Why is the pitching moment coefficient of an airplane said to be constant about the aerodynamic centre of an aerofoil
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$\begingroup$ You should read how it flies? and search in this website for other questions about pitch stability. $\endgroup$– Manu HCommented Sep 22, 2019 at 13:14
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2$\begingroup$ You should edit the title so that it is more specific (less generic) so that it is easier to browse questions about a specific subject (e.g. pitch stability) only reading the titles. $\endgroup$– Manu HCommented Sep 22, 2019 at 13:16
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$\begingroup$ Alright thank you so much $\endgroup$– caleb olojoCommented Sep 22, 2019 at 13:18
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1$\begingroup$ I don't understand what you are after. On one hand you ask about the "moment coefficeint an airplane", but on the other hand you talk about "an aerofoil". An aircraft is a 3D structure which has typically several lifting surfaces, and aerofoil is a 2D cross section of wing. Both have very different aerodynamic behaviour and their aerodynamic centres can't be compared. Please rephase your question to be more clear. $\endgroup$– DeltaLima ♦Commented Sep 23, 2019 at 10:34
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2 Answers
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Why is the pitching moment coefficient of an airplane said to be constant about the aerodynamic centre of an aerofoil?
Because the phrase "aerodynamic center" is defined as meaning "the point about which the pitching moment coefficient is constant."
That's it, that's the entire answer. If I've misunderstood the question, please let me know.
answered Sep 23, 2019 at 1:16
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Consider this equation:
$$ C_m = C_{m0} + \xi C_L $$
where $C_{m0}$ is $C_m$ at no lift, and $C_m$ is the pitching moment.
At the aerodynamic centre $\xi = 0$ and $C_L = 0$, $$ C_m = C_{m0} $$ which is a constant.
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1$\begingroup$ Hi Shishir Maurya. I edited the equation into the answer, as opposed to having it included as an image. Please check to make sure I didn't introduce any errors while doing so. You can find a Mathjax tutorial over here, and this tool is handy for fancy symbols. $\endgroup$– userCommented Sep 22, 2019 at 19:34
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$\begingroup$ Thanks, I am new here. I will surely learn the Mathjax and you edited correctly. $\endgroup$ Commented Sep 29, 2019 at 14:45