Aeroelasticity

Question 1

Divergence

Answer 1

Static Aeroelastic Phenomena
Lifting surface deforms under aerodynamic loads such that the loads increase. Increased loads deflect structure further, eventually leading to failure. Aerodynamic forces interact with structure to create loss of effective stiffness.

Question 2

Aileron Reversal

Answer 2

Static Aeroelastic Phenomena
Reversal of aileron expected response due to structural deformation of wing. Wing torsional flexibility can cause ailerons to gradually loose effectiveness as dynamic pressure increases. Above reversal dynamic pressure ailerons function opposite to intended purpose.

Question 3

Design decisions to increase dynamic divergence pressure

Answer 3

Change the shape of the wing so deformation decreases fluid loads. E.g. backward swept wing
Increase structural stiffness

Question 4

Flutter

Answer 4

Dynamic Aeroelastic Phenomena
Aeroelastic system can oscillate, combining structural vibration with unsteady aerodynamic loads. Amplitude of coupled oscillations increase with time until structure failure. Vibrating lifting surface extracts energy from surrounding airflow leading to exponentially growing amplitude of oscillation.