P4 disconnected in flight, found with battery missing

[RémyHeli]

Wondering how flight controller does manage conflicting rules;
1) auto order to reach RTH altitude
- Entering higher than restricted
2) auto order to reduce altitude or autoland

(with possible intermittent capability to detect noflyzone information if lacking satellites or going into Atti-mode)


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[WBN3]

Wondering how flight controller does manage conflicting rules;
1) auto order to reach RTH altitude
- Entering higher than restricted
2) auto order to reduce altitude or autoland

(with possible intermittent capability to detect noflyzone information if lacking satellites or going into Atti-mode)


Sent from my iPhone using PhantomPilots

As posted above, the altitude restriction for the area referred to as "Authorized" is the same as outside that region at the boundary, and slopes down to 20 meters (66 ft) at the boundary with the no-fly zone. My son said he received a prompt from the app asking if he wanted to request authorization when he reached the boundary (presumably after trying to cross it and failing) and he replied "no" then hit the Go Home button. Loss of contact was after that happened. It should never have been in an auto-land situation.

 

[RémyHeli]

I understand that In case of loss of contact the craft might switch to Atti mode and then not anymore follow geofence rules. If so, he might accept to go thru a restricted zone and, once further recovering contact/ P-GPS mode geofence rules are applied and trigger autolower altitude or autoland.

Rules are documented but I suspect a combination or a mix causing the issue.

All this may be not your scenario but per example I wonder about the benefits of an RTH altitude setting lower than restricted altitude so it will be able to return without hiting the 'ceiling'.

Any clarification welcome.




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[WBN3]

I understand that In case of loss of contact the craft might switch to Atti mode and then not anymore follow geofence rules. If so, he might accept to go thru a restricted zone and, once further recovering contact/ P-GPS mode geofence rules are applied and trigger autolower altitude or autoland.

Rules are documented but I suspect a combination or a mix causing the issue.

All this may be not your scenario but per example I wonder about the benefits of an RTH altitude setting lower than restricted altitude so it will be able to return without hiting the 'ceiling'.

Any clarification welcome.




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If you are discussing a hypothetical situation, I have no comment.

If you are discussing our situation, as has been stated, the RTH altitude was set well below local ceiling altitude, as well as ceiling immediately inside boundary of "authorization" zone. The aircraft was not inside the boundary at loss of contact, based on last known location. The loss-of-signal action is programmed as return to home. There were 17 GPS satellites visible at loss of contact per the flight log recovered from the app. We have not been able to recover the log from the P4 because we don't have a functional battery.

 

[WBN3]

DJI received the drone and apparently assessed it as functional. They sent my son a quote which involved replacing a couple of parts which cost less than $10 apiece (central cover component, top cover - neither of which I could find a decent description of). These were quoted with a cost of 2 hours' labor ($130). The comments in the quote were something to the effect of "flying the drone unsafely near trees, which it flew UP into when Go Home was activated". They did not in any way address the malfunction observed (uncommanded descent after Go Home activated) and have no basis upon which to say it flew up into branches. The Go Home function was triggered at 159 ft altitude and we have no trees anywhere close to that tall.

My son chatted with a DJI customer service rep, who initiated a dispute of the invoice. We've read posts describing successful warranty claims after doing so. The CSR said they will forward to their supervisor. We'll see what they say... I'm still skeptical we'll get a new battery out of it, but you would hope they want to maintain some level of customer retention..

 

[Neon Euc]

It may be worth doing a screen shot of the flight path using healthy drones and a screen shot of google of on the area to show there is no trees. That way they have to admit it was a malfunction

Neon Euc

 

[WBN3]

It may be worth doing a screen shot of the flight path using healthy drones and a screen shot of google of on the area to show there is no trees. That way they have to admit it was a malfunction

Neon Euc

I wish it were that simple... there were trees on the flight path and in the area the drone lost contact, which is what I'm sure they're basing their conclusions on. However, I've loaded the KML file from HealthyDrones into Google Earth, and on 3D view the trees are about half the height of the drone when contact was lost. Also I've measured the length of tree shadows in Google Earth using its ruler tool, and based on the maximum sun angle on the day the pictures were taken, the trees in the area the drone went down are all well below 100 ft. tall. I don't think the customer service reps from DJI will be able to understand the trigonometry of that proof, so I am going to hold off on laying all my cards on the table.

 

[lugerc]

I dont want to thread jack your post, but I believe something similar happened to my P4. The other night I was flying it around 160ft with 19 Sats within line of sight about 2000 ft away. Next thing I know the controller says "Aircraft Disconnected" and that was the last I ever heard from it. The flight data ends with the aircraft over the same point in which it says it was disconnected. I synced that data with DJI servers and they "offered" me a 30% discount because:

"For your recent flight incident, with the record ended without any sign of abnormality, our analysis is inconclusive.

As such, we could not provide service under warranty."


We never saw any lights after the thing disconnected. No idea what happened except maybe the battery fell out?

 

[WBN3]

I dont want to thread jack your post, but I believe something similar happened to my P4. The other night I was flying it around 160ft with 19 Sats within line of sight about 2000 ft away. Next thing I know the controller says "Aircraft Disconnected" and that was the last I ever heard from it. The flight data ends with the aircraft over the same point in which it says it was disconnected. I synced that data with DJI servers and they "offered" me a 30% discount because:

"For your recent flight incident, with the record ended without any sign of abnormality, our analysis is inconclusive.

As such, we could not provide service under warranty."


We never saw any lights after the thing disconnected. No idea what happened except maybe the battery fell out?

