Graupner SUMD failsafe problem, Versacopter


New member
Hi all,

I'm having a failsafe issue with my Versacopter V2, which otherwise is flying awesome and taking some serious abuse very well! :)

After switching my receiver and flight controller board to SUMD from PWM, I can no longer get the failsafe on the radio/receiver to work. When powering off the radio, the props keep spinning (seems like it is doing a hold) and now I'm too scared to fly it.

SUMD is Graupner's fast low-lag serial interface, I believe similar to SBUS on the Taranis. It is working fine for me using one wire on pin 4/uart2rx of the naze32, instead of 1 wire for each channel with PWM. I am using the recommended MZ-12, and have reset all channels set to POS with 0 throttle and the manual arm switch to unarm. The radio confirmed the failsafe was stored to the receiver, and I've done this again a few times after switching to SUMD. So the setup looks fine but for some reason the failsafe does not trigger when powering off the radio.

Setup details:
Versacopter V2
Flite Test Power pack E "good" with the EMAX 12A ESCs flashed to official BL Heli firmware 14.9
Naze 32 rev6
Graupner GR-16L receiver
Graupner MZ-12 transmitter
Betaflight 3.1.6 with OneShot125 enabled



New member
I've found the answer to my problem! On the MZ 12 telemetry menu when you set it up to use SUMD, you will also get an unlabled choice between FS/HD/OF. For failsafe to work it must be FS. I had it on the HD which does not stand for high definition ;)

Here's a google translation from a German site:
FS: In the case of a loss of reception, the values ​​configured in the failsafe are repeated
HD: In the case of a loss of reception, the last signal is repeated
OF: In the case of loss of reception, the sum signal goes OFF.

Time to fly!


Got Lobstah?
Site Moderator
Howdy Mike. Thank you for taking the time to say hi and especially to share the answer to your problem. It would be nice to know more about you. Would you mind introducing yourself a bit with whatever details you might like to share.
Welcome to the forum.


New member
Thanks Jim,

I'm new to the hobby and I'm sure I will have more questions and hopefully things to share in the future!

Started with some prebuilt toy copters like the hubsan x4. The Versa is my 2nd build. My first build was an arduino F450 frame quad. ( YMFC ) Next I will be looking into FPV for the Versa, and then building an upgraded small acro/racer. Also interested in trying the tiny whoop inspired indoor FPV quads, and a camera platform multirotor, probably running inav! A lot of the fixed wings look fun too!


New member
How to setup in betaflight?


How did You set up SUMD with betaflight? I've got set my gr12 to sumo and it worked as ppm (but without failsafe). I've tried to set reciver into SUMD FS mode and in betflight SerialReciver and SUMD type but this does not work. How did You manage to set up SUMD in betaflight (i'am using 3.17)


Wake up! Time to fly!
I believe there is a bug in 3.1.7 that does not save things properly. I think the solution was to drop back to 3.1.6.

Also FS setting from the original post seems to be last input known which is a bad thing. I believe "If" I am reading this correctly that OF is what is needed similar to the Taranis "no signal" fs mode where the receiver basically disarms the quad. The last known signal could produce a fly away condition if the quad happens to have a clear path to keep going.

I am not 100% sure that is what it means maybe read the manual or PDF to be sure or someone that uses Graupner gear can confirm. Anyways you want the quad to shut off when fail safe activates no matter how it is done.