APM 2.6 crash when switching from "Land" to "Stabilize". Twice.

I just setup a quad-copter - my first with auto-pilot, so there might be mistakes :-).

The setup is pretty vanilla, with a 1000K Turnigy motors, with 12" slowfly propellers and a 2S 4.4Ah LiPo.

The Ardu-Pilot setup is similarly vanilla - APM 2.6 with GPS, PowerSensor, and telemetry.

Stabilize mode worked great, telemetry was working good, showing the GPS positions, and a three position switch on Channel 5 was setup to change between "Stabilize", "Loiter" and "Land". The RTL was setup on Channel 7.

The first problem showed when I switched up from "Stabilize" to "Loiter": the copter, instead of staying put it started to drift approximately downwind, but apparently even faster than the wind (which was moderate at 5-7mph or so). I took control back with "Stabilize" and brought it back and landed manually. Note that it switched modes correctly as confirmed by the telemetry link.

However, the worst part was the test to land: after taking off again I wanted to test "land" mode and it would not land (or if it did come down, it did that very slowly, while drifting like crazy - maybe 20 - 30 yards in 5 seconds), so I wanted to get control back. The problem is that while flipping back to "Stabilize" from "Land" mode it just "flipped". The first time it was close to the ground and quite far from me (30-50 yards), so I could not see what went wrong, but I clearly lost control and crashed. The second time around it was a bit more clear: it was a bit closer, maybe 25-30 yards, and I could distinctly see that one propeller just stopped (front left in X) so the quad just flipped head over heels and smashed - this time was quite high (20 m maybe), so was a complete loss of airframe. The rest of the hardware seems OK, but all needs to be checked.

So.... questions:

1) Is there a rule against flipping from Land to Stabilize, or, in general, are mode transitions not safe on the arducopter?

2) Any idea what might have caused the flip? On this airframe I use Turnigy Plush 18A setup correctly according to the instructions

http://www.hobbyking.com/hobbyking/store/__30683__TURNIGY_Plush_18a...

Are there known incompatibilities?

3) Although the GPS readings were correctly displayed, the loiter did not hold anything (any of the 4 headings as far as I can tell).

4) Unfortunately I didn't have any logging enabled - apparently there are many different (and mutually exclusive?!) things I can log - what would be most illuminating on the next airframe?

5) Any ideas on what might have gone wrong?

Thanks,

Mihai

PS I initially posted this in the wrong forum (ArduPilot), and, perhaps not surprisingly got absolutely no reply.

First I would not have used loitered or land. You need to work through altitude hold first before moving onto loiter or land. Make sure that you get a good altitude hold before you try one of the more advanced features that use GPS.
When using logging use it sparingly. Use the basics logs to start with and then if you need to troubleshoot something turn on imu or motors and do a short flight.
when checking out a new copter always fly really low, couple of feet and 6 feet tops and work through all the flight modes at the low altitude so if something goes amiss it doesn't crash really hard and destroy the copter.
One more note when dealing with GPS, compass is really important. You need to verify that the compass is working properly and you don't have any interference from other electrical sources. You might have to run the compassmot procedure to check for interference.
Good luck fly safe.

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Richard Boyhan October 3, 2013 at 12:17pm

First I would not have used loitered or land. You need to work through altitude hold first before moving onto loiter or land. Make sure that you get a good altitude hold before you try one of the more advanced features that use GPS.
When using logging use it sparingly. Use the basics logs to start with and then if you need to troubleshoot something turn on imu or motors and do a short flight.
when checking out a new copter always fly really low, couple of feet and 6 feet tops and work through all the flight modes at the low altitude so if something goes amiss it doesn't crash really hard and destroy the copter.
One more note when dealing with GPS, compass is really important. You need to verify that the compass is working properly and you don't have any interference from other electrical sources. You might have to run the compassmot procedure to check for interference.
Good luck fly safe.

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APM 2.6 crash when switching from "Land" to "Stabilize". Twice.

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