Lost - Dont expect it to be found, but just in case

[jwashburn]

What I "THINK" happened goes like this.

Facts: I was in cinematic mode, flying backwards because I overshot my original target and was getting ready to make another run. The battery was fully charged. I had only been flying for a couple of minutes. It was cold outside, about 30 Fahrenheit. The drone was in my direct vision. Flying just over eye level above a small creek.

What I think happened next:
I remember stepping on something behind me, not enough to fall or anything, just enough for me to look away from my drone and my controller to see what I stepped on. When I turned my attention back to my drone I could no longer see it and my controller said disconnected. What seemed like a milisecond later I heard the sound of tree limbs breaking behind me and to my right. I presumed it was a pine cone or something falling. Its a typical sound in the woods. I did not even think it could be my Mavic. I began to scan the sky and realized that sound was my drone.

When you look at the photo of the flight line, you see it change direction just slightly and make a straight beeline for the trees. Looking at the logs it sped up to full speed and then crash

I have spent about 10 hours searching for it. I found two pieces of propellers and a small piece of the body.

My presumption is it hit the tree broke apart and fell into the creek. I have walked the creek multiple times over multiple weekends. Its fast moving and pretty cold. No luck yet.

My Mavic was 19 days out of warranty so DJI wont review my logs. I am in the middle of trying to appeal for the third time. I am not asking them to replace it, just review the logs. I want to know if it was a pilot error or a device error.

So if you are in the area of Antelope Lake in Plumas County California. Give it a search.

 

[MavicCF]

Here is the Phantom Log upload for anyone interested.

 

[jwashburn]

Here is the Phantom Log upload for anyone interested.

Thanks, I wasnt sure how to share that.

 

[jwashburn]

Right around 1:58 is when I am guessing it went wonky on me.

 

[MavicCF]

I would call @sar104 in on this one, at first I thought it was normal, but now I'm not as sure. For one, there appear to be no aileron inputs throughout the whole flight, even though the X-gyro shows significant movement, almost mimicking the Y-gyro speed in fact. Was it windy that day?

 

[jwashburn]

I would call @sar104 in on this one, at first I thought it was normal, but now I'm not as sure. For one, there appear to be no aileron inputs throughout the whole flight, even though the X-gyro shows significant movement, almost mimicking the Y-gyro speed in fact. Was it windy that day?View attachment 37805

No wind that I recall. Not of any significance. Just cold. Can you explain a bit more, I dont understand what I am looking at.

I just looked up the weather history and it was about 5mph that day.

 

[MavicCF]

No, not of any significance. Just cold. Can you explain a bit more, I dont understand what I am looking at.

Sorry, it is a little cluttered, I just wanted to put a lot on one graph.
The important part is that the black line is your Mavic's roll, it should correspond fairly well to the aileron inputs you made (light blue line). In fact it should look similar to how the green line (elevator) corresponds to the dark blue (pitch). Essentially, it shows that even though you make no aileron input, your craft was rolling a lot. It is weird, which is why I asked our expert analyzer to join in.

 

[jwashburn]

Sorry, it is a little cluttered, I just wanted to put a lot on one graph.
The important part is that the black line is your Mavic's roll, it should correspond fairly well to the aileron inputs you made (light blue line). In fact it should look similar to how the green line (elevator) corresponds to the dark blue (pitch). Essentially, it shows that even though you make no aileron input, your craft was rolling a lot. It is weird, which is why I asked our expert analyzer to join in.

Thank you so much. I truly appreciate the help. I am getting ready to buy a replacement and it would be nice to know if I made a serious error.

I do have plans on looking at a third party GPS transmitter and some very brightly colored sticker kits.

 

[MavicCF]

Thank you so much. I truly appreciate the help. I am getting ready to buy a replacement and it would be nice to know if I made a serious error.

I do have plans on looking at a third party GPS transmitter and some very brightly colored sticker kits.

From the flight path and the end of the log, I think your probably right about the river. Sorry for your loss.

 

[sar104]

I would call @sar104 in on this one, at first I thought it was normal, but now I'm not as sure. For one, there appear to be no aileron inputs throughout the whole flight, even though the X-gyro shows significant movement, almost mimicking the Y-gyro speed in fact. Was it windy that day?View attachment 37805

You plotted velocity N and velocity E (OSD_xSpeed__m_s_ and OSD_ySpeed__m_s_) instead of pitch and roll - that's why roll looked wrong. Pitch and roll look like this:



As you expected, roll is essentially zero with no aileron input and little wind.

