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If I have a requirement to fly a helicopter in a circle or racetrack over a point of interest that's stationary or moving relatively slowly, is there any reason to prefer left or right turns?

I'm not concerned about visibility and I'm not asking about turns in a landing pattern: I'm asking if - all other things being equal - there's any mechanical, aerodynamic or procedural reason that pilots would prefer to turn in one direction over the other.

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  • $\begingroup$ Related, perhaps duplicate: Why would a helicopter climb in a spiral? $\endgroup$ – CGCampbell Nov 19 '15 at 21:12
  • $\begingroup$ Who needs to have the best view? $\endgroup$ – Pondlife Nov 19 '15 at 21:15
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    $\begingroup$ Somewhat related, perhaps, @CGCampbell, but definitely not a dupe. $\endgroup$ – FreeMan Nov 19 '15 at 21:15
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    $\begingroup$ (Responding to your edit) If visibility isn't your objective then what is? That will probably determine the answer. Or are you asking that if all other things are equal, is there a preferred turn direction in helicopters for 'built-in' reasons of aerodynamics, torque, or whatever? $\endgroup$ – Pondlife Nov 19 '15 at 21:34
  • $\begingroup$ There some aerodynamic effects but insignificant compared to the need for lookout. Quite involved but I'll try to add an answer over the weekend. $\endgroup$ – Simon Nov 20 '15 at 16:36
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Most helis make CW turns because the pilots sit on the right and it is easier to judge position and drift when you can look out the window directly. Turning CCW is no problem however but it takes a tad more concentration.

one drawback of CW turns from the right seat is that the ALT and ASI would be out of your field of vision, so you'll have some head turning to peek at them. In a CCW turn, its easy to glance at the instruments in the center console.

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I am adding an answer as the outer 2 are incomplete. [Simon obviously forgot to add his answer].

Vision is a valid reason, but only In confined areas [think valley or other aircraft]

I will attempt to explain the aerodynamic reason this only apply to very slow speeds or very sharp turns.

If the turn is to sharp and slow, the wrong way and the wind is in a dis-favorable direction, it is possible to "run out of" power peddle meaning there is not enough anti-torque force to stop the turn resulting in a spin and crash. Most flight manuals recommend turns into the direction of the "power peddle" to avoid this.

Demonstration of a sharp turn power side vs non power side.

note how the first turn is a wide turn away from the [power peddle] and the second is almost a stationary spin [into the power peddle].

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Aerodynamically, if performing ground reference turns in a no-wind condition, there is no difference. On the other hand, if in a moderate to high wind condition, Loss of Tail Rotor Effectiveness can be a real danger. Many accidents have been attributed to LTE. LTE can be encountered by way of several different mechanisms, one being turning (orbiting) in prevailing wind at lower speeds. Effectively, main rotor vortices are blown toward the tail rotor at an angle which blanks the inflow to the tr, degrading its effectiveness, potentially to zero. Pilots can mitigate the effect by turning in the direction of the rotor (as viewed from top looking down). There are countless articles and video presentations on the www. Search for Loss of Tail Rotor Effectiveness LTE.

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I have seen turns in both directions. It probably does not matter anyways which way the turn is going, but if it is a single main-rotor helicopter, going with the counter-rotor spin is probably a little more effective at saving fuel although there is not much overall advantage either way if you are not looking for visibility.

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