Mirek6
Second Officer
Flight distance : 609724 ft
Canada
Offline
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Erlend,
Your backward flight path looks like trouble.
I have seen it many times and, inevitably (in all the cases I have seen), it meant that there is a discrepancy between Spark compass direction and Spark’s physical direction.
Here is how it works.
With well calibrated compass Spark’s direction and compass direction are in line. When you move your stick, Spark’s firmware calculates so called COMMANDED position - the position you ask your Spark to be in in a next while (after X ms). The commanded position is calculated based on where the compass is showing the Spark is facing, where the Spark is now (its exact GPS position) and the vector of your stick movement. The commanded position is simply a GPS position where the Spark should be in the next few moments (after X ms).
Spark starts flying. After X ms passed Spark checks its physical position. If it is equal to commanded position all is fine. It calculates new commanded position etc. If, however, physical position is not the same as commanded position Spark calculates adjustment vector which it adds to the directional vector from your stick input. If compass misalignment is constant, the flight path will be superimposed with a series of adjustments and will start to look like an arc. Read about toilet bowl effect and you will understand what I am talking about. And here is a rub. This ellipsoidal path is consistent with toilet bowl effect which is quite dangerous phenomenon (difficult to control if you are in GPS mode). So DJI design is to drop Spark to ATTI to allow full manual control. In most cases I have seen so far, the ellipsoidal path was sooner or later followed by drop to ATTI.
There is another factor – wind. If the wind was blowing from your right side to the left, it could have caused ellipsoidal path. But … I do not see arc in white line. Also, I only saw ellipsoidal path consistent with Spark fighting the wind when its sensor systems were already confused (in other cases I analyzed). And it also, inevitably, lead to later ATTI.
In the analysis of other similar cases (wind or no wind), DJI ended up replacing drone if it was still on warranty. This indicates issue with their h/w or firmware. We speculated that the December 2017 firmware (0900) is weak and can misinterpret sensory input causing constant adjustments and drop to ATTI. It is speculation, because, in a vast majority of Sparks (including mine which is on 0900) you do not see this problem. Also, in a majority of cases where the Spark was recovered, calibration of IMU and compass helped.
You calibrated IMU and you calibrated compass. You still see the problem. Next step would be to upgrade to newest firmware. But before you do this, read posts in Software section of this forum. You will see what people think about newest firmware and what kind of trouble they experienced. Be aware of that.
If you can, upload this particular flight record to phantom site – I would like to see logs so my recommendation is not biased.
No, you cannot share your flights directly from you flight list in DJI Go App. If you want to share it with forum members, upload to phantom site and share the link with us.
Mirek
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