Throttle active on power up!

Just moved to 3.9.8 and discovered a major safety issue.

If the plane is powered up and the transmitter is in Manual mode with the throttle raised the plane engine will run while motors are disarmed.

The issue is reproducible.

If the throttle is raised slightly the forward flight motor will only turn for an instant but if the throttle is set to full the engine will run for as much 30 seconds!

To reiterate…

Immediately on power up the forward flight engine will run at full throttle without arming!


A .bin file from the flight controller would help anyone who wanted to analyse what is happening.

I can confirm this happening. Kind of scary.

Hopefully more people will test it for them selves…



I have tried to reproduce the issue on my Durafly Tundra, but could not do so. Followed the steps mentioned above: Upgrade to 3.9.8 (ChiBiOS) on my Cube, set the system to boot up in manual mode, then booted up the system with the throttle set above zero. Nothing happened to the forward motor.

Hence, as Mike Boland said, if you are able to get a dataflash log from your flight controller, that would be very helpful. Set LOG_DISARMED to 1 to enable logging upon boot, then try to reproduce the issue again.

On my side, I don’t have a log since there isn’t really anything happening in the system. But here is the param file that I used in my test: IMG2_3.9.8.param (17.4 KB)

Okay I will generate a log file today.

Should probably add we are using RFD900s with PPM passthrough so it is a PPM signal that is generating the condition.