DJI Air stopped taking instructions and crashed

Meta4 · Oct 11, 2021

Phantomrain.org said:
So if the drone is above the restricted height when it enters Atti mode other than it being in Atti mode is it compromised in any other way ?

You'd have to do some testing to find out.

Sam789 · Oct 11, 2021

slup said:
Yeah ... besides that you took off without waiting for a recorded HP ... which could have turned out to be fatal if you had lost the AC/RC connection, you also powered on your MA1 near something magnetic that deflected the compass & by that initialized the IMU Yaw into a wrong direction (your MA1 mainly thought that it was pointing in a direction that wasn't true in reality).

As you had such a bad GPS position in the beginning your MA1 didn't have any horizontal positional hold ... meaning that the flight controller didn't intend to keep any position at all by means of using different motors to counter a possible drift, it instead only kept the height & if it were any horizontal drift it would just let it drift & leave that to you.

But as soon as you got a proper satellite lock with a good navhealth the MA1 started to hold position & started to counter effects of the wind there by using different motors to correct any positional errors. The only problem was that the MA1 didn't have the true facts about the heading direction ... so when a drift occurred it activated the wrong motors & by that just made the positional error larger ... & tried again, & again, but the error just got bigger & it started to ramp up the speed & flew away.

It's easily seen in the chart from the DAT log here below ...

The flight starts in the left side in the chart, the green graph is the IMUYaw (wrongly initialized), the red one, magYaw (compass). The black graph is the magmod (magnetic field).

To the left, before take off the green & red agrees rather OK (not exactly the same values which indicate that you powered on the MA1 before the RC & app) as the compass still is located in the magnetic disturbance.

Then comes the pink & green background stripes which is motor start & take off ... after that it's clear that your MA1 leaves the magnetic disturbed area ... the black magmod changes largely & the red (compass) correct itself, but the green IMUYaw remains wrong.

Then comes the broader blue background stripe which is ATTI mode & a bit later at 41,912sec after take off you get GPS lock & you gets the full effect of the Yaw error as the flight controller start to provide horizontal hold.

The blue graph is a calculation to more clearly see the deviation between the IMUYaw & magYaw ... at most it reaches 87 degrees (at 43,8sec). A nearly 90 degrees deviation usually results in a circular flyaway path ... exactly what we see here in your flight.

(Click on the chart to make it larger)
View attachment 136369

So the take away from this is that this whole incident was due to pilot errors ... nothing else. It consisted of 2 pilot errors out of both could have killed your MA1.

1.
Always wait until a HP is recorded (the lady voice announce clearly when it's been recorded) before you fly out horizontally from your take off spot. Otherwise it will be recorded in a unknown spot along the flight path when the navhealth reaches a sufficient level ... & in a case of a AC/RC disconnect the drone will return to that spot & not to where you took off ... in your flight the HP was located over water.

2.
Then ... after powering on the drone ALWAYS check the drone icon on the map in the app & confirm if that icon is pointing in the same direction relative other map objects as the drone does in reality ... if it doesn't, power the drone down, move away to another take off spot quite a distance from the first & power up again & repeat. In this way you can be sure that all is good & the IMU have been initialized by an undisturbed compass & you don't have to see your drone flyaway at speed.

Thanks a lot @slup . I really appreciate your response and the effort you put in to diagnose what really went wrong and explain the cause of weird behavior. It is due to people like you that newbies like me can learn from mistakes and understand the problem. I will be much more careful from now. I am glad my MA1 is intact.

tlswift58 · Oct 11, 2021

Phantomrain.org said:
So if the drone is above the restricted height when it enters Atti mode other than it being in Atti mode is it compromised in any other way ?

Phantomrain.org
Gear to Fly in the Rain.

I've never encountered "OPTI" mode that I'm aware of (Air2) and restricted to 5 meters. Even when flying in gorges, valleys, and other holes in the earth with trees all around the rim blocking GPS - I can and do ascend to the 98 ft max to try and grab GPS / sats if I can. Not always possible if obstacles of all types may block a good ascent. Sometimes it works, sometimes not. Have also gotten GPS and then descended and lost GPS so back into "ATTI" mode.

My Air2 did a wild maneuver once kind of like OP had. I was hovering above the Chattooga River about 25 feet+ or so and it went hard right for some reason and it was moving fast. As I was watching the drone and not the screen I caught it before impacting rocks or trees; but it did go about 40-50 feet sideways. Had clear skies above and wide open area, so should not have been in ATTI, but could have entered it and I wasn't watching the screen closely. Not issues in almost a year since that happened, but ATTI is a fly by the seat of your pants and butt clenching mode when over water. Even the small wind created by moving water like a river / creek / waterfalls will easily move the drone; so it's a must to be watching the drone and not your screen.

