Downed Mavic Air Flight log interpretation - Please help

[PWB1000]

Dear All,
I'm fairly new to flying (about 30 flights). My Mavic air went down at the weekend and I would be grateful for any help interpreting what went wrong. I took off at the side of an extremely small river with a view to filming. There were a low number of satellites but GPS was working. The water was shallow and I was standing on a pebbled area at the side. I was to the left of the river and took off and moved the Mavic over the water and went slowly forward. There were some bushes to the right of the river which were overhanging but nowhere near to where I was flying. as I took the drone forward it started to move sideways by itself. it became completely unresponsive and wouldn't pull back or move away from the bushes. It clipped the bushes and came down in about a cm of water.

I have no idea what went wrong. Going back trough the flight log a no satellite warning appeared which I hadn't noticed. Watching through the playback and having the controls movement displayed there seems to be a change of direction without the controls being touched. I would appreciate it if anyone with the technical know how could look at the flight log and footage and see if there are any clues as to what's gone on.

Many thanks.
Paul

 

[Simmo]

Hey bud, sorry for your loss.
In my amateur opinion......
You never gained any GPS health in that flight. 7 sats intermittently at best. In the last 10 seconds or so you were in full atti mode and drifted. The AC was reacting to your control inputs but unfortunately IMO they were not of any substance or direction to prevent the outcome.

 

[PWB1000]

Hi,
Thanks for taking the time to look at the log. I think my frustration was when the AC started moving off course by itself. All i had to do was bring it back towards me but it wouldn't respond. On reviewing the flight playback showing the controls. on several occasions the controls show a movement in a percentage term but no blue line showing the joystick direction. Forgive my ignorance but if i had pushed the stick in a direction would it not show a blue line.
Thanks.
Paul

 

[Simmo]

No worries. It was in Atti, and drifting. Seemingly the majority of your input was yaw?? Not really any definitive input to make the AC go in any direction??? (Please let me reiterate that I am a rank amateur at this, and I'm sure @sar104 or @msinger will put everything into perspective, and I could be way off??!)

 

[MavicCF]

I'm still not the expert here, but I would agree with @Simmo that ATTI mode is probably the problem here. Up until the AC shut off at 79.1 seconds due to impact, it seems to be accurately responding to your inputs although drifting due to ATTI. In the last few seconds, there are several random instances of pitch and roll that are probably caused by the Mavic hitting the bush just prior to impact. As you can see from the graph, it appears to have been correctly sensing and responding to your control inputs. I am curious what the experts will say here though, I could be missing things...

 

[PWB1000]

Hi, Thanks for looking at the log MavicCF. I hadn't realised that ATTI mode was so temperamental and unpredictable. I've just been reading some horror stories and will ensure any future flights only involve GPS.
cheers.
Paul

 

[sar104]

Hi, Thanks for looking at the log MavicCF. I hadn't realised that ATTI mode was so temperamental and unpredictable. I've just been reading some horror stories and will ensure any future flights only involve GPS.
cheers.
Paul

It's neither temperamental nor unpredictable - the FC simply holds the aircraft level and maintains altitude. Any movement is due to wind currents or pilot input.

 

[MavicCF]

It's neither temperamental nor unpredictable - the FC simply holds the aircraft level and maintains altitude. Any movement is due to wind currents or pilot input.

Have you looked at it yet Sar? Do our results look about right?

 

[MavicCF]

Also while I agree ATTI isn't unpredictable or temperamental, it can be unexpected and completely different for people who have never flown in it before making it appear to be both of those.

 

[MavicCF]

Hi, Thanks for looking at the log MavicCF. I hadn't realised that ATTI mode was so temperamental and unpredictable. I've just been reading some horror stories and will ensure any future flights only involve GPS.
cheers.
Paul

Definetly wait on each flight before taking off for the Mavic to acquired GPS signal and set the home point. Is you Mavic Ok? No water damage or anything?

