autorotation


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autorotation

[¦ȯd·ō‚rō′tā·shən]
(mechanics)
Rotation about any axis of a body that is symmetrical and exposed to a uniform airstream and maintained only by aerodynamic moments.
Rotation of a stalled symmetrical airfoil parallel to the direction of the wind.

autorotation

autorotation
Airflow in auto rotation.
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.
ii. The rotation of aircraft around its axes resulting from aerodynamic forces. An aircraft in spin autorotates (autorolls, autoyaws, and autopitches) because of aerodynamic forces.
iii. The tendency of an airfoil at high angles of attack to rotate to align with the relative airflow.
References in periodicals archive ?
Van den Hof, "Trajectory planning and trajectory tracking for a small-scale helicopter in autorotation," Control Engineering Practice, vol.
to enter an autorotation. (146) He apparently was distracted by text
Rogers, "A Real-time expert control system for helicopter autorotation," Journal of the American Helicopter Society, vol.
The autorotation and orbital angle of rollers are calculated by (2) and (3), respectively.
The mandibular plane showed counterclockwise autorotation. In the posttreatment panoramic radiograph, no sign of apical resorption was seen and maxillary third molars erupted and successfully replaced the second molars (Figure 2D).
The simulator enables pilots to practice challenging procedures without risk such as low-level flight, confined area operations, autorotation and landing on platforms at sea.
The upgrade from manual to autorotation has brought about revolutionary changes to the user experience when taking photos with a mobile phone.
Instead, he "inadvertently pulled-out the engine mixture control with the mixture control guard, which resulted in an immediate total loss of engine power." The ATP/PIC entered autorotation while the private pilot unsuccessfully attempted to restart the engine before the Robie struck trees, a fence and nosed over (into a ditch?).
The first simulated engine failure was a 180-degree autorotation. The maneuver, waveoff, and engine response were all on the numbers and per the book.
A cup anemometer can be studied from two different perspectives: as a meteorological instrument or as a body in autorotation. As a meteorological instrument, the cup anemometer has been studied for a long time, using different techniques and mathematical models, under different climatic conditions and focusing on particular aspects of their performance and response.
Il test del riflesso vestibolo-oculare (VOR) in autorotazione (vestibulo-ocular reflex autorotation test) (9) e un test sui riflessi centrali: l'input sensoriale e la velocita della testa e l'output motorio e la velocita degli occhi.
If both engines fail while it is flying fast (called "airplane mode"), the V-22 can glide like any fixed-wing aircraft, obviating the need for autorotation. So the only risk is when both engines fail while the V-22 is in "helicopter mode" (with the prop-rotors/ engines pointed upward).