So what could go wrong?

[alanh]

RTH does not, in my experience, fly to directly over the landing spot and then descent straight down. It will fly to the approx location +/- about 10 meters, begin descending, and adjust as necessary. If the trees are tight in to the landing area it may have difficulty.

Yes, I noticed that behavior. I've actually flown from this opening several times, including RTH landings and I've not had a problem. I watched carefully the first RTH, and actually every time since. Trust but verify. Good point - thanks.

 

[alanh]

I would test your RTH to see if it returned accurately and safely. Set RTH altitude with a good separation over your trees.
You can take over the landing if it dose not look safe or accurate.

Yes, I watched but have not had to adjust landings. I've actually flown from this opening several times, including RTH landings and I've not had a problem. I watched carefully the first RTH, and actually every time since. Trust but verify. Good point - thanks.

 

[alanh]

My dad said it also.
Set a fire to burn some rubbish, 3 hours later no rubbish or garage.

Murphy's law - "whatever can go wrong, will go wrong." Story of my life.

 

[alanh]

Murphy's law - "whatever can go wrong, will go wrong." Story of my life.

Here's one that's occurred to me, but thankfully hasn't happened: Flying under tree canopies and loosing signal with RC Signal Lost = RTH, and RTH altitude set to a couple of hundred feet.

 

[Mossiback]

Here's one that's occurred to me, but thankfully hasn't happened: Flying under tree canopies and loosing signal with RC Signal Lost = RTH, and RTH altitude set to a couple of hundred feet.

If you are planning on flying under obstructions, set RTH to hover.

 

[FlyGuy8675309]

If this is your "go-to" spot to fly from, I'd look at a remote mod to give you better signal propagation.

 

[alanh]

If this is your "go-to" spot to fly from, I'd look at a remote mod to give you better signal propagation.

I have a passive antenna range extender, but haven't experimented with it. Is this what you mean by remote mod? Are repeaters available? Battery powered or better yet, solar? Thanks for the suggestion.

 

[alanh]

If you are planning on flying under obstructions, set RTH to hover.

Yep. That covers loss-of-signal RTH. What about low battery RTH?

 

[FlyGuy8675309]

I have a passive antenna range extender, but haven't experimented with it. Is this what you mean by remote mod? Are repeaters available? Battery powered or better yet, solar? Thanks for the suggestion.

No not the parabolic thingings... more along the lines of something like this:
Drone World

 

[mrreddog]

Just set the RTH above the highest tree or object and give it a try, you will see the signal bars drop and then start to get lag and stutering on the screen if your signal starts to get bad, then stop, back up and raise your height some and fly back to takeoff point.
You guys arent giving the Mavic enough credit.. I bet you will be able to do it...

 

[Mossiback]

Yep. That covers loss-of-signal RTH. What about low battery RTH?

Low battery RTH gives you a 10 second countdown before activating and you can cancel it before or after it activates.

 

[Qoncussion]

Yep. That covers loss-of-signal RTH. What about low battery RTH?

Low battery RTH gives you a 10 second countdown before activating and you can cancel it before or after it activates.

And it's worth noting that Critical Battery RTH, 1) Cannot be canceled, and 2) When set to, say 10%, is programmed to be ON THE GROUND at 10%. That is not where it starts to descend - that is its target for landing. So depending on the altitude, it could begin to descend at a much higher percentage. One thread here from a few months back, had critical battery RTH kick in at around 22%, as the operator was flying at something like 1,400ft in altitude.

 

[gnirtS]

50ft and a distance of "up to a mile" combined with trees sounds like a good way to lose signal. I'd class that as "highly likely".

Also how big is the gap to take off from?

You MAY struggle getting GPS if its thick tree cover (or worse, it loses it descending below and drifts into one). Also if the gap is high enough if it tries to RTH auto land it might hit the trees BEFORE its close enough on the ground for precision landing to kick in. The mavic is only accurate to a couple of metres until it gets to that last 30ft altitude or so where precision landing takes over
Class it as "moderately likely" but without knowing specifics can't get any more accurate.

