Proprotor

Several proprotor-equipped convertiplanes, such as the Bell Boeing V-22 Osprey tiltrotor, are capable of switching back and forth between flying akin to both helicopters and fixed-wing aircraft.

[1] Accordingly this type of airfoil has been predominantly applied to vertical takeoff and landing (VTOL) aircraft.

The dual-role airfoil is accomplished by one of several design approaches: On several aerial vehicles such as the AgustaWestland AW609 and V-22 Osprey, a pair of three-bladed proprotors have been used.

In the case of the AW609's, while flown in helicopter mode, the proprotors can be positioned between a 75- and 95-degree angle from the horizontal, with 87 degrees being the typical selection for hovering vertically;[4] and in aeroplane mode, the proprotors are rotated forward and locked in position at a zero-degree angle, spinning at 84% RPM.

[6][7] Typically, flight control software would perform much of the complex transition between the distinct helicopter and aeroplane modes;[5] while automated systems are usually provided to inform crews on the optimal tilt angle and air speed to pursue.