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Re: Pitot tube vs. GPS speed

PostPosted: Thu Sep 30, 2010 6:57 am
by Tom
Oh ok I get it. It kinds of measures the angle between your forward airspeed and your wing's chord.

Re: Pitot tube vs. GPS speed

PostPosted: Thu Sep 30, 2010 11:00 am
by lukasz
Ok, now I know while flying in AP in strong wind my plane was descending while flying up the wind, and raising when flying together with the wind.

I was flying in AP mode, doing circles at given height and the plane was loosing altitude (about 20-30m) when flying up the wind, and raising when flying with the wind.
Wind speed was around 5m/s.

Re: Pitot tube vs. GPS speed

PostPosted: Thu Sep 30, 2010 11:04 am
by Tom
Strange... my funjet looses altitude when flying downwind.
Did you use altitude hold (and not pitch hold)? Did you enter "cruise speed" correctly?
If you use v0.5 beta, you should increase the P-gain of the altitude to pitch PID. This will make the AP respond better to changes in altitude.

Re: Pitot tube vs. GPS speed

PostPosted: Thu Sep 30, 2010 11:21 am
by lukasz
Tom, this was two weeks ago when I was flying on v0.4.

If i remember correctly I used pitch hold and cursing speed had the value of "0"

Re: Pitot tube vs. GPS speed

PostPosted: Thu Sep 30, 2010 3:02 pm
by Chris
Well, in the case of altitude hold, the PID loop should automatically command an elevator deflection to pitch the airplane to the correct angle of attack. The AoA vane would just give you a measure of what that angle is since the elevator deflection doesn't necessarily correspond to AoA.

So yea, it makes sense that using pitch hold, you would descend or ascend, unless you chose the exat right pitch to create the lift = weight, and thus hold altitude.