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DJI Spark - My Theory about problem - Fall of the sky like a brick
1216 1 2017-7-28
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Second Officer
Flight distance : 459094 ft

A Pilot created a topic about his spark trying to land when are 70m high midflight.

I created a theory on his post, just a theory about why this happens:

Just a theory, but..

Did you clean VPS sensors before take off? Spark does not appear to use the same ultrasound technology on VPS as P3 or P4, maybe the sensor are dirty and give incorrect data , making the drone think its very close to the ground and land when are 70m high or even on thinking the drone are close to a hand and  do a palm land.

Anyone knows whats the VPS techology used on spark? And why the sensor are not like P3 or P4 (ultrasound)? Looks like infrared.

Aswer: Infrared, its not ultrasound like others DJI drones , p3 - p4 - Mavic.

So i contiued with my theory..

Dji Spark Manual advises twice about keep sensors clean or this maybe cause problems. Maybe land at 70m high its one of the problems (just a theory), other problem may be the difficult to use hand gestures, people may forget about clean the drone before take off or dont even read the manual ( i not saying its the case of the owner of this post).

Dji implemented a bunch of new functions and technologies (new vps? new colision system, hand gestures, etc) to a "affordable price drone" that targets a new drone users that maybe never flow before a drone, when even the old drone users never have contact with this new technologies and functions at the moment, its really not a good idea.

All new technologies have their own peculiarities, in the case of a drone, this may lead to accidents and problems until its 100% learned.

And finally, ended my theory:

Maybe infrared if used as VPS has some tipe of peculiarities, like be susceptible to dirt on glass that covers it, fog or something that makes the infrared sensor think the ground its closer than they are. If infrared works calculating the distance to the ground as a laser tape.   Makes sense for me if there are dirt between the sensor and the ground, sensor will think dirty is the ground.

What this has to do with Spark fall of the sky problem?

Spark , as all VPS DJI drones, uses VPS to hover and when landing to determine more acurately distance to the ground and shut off motors, if the distance on VPS = 0 , the drone will turn off, assuming it was landed (try to push stick down near ground, spark will land if very close to the ground, not showing on phone that it will land, like always do, just stop motors).

And if the VPS sensors are not clean? If infrared works calculating the distance to the ground as a laser tape.  Makes sense for me if there are dirt between the sensor and the ground, sensor will think dirty is the ground. If dirty VPS assume midflight it was at 0 altitude and turn off motors, even if GPS says other altitude, drone will fall of the sky like a brick thinking it was at the ground or hand, stopping motors.

Remenber the spark has new functions, like palm landing, precision landing and other tipe of VPS ( infrared based, not ultrasound), this may lead to problems like this, its so many functions to deal all at the same time, and not all are safe compatible between the other.

Its easy to a phantom deal with VPS , nobody will try to land on hand like spark (assuming using VPS to know that spark are on hand), he does not need to turn off drone on other place than real ground.

I need to make clean thats just a theory, if somebody has one, please share with us.

Sorry for my english, its not my main language.

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Flight distance : 8673241 ft
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I think every manual P4Pro Mavic inspire spark, have notice to keep sensors clean, yes I have seen some where aircraft went into landing at 70m , but that was a regular occurrence with Mavic , this can be cancelled. Also it won't drop out of the air. It is your IMU that switches of power to the motors it will do this 3 seconds after it realises that the aircraft can no longer move down any further, hence holding down left stick for 3 seconds.

Yes it is an unfamiliar 3D vision sensor and it might take a while to understand it, but I wouldn't be to quick to hang all the dropouts on vision sensors, but who really knows.
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