autorotation

i. A condition in which a rotor of a helicopter is driven solely by the action of air ascending through its blades rather than by engine power. In helicopters, descending with the power off, air flows in the reverse direction upward through the main rotor, causing it to continue rotating at cruising RPM. To maintain the rotor RPM, the helicopter is allowed to descend by lowering the collective lever so that the relative airflow strikes the blade in a manner in which the airflow itself provides the driving force. Under these conditions, the rate of descent becomes the power equivalent, and the helicopter is said to be in a state of autorotation. The angle of descent in an autorotation is very steep. Autorotation landings are practiced to train pilots to enable them to land in case of actual engine failure. Various expressions used by pilots while carrying out autorotations are autorotative landing, touchdown autorotation, or autorotation to touchdown. All these mean that the pilot will land without applying power to the rotor. A 180° autorotation means one initiated from a downwind heading, with a turn into the wind; it commences well inside the normal traffic pattern. Low-level autorotation commences at an altitude well below the traffic pattern, usually below 100 ft AGL (above ground level), and is primarily used for tactical military training.
Airflow in auto rotation.
ii. The rotation of aircraft around its axes resulting from aerodynamic forces. An aircraft in spin autorotates (autorolls, autoyaws, and auto-pitches) because of aerodynamic forces.
Auto-rotation in pitch, roll, and yaw axes.
iii. The tendency of an airfoil at high angles of attack to rotate to align with the relative airflow.

Aviation dictionary. 2014.

Look at other dictionaries:

  • Autorotation — ist das nur durch Luftströmung (Fahrtwind) erzeugte freie Rotieren eines Hubschrauberrotors oder Flugkörpers. Beim Rotor eines Drehflügelflugzeugs setzen die Rotorblätter die Energie des Luftstroms dabei in dynamischen Auftrieb um, vergleichbar… …   Deutsch Wikipedia

  • autorotation — ● autorotation nom féminin Mode de fonctionnement d un rotor d hélicoptère dont le système d entraînement mécanique ou par réaction n agit plus …   Encyclopédie Universelle

  • Autorotation — Autorotation,   Selbstdrehung, Luftfahrt: 1) Flugzustand eines Hubschraubers, der bei Triebwerkausfall durch Verstellung der Rotorblätter eingenommen werden kann. Der durch einen Freilauf vom Triebwerk entkuppelte Rotor wird im Sinkflug durch den …   Universal-Lexikon

  • Autorotation — In aviation, the word autorotation is applied to operation of fixed wing aircraft and rotary wing aircraft. The word has significantly different meanings in each of these two applications.In the operation of fixed wing aircraft, autorotation is… …   Wikipedia

  • Autorotation — L autorotation est le mouvement de rotation sur lui même qu un mobile subit éventuellement lors de son déplacement dans le fluide : il peut par exemple s agir d une hélice non motorisée, fonctionnant à la manière d une éolienne. Pour les… …   Wikipédia en Français

  • autorotation — noun Date: 1918 the turning of the rotor of an autogiro or a helicopter with the resulting lift caused solely by the aerodynamic forces induced by motion of the rotor along its flight path • autorotate intransitive verb …   New Collegiate Dictionary

  • autorotation — autorotational, adj. /aw toh roh tay sheuhn/, n. Aeron. the condition of flight occurring when lift is derived solely from the action of air upon the unpowered rotor of a moving helicopter or autogiro. [1915 20; AUTO 1 + ROTATION] * * * …   Universalium

  • autorotation — noun The rotation of the blades of a helicopter driven solely by the action of ascending air …   Wiktionary

  • Autorotation — Au|to|ro|ta|ti|on die; , en <zu ↑auto... u. ↑Rotation, eigtl. »Selbstdrehung«>: a) die auf ↑aerodynamische Kräfte zurückzuführende Drehbewegung des ↑Rotors eines Hubschraubers um seine eigene Achse; b) die bei zu hohem Anstellwinkel… …   Das große Fremdwörterbuch

  • autorotation — noun rotation of an object caused by the flow of moving air or water around it. Derivatives autorotate verb …   English new terms dictionary

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