Hi everyone!

During Loiter, my throttle oscillates rather consistantly.  The tuning graph suggests that APM is responding to airspeed (as opposed to altitude) because of the frequency of the oscillations and how it relates to my target alt.

If there were a PID for airspeed alone, I'd probably be able to make sense of it.. .maybe lower P and increase D a bit.  However, i don't see such a loop for that particular aspect, so I'm a bit lost.  

What would be the best way to smooth out throttle oscillations during loiter (and probably auto)?

i'm using the airspeed sensor (enabled) and while my alt is oscillating as well, it is doing so on a much slower rate--pretty sure that's the pitch/alt PID loop that needs work.  This throttle thing seems separate.

Here is a clip of what the tuner shows me:

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I know this one's a puzzler, but doesn't anyone else have this in operation on their plane?


If I may ask, what does the airspeed sensor installation look like?
 Is the pitot tube installed in an undisturbed airstream?

I'm just curious because I need to install the one I've recently received from the store here. Thanks.


Hi Tim,

My pitot tube is protruding from the nose of my skywalker about 2".  I melted a track in the top of the foam for the tube and the foam canopy holds it in place snugly while still letting it sneak inside if I land poorly.


Thanks spag,

I appreciate the installation information. I have to install it on my X8 and would like to have it somewhat protected from damage during landings. A camera bay on this model pretty much excludes the upper front center for mounting the tube. I'll try it off center and see how it goes. Thanks again.


I'd think off center would be just fine, so long as the tube is parallel with the forward direction of the plane.  And keep those static holes at least an inch away from surfaces.


Did you get this issue resolved? What was causing this?

Never did figure it out.. either this is something nobody else deals with, or maybe it's just something that the code hasn't been taught to solve yet.

A bad pitot tube can be the problem!

The tube end is not glued and therefore the pressure to the sensor is not constant, ie. it leaks. You should be able to test this if looking at the numbers in MP and put constant pressure on the end of the tube. The number should not increase too much while holding a finger over the hole. (wet the finger or use latex glove to seal proper)



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