 

[sar104]

Have you looked at it yet Sar? Do our results look about right?

I haven't had a chance to look at the log, but your graph above seems fairly definitive - the aircraft responded appropriately. I guess one important distinction to make regarding ATTI mode that catches out unfamiliar users is that when the sticks are centered the aircraft doesn't stop. It's a Newton's 1st Law kind of mode, and so once the aircraft is moving, opposite stick has to be applied to stop it. You can see that change in behavior at 69 s when the FC gives up on the GPS data.

 

[MavicCF]

I haven't had a chance to look at the log, but your graph above seems fairly definitive - the aircraft responded appropriately. I guess one important distinction to make regarding ATTI mode that catches out unfamiliar users is that when the sticks are centered the aircraft doesn't stop. It's a Newton's 1st Law kind of mode, and so once the aircraft is moving, opposite stick has to be applied to stop it. You can see that change in behavior at 69 s when the FC gives up on the GPS data.

I agree, you do get used to being able to let go of the sticks and everything stops.
This is the scenario I always point to when suggesting starting out with a cheap ATTI drone and learning the ropes of flying it before moving up to something like a Mavic. The Mavic is amazing and easy when it works properly, but if it loses GPS or disregards it, it can become a whole different animal.

 

[PWB1000]

Definetly wait on each flight before taking off for the Mavic to acquired GPS signal and set the home point. Is you Mavic Ok? No water damage or anything?

Will do. At least I know for the future. Unfortunately, the MA is not happy, it's displaying battery error. Everything else is working. It goes through the start up sequence, camera, gimble, memory all working. It then shows all red lights and shows no battery info. An expensive mistake i fear. Thanks again for your input.

 

[SeaParrot]

It's a shame that the MA can't be forced to be in ATTI mode. It would be extremely useful to be able to fly in ATTI mode to be able to get practice at flying the MA in that mode. This could be done in a nice big empty field.

The end objective would be for the pilot to be exprienced enough to able to safely fly in ATTI mode if GPS lock was unexpectedly lost.

 

[MavicNoob79]

It's a shame that the MA can't be forced to be in ATTI mode. It would be extremely useful to be able to fly in ATTI mode to be able to get practice at flying the MA in that mode. This could be done in a nice big empty field.

The end objective would be for the pilot to be exprienced enough to able to safely fly in ATTI mode if GPS lock was unexpectedly lost.

Is there any official reason why DJI didn't include atti mode? It gets brought up often that being and to switch to atti would help

 

[sar104]

Is there any official reason why DJI didn't include atti mode? It gets brought up often that being and to switch to atti would help

I've never heard a reason stated. It's a simple switch in the firmware and ATTI works just fine on the Mavic when enabled in that way. And it's still available on the Phantoms.

 

[MavicCF]

I've never heard a reason stated. It's a simple switch in the firmware and ATTI works just fine on the Mavic when enabled in that way. And it's still available on the Phantoms.

Do you like having ATTI as an option? I've been looking into doing the mod where the switch on the side does ATTI instead of sport. Any disadvantages?

 

[sar104]

Do you like having ATTI as an option? I've been looking into doing the mod where the switch on the side does ATTI instead of sport. Any disadvantages?

That's how I have mine programmed. I don't use sport mode anyway, so no disadvantages as far as I'm concerned.

 

[MavicCF]

That's how I have mine programmed. I don't use sport mode anyway, so no disadvantages as far as I'm concerned.

I just did it and took it out for a flight, I like how much smoother the controls feel especially when you want to stop, no hard braking here! Plus you can still go 40MPH so essentially you didn't lose sport mode.

 

[zero1981]

That's how I have mine programmed. I don't use sport mode anyway, so no disadvantages as far as I'm concerned.

I would have to respectfully disagree. Sports mode has got me out of one or to jams when the wind picked up suddenly and also near sunset when the sensors wouldn’t let me fly forward. I would say that having a att mode button would also be handy in certain situations. Like flying in a big warehouse or gym.