I have 4 questions about the Auto RTH Altitude setting

I’ve always had my RTH altitude height set just below the legal 400 ft limit, but another user made the point that it should always be set higher than any potential obstacles, even if it’s much higher than 400 ft.

The argument was that losing connection is an emergency situation, and if in low-light the bypass feature may be a death sentence for the drone if it collides with the obstacle auto-returning. The alternative would be setting the RTH altitude above any obstacle, and to have it rise to that illegal altitude before approaching the obstacle (and hence reconnecting for you to manually bypass and lower down again). This made sense since a friend lost a Mavic 3 classic when it disconnected and likely colided with an obstacle coming straight back home--naturally the drone will fly towards the obstacle blocking the transmition since that's the direction of home until the sensors activate to tell it to "bypass." With the RTH height properly set, the Mavic would have risen in place and reconnected above the obstacle.

• 1. Is this a good practice and do I have it’s working mostly correct?
  

• 2. What do you do personally, if you happen to have obstacles higher than 400’ around?
  

• 3. Does this mean that simply hitting the RTH button will have it rise to that altitude before returning home, or is that setting for disconnect-only RTH?
  

• 4. If a Mavic 3 Pro disconnects and tries rising to the set RTH altitude of 300m, but the location has a 100m height cap, what will it do?
  

Thank you for your time. Hopefully this info will be helpful to others too.

2. What do you do personally, if you happen to have obstacles higher than 400’ around?
You could avoid flying behind obstacles because that's inviting signal loss and further potential issues.

I think if the mavic 3 pro disconnects and it tried to return to home it will go to 300 meters because you probably set it that high to avoid obstacles while its returning it could be 100 meters but I think it would be 300

Labroides Posted at 1-13 16:49
2. What do you do personally, if you happen to have obstacles higher than 400’ around?
You could avoid flying behind obstacles because that's inviting signal loss and further potential issues.

Thanks for posting. That obviously makes sense as a general practice but I'm referring more to emergency situations where that may happen accidentally. For instance I was filming in a semi-circular motion and accidentally wrapped too far around the obstacle I was filming. It cut off RC momentarily but was able to jerk it back into RC range. If 1. I wasn't able to jerk it back and 2. it was night time, the MV3 would have activated RTH and likely crashed straight into the obstacle.

lofe Posted at 1-13 17:15
I think if the mavic 3 pro disconnects and it tried to return to home it will go to 300 meters because you probably set it that high to avoid obstacles while its returning it could be 100 meters but I think it would be 300

The height ceiling will limit my ability to ascend higher in certain areas. You're saying you think the drone in RTH mode would override that height limitation? thanks for chiming in.

NYC Posted at 1-14 02:24
Thanks for posting. That obviously makes sense as a general practice but I'm referring more to emergency situations where that may happen accidentally. For instance I was filming in a semi-circular motion and accidentally wrapped too far around the obstacle I was filming. It cut off RC momentarily but was able to jerk it back into RC range. If 1. I wasn't able to jerk it back and 2. it was night time, the MV3 would have activated RTH and likely crashed straight into the obstacle.

That obviously makes sense as a general practice but I'm referring more to emergency situations where that may happen accidentally.
It's good practice all the time and the longer you fly, the better you recognise it.
The way to avoid "accidents" is to understand what can go wrong and how to prevent that happening.
Fly behind substantial obstacles and you will lose signal.

For instance I was filming in a semi-circular motion and accidentally wrapped too far around the obstacle I was filming. It cut off RC momentarily but was able to jerk it back into RC range. If 1. I wasn't able to jerk it back and 2. it was night time, the MV3 would have activated RTH and likely crashed straight into the obstacle.
Probably not.

