Suicidal Pixhawk?

Hello all. Figured it was time to call in the experts. I have an FX-79, running on the Pixhawk, Newest firmware. The Model flies wonderfully in FWB-A, and does great in loiter, but in Auto and RTL seems to have a deathwish as it dives towards the ground every time. Not sure whats causing this, and as of sunday, my plane needs a new motor mount due to it crashing at full speed into a gravel road during an emergency RTL. I’ve flow it in auto tune for at least 100 throws each direction. One problem for sure is that the Airspeed sensor seems to be not working, despite being checked for leaks, has no tube blockage, and is front and center in the nose of the aircraft. 99% of the time in flight it reads zero. Not sure whats going on there, but the autopilot knows its plummeting towards the ground, as seen in the following logs, but does nothing to stop it. While I work on rebuilding, I figured I would call on you for help. Thanks in advance.

Tlogs attached, dataflash and parameters via the droneshare links below:
Flight 1:
Flight 2:

your airspeed data make no sense. (too low, not real speed) , I just see a lot of spikes.
you enabled use of airspeed, it dives to recover from stall.
set ARSPD_USE=0 until you set it up correctly.

That makes sense. Good catch. Thoughts on why the pixhawk airspeed sensor is not working correctly? It’s currently in autocal, and I’ve verified it’s connected correctly, that its set for the proper pin. I can’t seem to figure out why it’s not reading. It’s plugged into the I2C splitter with the magnatometer, and that’s working, so I’m stumped.

Try another port or just connect directly, - there are also different kinds of sensor supported, check that your ARSPD_PIN is correctly configured.
You should be able to get some decent IAS on ground when pressing a finger on the tip of the pitot tube or blowing on it.

  • you can also run airspeed test in console to see raw values.

Maybe you would like to double check what unit (meter / cm) the altitudes are entered in.
I vaguely recall reading about someone who had a similar issue because a false assumption about the unit.


Pin has been verified, I will try checking the console airspeed as suggested. As far as the units go, I was following the same units that are displayed on the HUD, and the altitude, if I remember correctly, was right around 200 ft, and if not feet, then Meters. I don’t think this was the issue. The airframe has been rebuilt, and I will be testing to see if this change fixed my issue this weekend. Wish me luck!