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During an unaccelerated flight...

  • A

    the vertical component of thrust equals the horizontal component of thrust and drag equals gravity.

  • B

    the vertical component of thrust equals gravity and the horizontal component of thrust equals drag.

  • C

    the vertical component of thrust equals drag and the horizontal component of thrust equals gravity.

  • D

    the horizontal component of thrust equals the sum of drag and gravity.

Refer to figure.
When the pilot applies forward cyclic to transition to forward flight, the rotor disc will be tilted forward. Wherever the rotor disc is pointing, so too is the direction of the Total Rotor Thrust (TRT).

Thus, the TRT is split into two components:

  • A vertical component of TRT, which opposes the weight.
  • A horizontal componet of TRT, which opposes the total drag.

Level and unaccelerated forward flight means that the helicopter has a constant speed and neither climbs nor descends. Therefore:

  • The vertical component of TRT is equal and opposite to weight. If it's not equal, the helicopter climbs or descends.
  • The horizontal component of TRT is equal and opposite to total drag. If it's not equal, the helicopter accelerates or decelerates.

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