Goblin 500 Sport uncontrolled descent

Hey all, I’ve just recently flown a Goblin 500 Sport with Arducopter 3.4.4, and a few seconds after takeoff in Stabilize mode, it came straight back down and hit the ground hard even with close to max collective and fairly high throttle. I’m using a Hobbywing Platinum 100A V3 ESC in governor mode and have roughly 2000-2100 RPM headspeed. I can’t conclude much from the logs except the throttle and collective values, perhaps someone else could take a second look?

2017-01-08 08-09-47.bin (1.3 MB)


I’ve taken a quick look at your logs and a couple of things need fixing first before you fly again.

Your vibration levels in Y and Z axis are outside the acceptable range.

Also, it looks like you have your collective CH3 reversed.

Hey Steve,

Thanks for looking at the logs, much appreciated. Regarding the Channel 3 reversal, with the current settings, the direction of stick movement on my transmitter corresponds correctly with the swashplate moving upwards - do you mean reversal in some other sense?

Also, what are the acceptable vibration levels I should be aiming for? I’m using a Pixhawk 2 and I believe they’re quite a lot more hardened to vibration than the original Pixhawk (which had acceptable vibration levels of 0.3/0.5G) due to their redundant and dampened IMUs.

Thanks for your time!

Hey Sriram,

I’m very sorry for not getting back to you earlier with answers to your questions. Hopefully you have sorted it out by now?

I think it’s called a double reversal, the channel is reversed in your TX and also reversed in the Pixhawk. i.e. if you flip both, you will still get the same stick/ swashplate movement but the autopilot will climb/descend correctly.

Don’t quote me but I believe vibration levels that we should aim for are still 0.3/0.5G, even in the Pixhawk 2. (The sensors are still the same as P1 but your airframe vibration is get passed this extra level P2 onboard dampening.) Your Y-axis is about 1.1G and if you look at IUM1 and IMU3 (IMU3 is not dampened). IMU1 has higher levels than IMU3 and internal dampening is not helping/ making it worse for you.

I hope this make some sense?


Hey Steve,

No problem, thanks for the help! I’ll get right on it, what you’ve said about the double-reversal makes sense. Working on the dampening problem as well.