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DJI Phantom 3 Pro got a mind of its own
593 4 2017-9-6
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Flight distance : 25292 ft

[size=14.6667px]So I will talk you all through this issue. I would be interested to find out if many people have had the same or similar issues with the P3 pro or P3 series aircraft.

[size=14.6667px]Wind speed on the day was less than, or equal too 5kph mostly still and settled and there was no rain.
[size=14.6667px]Battery was full on takeoff and the aircraft flew normally throughout the mission. Our mission parameters as filed with the Irish Aviation Authority where that the aircraft would takeoff from point A, fly to point B and then onward to point C for landing and battery swap if required. On approach to LZ (point C) at 29% battery the aircraft tried to initiate RTH which I canceled as the aircraft was landing at point C NOT point A. As I was on approach the battery dropped to 27% ~70m away from the LZ. So still plenty of power. Then without warning the video image went grey, telemetry and control signals dropped all at the same time. Personnel present at the LZ stated "I saw it on approach it then seemed to halt for a second and drifted around for a few seconds before flying off eastwards". The P3 was not recovered and the area was canvassed.

[size=14.6667px]I contacted DJI support and submitted my logs as they requested, this was their response:
[size=14.6667px]1. Aircraft worked at GPS mode;
[size=14.6667px]2. T=14-28, h=4m, d=728m, 29% battery power, RTH was triggered due to low battery; T=14-32, pilot cancelled the RTH and flew the aircraft more far away from home point by pushing pitch stick forward;
[size=14.6667px]3. T=15-13, h=5m, d=1032m, the record stopped while the aircraft was flying forward. At the end the aircraft would not have enough battery power to return home.
[size=14.6667px]According to the analysis, the incident was not caused by any product malfunction factors. As such, we could not provide warranty service.

[size=14.6667px]DJI stated there was no malfunction, but in the same email they stated that "the record stopped while the aircraft was flying forward" How can the flight recorder stop mid flight? Doesn't it continue until landed and motors powered down? Has anyone else had all transmission signals from their aircraft just drop simultaneously and lead to loss of the aircraft? They have stated this is not a warranty case as their was no malfunction when there must have been. Any advice or stories similar to mine would be appreciated guys.

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Flight distance : 10442687 ft
United States

Must have had your hand on the sticks.
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Mark The Droner
Flight distance : 2917 ft
United States

The log is held at the controller.  When you lost signal, the log ended since there was no regain of the signal / continuance of the log  That's normal.  

This is pilot error since the pilot deliberately cancelled the Fail-Safe.  

If you want, you can upload your log to (site credit:  msinger)

...paste the link

...and the membership can take a closer look at what happened...

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DJI Thor
Flight distance : 13602 ft

We are so sorry to hear about your loss. The flight records might end when the transmission is lost, the RC signal is lost or the connection between RC and the mobile device is interrupted. So when the records ended without any sign of abnormality, we can not predict and evaluate what happened afterward. Could you please provide me with your case number so I can check more info about your case? Thank you.
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Flight distance : 503241 ft


This is unfortunately classed as a case of pilot error.  DJI aren't great at explaining the incident, but they do identify the relevant parts in making their decision.  Bear in mind they are probably investigating and answering many crashes and cases of a perceived fault for warranty purposes, and are likely to be concise in their reply.

I read the analysis as follows:  as you got close to point C and expected it to land, you coincidentally hit a low-battery level which triggered a low battery RTH.  The battery level was calculated to be sufficient to RTH safely directly to point A before a critical battery landing.  Your action was to choose to retain control and complete your mission.  You cancelled RTH.  You now assumed full responsibility for the following flight.  There is absolutely nothing wrong with this decision based on remaining battery levels etc.,  but keep in mind you over-rode the DJI failsafe.  You continued to fly to point C manually and appeared to descend.  You lost telemetry and video from the aircraft, probably because it was low behind an obstruction such as terrain and foliage, which is probable and to be anticipated. The flight records showed you were pushing the pitch stick forward.   When the connection was severed, the aircraft was observed to "halt" and "drift around" for a few seconds (it would be 3 seconds of loss of control) at which point it initiated another (lost control) failsafe RTH.  The normal behaviour in this situation would be for the aircraft to ascend to the preset altitude prior to RTH.  If the aircraft rose enough to once again re-establish a connection with the controller, it would have received the "stick forward" command.  Any stick movement received during the rise phase of a lost-signal-initiated RTH has the effect of cancelling the RTH process immediately, to return control to the pilot.   It would stop climbing and you would be in control, unless it was in a poor reception/edge of range scenario. There are three types of RTH procedure:  Smart RTH, Low Battery RTH and Failsafe RTH. It is worth re-reading the manual around page 12 onwards to understand the differences and limitations.

Video can and often does drop out before flight control is lost, which is why it isn't a great idea to rely on the video feed only and not have the aircraft in LOS (line of sight).  The aircraft probably flew off east due to your last stick movement, and possibly because you held the stick off center until it was out of range.  It is likely you then reached critical battery and the aircraft landed in place to protect itself, however that doesn't rule out impact with trees or terrain.  There will be a flight record inside the aircraft to determine what happened if it is ever recovered, but the record in the controller is only that part that was successfully transmitted back to your position, and will be incomplete.  It is normal for the (controller) flight recorder to stop recording if the radio signals are interrupted.  Radio waves travel in a straight line and only reflect off certain objects under certain conditions.  They won't deviate much in a natural hilly woodland environment.

Depending on your critical battery setting and other data, we on the forum can generally work out what went wrong and where the likely search point is.   Bear in mind that wind can play a large part in skewing the results and a measured 0-5km/h windspeed on the ground doesn't mean it isn't much stronger a few feet above.  This could explain it being observed "drifting around", which is not normally expected.   If you post your flight record from the controller to the Phantom Help website in post #3, then post the resultant link back here we can analyse it for you in greater detail.

It would seem from the descriptions there are no faults or malfunction in their product, therefore DJI are not liable as the incident occurred out of their control.
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