Sadly, some of us learn some very hard and expensive lessons not being AWARE of what the drone / RC is telling you. Never ever think GPS is automatic, as it's not and even if you get a GSP lock, you can lose it just as easily. If you're flying in non-wide open spaces around trees, bridges, and obstacles of any type - practice, practice, and practice some more to have a better understanding of how the drone will react under those conditions. None of us jumped on a bicycle for the first time and rode off straight away for 5 miles. Every new activity / hobby takes practice and understanding what's involved - drones are no different and actually harder as there are so many variables - even the drones themselves fly so differently.

tlswift58 · Oct 11, 2021

Phantomrain.org said:
So if the drone is above the restricted height when it enters Atti mode other than it being in Atti mode is it compromised in any other way ?

Phantomrain.org
Gear to Fly in the Rain.

Are you asking going from "OPTI" to "ATTI?" I see no reason for the drone to be compromised if it went into ATTI. Had the OP vertically ascended to 98 feet max level of ATTI, they may have been able to grab GPS and a homepoint should have been activated at that point (right overhead of them). As I don't have a MA1, I cannot state what it does as compared to the Air2.

Yet, where I live in the mountains - gaining GPS at ground or up to 15 feet is a hit or miss. Since I'm surrounded by trees, my only real maneuver is to go straight up and hope to grab GPS within the 98 foot ceiling. I do clear most trees and typically do get GPS by that 98 foot point and then HomePoint sets directly above where I took off from.

I don't depend on GPS for some of my flying, so ATTI is something I'm a bit used to; but no pro for sure. Don't think anyone can say that, as ATTI can and does some very strange things and the drone can go off on it's own (or seems to). If I'm in ATTI - I rarely look at the screen, I'm watching the drone as it's moving around a fair amount and I'm in tight spaces - that is not my idea of fun. Stick inputs also seem overexaggerated as well; much like what others have said that even when you let off on the sticks the drone keeps on a going - whereas in GPS mode it comes to something of a stop.

cgmaxed · Oct 11, 2021

eEridani said:
DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

Taking off before enough GPS sats were in view, so Home wasn't set until 41 seconds into the flight, those alone are conditions for a wild ride. Max altitude was set quite low; too. I'm thinking you were very lucky the drone didn't fly off into the sunset or decide to land in the river where it had set the Home point.

At 47 seconds your sticks were spinning the drone around and in full reverse (click through the rows in the link above). Can't say for sure why it continued at speed after you let go of the sticks - I'm guessing some GPS heading vs magnetic compass difference. But I'm a novice.

I fly without a gps signal all the time. It's called ATTI mode. He shouldn't lose control of the drone, just because of no gps signal.

eEridani · Oct 12, 2021

cgmaxed said:
I fly without a gps signal all the time. It's called ATTI mode. He shouldn't lose control of the drone, just because of no gps signal.

I've flown in ATTI a couple of times, it was always not fun trying to control the drone. If you do it routinely, maybe it gets easier, but if there is any wind, or low light where the visual sensors can't help, well, the drone has always gone bye-bye.

Phantomrain.org · Oct 12, 2021

eEridani said:
I've flown in ATTI a couple of times, it was always not fun trying to control the drone. If you do it routinely, maybe it gets easier, but if there is any wind, or low light where the visual sensors can't help, well, the drone has always gone bye-bye.

We know all about that Bye bye, Atti mode is better off left for the Olympians. I think if we started off in Atti mode with a purpose we can manage but when its happens by Trauma , its a critical hard time to get the drone back this i Agree.

Phantomrain.org
Gear to fly in the Rain.

eEridani · Oct 12, 2021

Phantomrain.org said:
We know all about that Bye bye, Atti mode is better off left for the Olympians. I think if we started off in Atti mode with a purpose we can manage but when its happens by Trauma , its a critical hard time to get the drone back this i Agree.

Phantomrain.org
Gear to fly in the Rain.

I've found having a wall nearby helps - usually improves control - most of those were HolyStone training exercises. So far, only had the crazy drone syndrome with the DJI once, an evening indoors, and it turned the landing light on automatically (or I had the reflex to do it and don't remember pushing the button).

Phantomrain.org · Oct 12, 2021

eEridani said:
I've found having a wall nearby helps - usually improves control - most of those were HolyStone training exercises. So far, only had the crazy drone syndrome with the DJI once, an evening indoors, and it turned the landing light on automatically (or I had the reflex to do it and don't remember pushing the button).

Yes the wall to break the wind, , good call we use that to get up in the extreme winds at times. We had the Atti mode a lot with the Phantom 4 so that was our holy stone. .

Phatomrain.org
Gear to fly in the Rain.

eEridani · Oct 12, 2021

Phantomrain.org said:
Yes the wall to break the wind, , good call we use that to get up in the extreme winds at times. We had the Atti mode a lot with the Phantom 4 so that was our holy stone. .

Phatomrain.org
Gear to fly in the Rain.

No - the wall is there to stop the crazy drone ... lol. Props not included, so use bumpers. Actually, the times the HS crashed into the wall, it usually hit the screen door - so any damage was from when it hit the ground sideways. Never broke anything, got a few scratches and nicked a prop.