Help analyzing Litchi flight data

[Lefty63]

Forum member needs help analyzing flight logs. Running a mission for the third time, bird just drops altitude and hits building. Not sure what to make of the info in the flight log that would cause inaccurate altitude readings. The data that stands out are the max speed of 127.39 mph., (with no tail wind, lol), and the altitude of -178.8 ft. I ran this mission successfully just minutes before this flight. All altitudes and speeds were normal, and inline with the mission settings. On this mission, the data shows the bird at 20 ft when it struck my garage. The peak of my garage is 16 ft. and the flight path was nowhere near the peak. The speed seemed a little faster than the mission settings too. Just curious what I'm missing. I also am looking for a repair facility, other than DJI, as I've had nothing but poor experiences with them.

Flight data-
Jun 22nd, 2018 07:13PM | General / Overview | Drone Flight Log from Litchi app, version 2.2 on iOS | Total Mileage: 264 ft | United States | Airdata UAV

 

[LarBear360]

Forum member needs help analyzing flight logs. Running a mission for the third time, bird just drops altitude and hits building. Not sure what to make of the info in the flight log that would cause inaccurate altitude readings. The data that stands out are the max speed of 127.39 mph., (with no tail wind, lol), and the altitude of -178.8 ft. I ran this mission successfully just minutes before this flight. All altitudes and speeds were normal, and inline with the mission settings. On this mission, the data shows the bird at 20 ft when it struck my garage. The peak of my garage is 16 ft. and the flight path was nowhere near the peak. The speed seemed a little faster than the mission settings too. Just curious what I'm missing. I also am looking for a repair facility, other than DJI, as I've had nothing but poor experiences with them.

Flight data-
Jun 22nd, 2018 07:13PM | General / Overview | Drone Flight Log from Litchi app, version 2.2 on iOS | Total Mileage: 264 ft | United States | Airdata UAV

You should post a link to your mission as well as the .dat file off of the drone.

 

[Lefty63]

You should post a link to your mission as well as the .dat file off of the drone.

Right, sorry.
Mission Hub - Litchi
Does this work?
How do I extract the data file from the drone? It's pretty well toast, but I may be able to attempt it.

 

[Fly Dawg]

Either adjust your Airdata account to make the .csv sharable such the it can be downloaded, or upload the log file from your device to the link below and share that link back here. If that doesn't reveal enough to determine the anomaly then you can try the aicraft .dat logs.
Instructions are on the link for the device data files.

DJI Flight Log Viewer

 

[Fly Dawg]

Also, your hub link above doesn't link to a flight.

 

[Lefty63]

Either adjust your Airdata account to make the .csv sharable such the it can be downloaded, or upload the log file from your device to the link below and share that link back here. If that doesn't reveal enough to determine the anomaly then you can try the aicraft .dat logs.
Instructions are on the link for the device data files.

DJI Flight Log Viewer

Will this allow a downloadable .csv?

Jun 22nd, 2018 07:13PM | General / Overview | Drone Flight Log from Litchi app, version 2.2 on iOS | Total Mileage: 264 ft | United States | Airdata UAV

I'll look for the data file.

 

[Lefty63]

Also, your hub link above doesn't link to a flight.

Mission Hub - Litchi Is this better? I unchecked the make private box in settings.

 

[Fly Dawg]

Yes those work.

 

[Lefty63]

DJI Flight Log Viewer - PhantomHelp.com
I switched to atti mode to stop the mission, and hopefully avoid a collision, once I realized the drone was going to crash.

 

[Fly Dawg]

This data looks quite odd. Question. Have you calibrated the IMU recently?

 

[Fly Dawg]

In fact the data suggests that you took off before the home point was established. Did you?

 

[Fly Dawg]

There is no location data until 43 seconds after takeoff it appears. This will throw off the mission parameters, as well as the FC calculations for certain data points. This is probably why there are unusual speed and altitude numbers in the data. Also, I do not see a Waypoint 1 in your mission plan. The RED circle indicates the first location upon GPS lock, which makes this the home point and not the takeoff location.

 

[Lefty63]

I have not flown, or done an IMU calibration, in sometime. The red dot is where I took off from, (level surface) and the top of the Litchi screen showed GPS, so I believe it had a GPS lock, then I proceeded to Waypoint 1. Waypoint 1 and Waypoint 7 are the same point. Honestly don't remember if the home point was established. Thank you for the analysis. Some of this stuff is just meaningless numbers to me.
Now to find a repair facility.

 

[Fly Dawg]

The red dot is where I took off from, (level surface) and the top of the Litchi screen showed GPS, so I believe it had a GPS lock

Just for future reference, always check the map for the "H" to appear by the aircraft directional icon. GPS will show on the screen once 6 or so satellites are aquired, but that does not mean the home point is set. Unlike GO, there is no voice prompt for that. The "H" indicates that the home point has been set. I this case you were so close after takeoff to the actual takeoff point it would not have made that much difference in the mission plan, but the other data points it very well could.

 

[Lefty63]

Just for future reference, always check the map for the "H" to appear by the aircraft directional icon. GPS will show on the screen once 6 or so satellites are aquired, but that does not mean the home point is set. Unlike GO, there is no voice prompt for that. The "H" indicates that the home point has been set. I this case you were so close after takeoff to the actual takeoff point it would not have made that much difference in the mission plan, but the other data points it very well could.

Thank you again for the help. I've had my drones for a few years, and don't fly them enough to learn, and understand all this stuff.
I'd have to turn the drone on to double check, but aren't the VPS enabled during a mission, and wouldn't they have avoided this?

 

[Fly Dawg]

You mean OA. Those are the avoidance sensors. VPS is positioning. I can't answer your question for certain, P3's do not have OA. Only VPS, which by the way I never use. And to answer your question, yes they were operational during the mission, but once you switched to ATTI, all bets are off on the OA's doing anything to assist. In ATTI, the aircraft only maintains altitude and bypasses certain calculated functions, so its up to the pilot alone basically. You switched to ATTI and should have switched to P-GPS. That way it would have stopped where it was and hovered.

 

[Meta4]

Running a mission for the third time, bird just drops altitude and hits building. Not sure what to make of the info in the flight log that would cause inaccurate altitude readings. The data that stands out are the max speed of 127.39 mph., (with no tail wind, lol), and the altitude of -178.8 ft. I ran this mission successfully just minutes before this flight.
... On this mission, the data shows the bird at 20 ft when it struck my garage. The peak of my garage is 16 ft. and the flight path was nowhere near the peak.

It looks like the main problem was that you were running a waypoint mission too close to obstacles.
Because GPS is not pinpoint accurate and barometers can heat up, causing altitude drift, you need a comfortable safety margin between your Phantom and any obstacles on a waypoint mission.
(+/- 10 feet isn't enough)
The crazy speed and altitude data is all after the crash and is due to the IMU being knocked around.

I switched to atti mode to stop the mission, and hopefully avoid a collision, once I realized the drone was going to crash.

Switching to atti mode cancels any automated flight such as a Litchi waypoint mission but it also disables the horizontal position holding that GPS provides.
That means the Phantom has no brakes and will continue in the direction it is moving.
Flicking to atti and back to GPS will stop the mission and the movement but in this case it would have been too late as you flicked to atti at 1:39.4 and the crash happened 0.3 seconds later.

 

[Lefty63]

It looks like the main problem was that you were running a waypoint mission too close to obstacles.
Because GPS is not pinpoint accurate and barometers can heat up, causing altitude drift, you need a comfortable safety margin between your Phantom and any obstacles on a waypoint mission.
(+/- 10 feet isn't enough)
The crazy speed and altitude data is all after the crash and is due to the IMU being knocked around.

Switching to atti mode cancels any automated flight such as a Litchi waypoint mission but it also disables the horizontal position holding that GPS provides.
That means the Phantom has no brakes and will continue in the direction it is moving.
Flicking to atti and back to GPS will stop the mission and the movement but in this case it would have been too late as you flicked to atti at 1:39.4 and the crash happened 0.3 seconds later.

Thanks Meta4. With your explanation, and that of Fly Dawg, I guess the long and short of it was I launched before the bird was fully initialized, and then despite two successful missions, flew in an area too tight for safety. I learned that I should slow down before launch, and make sure all is good before go. I should also allow more room for flying, and if faced with trouble, changing from P to A back to P modes is the preferred method over just going to A mode.
You both have been very helpful. Thank you both so much.

 

[Meta4]

I guess the long and short of it was I launched before the bird was fully initialized

It's a good idea to get GPS sorted out first but sometimes it's not possible because of the location.
As it turns out, launching before getting GPS wasn't a factor in your incident.
It rarely makes any difference.
Your waypoints are defined by GPS locations, not a distance from home, so where/when the Phantom gets GPS lock makes no difference to the mission.
This week I've been working on a site with a lot of forest cover and have had to launch and get my Phantom up 100 feet before GPS is good enough to load a mapping mission or fly a waypoint mission.
Once I get GPS, it's all systems go