JJB*
Core User of DJI
Flight distance : 12225059 ft
Netherlands
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Guorium Posted at 2-25 16:50
I find the response a bit hard to interpret. Let me make sense of it.
I suppose you say when GPS registers a bad location (not true) when reception is not good, then it registers a good signal. The difference in coordinate makes MM want to fly to the wrong location thus fly away? I suppose that could happen. I did an opti takeoff with poor GPS reception and 5 sat over water. VPS kept it steady til I gathered a solid reception higher up, the flight was very safe.
Hi Guorium,
On this forum it is promoted to do before take off checks, especially check the compass heading at the ground. Why? to prevent a fly away due to compass/yaw error.
Situation1 : all OKE ;
Craft on the ground is actual facing N and compass is showing N,Into hover and than no stick input,
Wind breeze wich moves craft backwards,
SW calculates (using GPS + compass data) needed input to steer to the old postion > forward input = all OKE
Situation2 : N-OKE ;
Craft on the ground is actual facing N and compass is showing W, (but not checked by pilot)Into hover and than no stick input,
Wind breeze wich moves craft backwards,
SW calculates needed input to steer to the old postion > right input = craft moves to the right (back already) of the old position, thus further away and more correction needed etc ect
A great example of this type of flyaway to see at > https://forum.phantomhelp.com/t/mavic-mini-flew-away-on-me/4477
Craft heading on the ground South and takeoff South (told by the pilot and can be checked by the video, drone compass 055), see the result.
Compass indicated heading is not changed after take-off, during takeoff and gaining height, as long as the position is not really changed no correction is needed, same when flying forward, no problem yet. Once there is a change in position with some heading changes too (not done by RC input as yaw signals are both changing) the fly-away starts.
On few flights on this forum this was the problem, checking logs is hard as in the log it is not seen at wich heading the craft actual was heading at takeoff.
Only asking the pilot to inform the forum this heading makes the analysis to be done correct.
What we do not see in logs is that the compass heading is changed after takeoff at few meters above the ground, so compass interference/wrong heading is not see by a moving compass back to the real actual heading after takeoff. (well i have not seen any of this in my large database of error flights). Apparantly in this situation the app does not give a warning.
In some flights suddenly during flight (after 1 minute, or 2 or 14 minutes) compass heading is changed, not few degrees but large changing values.
I have no clue how that is possible. A hardware fail, power peak to this part of the system??. During flight at height hardly possible to 'eat' an interference to the compass/yaw system. But the effect on the drone is the same, SW steering into to wrong direction, a fly away.
Some cases seen on this forum when the flight was screen recorded, you will see a rapid change on the compass indicator where the drone does not yaw ofcourse.
Cannot explain really but sometimes entering a RTH mode does bring yaw signals back to each other.
So is it important to check your compass indication in the app before takeoff? Ofcourse a 100% YES, as this is a simple way to prevent a fly-away right after take-off!!
For other fly-aways wich occur during a normal started flight, wish i had the knowledge to pin point the cause of this!
For the GPS part, when starting a flight in OPTI due to low sat and/or reception ; guess it depends how the GPS signals (quality) getting in the system and how fast from 0 to normal number and reception. So not all in OPTI started flight goes wrong, but is it a coincidence that few fly-aways started their fligt in OPTI? guess yes...a coincidence but not sure about that.
cheers
JJB
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