RTH - Questionable behaviour.

[Ziggy01]

Hmm. So I sent the bird up for a flight, nothing unusual with clear conditions, blue sky,no wind, etc. It was about 800 meters away when I noticed I had a "weak signal" display. I've never seen that before so I hit RTH and had two peculiar events:

1) I was at maximum height. The Mavic attempted to climb as my RTH settings describe but couldn't because it was already at ceiling. So it just hovered there while the "maximum height" display flashed on and off. Is that normal if maximum height is reached and the "rise 20 metres and RTH" is preset?

2) It couldn't fly back to me as a low sun was directly hitting its return path and causing it to read as an obstruction. After mildly panicking I turned it away from the sun and flew it sideways back to me. In retrospect I suppose I could have switched over to sport mode.

Is the sun/obstruction issue an event that is caused by the camera view or is it caused by a sensor? Does Sport mode switch it off?

 

[JLane]

The low Sun triggering forward OA is a fairly common occurrence. Switching to Sport mode does disable forward OA, but first it would cancel the RTH. If you were to try RTH again after switching to Sport mode, forward OA may or may not still be active, because that depends on your setting for OA during RTH in the app (DJI seems to have changed this behavior recently).

Your description about the RTH height is unclear. You said you were flying at maximum height, and then the Mavic tried to rise 20m. Was your RTH height set to 20m? If it was set to 20m, and you were already at max height, then the Mavic would not have tried to climb any higher. The RTH height setting is relative to takeoff point, not the current flying altitude. More likely the Mavic was trying to rise to clear the "obstacle" it was detecting.

 

[Ziggy01]

The low Sun triggering forward OA is a fairly common occurrence. Switching to Sport mode does disable forward OA, but first it would cancel the RTH. If you were to try RTH again after switching to Sport mode, forward OA may or may not still be active, because that depends on your setting for OA during RTH in the app (DJI seems to have changed this behavior recently).

Your description about the RTH height is unclear. You said you were flying at maximum height, and then the Mavic tried to rise 20m. Was your RTH height set to 20m? If it was set to 20m, and you were already at max height, then the Mavic would not have tried to climb any higher. The RTH height setting is relative to takeoff point, not the current flying altitude. More likely the Mavic was trying to rise to clear the "obstacle" it was detecting.

The mavic was at max height and wouldn't engage forward rth as it couldn't rise above to meet its preset clearance.

I checked the video and it was stalled rather than hitting an obstacle.

Very odd.

 

[JLane]

The mavic was at max height and wouldn't engage forward rth as it couldn't rise above to meet its preset clearance.

I checked the video and it was stalled rather than hitting an obstacle.

Very odd.

Please clarify what altitude you were flying at (the max height) and what your RTH height setting was.

 

[Ziggy01]

Please clarify what altitude you were flying at (the max height) and what your RTH height setting was.

Hmm, I not sure how those specifics could matter, but sure.
Max alt set to 120 meters (which is where I was at).
RTH set to 20m up then home.

 

[HFMan]

When you say "RTH set to 20m up then home", it sounds like you don't know how it works. Are you saying RTH altitude is set to 20 meters?

 

[JLane]

Hmm, I not sure how those specifics could matter, but sure.
Max alt set to 120 meters (which is where I was at).
RTH set to 20m up then home.

As I pointed out in my fist reply, the RTH height is relative to the takeoff point. If the RTH height was set to 20m and the Mavic was already at 120m, it would RTH at 120m, not try to climb to 140m.

 

[Ziggy01]

When you say "RTH set to 20m up then home", it sounds like you don't know how it works. Are you saying RTH altitude is set to 20 meters?

Quite right. Total seniors moment here. I've just rechecked my setup and the RTH minimum is set to 80mtrs. I don't know how I had it in my head that the setup involved a 20mtr rise from the point of RTH activation - must be the drugs.

Either way, it's odd that she just sat there and had to be manually brought home even though RTH was activated and there were no warnings issued.

 

[Ziggy01]

As I pointed out in my fist reply, the RTH height is relative to the takeoff point. If the RTH height was set to 20m and the Mavic was already at 120m, it would RTH at 120m, not try to climb to 140m.

Yes.

As I just replied to the other poster, I must have put extra psilocybin on my corn flakes that morning.

And as you say, the magic should have dropped to the preset RTH height - which in my case is 80mtrs.

 

[HFMan]

No, if the Mavic is above the set RTH height, it will return home at its present altitude- it does not "drop to the preset RTH height".

 

[Ziggy01]

No, if the Mavic is above the set RTH height, it will return home at its present altitude- it does not "drop to the preset RTH height".

No, if the Mavic is above the set RTH height, it will return home at its present altitude- it does not "drop to the preset RTH height".

Ok.

Regardless. It just sat there, looking about as confused as me.

 

[Ziggy01]

No, if the Mavic is above the set RTH height, it will return home at its present altitude- it does not "drop to the preset RTH height".

Btw -

On screen info - Return to home altitude = X

"The aircraft will go to the altitude listed here (X) when returning to home point."

Is that on-board statement incorrect?

 

[JLane]

Btw -

On screen info - Return to home altitude = X

"The aircraft will go to the altitude listed here (X) when returning to home point."

Is that on-board statement incorrect?

Yeah, I guess that message is not quite accurate. It will rise to the RTH height if necessary, but not descend to it.

I'm still quite sure your Mavic was stuck trying to rise above the false obstacle. I've seen other people report that the flight playback doesn't seem to indicate this. But there's a good chance that information could be seen in the full flight data contained in the Mavic's internal .dat file. If you want to try and confirm what happened, you could try getting the .day file and having a look with DatCon or CsvView

 

[Ziggy01]

Yeah, I guess that message is not quite accurate. It will rise to the RTH height if necessary, but not descend to it.

I'm still quite sure your Mavic was stuck trying to rise above the false obstacle. I've seen other people report that the flight playback doesn't seem to indicate this. But there's a good chance that information could be seen in the full flight data contained in the Mavic's internal .dat file. If you want to try and confirm what happened, you could try getting the .day file and having a look with DatCon or CsvView

You may well be correct, it's the most likely explanation.

Certainly there was no "attempt/flare" as I experienced as I attempted to manually bring it in, but it may well be that the Mavic perceives the "obstruction" and doesn't move at all...which actually makes perfect sense.

I'd say that one's solved. Thanks for your help.

 

[JLane]

You may well be correct, it's the most likely explanation.

Certainly there was no "attempt/flare" as I experienced as I attempted to manually bring it in, but it may well be that the Mavic perceives the "obstruction" and doesn't move at all...which actually makes perfect sense.

I'd say that one's solved. Thanks for your help.

The default behavior during RTH would be for the Mavic to try and climb until it no longer sees the obstacle. In your case, since it was already at the max height, it could not climb any further, and therefore just sat there.

 

[Ziggy01]

The default behavior during RTH would be for the Mavic to try and climb until it no longer sees the obstacle. In your case, since it was already at the max height, it could not climb any further, and therefore just sat there.

Makes perfect sense. I don't have "go around " assigned.

 

[JLane]

Makes perfect sense. I don't have "go around " assigned.

Actually, the "go around" option doesn't apply to RTH, anyway