Although helicopters are relatively quiet compared to large commercial jet aircraft, they often operate from small airports or heliports, which are close to the communities they are serving. This proximity creates a need for quiet design and operation, especially at low altitudes when the helicopter is taking off and landing. A particularly loud source of noise, called Blade Vortex Interaction (BVI) noise, often occurs on an approach to a landing. BVI noise is generated when the vortices shed from rotor blades pass in close proximity to following blades causing instantaneous blade pressure fluctuations on the following blades. This normally occurs in descending/decelerating flight on approach to a landing when the helicopter is close to the ground. A part of these instantaneous pressure fluctuations radiate as acoustic energy to positions far from the helicopter. Radiation directivity characteristics of BVI noise are determined to a first-order by the particular geometry and operating condition of the rotor system (Refs. 2,3). A straightforward way of minimizing BVI noise radiation is to operate the helicopter in such a way that the vortices trailed from the blades do not pass in close proximity to the following blades. The effect of steady headwinds and tailwinds on helicopter Blade Vortex Interaction (BVI) ground-noise exposure levels is analytically investigated using a Quasi-Static Acoustic Mapping (Q-SAM) method. The analysis combines a quasi-static point performance model of an AH-1 helicopter with dipole acoustic modeling of BVI noise radiation to develop ground noise exposure trends during landing approaches under steady uniform longitudinal wind conditions. Two distinct landing approach procedures have been formulated, and their impact on ground noise exposure assessed. For the AH-1 helicopter, shallow, upwind and steep, downwind approaches can significantly reduce radiated BVI noise. The relative requirements of the resulting noise abatement landing trajectories are discussed.


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    Titel :

    Quasi-static flight path control of helicopter blade vortex interaction noise in a steady wind


    Weitere Titelangaben:

    Quasi-stationäre Flugbahnregelung zur Abminderung der Geräuschentwicklung bei der Rotorblatt/Wirbel-Wechslwirkung bei Hubschraubern in stationärer Anströmung


    Beteiligte:

    Erschienen in:

    Erscheinungsdatum :

    2007


    Format / Umfang :

    9 Seiten, 12 Bilder, 12 Quellen




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch