1. AAE 556 Aeroelasticity Lecture 7 – Control effectiveness (2)
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2. Homework for next Friday?
Five problems handed out in class and posted on-line
Watch for updates
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3. Review from last lecture
The ability of an aileron or elevator to produce a change in lift, pitching moment or rolling moment is changed by aeroelastic interaction
Review from last lecture
aileron
deflection
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4. The aeroelastic lift due to control deflection
Compare answer to the lift computed ignoring aeroelastic interaction
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5. Solve for the q to create a reversal condition
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6. Purdue Aeroelasticity
The aileron deflection required to generate a fixed increases as q increases
Aileron deflection increases as q approaches reversal
The required control input is …
Is aileron reversal an instability?
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7. Purdue Aeroelasticity
Lift effectiveness (aileron effectiveness) expression when qD is less than qR
<1
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8. Aileron effectiveness when R>1
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9. Purdue Aeroelasticity
Add upward wing motion, constant v, to simulate rolling motion - steady state motion means L=0
No initial angle of attack
v is an unknown, the airfoil will accelerate until it reaches steady-state
Is this reversal?
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10. Write moment equilibrium equation for this moving 1 DOF system
Lift (L) doesn’t appear in this equation!!! Why?
twist angle
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11. Now, use this expression for q to solve for the terminal velocity, v
When is v/V = 0?
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12. Roll response in terms of reversal q
Let’s plot this equation
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13. An example plot of steady-state upward velocity
aileron reversal
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14. Purdue Aeroelasticity
Understanding what the aileron does Two different ways to compute pressure distribution resultants due to aileron deflection
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15. Force equivalence the same moment at the AC with 2 different models+
Solve for the distance d to find the CP distance from the AC = Ld d e
A lift force at d produces the same result at the AC as a lift force and moment at the AC
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16. Resultant lift position
mid-chord
small
aileron
Distance aft of 1/4 chord
big aileron AC
Aileron flap to chord ratio, E
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17. Reversal in terms of divergence parameters
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18. Summary aileron deflection creates ...
(a shift in zero lift line due to "camber" created by control surface deflection)
twisting downward if lift vector due control deflection is behind section shear center
downward
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