That sounds VERY similar to our situation. It wasn't clear from your post whether you were able to locate the drone or not. I uploaded my log file to HealthyDrones, then downloaded the KML and opened it in Google Earth, where you can view the flight path in 3 dimensions. When I extrapolate the path of descent recorded while it was still connected, it points very close to the location where I ultimately found the drone on the ground. If you haven't tried that and cannot find the drone, it may help. We're still waiting on a response from DJI...

 

[lugerc]

I was not able to locate the drone. A friend and I searched last known areas for at least three hours. Here is the flight record if youre interested:
Phantom Log Viewer - PhantomHelp.com

 

[AlecW]

I was not able to locate the drone. A friend and I searched last known areas for at least three hours. Here is the flight record if youre interested:
Phantom Log Viewer - PhantomHelp.com

I'd start a new thread, some of the guys here are good at plotting potential landing places. That's an odd GSP path, looks like you took off in the middle of a river?

 

[WBN3]

I was not able to locate the drone. A friend and I searched last known areas for at least three hours. Here is the flight record if youre interested:
Phantom Log Viewer - PhantomHelp.com

Why is the Home Point set in the middle of the river? Were you on a boat when you launched? Was the app set to Return to Home if contact is lost? The flight path at last known location was taking it toward Plant Hall... assume that is where you were looking.

 

[lugerc]

the drone was launched from a boat. It was set to hover in case of lost comms with the controller. Either way, there was at least one person watching the drone as it hovered in its final seconds who said they no longer saw its lights.

 

[WBN3]

the drone was launched from a boat. It was set to hover in case of lost comms with the controller. Either way, there was at least one person watching the drone as it hovered in its final seconds who said they no longer saw its lights.

Well based on the last location, with no power it could've fallen in the river or it could've fallen on the north side of the river if there was any breeze out of the southwest... hard to believe it could make it all the way across to the UT side. We are hoping to get the log file from our on-board memory to see if it lost the battery or if it continued flying after we lost contact. We were lucky to find it... I'm not optimistic you'll be as lucky.

 

[lugerc]

The other issue is that there was a concert going on within 30 yards of the drones last location. There were no reports of anyone getting smashed in the head by a battery or drone. Security also said they had no reports of a drone crash either. There were also two other drones flying within 100 yards of mine but they were not in the near vicinity of mine when the lights went out.

 

[F3honda4me]

Just a suggestion on courtesy, you should probably keep this all in your own thread that you made.

"Aircraft Disconnected" Warning. Flight Log Ended

 

[lugerc]

Thanks Albert

 

[WBN3]

Just an update - the DJI folks finally got back to my son with a response to the dispute. As you would imagine, they weren't immediately forthcoming with free stuff. The text of their reply -

"Our Data Analysis experts re-evaluated and double checked your RTHF height is been automatically lower because he is right next to an airport, he is flying at a no-fly zone, the height needs to be limited, and that is why the altitude is been auto lower. Please do not fly close to any AIRPORT as this affect the flight of your unit."​

This demonstrates their lack of understanding of the "no fly" vs. "authorized flight" boundaries, and the fact that they don't look to what happened after RTH initiated. My son has replied to this with facts and we'll see if they escalate this to a higher level within their customer service group. Feels like the run-around to me.

 

[WBN3]

My son received an email, but it did not contain a conclusive analysis. Here is the text:

"After re-reviewing your flight analysis, the conclusion will remain as previously stated.
The aircraft was too close to an airport and the altitude was limited due to safety and regulation concerns.
The Return to Home Function operated normally, however due to the environment and restriction of height distance, the unit struck and object.
However, there were no hardware, software or application malfunctions detected. Based on this data our data analysts were unable to apply warranty.
Please refer to the data attached to this email."​

Here are the two screen shots that they provided, which are from the on-board flight log:

We have several issues with this analysis:

1. As with the previous email, it refers to being in proximity to the airport (circled in red on the first picture) but does not explain what flight rule caused the drone to change altitude. You can see that we were nowhere near the NFZ.
2. The statement that the "Return to Home function operated normally" is wrong. In the second picture, the commanded RTH is circled in the text field below the graph. However, the drone did not return to home. In the low-resolution text at the bottom of the top picture, it indicates "fail-safe action hovering", yet that is not the way my son programmed it to respond to loss of contact. As you can see from the behavior in the first flight of the day, when RC connection was lost, it initiated a RTH.
3. The email also repeats the claim that it flew into an object, yet there is no proof of that (picture, video, etc.).
4. The second picture shows the altitude, and has data showing the drone went into hover at 20 meters, which it held for about 250 seconds. Based on our reading of the wiki page linked in the first post, that is the altitude limit at the boundary of a no-fly-zone (i.e. the red circle in the top picture). We were clearly not anywhere near the no-fly-zone!!!
5. Look at the title of the window in the second screen capture - "Viewer (build v1714) vision 1.25.11 with some unknown bug" - it basically says it all right there...

We would like to learn from this, but we have been given no explanation that we can use to change our future flight plans. This seems to be a blatant attempt to avoid responsibility on the part of DJI. Our understanding of the altitude restricted flight zones is outlined in one of my earlier posts. I'd love for someone to explain how the drone flew into an area that it thought it should be hovering at 20 meters when my son followed the rules and commanded a RTH when he reached the boundary of the Authorized Flight zone. After 4 minutes, were the batteries depleted enough to trigger an auto-land? I could definitely see that causing the drone to strike a tree, since there were trees in the vicinity. The failsafe return to home should have protected from this scenario happening.

 

[turbmeister]

Get a parrot mambo , Problem solved.


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