Question

Regarding the horizontal tail of a conventional airplane, which one of the following statements is true?

• A. It contributes to \(c_{\alpha}<0\)
• B. It makes \(c_{\alpha} = 0\)
• C. It makes \(c_{\alpha}>0\)
• D. It makes \(c_{m0}>0\) and \(c_{\alpha}>0\)

Hint:

The horizontal tail on an airplane is designed to provide a stabilizing moment, which generally makes \(c_{\alpha}\) negative to counteract the pitching moment caused by the wings.

Answer 1

The Correct Option is A

Step 1: Understand \(c_{\alpha}\).
In the context of aerodynamics, \(c_{\alpha}\) represents the change in the aircraft’s pitching moment due to changes in the angle of attack (\(\alpha\)). For most conventional airplanes, the horizontal tail contributes negatively to \(c_{\alpha}\) because it generates a counteracting moment to the main lifting surface. Step 2: Explanation of Other Options.
- Option (B) is incorrect because the horizontal tail does not make \(c_{\alpha} = 0\).
- Option (C) is incorrect because it would imply the tail is producing a positive pitching moment, which is contrary to typical airplane designs.
- Option (D) is incorrect because the horizontal tail does not contribute to a positive \(c_{m0}\), and \(c_{\alpha}\) is typically negative for conventional airplanes.