Sori englanti, mutta laitan tarinan opiksi jakoon laajemmin... Heikkit
I wanted to share my experience to help & protect you all. No multicopter is worth personal damage & stitches.
BackgroundWe 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.
What happend?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
1.land
2.disconnect reciver battery -> gimbal levels
3.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.
Key learningsFC 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.
1.Always start FC first, then connect drivebatteries
2.Always disconnevt drivebatteries first, then FC
3.Multicopters are very dangerous tools. If I continue with multicopters, a mechanical securing is required on startup & disconnect. Errors (hw, sw & user) will happen.
4.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!