pitch oscillation

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surzo
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Joined: Fri Jun 10, 2022 11:15 am

pitch oscillation

Post by surzo » Mon Jul 04, 2022 5:37 pm

Hi everyone,
I can't seem to fly any aircraft with a stable attitude. Even with no wind there's always this pitch oscillation I can't get rid of completely. It's as if the glider had neutral (not positive) dynamic stability. I've tried different input configurations, sticks, etc. I can't replicate the "hands off" flying I often read about. I trim for a given speed, but there's still a constant variation of up to 20kph. To really get a consistent speed I have to make continuous small stick adjustments. Maybe this is just the flight model reflecting real life gliding.
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KäseKuchen
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Re: pitch oscillation

Post by KäseKuchen » Mon Jul 04, 2022 6:42 pm

Can you tell me, what frequency the oszillation has? Do you mean, that the speed increases, glider pitches up, than the speed dereases and pitches back down and so on...? Gliders tend to be dynamicly unstable at very low frequencies in real life. Thats not a problem, because the frequency is low enough, that a pilot can easily correct it.
In Condor multiplayer you can use the autopilot.

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wickid
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Re: pitch oscillation

Post by wickid » Mon Jul 04, 2022 8:16 pm

In fact, it is not only gliders. All planes exhibit this behaviour. It should be a long period oscilation of around 20 seconds. If this is what happens in Condor than the flightmodel is good :wink:

It is called "phugoid":

https://en.m.wikipedia.org/wiki/Aircraf ... 0variation.
PH-1504, KOE

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Bre901
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Re: pitch oscillation

Post by Bre901 » Tue Jul 05, 2022 9:10 am

A long time ago, I had taken a look at the phugoid oscillations and a simple model (with control surfaces fixed) showed that the oscillation damping was proportional to the inverse glide ratio
CN: MPT — CondorUTill webpage: https://condorutill.fr/

surzo
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Joined: Fri Jun 10, 2022 11:15 am

Re: pitch oscillation

Post by surzo » Tue Jul 05, 2022 8:06 pm

Thank you KäseKuchen, wickid and Bre901 for your useful information. It's been interesting to learn about phugoid. I'm not sure yet, but after a quick test flight I think the problem was that I didn't trim quite right to begin with. I've found that trimming down farhter than I did before causes more pitch oscillation damping.

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