Plane 3.9.1 stable released

The ArduPilot dev team are delighted to announce a new stable plane release, version 3.9.1. This is a minor release, but does include some important fixes.

The only change over the 3.9.1beta3 release is an increase in the USB buffer size to give faster log download over USB.

Other important changes from the 3.9.1beta releases include:

  • updated to default values for some tuning parameters

  • fixed a critical safety issue found by Oliver Volkmann, and fixed by Michael du Breuil. The problem could lead to quadplane motors starting on reboot

  • fixed a bug where RC failsafe could lead rudder input stuck at the last rudder input value in some modes. Thanks to Michael du Breuil for the fix

  • improved DShot and BLHeli-passthrough support, fixing errors reported by BLHeli32 ESCs and making using BLHeliSuite32 much more reliable

  • new tonealarm system, bringing the tones produced under ChibiOS and Linux HALs in line with tones produced under the HAL_PX4 HAL.

  • added a new LED driver for the NCP5623 LED

  • fixed delay caused by parameter writes in AP_Stats

  • fixed default RSSI input pin on some boards

  • fixed the incorrect display of “no io thread heartbeat” message

  • fixed microSD support on some boards due to running out of DMA capable memory

Many thanks to everyone who has been testing the beta releases.

Happy flying!


I flashed this 3.9.1 stable firmware on my Pixhawk2.1 setup. Suddenly, my OLED does not work… I rolled back to 3.9.0-dev arduplane and then the OLED works even without changing anything on the parameters…

I tried looking for the firmwares where the OLED could work. So I tried the 3.10-dev and found that the OLED is not working…I also tried the 3.9.1 from the BETA release and still the OLED is not working. Now I rolled back to the Arduplane 3.9.0-dev, the ssd1306 OLED is working…

is there a bug on the latest firmware starting from 3.10 dev with regards to the OLED on pixhawk2?

Where is all features list for this release? Where is looking discription for all OSD parameters? OSD1_XTRACK and other… Thx!

update regarding the suspected OLED Bug on arduplane 3.9.1 stable:

I flashed the 3.9.1 Arduplane (stable) on my pixhawk lite setup that has an OLED module too, from 3.8.x it was just an upgrade, i did not change anything on my parameters. After the update, the OLED still works as it should. While on my Pixhawk 2.1 setup, updating it to the 3.9.1 disables the OLED…

It should be noted that pixhawk lite is FMU v2 and the pixhawk 2.1 is FMU v3… Maybe someone could point out why there seems to be the OLED bug on the stable 3.9.1 firmware I loaded on the Pixhawk2.1?I would want to use the latest stable firmware on my Pixhawk2.1 setup too, but the suspected OLED bug on FMU v3 board is holding me back…

Any insights from the devs?

Why RTL mode activated when plane disarmed?

RTL can trigger if you turn off the radio, even if the plane is disarmed. but it should not start the motor.

Not working onboard led indicator on Omnibus F4 Pro V2. Working well on 3.9.0.

Rssi in 3.9.1 not working in arduplane Chibios and non Chibios.
Version 3.9.0 was working only in non Chibitos

@Mr_Green what type of RSSI do you use? What pin is it connected on? Is it analog or PWM? Can you upload your full param list?
Cheers, Tridge

Hi Andrew as far as i can tell you its never worked on Chibios builds plane or chopper this is why i have not move to Chibitos as i do test each betta
my one is the cude 2.1 analog pin 103 (Sbus out pin )
prams file
2018-08-23 11-57-46.log.param (14.7 KB)

I have installed 3.9.1 NuttX and analog RSSI works correctly.