take off on its own.

So yes, unchecking 'autonomous' at one time or another won't prevent the UAV to take off on its own under certain circumstances.

I will try to reproduce your issue tomorrow (21.03.15) and will leave a reply.

Are you sure, that there is no waypoint left?

Maybe try to change behaviour to "Never fire" (first option) and try to reproduce your issue.

UAVs are sometimes really stubborn.

It doesn't move to (old) waypoints. It ignores the waypoints and start circling directly after take-off.

Even if there are waypoints in its wp list, I think its wrong if it takes off and moves to waypoints on its own if I unchecked its 'autonomous' function.

I will try the 'never fire' option. Notice however that this situation can be replicated without enemies on the map.

I wasn't able to reproduce your issue. All I did was the following:

1. I opened the editor
2. I placed a flying autonomous unit MQ4A Greyhawk
3. I created a simple "Move" waypoint for the MQ4A
4. I placed a "UAV operator" (player unit)
5. I previewed the mission
6. I waited until the UAV reached its waypoint (it started circling the area afterwards)
7. I connected with the UAV and choosed "auto landing"
8. The UAV landed and I switched off the engine.
9. I watched the UAV peacefully waiting on its landing position

If there are waypoints left, the UAV will start its engines again. You have to make sure, that all waypoints are canceled before landing.

There is no need of unchecking the autonomous option (as long as there are no enemies in the area).

Maybe you are doing something different than me? Please let me know.

I have tested it with the latest dev-branch 1.43.129826.

annoying bug and make UAVs more bothering than useful.

Did some more testing:

1. Koala's test was replicable
2. My test was replicable as well. The difference is that I have the last waypoint on 'CYCLE' to create a custom loitering pattern

Using the CYCLE waypoint results in the situation that there are always waypoints for the UAV. This causes the UAV to take off on its own after landing in two possible ways:

1. With 'AUTONOMOUS' ON the UAV returns to its cycling waypoints
2. With 'AUTONOMOUS' OFF, the UAV takes off and starts a default loitering pattern around the airfield

In fact, 'AUTONOMOUS' ON always activates attempt to fly along waypoints, or straight on if there are none. 'AUTONOMOUS' OFF activates default loitering pattern.

I did manage to ground the UAV permanently WITH active (cycling) waypoints by deleting the waypoints with a script during the flight, proving that the active waypoints lead to the UAV taking off without permission.

My conclusion:
Taking off with 'AUTONOMOUS' OFF makes little sense to me. Especially in combination with the fact that this is caused by remaining waypoints which the UAV will ignore anyway and will start default loitering instead.

Possible solutions:

• Setting 'AUTONOMOUS' OFF deletes active waypoints
• UAV is not allowed to start engine on its own

What do you guys think?

Re-reading your post Koala I noticed 'You have to make sure, that all waypoints are canceled before landing.'

I didn't realise you can cancel the waypoints yourself with the UAV terminal, even with cycling waypoints. So fortunately you can make sure yourself that all wp's are gone before landing, to permanently ground the UAV. UAV's are stubborn indeed.. :-)

The autonomous behaviour is like an AI controlled aircraft.

It will cause, that the UAV has its own will on the battlefield.

As long as there are no enemies, the autonomous behaviour won't has any influence (my experiences so far).

If there are enemies around, the UAV will attack them until they are fought.

Koala, while doing these tests I noticed another issue: double engine shut-down sounds for the UAV, at least with 3rd person perspective. Did you notice this as well? If this is consistent I'll open another ticket for it.

@joostSidy

I can clearly hear the double engine sounds too (start up sound is doubled too).

I felt free and created the ticket: #0023304