P4P crash - GPS Position NoMatch for last 0.02 seconds of flightlog.

elevatedmedianz · May 19, 2018

Hi all,

First time post for me as I need some advice please. My beloved P4P is 7 months old. No issues until today. Was bringing it back after a short flight in sport mode (plenty of battery left) just bringing it to a hover around 26 feet/8 metres high and it just started tumbling out of the sky before my eyes and crashed onto a wooden deck then bounced into a bush.

Flight log is here

Some pics of the damage:

Camera/gimbal seem OK and all 4 motors still seem to run ok (not that I've taken off) but rear left arm is broken.

No DJI care/refresh but I have the warranty through the retailer (JB hi-fi NZ) which apparently is two years.
Should I approach DJI or my retailer first?

Cheers

Andy

Meta4 · May 19, 2018

I'll look at the log when I get home.
But the gps nomatch msg is completely meaningless. You see it frequently with nothing going wrong.
It wasn't related to the crash.

Meta4 · May 19, 2018

elevatedmedianz said:
Was bringing it back after a short flight in sport mode (plenty of battery left) just bringing it to a hover around 26 feet/8 metres high and it just started tumbling out of the sky before my eyes and crashed onto a wooden deck then bounced into a bush.

The flight data doesn't give many clues.
Your battery can be ruled out as a potential cause. It was full at the start and was good at the end of the data.
As mentioned above the GPS nomatch messages are a false alarm.
It showed up on your flight at 3:41 as well as right at the end.
There is nothing in the data to point to a cause because the data just stops when the drone is climbing and before the fall.
This points to a sudden power loss as the most likely cause.

sar104 · May 19, 2018

I concur with @Meta4. This was caused by sudden power loss at the end of the flight, and is the latest in a rash of such incidents with P4Ps. The flight data shows that just before the end of the record at 267.3 seconds you applied full forward elevator, and then recentered the sticks 0.8 seconds later. 0.1 seconds after that the record stops. My primary suspicion would be that the battery was dislodged during that maneuver, shutting down the aircraft.

spirytus · May 19, 2018

sar104 said:
I concur with @Meta4. This was caused by sudden power loss at the end of the flight, and is the latest in a rash of such incidents with P4Ps. The flight data shows that just before the end of the record at 267.3 seconds you applied full forward elevator, and then recentered the sticks 0.8 seconds later. 0.1 seconds after that the record stops. My primary suspicion would be that the battery was dislodged during that maneuver, shutting down the aircraft.

View attachment 99064

Possibly but you can't say for certain without looking at the flight controller logs. In his case you want to look at the motor speeds, current draw / voltages, ESC status etc... You wont find this in the Go 4 flight records posted.

OP: Seeing that she's still powering up; Fire up Assistant 2, and download the .DAT logs for that day. This looks like a long file so the DAT I would review is likely quite big (200+ MBs). Uploaded to google drive (or equivalent) and share the link.

sar104 · May 19, 2018

spirytus said:
Possibly but you can't say for certain without looking at the flight controller logs. In his case you want to look at the motor speeds, current draw / voltages, ESC status etc... You wont find this in the Go 4 flight records posted.

OP: Seeing that she's still powering up; Fire up Assistant 2, and download the .DAT logs for that day. This looks like a long file so the DAT I would review is likely quite big (200+ MBs). Uploaded to google drive (or equivalent) and share the link.

Can't say what for certain? That it was sudden power loss? Based on many previous logged events I can say that. What I can't tell for certain is what caused the power loss, but the DAT file isn't going to help with that either, since it will almost certainly show motor voltage collapse to around 7 V over the last 80 - 100 ms of the record.

spirytus · May 19, 2018

sar104 said:
Can't say what for certain? That it was sudden power loss? Based on many previous logged events I can say that. What I can't tell for certain is what caused the power loss, but the DAT file isn't going to help with that either, since it will almost certainly show motor voltage collapse to around 7 V over the last 80 - 100 ms of the record.

Yes, you're probably right, however when you sill have a functional FC, why would you dismiss its logs? At the very least he would have corroborating data which could help him with the warranty claim...

sar104 · May 19, 2018

spirytus said:
Yes, you're probably right, however when you sill have a functional FC, why would you dismiss its logs? At the very least he would have corroborating data which could help him with the warranty claim...

I agree - and I generally request the aircraft DAT file just to observe the voltage collapse in these events. It typically doesn't help the warranty claim since an improperly secured battery generally would not be covered. However, looking back it appears that I've seen one case where there was no recorded voltage drop, suggesting that possibly the FC froze so actually you were correct - that can't be ruled out without the DAT file.

In the last couple of weeks there has been a rash of these incidents with relatively new P4Ps, and DJI has added a latch sensor to the v2. Perhaps there have been some issues with the security of the battery latches.

elevatedmedianz · May 20, 2018

Thanks team. You guys are awesome. Here is the DAT file

Also attached is the last frame of the video that wrote to the card. I thought I was going to have some epic crash footage but alas, no!!

Assume it takes time to write the image to the card. (the date of the folder of this last video file was 01JAN16. Don't know if that helps)

Blue circle was where I was.
Yellow arrow is my guess at where it lost power
Red arrow is where it came to rest

Cheers

sar104 · May 20, 2018

elevatedmedianz said:
Thanks team. You guys are awesome. Here is the DAT file

Also attached is the last frame of the video that wrote to the card. I thought I was going to have some epic crash footage but alas, no!!

Assume it takes time to write the image to the card. (the date of the folder of this last video file was 01JAN16. Don't know if that helps)

Blue circle was where I was.

Yellow arrow is my guess at where it lost power

Red arrow is where it came to rest

CheersView attachment 99088

OK - this shows the final second of the motor voltage data, with the expected collapse to around 7 V in around 100 ms, at which point the FC shuts down due to low voltage. That confirms that it was power loss. Since it still powers up, that strongly suggests that the battery disconnected.

elevatedmedianz · May 20, 2018

Fascinating stuff. Many thanks. I guess that leads onto the next question. Was that my fault or is it an issue with the battery latching system?

I guess the upside is it crash landed within a few feet of me rather than somewhere where I couldn't retrieve it.

sar104 · May 20, 2018

elevatedmedianz said:
Fascinating stuff. Many thanks. I guess that leads onto the next question. Was that my fault or is it an issue with the battery latching system?

I guess the upside is it crash landed within a few feet of me rather than somewhere where I couldn't retrieve it.

Previously I would have said that it was clearly operator error, but recently there have been numerous cases of this - all with the P4P. That raises the obvious question as to whether there is a design or manufacturing fault in the battery latches. DJI has added a battery latch interlock to the P4P v2.