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Flutter occurs when an external force is applied to the aircraft with a periodic frequency that is (1) _____ the natural structural frequency of that aircraft.

Flutter can be avoided by ensuring that the aircraft remains inside the certified flight envelope, particularly for (2) _____ and during turbulent conditions.

  • A
    (1) higher than; (2) speed limitations.
  • B
    (1) higher than; (2) the CG position.
  • C
    (1) equal to; (2) speed limitations.
  • D
    (1) equal to; (2) the CG position.

Flutter of control surfaces is a divergent oscillatory motion of a control surface caused by its natural frequency, the interaction of aerodynamic forces, inertia forces and the stiffness of the structure. Flutter occurs when the frequency of the oscillations is the same as the natural frequency of the aircraft.

With increasing airspeed, these vibrations may lead to damages or even a total destruction of the structure and therefore has to be damped out within the flight envelope. Aircraft are rigorously test flow prior to certification where maximum speeds are established. Provided that these speed limitations are never exceeded, flutter should not be encountered.

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