Hello all, my PixHawk Quadcopter copter was doing fine the day before yesterday but when I was trying to arm it yesterday it gave me a long beep and couldn't arm it. I left the copter on the lawn and booted up my laptop on the terrace because I wanted to connect to the UAV with the 3DR radio in order to check with MissionPlanner what the reason was. While my notebook was still booting, I heard a sizzling sound from the lawn and noticed that the UAV was on fire! Grey smoke emerged from the end of one arm where the ESC was located. I immediately ran to the UAV and disconnected the battery, the fire was still burning. After a while the fire stopped and I took a look at the ESC. Only black crisps were left.
My question is: What could have caused that fire? The fire started maybe 3 minutes after trying to arm it. The copter was not armed and the transmitter was untouched, so my understanding is that no current was flowing at the motor side.
A closer look at the ESC revealed that the fire must have started from the motor side of the ESC because the cables at the battery/pixhawk side are still intact.
The grass on the lawn might still have been wet when I placed my copter there so could water have caused a short-circuit at the A B C connectors between ESC and motor?
I have little knowledge about electronics but I assumed that if no voltage on the motor side is applied, nothing can happen even if A B or C connectors are connected. Is it likely that it was a short-circuit? Could a defect motor cause this kind of disaster?
Background Info: I used Tiger Motor S25A ESC and Tiger Motor U8-16 100kv motors. Is it save to replace the ESC and try again or do I risk to burn more than the replaced ESC again?
Replies
if your copter is made of carbon fiber all it take is an exposed wire to cause smoke when in contact with Carbon fiber.
Thanks OG for this comment. In fact I didn't know that carbon fibre is an electric conductor. The "good" thing about my drone was that the ESC fit inside the tubes because they are of 30mm in diameter.
But I suppose there is no coating inside those tubes. Anyways, the ESC are completely wrapped in shrinking hose so I wonder how any metal part could have been exposed to the frame, especially because the tubes used to be round so only the edges of the ESC get in contact with the tube.
But this is definitely something I need to consider since my power distribution is also very close to the frame and it is not covered with anything (floating above the frame).