Also the risk of an unseen power line, phone wire, radio mast, piece of rope or something not being seen. Seeing small things like that on the screen is near impossible and chances are drone sensors wont either.

 

[nealh]

Mavic transmission signal easily goes miles over open terrain.

I just moved to a new place that has trees much like you describe. Transmission range is less than 1 mile for me. I was surprised how much the trees block the signal.

Yesterday I was flying surrounded by trees and lost signal after about 1300 feet. I can usually get 3-4000 feet, if there aren’t too many trees or buildings around. So that answers my question about limited distances.
This is a Great forum for anyone with a Mavic!

 

[alanh]

50ft and a distance of "up to a mile" combined with trees sounds like a good way to lose signal. I'd class that as "highly likely".

Also how big is the gap to take off from?

You MAY struggle getting GPS if its thick tree cover (or worse, it loses it descending below and drifts into one). Also if the gap is high enough if it tries to RTH auto land it might hit the trees BEFORE its close enough on the ground for precision landing to kick in. The mavic is only accurate to a couple of metres until it gets to that last 30ft altitude or so where precision landing takes over
Class it as "moderately likely" but without knowing specifics can't get any more accurate.

Also the risk of an unseen power line, phone wire, radio mast, piece of rope or something not being seen. Seeing small things like that on the screen is near impossible and chances are drone sensors wont either.

Thanks for your comments. I get excellent GPS coverage from takeoff point, and have not lost GPS lock with 13 TOs and landings. The opening in the trees is roughly 33' x 36'. So far, it has been more than adequate. With RTH set to 396 feet, I'm not too worried about power lines, trees or other fixed objects in the flight path. So based on all the excellent comments in this thread, and with care in not overflying the battery, maybe the two highest risks are Mavic nav. failure or collision with flying objects. We do have a family of hawks living in the area with approx. 6' wingspan.

 

[beejAMG]

With that scenario, all you have to worry about is weak or loss of signal. Otherwise, throw caution at the wind and have fun flying.

 

[sar104]

And it's worth noting that Critical Battery RTH, 1) Cannot be canceled, and 2) When set to, say 10%, is programmed to be ON THE GROUND at 10%. That is not where it starts to descend - that is its target for landing. So depending on the altitude, it could begin to descend at a much higher percentage. One thread here from a few months back, had critical battery RTH kick in at arou and 22%, as the operator was flying at something like 1,400ft in altitude.

One point worth noting - the variation that you describe is not due to the aircraft attempting to be on the ground at the user-set critical battery level - that's just a warning level. The FC continuously calculates (not necessarily accurately, due to wind etc.) the battery level at which it needs to start RTH (based on distance from home point), and the battery level at which it needs to start landing (based on altitude above home point).

 

[Qoncussion]

One point worth noting - the variation that you describe is not due to the aircraft attempting to be on the ground at the user-set critical battery level - that's just a warning level. The FC continuously calculates (not necessarily accurately, due to wind etc.) the battery level at which it needs to start RTH (based on distance from home point), and the battery level at which it needs to start landing (based on altitude above home point).

With Critical RTH (correction, critical battery) - is the home point still relevant? I thought at that point, it goes into auto-landing mode. I've never gotten that far into trouble, so I can't say from experience.

 

[sar104]

With Critical RTH (correction, critical battery) - is the home point still relevant? I thought at that point, it goes into auto-landing mode. I've never gotten that far into trouble, so I can't say from experience.

The two computed values are "SMART_BATT:goHome%" and "SMART_BATT:land%". When the battery level drops below the first one the FC will initiate RTH to the home point. When the battery level drops below the second one it will start landing, wherever it is.

 

[alanh]

With that scenario, all you have to worry about is weak or loss of signal. Otherwise, throw caution at the wind and have fun flying.

Thanks for the reassurance. I am having fun flying.