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A helicopter flying at the best range speed, when reaches at the Point of Safe Return, the Pilot decides to return to the departure airfield in headwind conditions. What change must be made to the indicated airspeed?
  • A
    It should be increased.
  • B
    It should be decreased.
  • C
    It should remain the same.
  • D
    It should be slightly increased.

Refer to figure.
The ground range (horizontal distance covered) is affected by the wind, whereas endurance (airborne time) is not affected by any headwind or tailwind component.

Flying slower in a tailwind and faster in a headwind is necessary. The figure plots power for a particular helicopter against three horizontal scales and gives a graphical representation of how much the speed must be adjusted.

1. TAS is the upper scale and the tangent from a TAS equal to zero (0) gives the still air best range speed, VMR or VMD at 105 kt, approximately.

2. The middle scale (named 50 kt tailwind), rebases the graph into a Power vs Groundspeed graph and taking a tangent from the groundspeed of zero shows that the new best range speed is a slightly lower airspeed of 95 kt and a grounspeed of 145 kt, approximately.

3. The bottom scale (named 50 kt headwind) shows that the best range speed in this case has increased to 140 kt, as a TAS, and Groundspeed decreased to 90 kt, approximately.

Therefore, when flying for range and a headwind is experienced, increase your speed, conversely if a tailwind is experienced, decrease your speed.

It is worth mentioning that the headwinds components require a greater speed changes than the equivalent tailwind component would.

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