I've been off flying for several months now, mostly due to weather and schedule. As I look forward to warmer air and some time to tinker, I've been picking up where I left off with my quadcopter. Unfortunately, this is trying to determine whether or not my 3DR quad running APM 2.5 is still safe to fly after a strange event led to a minor injury for me.
On one of my last flights in the fall the quad did something I had never seen before. Upon connecting the battery (and while I was still crouched over the UAV) the four motors kicked on at ~25% throttle. Sensing the vehicle might rise towards my face, I attempted to get my hand out from underneath to guard myself. I doing so, I clipped one of the props, giving me some minor lacerations to my thumb and little finger. Within 3-5 seconds the engines stopped, and I pulled the battery (then went to get help to stop the bleeding!). The quad did not leave the ground, though it was close to doing so.
To clarify, this was within 5 seconds of connecting the battery, and long before I had even touched the transmitter, let alone time to arm/engage the motors. This particular vehicle, while it has been beat up a few times, had many hours of flight time over the course of six months. This particular event was anomalous.
I did several tests to see if the error would repeat before flying a few more times to run down the batteries for winter storage. The quad did not show any similar issues on 20+ battery connections (without props), or on those last two flights, where it flew without issue.
I have attached the (very short) dataflash logs for this event. The only thing I can get from them is that the craft was in stabilize (which is where the transmitter switch was set), and the throttle was non-zero for a short period of time before shutting off, which agrees with observation.
I have had some other issues with the APM unit, which mostly had to do with loss of orientation, and do not seem immediately related. I have telemetry logs for these events which I can dig up if needed.
I would love any information/advice I can get about what might have happened, and whether or not this was a fault of mine, or if I should retire this quad/APM to prevent further issues.
Observed Timeline:
Battery Connection.
(3-5s) Quad sitting as normal, LEDs on/blinking.
(3-5s) All motors up to ~25% throttle, no liftoff.
Motors stop.
Battery is pulled.
Replies
I'll jump in again but this level of oddness is above my pay grade. The first few lines of the log said the APM though it was in a Simple mode and it was seeing a throttle in of about 55%. The Simple mode was even giving it a heading. Apparently that was enough to let it arm itself. I wouldn't think that was possible.That heading of 336.17 degrees (I slipped a decimal place in my initial post) was held in the NavYaw readings until the Stabilize mode was reinvoked and the Simple mode was terminated.
I'd suggest going into Mission Planner, and see if you have any Simple Mode check boxes checked on the Flight Modes screen. I say that because in your Parameters you have a Simple value set to 20. That's some sort of mask that I don't really know how to interpret. I think it identifies which flight modes the Simple function applies to.
My only thought is that perhaps the RC controller was bumped (you said it was the first flight of the day), and somehow go into a flight mode that Simple was enabled for (note that I'm not referring to Supersimple). Then, the throttle gets bumped to half way before the batteries get plugged in. This assumes the unlikely event you didn't look at your RC transmitter before plugging the batteries in.
I just had a thought....In your RC transmitter setup, how well centered in your Stabilize mode in its PWM range? Some transmitters can drift, and if it were close to the edge of its range, it's possible it could momentarily toggle over into the adjacent range.
I did have two modes which had simple enabled. I am almost certain I was not in one of these, but even if I was, I definitely did not switch modes (I didn't even have the transmitter in my hand, since I was plugging the quad in). The PWM range was well-centered the last time I check it, and seems fine now, though I suppose it's possible that it somehow slipped between the ranges...
I will accept it's possible that the throttle was non-zero.
But that still doesn't explain how it ended up armed (and SO quickly), does it?
Doesn't the APM auto disarm after a set amount of time sitting on the ground? I know it does on me if I arm and don't do anything for awhile.
(Shameful, shameful bump.) I'd love to get some feedback on this, if I can't figure out why the quad did this I will likely have to retire this APM for fear of a repeat.
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