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Old 01-20-2019, 09:50 AM   #11
jcomm
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It's P-Factor Lixma, imo overdone in it's effects...
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Last edited by jcomm; 01-20-2019 at 10:24 AM.
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Old 01-20-2019, 11:44 AM   #12
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It's P-Factor Lixma, imo overdone in it's effects...
It's just calculated or modeled, if you wish. In both cases. As a prop downwash with X-wind...


For those who do not understand why stopped 4-bladed prop can produce Lissajois-like movement:

the P-51 prop blades have total area about 1 sq. m and they are not less than 4 wings. Let's say that blades stopped as a straight cross (the actual position does not matter much, but it will be easier to understand the reason). Let's imagine that the plane got small AoS increment. The angles of attack for horisontal pair of blades changes are insufficient, but for vertical pair the changes are close to the plane AoS changes. One of them, so, increases drag and the opposite - decreases. Thus, the plane gets LONGITUDINAL moment, and it begins to change AoA. As AoA starts to change, yawing moment appears.
So, there is 90 deg shifted constant destabilising pair of moments.

The plane has damping moments, so, from the point of view of classical stability theory the system is nonlinear with positive feedback, and we can see typical oscillation.
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Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів
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Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me
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Old 01-20-2019, 07:30 PM   #13
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It's just calculated or modeled, if you wish. In both cases. As a prop downwash with X-wind...
Touché :-)

Then, I believe it can actually be realistic, although not easy to replicate IRL because certainly few pilots, alive, have been able to experience flying under such circumstances and living to tell about the effect.

It makes sense, as my previous posts suggest - trying to explain it as a "generalized form of P-Factor", but I was somehow renitent to accept it could make a heavy 51d move that way… Probably it would.
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Old 01-20-2019, 08:18 PM   #14
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Touché :-)

Then, I believe it can actually be realistic, although not easy to replicate IRL because certainly few pilots, alive, have been able to experience flying under such circumstances and living to tell about the effect.

It makes sense, as my previous posts suggest - trying to explain it as a "generalized form of P-Factor", but I was somehow renitent to accept it could make a heavy 51d move that way… Probably it would.
1 sq m at the end of the plane... it's a good reason to swing the plane
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Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів
There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.
Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me
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