DeuceDriv3r
 Second Officer
Flight distance : 4698533 ft
United States
Offline
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DJI have a real problem on their hands here... this issue is now prevalent across their entire line of consumer drones...
firmware updates for the mavic pro/air spark now all have threads stating an increase in issues relating specifically to compass performance and unwanted yaw performance issues in the aircraft and gimbal systems
It has sounded to me having talked with DJI several times they know this is and issue and also by the sound if it.. these aircraft are using similar if not the same code base for at least some of their firmware...
my GUESS is that they have been tweaking the filtering and possibly even the euler angle equations as newer hardware like the mavic 2 and air were coming on line to have their algorithms perform well across the spectrum of aircraft rather than having to fork and maintain code bases for each aircraft separately..
could also be, but less likely. that the actual hardware (chips) that DJI have chose degrade rapidly.. since this all seems tied to firmware updates..
in my case I had 2 brand new sparks bought in Sept of '18 ... all came with 2017 vintage firmware and flew great for 2 weeks.. after updating to the latest firmware as nagged by the Go app... both aircraft began having issues immediately.. no refreshing of firmware, compass or IMU cals would rid it.. and curiously ... one was worse than the other..
just bought a Mavic Pro, and it too came with 2017 firmware, this was Nov '18 and they still have product in the pipeline with '17 era firmware (because they know its flies better probably) .. as soon as I updated I started having the same issues as the spark...
analysis in csvview you can clearly see on ANY flight... there is a discrepancy between yaw and magyaw... and when that separation gets to the internal limit.. you guessed it. you start seeing anywhere from dozens to hundreds of compass and yaw warnings.. followed by the dreaded cascade of IMU WORKING Exception, the GPS weak when it turns off GPS and finally ATTI MODE... at which time I believe that it likely does what we called and in flight alignment in the military.. and the aircraft resets the kalman filters and re-aligns the INU.. during which time people have reported various levels of control and even times where the aircraft did not just drift with the wind but decided to bolt...
all you can see in the GO app is the biases.. and only if the aircraft is at rest.. in flight you have no way of knowing just how jacked up the IMU is becoming .. there is no raw readout of heading ..
the only way to tell how jacked up your system is getting is the following..
comparing aircraft heading to your known position via the map or the radar.. in both cases your phone must be operating properly.. i.e. ... if you have the map up and standing near a road.. the road MUST be aligned like it is in the map, not in N UP mode but in compass mode..
another way to tell if the aircrafts heading is really matching reality is to hit RTH from a distance of at least 300 meters... the more the better... when RTH is initiated .. the aircraft takes present position and calculates a NAV solution to the HOME POINT then plots the HEADING of the RHUMB line to make that navigation good.. THEN ROTATES to that HEADING...
the spark, mavic line IS SUPPOSED to POINT DIRECTLY as the home point on RTH ... if its NOT CENTERING UP THE HOME POINT .. that ANGLE OFF is how far OFF THE COMPASS is...
one of my sparks RTH at over 40 degrees... and that one I returned to where I bought it from rather than deal with DJI
another way it to do a precision take off... fly a bit.. aggressively if you use sport mode... initiate a RTH TO A PRECISION landing... should work with any landing but precision works better
when the aircraft gets overhead it ROTATES to the HEADING it TOOK OFF FROM
if you line your craft up with a cement crack, chalk line on a sports field etc.. you will notice IT NO LONGER FACES THE SAME DIRECTION... the angle off is the COMPASS ERROR since TAKEOFF....
again my sparks would be way off.. and now my mavic is doing it although to a slightly lesser extent than the sparks.. so far about 15 degrees....
curiously .... HOW MANY PEOPLE when flying at EXTENDED RANGE...LOOSE SIGNAL at the moment ATTI kicks in?????
does anyone think that the way DJI gets such performance out of WIFI is by using BEAM STEERING ????? and if so.. instead of beam steering off signal gain... are they beam steering again based on the calculation of the heading to the home point...????
that would explain why signal drops occur coincidentally with ATTI mode and IMU reboot..,.
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