Helicopter tail rotor thrust and main rotor wake coupling in crosswind flight

Timothy M. Fletcher, Richard Brown

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The tail rotor of a helicopter with a single main rotor configuration can experience a significant reduction in thrust when the aircraft operates in crosswind flight. Brown’s vorticity transport model has been used to simulate a main rotor and tail rotor system translating at a sideslip angle that causes the tail rotor to interact with the main rotor tip vortices as they propagate downstream at the lateral extremities of the wake. The tail rotor is shown to exhibit a distinct directionally dependent mode during which tail rotors that are configured so that the blades travel forward at the top of the disk develop less thrust than tail rotors with the reverse sense of rotation. The range of flight speeds over which this mode exists is shown to vary considerably with the vertical location of the tail rotor. At low flight speeds, the directionally dependent mode occurs because the tail rotor is immersed within not only the downwash from the main rotor but also the rotational flow associated with clusters of largely disorganized vorticity within the main rotor wake. At higher flight speeds, however, the tail rotor is immersed within a coherent supervortex that strongly influences the velocity field surrounding the tail rotor.
LanguageEnglish
Pages2136-2148
JournalJournal of Aircraft
Volume47
Issue number6
DOIs
Publication statusPublished - Nov 2010

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Helicopters
Rotors
Vorticity
Rotational flow
Turbomachine blades
Vortex flow
Aircraft

Keywords

  • helicopters
  • airctaft
  • tail rotor
  • velocity

Cite this

Fletcher, Timothy M. ; Brown, Richard. / Helicopter tail rotor thrust and main rotor wake coupling in crosswind flight. In: Journal of Aircraft. 2010 ; Vol. 47, No. 6. pp. 2136-2148.
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Helicopter tail rotor thrust and main rotor wake coupling in crosswind flight. / Fletcher, Timothy M.; Brown, Richard.

In: Journal of Aircraft, Vol. 47, No. 6, 11.2010, p. 2136-2148.

Research output: Contribution to journalArticle

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AB - The tail rotor of a helicopter with a single main rotor configuration can experience a significant reduction in thrust when the aircraft operates in crosswind flight. Brown’s vorticity transport model has been used to simulate a main rotor and tail rotor system translating at a sideslip angle that causes the tail rotor to interact with the main rotor tip vortices as they propagate downstream at the lateral extremities of the wake. The tail rotor is shown to exhibit a distinct directionally dependent mode during which tail rotors that are configured so that the blades travel forward at the top of the disk develop less thrust than tail rotors with the reverse sense of rotation. The range of flight speeds over which this mode exists is shown to vary considerably with the vertical location of the tail rotor. At low flight speeds, the directionally dependent mode occurs because the tail rotor is immersed within not only the downwash from the main rotor but also the rotational flow associated with clusters of largely disorganized vorticity within the main rotor wake. At higher flight speeds, however, the tail rotor is immersed within a coherent supervortex that strongly influences the velocity field surrounding the tail rotor.

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