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ground resonance
- Definição1
- A resonance that manifests itself as a violent rocking of the helicopter when it is on the ground. This phenomenon is most evident when the helicopter is on hard surfaces that do not absorb vibration. It is caused by the resonance between the skid and the rotor system. It is most likely if the helicopter has a fully articulated rotor system that experiences a hard impact, such as the helicopter hitting the ground with a single skid while landing. The resonance can either build up slowly, with the oscillations gradually increasing in amplitude, or extremely rapidly. If uncorrected, the helicopter can roll over and break up. To prevent this critical situation, either the engine should be switched off if the rotor RPM is low or the helicopter should takeoff by applying more power.
- Fonte1
- KUMAR, Bharat (ed.). An illustrated dictionary of aviation. New York: McGraw-Hill, c2005. 752 p.
- Definição2
- Self-excited vibration occuring whenever the frequency of oscillation of the blades about the lead-lag axis of an articulated rotor becomes the same as the natural frequency of the fuselage.
- Fonte2
- FEDERAL AVIATION ADMINISTRATION. Helicopter flying handbook (FAA-H8083-21A). Washington, DC: FAA, 2012.
- Definição3
- Dangerous natural vibration of helicopter on ground caused by stiffness and frequency of landing-gear legs amplifying primary frequency of main rotor; potentially unless designed out, and even with certificated helicopter can occur as a result of severe landing shock.
- Fonte3
- GUNSTON, Bill. The cambridge aerospace dictionary. Cambridge: Cambridge University, 2004. vii, 740 p. (Cambridge aerospace series.)
- Fonte4
- FEDERAL AVIATION ADMINISTRATION. Rotorcraft flying handbook (FAA-H-8083-21). Washington, DC: FAA, 2000. Disponível em: http://www.faa.gov/library/manuals/aircraft/media/faa-h-8083-21.pdf. Acesso em: 10 fev. 2012.
- Contexto
- If the r.p.m. is low, the corrective action to stop ground resonance is to close the throttle immediately and fully lower the collective to place the blades in low pitch.
- Subárea
- Rotorcraft
- Français
- résonance sol