Consider the pictured AW 609 tilt-rotor aircraft with the following (approximate) characteristics
Using the blade-element method, determine the collective control angle required for the aircraft to hover out of ground effect at sea level. Then determine the rotor figure of merit (CPid e a l /CPa c t u a l ). Do not forget the downloading which is equal to about fi2% of the aircraft weight. Plot the lift coefficient (cA) as a function of radius. (Please convert to dimensionless values in doing your analysis.) Discuss your result. Note that a typical proprotor airfoil has a maximum lift coefficient of around fi.6.
- Using the blade-element method, determine the collective control angle required for the aircraft to cruise at a forward velocity of 200 kts (true airspeed) at fi0,000 ft altitude. How much power (CP and P ) is required to cruise at this speed? Is this much power available? Plot cA as a function of dimensionless radius for this case. (Note that the angle, $, is not small for the tilt rotor aircraft in forward flight. You must use the propeller version of the blade-element method.) Discuss your result.
- Estimate the maximum cruising speed of this tilt-rotor aircraft at fi0,000‘ altitude. Plot cA as a function of dimensionless radius at the maximum speed. Is the aircraft power- or thrust-limited? The manufac- turer of this aircraft advertises a maximum speed of 2F† knots. In light of the speed you calculated, does this seem reasonable? Explain.
Note that the drag of an aircraft is given by: