Fly away crash during Alt Hold - SOLVED

SOLVED - I am going to put this down to loss of radio signal.

I have:

- Setup failsafes with the current orange radio receiver. The signal now defaults to center stick for all inputs and is set to RTL.

- Purchased a frsky transmitter & receiver that will hopefully prove more reliable


My quadcopter crashed today during Alt Hold. This is not the first time it has happened but last time was on a different frame.

I have looked through the logs and can see the event, but not the underlying cause.

The data I have include is:
- tlog (view from 98% onwards)
- Screenshot of Mavlink Log Graph
- Raw logs
- KML file
- Google Earth Snapshot Google%20Earth%20Snapshot.png
- Video
- Parm file

Additional Information

- Hardware: APM 2.5
- Modes: All in simple
- Quadcopter - X configuration
- Arducopter v2.9.1b

- 3DR Radio (US 915Mhz)

- Turnigy 9xr

- Orange DSM2 Transmitter & Reciever

Events that led to the crash (See Google Earth Screenshot)

- Climb to 30m
- Landed / hovered low (can't quite remember)
- Took off again
- Flew from one side of the oval to the other
- Turned (quadcopter) 180 degrees. [Not my body]
- Changed to Alt Hold (although I think my intention was to switch to RTL)
- Quadcopter bank left (my left) & speed up
- I tried to counteract the roll immediatley without success
- I attempted to switch to Stabilise (maybe too late)
- Slowly lost altitude and crashed
- Motors were still spinning at full speed when I found it

View the tlog from about 98% onwards to see the incident.

I really don't understand why it would so aggressively roll and increase throttle to the maximum.
I have never altered the ALT HOLD PID settings as they are unfamiliar to me. But generally ALT HOLD seems to work reasonable well without modifications.

It would be greatly appreciated if someone could provide some insight as to what to look for or alternatively have a brief look.



Crash - 23rd April

Tlog Screenshot.jpg

HUD Screenshot.jpg

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  • I am starting to think it is a radio issue. See attached graph.
    I am using relatively cheap RX equipment. Turnigy 9xr with Orange RX transmitter & receiver

    Channel 1 = roll
    Channel 3 = Throttle

    During my post crash test, the input for channel 1 & 3 look almost the same when I switch of the radio.
    It could also explain why I was not able to counter act the roll at the time of the event.

    I will look at configuring fail safes for both the apm and receiver.

    Is there a better metric to see the strength of the transmitter signal?

    Log Graph - RX Signal.gif

  • Hi Chris,

    i had a short look in the kmz and it doesn't match what i see in the video :-( according the log the ALT is between 20-30 m above Ground...

    just load it in google earth and have a look ! i can see you fly in simple mode, did you turn your body ?

    what version are you running on which hardware ?



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