Airspeed sensor causes altitude drop in RTL

Every time when airspeed sensor is activated and you try RTL the plane starts to descent and would hit ground if not switched to manual and saved.

(Use AS sensor) When I set RTL at 50m the plane starts descent with nose pitch 0°

(Don't use AS sensor) When I set RTL at 50m the plane starts climbing with nose pitch 10-15° and goes straight to the target altitude.

If you dont use the airspeed sensor everything is fine. What is causing this? This problem has existed quite long know and many people have written about it.


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  • I have noticed an issue with my newly arrived AS sensor. It's all over the map. It varies from 5-9 mph sometimes 11 mph just sitting. The first thing I noticed was it would vary with it's orientation. [ I'm speaking about the circuit board and chip not the tube] Then yesterday I finally noticed that if I squeeze the little board it works perfect. It floats around 0-1 mph. Rock solid and consistant. Blow on the tube it works great. Stop blowing and bam right back to zero. Stop squeezing and it's back to highly inaccurate. So there is certainly and issue with the board / chip. I carefully pushed on each solder connection, both mine and the factory solder joints, and it made no difference. I was thinking of trying just putting some silicone around the chip?? It seems like it has two 1/2's.. might be leaking between them? I have ask to return it for another one however so will wait before I try that. But at any rate it does not inspire a great deal of confidence. Personally I will only use min max throttle,,, no AS for flight control. I noticed two boxes in the hardware section on MP. One is enable and one is use? I wish I knew if I had it enabled checked but not 'used' would the amp not use any of the AS data for flight control? It would then only be in the HUD for reference? Sorry to ask a question in another persons thread but it seems relevant to the subject. 

  • Veikko:

    Today I was flying some short test missions and had the same problems as you described.  The aircraft would descend in RTL or AUTO mode when the airspeed sensor and use airspeed boxes were checked on the hardware configuration page.  I too would like to know what is causing this.

    The indicated airspeed on the HUD display appears to be accurate.

    Thank you.

    Bret C

  • I wonder if this is in any way related to the issue that without GPS lock airspeed and pitch readings become negatively correlated. I added a comment on the issue list and pointed to this post.

  • And I was thinking to buy the AS sensor for my 2m glider.

    But now I am afraid I need to wait until other people will provide the answer.

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