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Control surface flutter can be avoided by:

1. a high stiffness of the structure to which the control surface is attached
2. a low stiffness of the structure to which the control surface is attached
3. locating a balancing mass in front of the control surface hinge line
4. locating a balancing mass behind the control surface hinge line

The combination that regroups all of the correct statements is…

  • A

    2, 3.

  • B

    1, 3.

  • C

    1, 4.

  • D

    2, 4.

Refer to figure.
To prevent flutter, the structure needs high stiffness and the balancing mass located in front of the control surface hinge line.

A low stiffness would make a control surface more susceptible to flutter because a flexible structure will keep vibrating longer after a disruption than a stiff structure.

The more forward the CG of a control surface, the more stable it will be. Therefore, most control surfaces are equipped with a Mass balance in front of the hinge line. See figure

Therefore, statements 1 and 3 are correct.

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