AAE 556 Aeroelasticity Lecture 7 Control effectiveness 2

AAE 556 Aeroelasticity Lecture 7 – Control effectiveness (2) Purdue Aeroelasticity 7 -1

Homework for next Friday? i Five problems handed out in class and posted on-line i Watch for updates Purdue Aeroelasticity 7 -2

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 Purdue Aeroelasticity 7 -3

The aeroelastic lift due to control deflection Compare answer to the lift computed ignoring aeroelastic interaction Purdue Aeroelasticity 7 -4

Solve for the q to create a reversal condition or Purdue Aeroelasticity 7 -5

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? Purdue Aeroelasticity 7 -6

Lift effectiveness (aileron effectiveness) expression when q. D is less than q. R <1 Purdue Aeroelasticity 7 -7

Aileron effectiveness when R>1 Purdue Aeroelasticity 7 -8

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 steadystate Is this reversal? Purdue Aeroelasticity 7 -9

Write moment equilibrium equation for this moving 1 DOF system Lift (L) doesn’t appear in this equation!!! Why? twist angle Purdue Aeroelasticity 7 -10

Now, use this expression for q to solve for the terminal velocity, v When is v/V = 0? Purdue Aeroelasticity 7 -11

Roll response in terms of reversal q Let’s plot this equation Purdue Aeroelasticity 7 -12

An example plot of steady-state upward velocity aileron reversal Purdue Aeroelasticity 7 -13

Understanding what the aileron does Two different ways to compute pressure distribution resultants due to aileron deflection Purdue Aeroelasticity 7 -14

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 A lift force at d produces the same result at the AC as a lift force and moment at the AC =d e Purdue Aeroelasticity Ld d 0 7 -15

mid-chord small aileron big aileron Distance aft of 1/4 chord Resultant lift position AC Aileron flap to chord ratio, E Purdue Aeroelasticity 7 -16

Reversal in terms of divergence parameters Purdue Aeroelasticity 7 -17

Summary aileron deflection creates. . . (a shift in zero lift line due to "camber" created by control surface deflection) i twisting downward if lift vector due control deflection is behind section shear center i downward Purdue Aeroelasticity 7 -18