Had an interesting crash...

I'd just fitted my sonar sensor and had taken my quad to the local park to test it out (using the pirates code). I took off, engaged altitude hold and everything looked good, until it the quad fell out of the air.

I discovered later that the crash was completely my fault - the bolts hold down one of the motors had come loose and allowed the prop to come into contact with another part of the quad, breaking 2 of the 3 blades on that prop.

This part I can't explain - when the quad crashed to the ground all the other three props were still spinning and nothing I could think to do would shut them off! I tried disengaging altitude hold, turning the trottle down to off, disarming the motors, the motors stayed on full. In the end I had to gingerly pick up the prop and pull the battery.

I found that the loose prop had by chance managed to sever the servo line controlling altitude hold. I didn't have the presence of mind to check if the altitude hold LED was still on while I was trying to shut off the quad, but wouldn't no input on that channel mean AH was off? All the other servo leads seemed to be intact.

Either way, I have no idea why I was unable to turn off my quad. Any thoughts guys?

Cheers,

Chris

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  • Well I did the experiment and unplugged the "mode" channel with my quad connected to the Configurator. When nothing is connected to that channel input, the APM reads the input as ~1509. As altitude hold turns on for anything under ~1800 it looks like it would default to ON if the channel gets disconnected. This doesn't strike me as particularly failsafe.

     

    According to the manual, the yellow LED is supposed to illuminate to indicated Alt hold and the red for Pos hold. These are supposed to be controlled by the Mode and Aux channel respectively. When I adjust my Mode channel knob I see BOTH LEDs illuminate when the input gets below ~1800, and then only the yellow LED for inputs lower than ~1250. Same thing for the Aux channel, both LEDs come on for inputs lower than 1800, and the red stays on when the input is lower than 1250. Mybe I should just get a Tx with switches instead of knobs for channels 5 & 6.

  • That is indeed a quandry, does the last known state exist on the line after drop off or should it go to zero?

    I suppose it comes down to capacitative strength of the circuit, and how rapid depletion of the stored energy.

    How bad was the damage?

    To better an emergency land mode for a quad for example... I'm thinking of staged events, first cutting props away and then deploying airbags :) too bad it requires the craft to be below 400' AGL to slow decent to below smitherinez condition.

     

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