So what could go wrong?

[NRRTRAINS]

This is a hypothetical scenario. The Mavic Pro is to be launched from a back yard surrounded by 55’ high trees. There is an opening in the trees sufficiently large to safely reach open sky launching vertically. The flight plan is to climb to 120 meters (396’) and then proceed horizontally for one mile against the wind, which is light and gusting to 5 MPH on the surface. The flight path will be mostly-open ranch land, with random groves of trees, none of which will exceed 80’ in height, and over some small lakes. The terrain is virtually flat. The flight will take place totally over pilot’s private property, so there are no privacy issues or risks to people. Restricted air spaces are not an issue. The flight path will be visually-checked while outbound to endure no obstacles exceed 396’ in height anywhere on a potential return path. Video will be made of ranch cattle during the return flight, during which time the craft will descend to as low as roughly 50’ AGL. DJI Go 4 will be running on a Samsung 9.7” Galaxy Tab S2.

Settings:

RC Signal Lost = RTH
P Mode
Enable Obstacle Avoidance = On
Landing Protection = On
RTH Obstacle Detection = On
Smart Return Home = On

I’m not trying to wave a red flag at the VLOS crowd – this is intended to be strictly a technical question. What is the worst that could happen and how likely is it? What else could be done to mitigate the risk?

why even dream of this " hypothetical scenario " . the first dream , There is an opening in the trees sufficiently large to safely reach open sky . i don't know if your MP will come through the opening in the trees . why not just walk to an open area to take off ?.

 

[alanh]

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.

So to clarify Qoncussion's point, SMART_BATT:goHome can be overridden but SMART_BATT:land% cannot? I think this is consistent with the manual's description of the Low Battery RTH behavior. Also, apparently, the FC does not (cannot?) take wind speed or direction into account in calculating SMART_BATT:goHome%. So wouldn't it be a good rule to always fly the first half of the BLOS scenario I described into the wind?

 

[alanh]

why even dream of this " hypothetical scenario " . the first dream , There is an opening in the trees sufficiently large to safely reach open sky . i don't know if your MP will come through the opening in the trees . why not just walk to an open area to take off ?.

Yes, one could walk to an open area. My question was posed to learn more about real-world experience from others about radio range when surrounded by trees. I learned of two owners who only got about 3/4 mile range. That is useful information to me.

 

[sar104]

So to clarify Qoncussion's point, SMART_BATT:goHome can be overridden but SMART_BATT:land% cannot? I think this is consistent with the manual's description of the Low Battery RTH behavior. Also, apparently, the FC does not (cannot?) take wind speed or direction into account in calculating SMART_BATT:goHome%. So wouldn't it be a good rule to always fly the first half of the BLOS scenario I described into the wind?

Correct on all points.

 

[AirStag]

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.

Yep it's all fun, until THIS....

 

[alanh]

Yep it's all fun, until THIS....

Ha - so I just have to ask - is that a real shot or did someone Photoshop it? The timing is excellent though. After my post about hawks, one of the family took a pass at the Mavic late yesterday and veered off at the last second. Not that I'd want to sacrifice either my drone or a bird, it would be interesting to see which comes out better in an altercation.

 

[AirStag]

It's a real shot from last week. I'm working on a video about it and will post it soon. My MA survived with two damaged props. The hawk flew away so I don't have a damage assessment for that. I was at 300 ft AGL and was able to land it in tact.

 

[alanh]

It's a real shot from last week. I'm working on a video about it and will post it soon. My MA survived with two damaged props. The hawk flew away so I don't have a damage assessment for that. I was at 300 ft AGL and was able to land it in tact.

Wow! Glad you were able to land safely.

 

[wytnyt]

...

 

[HighlandsVideo]

I think your flight plan is well thought out and plenty sound. I would set my RTH altitude to the 120m and go for it. If the signal strength doesn't make it the full mile, I'm betting you will make most of it and the RTH can always be cancelled as soon as the signal is restored. So long as the controller is working, there is never any legitimate reason to allow the RTH to land your bird. Thanks for asking and I'll look forward to seeing the video.

 

[Aerial West]

Being in side a stand of large trees, as dirklod suggests will dramatically affect range. Can you find a take off point out in the open?

Or take off from there, then walk to a better position for the flight. i have done this many times.

 

[Dabrain]

Ha - so I just have to ask - is that a real shot or did someone Photoshop it? The timing is excellent though. After my post about hawks, one of the family took a pass at the Mavic late yesterday and veered off at the last second. Not that I'd want to sacrifice either my drone or a bird, it would be interesting to see which comes out better in an altercation.

There are several posts on the forum of said altercations just make a search. Save you some time the Hawks win.

 

[Dabrain]

I think your flight plan is well thought out and plenty sound. I would set my RTH altitude to the 120m and go for it. If the signal strength doesn't make it the full mile, I'm betting you will make most of it and the RTH can always be cancelled as soon as the signal is restored. So long as the controller is working, there is never any legitimate reason to allow the RTH to land your bird. Thanks for asking and I'll look forward to seeing the video.

Yes there is. Was flying over neighbors, he saw me a texted me, wife came out of house with a call from Doctors office on home phone, flying, texting, and call from Doctors office, too much for my little brain, plus wife inquiring about dates for doctor. It was just easier to RTH. Don't know if that's good enough reason but it worked for me.