I wanted to share my experience to help & protect you all. No multicopter is worth personal damage & stitches.

Background

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.

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 learnings

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.

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!

Our OctaV project is progressing. Now it was time to test the gimball with Gopro. The end result was surprisingly good.

We still have challenges with the basic flight. The amperage is quite high - 2x 20C 4ah 3S lipos are at their limit. We could add some more copper to few spots or good solution could be to go straight from 3S to 6S.

Also the Gimbal needs some fine tuning. On the next test I will put the Nex5 on board!

Our target is to have a multicopter

• to capture smooth video --> choose to make a flying steadycam
• to have redundancy for safety--> choose an octa / 8 motor configuration.

V-frame was chosen over X-frame due to better fit with with steadycam.

Arducopter works fine - we have noticed 2 bugs with MissionPlanner

• Octa X gets changed to the frame form every time when PIDs are tuned in mission planner. Terminal must be used to set the V-frame form back.
• Motor test does not seem to work with terminal for octa V.

2.9.0 seemed to work fine, so we used that.

Frame is fully DIY-frame - Octa V is a rare frame form. Better do-it-yourself.

Some specs:

• Turnigy 2217 x 8
• 1147 APC props x 8
• Arduflyer chip
• 2 x 4 Ah 3S Lipos. 20C seems to be a bit too little for this beast.

We have maidened the octa V. Now the next challenge is to tune the gimball. So eager to see the first video captures with this ship!

It has been a wonderful multicopter year!

Thank you DIYdrones & ArduCopter & all the member of the community!

I have tested strongly APM2.0 2.8.1 with my hexa.

On the left is the plan. On the right the realization.

Attached is the flight video:

Couple of "circles" around few waypoints + one bigger loss of direction. Looking forward on ways how to make it even more "tighter"

Wind was gusty and strong (around 6m/s). Temperature -6 degrees.

In total I am happy with the waypoint performance, but there is still room for tuning (as I am running with standard parametres)

I will also update ESCs with simonk firmware. That should smoothen the flight generally.

2.8.1. APM2.0. Talon Hexa. Turnigy 2217 kv750, Turnigy Multistar 45A with orginal firmware.