Regarding Coptor Rejecting Takeoff

I have a Pixhawk that has been calibrated and properly assembled with an external GPS. I am communicating with the coptor from QGC using a Telemetry radio and the communication works. However, I have not connected an external magnetometer and am using the internal mag. Now when I give the command to takeoff in Stabilized flight mode, even though there is a solid GPS lock with 9 satellites, QGC says “Takeoff denied, please disarm and retry”. The coptor is already disarmed. I dont have a manual radio control (Taranis or otherwise) although I have disabled the RC failsafe and the requirement for RC control altogether. I just need to coptor to only run autonomous flights. Please help!

The stabilized mode is for manual control, can you try to switch to HOLD mode and then click takeoff?

What version of PX4 are you using?

I tried to switch to Hold, but QGC does not switch the mode instead it just remains in manual or stabilized. I can switch from Manual to Stabilized. When I try to switch from stabilized to Hold, the Pixhawk blinks Red three times. The version of PX4 is 1.9 stable for mro Pixhawk.

If it blinks like that when you’re trying to switch to HOLD it usually means that the GPS signal is not accurate enough.

I have a solid GPS lock I think with good HDOP and VDOP. Is there any other reason why this might be?

Also when I try commander takeoff in NSH, it returns no position lock yet.

@MaEtUgR didn’t you find some issue like this recently?

Having a GPS lock isn’t enough, the EKF monitors several metrics to determine is the local position/velocity is stable: https://docs.px4.io/v1.9.0/en/advanced_config/tuning_the_ecl_ekf.html#gps-performance-requirements

Is there anyway I can monitor if the EKF values are stable or not? Or is there something set in the log files? Interestingly, even though automated flight does not seem to take off, I can still arm the vehicle and increase throttle manually using on-screen controls in QGC (after removing props of course).

Hey guys, so turns out, that the Pixhawk’s internal mag has too much noise also, I had done the mistake of mounting the gps unit next to the pixhawk instead of mounting it on the elevated platform. When I resolved both these issues the Pixhawk started to become ready to fly.