Today I had a mishap (thankfully recoverable) with my Arducopter. Here's what happened. I engaged ALT_HOLD and for a while it held altitude and then slowly began to climb. I don't have sonar, just baro. In trying to bring it down, I lowered the throttle stick to the point where it had bottomed out. It still kept climbing.

At this point, I switched it to STABILIZE and you can guess what happened next. Since throttle was minimum, it started to fall out of the sky. I suppose I instinctively raised the throttle, but either there was a lag, or the upward airflow through the props created a counterspin that the motors couldn't overcome. So it thumped to the ground. Then the motors revved up to max and it took off, flipped forward and crashed. The last part was scary -- luckily it went away from me rather than towards me.

I felt like those (alleged?) Toyota Camry drivers who slammed on the brakes, only to find their foot was on the gas pedal!

Anyway, the root cause of the crash was because I hadn't thought through a procedure to transition out of ALT_HOLD. If I had planned before hand, then prior to transitioning back to STABILIZE, I should raise throttle to about hover before switching back.

Any other suggestions for best practices? Also, what to watch out for when in other auto modes (LOITER, RTL, GCS_AUTO)?


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  • One more thing: Don't stand in the path between quad and home when activating RTL...  ;-)

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