It sounds like you aren't properly familiar with how Failsafe RTH works when your drone loses signal.
DJI have a very clever system in place, which you'll find described on p 48 of your manual.
Here's a little from the relevant section.
  Original Route RTH Procedure:
  1. The aircraft brakes and hover in place.
  2 . a. If the aircraft is farther than 50 m from the Home Point, the aircraft adjusts its orientation
  and flies back for 50 m on its original flight route before entering Straight Line RTH

If your drone lost signal, you probably wouldn't have been  able to "jerk it back into RC range" at all.
It sounds like DJI's Failsafe RTH saved your drone.

Labroides Posted at 1-14 02:59
That obviously makes sense as a general practice but I'm referring more to emergency situations where that may happen accidentally.
It's good practice all the time and the longer you fly, the better you recognise it.
The way to avoid "accidents" is to understand what can go wrong and how to prevent that happening.

Wow, very helpful info, thanks for providing that snippet. Makes sense it would navigate laterally first to reconnect instead of directly on the return path.

Absolutely a good practice all the time. I just always like to plan for extra failsafes when it's possible to.

I think in the situation I was describing, it didn't fully lose connection but was weakened for a moment until I was able to jerk it back to better RC.

Thanks for your time. I'll check out pg 45 in the manual next.

NYC Posted at 1-14 03:05
Wow, very helpful info, thanks for providing that snippet. Makes sense it would navigate laterally first to reconnect instead of directly on the return path.

Absolutely a good practice all the time. I just always like to plan for extra failsafes when it's possible too.

I think the retrace will be in 3D, so vertical as well as horizontal.
I think you will find that if you are flying UNDER the floor of a ceiling cap and lose connection the drone WILL NOT break the cap.
If you are flying beyond the walls of an air corridor etc. and an RTH occurs, the drone will, in a std behaviour RTH, climb to the set RTH height then fly towards the home point.
Surren demonstrated, with a Mavic 3 * that was flown ( RTH'ed ) towards an air corridor etc. and was above the corridor's floor, that,  as it approached the corridor it automatically descended so as to pass beneath the corridor.

It DID NOT climb once it cleared the corridor.
I do not know if the latter behaviour applies to all Mavic 3, ditto the Air 3 but it would be nice if it could be extended to all Fly App drones.

With regards to your questions, ask yourself the question, "Who do I think would carry the brunt of the punishment and guilt if I set the RTH height to greater than 400ft and something happened and I end up in court?
I'd rather lose the drone than end up in court and I am pretty sure the "but it was an emergency situation" argument will not carry weight, in fact it might be seen as a negative argument demonstrating a reckless attiitude.

Hi there. When the aircraft is in altitude-restricted zones:
1. The preset RTH altitude of the aircraft is higher than 120 m. When the RTH procedure begins, the aircraft will not ascend to the preset RTH altitude after it reaches the maximum altitude of 120 m, and it will then perform a normal RTH procedure at 120 m.
2. When the preset RTH altitude is lower than 120 m, the aircraft will perform the normal RTH procedure and return home after reaching the preset RTH altitude.

When the aircraft is restricted to a maximum altitude of 30 m (For example, the aircraft is not connected to the app and flies using the remote controller):
1. The preset RTH altitude of the aircraft is higher than 30 m. When the RTH procedure begins, the aircraft will perform a normal RTH procedure at 30 m after ascending to 30 m.
2. When the preset RTH altitude is lower than 30 m, the aircraft will perform the normal RTH procedure and return home after reaching the preset RTH altitude.
Note: When Obstacle Avoidance is enabled during the RTH procedure if the aircraft ascends and reaches the maximum altitude but still cannot avoid an obstacle, it will hover in the air.
Have a nice day.

Sean-bumble-bee Posted at 1-14 04:16
I think the retrace will be in 3D, so vertical as well as horizontal.
I think you will find that if you are flying UNDER the floor of a ceiling cap and lose connection the drone WILL NOT break the cap.
If you are flying beyond the walls of an air corridor etc. and an RTH occurs, the drone will, in a std behaviour RTH, climb to the set RTH height then fly towards the home point.

Ah, thanks for the heads up about Surren's demonstration. This makes sense.