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

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

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 Purdue Aeroelasticity

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

Solve for the q to create a reversal condition Purdue Aeroelasticity

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? Purdue Aeroelasticity

Purdue Aeroelasticity Lift effectiveness (aileron effectiveness) expression when qD is less than qR <1 Purdue Aeroelasticity

Aileron effectiveness when R>1 Purdue Aeroelasticity

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? Purdue Aeroelasticity

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

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

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

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

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

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 Purdue Aeroelasticity

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

Reversal in terms of divergence parameters Purdue Aeroelasticity

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 Purdue Aeroelasticity