rotation. That portion of the takeoff of an airplane equipped with a tricycle landing gear in which the airplane has gained enough speed for the nose wheel to be lifted to increase the angle of attack and thus the lift. The rotation speed is identified as the VR speed.
rotometer. A form of flow measuring instrument. A rotometer is made of a tapered glass tube holding a metal indicator float. The fluid whose flow rate is to be measured enters the bottom of the rotometer and flows upward, lifting the float. The taper inside the tube causes the pressure drop across the rotometer to remain constant as the rate of flow changes. Rotometers can be used to measure the flow rate of either gases or liquids.
rotor (axial-flow compressor component). The moving part of an axial-flow compressor. The rotor is made of a series of disks, containing the compressor blades, that rotate between stages of fixed stator vanes. Air is moved through the engine by the aerodynamic action of the rotor blades.
rotor (DC alternator component). The rotating component in a DC alternator. The rotor contains a field coil mounted between two hard steel plates with interlacing fingers around their periphery. These fingers form the poles for the rotating magnetic field. Excitation current is fed into the field coil through brushes riding on two smooth slip rings.
rotor brake (helicopter rotor component). A brake used to stop the rotation of the rotor when a helicopter is being shut down. The rotor brake may be actuated by either a mechanical or a hydraulic mechanism.
rotor cloud (meteorology). A turbulent cloud formation found on the lee of some large mountain barriers. The air in the cloud rotates about an axis parallel to the range, and rotor clouds indicate the possibility of violent turbulence.
rotorcraft. A heavier-than-air aircraft whose aerodynamic lift is produced by a set of rotating airfoils called rotors. Helicopters and autogiros are types of rotorcraft. 14 CFR Part 1: “A heavier-than-air aircraft that depends principally for its support in flight on the lift generated by one or more rotors.”
rotorcraft-load combination. 14 CFR Part 1: “The combination of a rotorcraft and an external-load, including the external-load attaching means.
Rotorcraft-load combinations are designated as Class A, Class B, Class C, and Class D, as follows:
(1)
Class A rotorcraft-load combination means one in which the external load cannot move freely, cannot be jettisoned, and does not extend below the landing gear.