Need help with P4P Crash analysis

aperry · Jul 30, 2017

My P4P crashed at a construction site where I've been taking monthly progress photos for over a year. Got a compass error in preflight, so calibrated before takeoff. About 2 minutes in, heard the motors rev higher than normal and heard the drone crash into a wooded area. Need some help trying to figure out what happened.

Airdata flight log

Phantom Help Flight log

Currently, drone is being held hostage by DJI support. They've had it since July 5th waiting for data analysis. I just want to know what happened.

Any help is appreciated.

Meta4 · Jul 30, 2017

aperry said:
My P4P crashed at a construction site where I've been taking monthly progress photos for over a year. Got a compass error in preflight, so calibrated before takeoff. About 2 minutes in, heard the motors rev higher than normal and heard the drone crash into a wooded area. Need some help trying to figure out what happened.

The flight record you linked shows nothing. It ends at 2:53 with the Phantom 362 feet up and flying south at 19mph with all indications looking normal.
Whatever happened, was after that but we can't tell from this flight record.
DJI should have a lot more luck with the data recorded in the Phantom as it does not rely on the app or control signal.

Something in your story is a concern.
A compass error, is your compass telling you that it's detected a magnetic influence that's significantly different from the earth's normal magnetic field.
Recalibrating the compass close to that magnetic influence is risky and likely to cause problems.
Normally you would expect those problems to show up before 2:53 and the height/distance your Phantom attained but there's no evidence to say what happened.

desert phantom · Jul 30, 2017

From my non-expert analysis it looks to be inconclusive(?).

aperry · Jul 30, 2017

Yes, Meta4, i thought about that also. When I launched, I ensured all controls were functioning properly before starting my ascent to the desire height. I also mentioned that because there is no descending altitude reading during the crash. I also noticed that the speed of the craft increased significantly during the last 5 seconds of the log, which is consistent with me hearing the motors rev higher. There would be no reason for me to fly that fast as my next photo point was only about 50 feet away.

Meta4 · Jul 30, 2017

aperry said:
I also mentioned that because there is no descending altitude reading during the crash. I also noticed that the speed of the craft increased significantly during the last 5 seconds of the log, which is consistent with me hearing the motors rev higher.

It looks like the app crashed or you lost signal which is why there is no record of the crash - only some flight before it.
From 2:19.8 you have pulled the right stick hard over to the right or left (I'm not sure which).
This matches the increase in speed.
The right stick was still hard over at the end of the flight record.
We can't tell how soon after the end of record, the problem happened.

Where did you calibrate the compass and launch from?
Was it on a concrete slab?

aperry · Jul 30, 2017

I calibrated in a grassy area near the home point. I launched from a concrete slab to avoid kicking up so much dirt.

Meta4 · Jul 30, 2017

aperry said:
I calibrated in a grassy area near the home point. I launched from a concrete slab to avoid kicking up so much dirt.

Launching from reinforced concrete is very risky.
There have been lots of cases of Phantoms being lost because of this.
Here's an example and explanation of how that happens:
Looking for Trouble ??
This isn't necessarily what happened to yours.
Usually it would happen sooner if that was the case.

Neon Euc · Jul 30, 2017

Another thing is when you said you heard the motor rev up higher then normal. To me it sounded like it got snagged on something and tried to pull away. Could have got a wire or cable you didn't see and causing it to crash