Looking at elevator, pitch and velocity transformed into forwards/backwards in the aircraft frame of reference:



The behavior is completely normal throughout - positive elevator gives negative pitch and forward motion. In particular, considering the end of the flight:



The rapid motion backwards at the end was due to 6 seconds of full backwards elevator starting at 118 seconds. That was pilot error.

 

[jwashburn]

You plotted velocity N and velocity E (OSD_xSpeed__m_s_ and OSD_ySpeed__m_s_) instead of pitch and roll - that's why roll looked wrong. Pitch and roll look like this:

View attachment 37809

As you expected, roll is essentially zero with no aileron input and little wind.

Looking at elevator, pitch and velocity transformed into forwards/backwards in the aircraft frame of reference:

View attachment 37810

The behavior is completely normal throughout - positive elevator gives negative pitch and forward motion. In particular, considering the end of the flight:

View attachment 37811

The rapid motion backwards at the end was due to 6 seconds of full backwards elevator starting at 118 seconds. That was pilot error.

Thanks. I must have yanked the stick when I stepped backwards and lost my attention for a moment

 

[MavicCF]

You plotted velocity N and velocity E (OSD_xSpeed__m_s_ and OSD_ySpeed__m_s_) instead of pitch and roll - that's why roll looked wrong. Pitch and roll look like this:

View attachment 37809

As you expected, roll is essentially zero with no aileron input and little wind.

Looking at elevator, pitch and velocity transformed into forwards/backwards in the aircraft frame of reference:

View attachment 37810

The behavior is completely normal throughout - positive elevator gives negative pitch and forward motion. In particular, considering the end of the flight:

View attachment 37811

The rapid motion backwards at the end was due to 6 seconds of full backwards elevator starting at 118 seconds. That was pilot error.

Learn something new every day. I started with standard pitch and roll (that’s why I though at first that everything was normal) but for some reason I though that the X and Y speeds were fairly comparable with pitch and roll so I did it with those too and it looked wrong. Thanks for correcting me.

 

[MavicCF]

Thanks. I must have yanked the stick when I stepped backwards and lost my attention for a moment

That’s why I called him in, much better at these things. Sorry I gave you a false reading.

 

[sar104]

Learn something new every day. I started with standard pitch and roll (that’s why I though at first that everything was normal) but for some reason I though that the X and Y speeds were fairly comparable with pitch and roll so I did it with those too and it looked wrong. Thanks for correcting me.

The X and Y velocities are north and east - they are not relative to the aircraft. As a result there is no specific relationship between those speeds and the pitch or roll values. You have to transform the X and Y velocities (earth frame of reference) into the aircraft frame of reference to see the correlation. And, especially if there are significant yaw maneuvers happening, a better correlation, of course, is between pitch/roll and the first time derivatives of the forward and sideways velocities in the aircraft FOR.

The required velocity transformation is given by:

Vf = velocityX*cos(yaw*pi/180) + velocityY*sin(yaw*pi/180)

Vr = -velocityX*sin(yaw*pi/180) + velocityY*cos(yaw*pi/180)​

where Vf and Vr are velocity forwards and right respectively.

 

[MavicCF]

The X and Y velocities are north and east - they are not relative to the aircraft. As a result there is no specific relationship between those speeds and the pitch or roll values. You have to transform the X and Y velocities (earth frame of reference) into the aircraft frame of reference to see the correlation. And, especially if there are significant yaw maneuvers happening, a better correlation, of course, is between pitch/roll and the first time derivatives of the forward and sideways velocities in the aircraft FOR.

The required velocity transformation is given by:

Vf = velocityX*cos(yaw*pi/180) + velocityY*sin(yaw*pi/180)

Vr = -velocityX*sin(yaw*pi/180) + velocityY*cos(yaw*pi/180)​

where Vf and Vr are velocity forwards and right respectively.

Thanks, I at least partially understand the above equations, which is good.
It seems rare to have a flight where essentially no aileron is used throughout its entirety, I couldn't live without it!

 

[sar104]

Thanks, I at least partially understand the above equations, which is good.
It seems rare to have a flight where essentially no aileron is used throughout its entirety, I couldn't live without it!

Agreed. This flight was cut somewhat short, however.