Hello everoyne,
yesterday my plane (Eflite Aprentice) crashed during
transition from cruise to RTL.
My pixhawk gave a large bank angle (>70 degrees altough bank max was 45)
and also gave a full throttle (75%).so the plane nose down rapidly and got a insane spinout.
the alt was 100 meters during cruise and the wind was < 1m/s.
a made an autotune previous week and the PID params were very “light” (small K gain etc).
during cruise everything was fine !
Can anybody suggest why pixhawk gave full throttle during RTL?
the cruising speed was 17m/s.
You had RC2_REV set to -1 meaning that your elevator was reversed. Is that the case? Because if not then when you went into RTL it would of moved the wrong way and gone into the ground.
Thanks, Grant.
[quote=“gmorph”]You had RC2_REV set to -1 meaning that your elevator was reversed. Is that the case? Because if not then when you went into RTL it would of moved the wrong way and gone into the ground.
Thanks, Grant.[/quote]
no! the elevator was fine!
as i repaired my apprentice and had 3-5 more flights, I noticed that the transition from CRUISE to RTL needs a lot of throttle even if you have the same alt.
So i believe that the battery (was only 30%)had no more current to feed the motor!!!
If you can provide a dataflash log from the pixhawk SD card when the plane crashed we should be able to tell if it was the battery providing the battery was being monitored of course via the 3DR Power Brick and you had that setup correctly.
Thanks, Grant.
Actually I was able to tell from your tlog. See the graph below. Your battery starts around 15.3 volts so if your using a 4 cell battery its already partly flat. When it went into RTL mode at the end and throttled up the voltage dropped to 14.05 volts. That’s 3.5 volts per cell. However, during the RTL it continues to go down and the logging stops with the volts being 13.8. I’m not convinced it was the battery. The pixhawk was sending telemetry back all the way until the end which means it didn’t reboot from low voltage so it was running. Sure it was very low but still ok I think.
Unless of course the ESC for the motor thought the voltage was too low and wouldn’t run the motor. In that case yes you are probably right - battery voltage too low.
As i wrote before, i flew the plane a lot of times after the crash and
i noticed high currents from transitions cruise to rtl.
the pixhawk was never rebooted, thats for sure.
so i think you are right.
i made a test with low battery on the plane.The motor
didnt stop but had such a low power that couldnt fly the plane…