Why not to test RTH when the flight controller has frozen!

Flying in gusty conditions, my OSD seemed to freeze and I hit RTH (thinking it was just the OSD feed) - It was not! the FC gyro seemed to be stuck on a 90 degree angle.

I lost video feed just as I entered the trees and a good dose of throttle and blind luck pulled me out in time!

A VERY lucky escape and lesson learned.


That was close! Well done!


It was a bit of a wake-up! I landed and reset everything and the next flight was faultless.

This is what I was flying:


Do you know what caused the fc to lock up?

1 Like

I don’t, I might re-flash the firmware just to be safe.

Out of curiosity what radio system and flight controller were you using?


@Nidge I use the Lefeirc SN-Navi FC and a modified Flysky FS-i6 running a Frsky R9M module tx and R9MM rx.

Fantastic setup which is usually flawless.


Glad it ended well :+1: - even if there was an increase in the laundry bill :rofl:

Thanks for the info, Matty.

Assuming you initiated the right hand roll I’m thinking of two possible causes.

  1. You experienced a momentary servo stall.

  2. You experienced a momentary failsafe.

I’ve yet to have a play with an iNav system but I understand it shares many similarities to the Pixhawk/APM/Cube. If it has a similar logging capability to these systems any issues should be recorded, including loss of signal or a drop in the 5Volt supply caused by a stalled servo, which could also result in a brownout and cause a failsafe trigger.


I’ve always preferred a separate battery and BEC for the RX and servos, a bit inconvenient but saves the day in the end.

1 Like

Hi Nidge,

It was me that hit the RTH switch as a test to see if the FC responded as the OSD display was frozen.

What I didn’t allow for was the FC had frozen thinking it was banked over so when I hit RTH it banked over twice as far and went into the death plummet. I had perfect RSSI the whole time though which how I punched out. I think the loss of video is because I was using a high gain helical on my monitor and it just lost signal below the tree line.

My next project is to get the Mavlink telemetry through the S-Port on the R9M so I can ditch the bulky 3DR tx.

I’m also awaiting some 18650’s to make a 3S 6,000Mah pack for longer flights.

Great bit of flying. Well done on saving that .

1 Like