I wanted to share my experience to help & protect you all. No multicopter is worth personal damage & stitches.
We have been building & testing ardu-based octa-V craft. Part of the challenge has been power usage / high amperage. Orginally we used 3S, but changed motors and went to 6S. Target being lower power losses to increase flight time & max power.
My BEC's man voltage was 3S so I used a separate battery to drive FC & Gimball system. 2 separate 6S batteries were used to drive motors.
I tested OctaV on a field alone. On the 2nd flight the gimball (steered with Multiwii) had a tendency to drift. To reset the gimball 3S battery needs to be disconnected. I had already succesfully reseted the gimball once - with drivebatteries connected.
On the 2nd try octaV takes max power for a split second and flips backward. (seen on attaced video) One propeller hits my hand and another my feet. Situation was clear to me and I left OctaV as is and went to seek for medical assistance.
In the video
- disconnect reciver battery -> gimbal levels
- connect reciver battery -> craft shoots at me
A quite big wound was stitched on my hand and one tendon was partly torn & fixed. Recovery should be full after few weeks time.
FC can output at start / disconnect any signal to ESCs --> anything can happen. Arming does not prevent this - unarmed craft can start (as happend to me). 0.2 secs is enough.
- Always start FC first, then connect drivebatteries
- Always disconnevt drivebatteries first, then FC
- Multicopters are very dangerous tools. If I continue with multicopters, a mechanical securing is required on startup & disconnect. Errors (hw, sw & user) will happen.
- Tuning is dangerous. Untypical situations occur, shortcuts are applied. Be careful. Do not shortcut.
Spec of octaV
- 8x Sunnysky V3508-29 380kv with 12x38 APC props
- 8x F-A 40A esc with Simonk
- 2x 2600 6s drivebatteries 2200 3s reciever battery
- FC: RCtimer Arduflyer 2.9.1B Arducopter (I have APM 2.0 on my hexa)
Happy & safe flying to you all!