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An image search for 'helicopter' indicates that there isn't a consensus on whether to place the tail rotor to the left or the right of the tail boom, although I'm believe there may be a bias for left.

There never seems to have been a consensus: taking two popular early helicopter designs, the Bell 47 has its rotor on the right; the Hughes 269 on the left.

Bell 47 Bell 47 source

Hughes 269 Hughes 269 source

There are many left/right conventions in aviation, e.g. where the pilot sits, which side the passengers exit etc. So the question is, what governs the choice, and would it be beneficial if a 'right' side was generally agreed on?

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    $\begingroup$ Perhaps you'd also be surprised that there is no consensus regarding the rotation direction of the main rotor. Generally speaking, western helicopters' rotor will spin counterclockwise (except for helicopters built by Aérospatiale), while eastern will spin clockwise $\endgroup$
    – DeepSpace
    Aug 28, 2018 at 11:12
  • $\begingroup$ Which may go part way to explaining rotor position: assuming tail rotors always pull rather than push (that's a guess), then it's the main rotor's spin direction which would dictate left or right for the tail. (However, there are lots of examples of both left and right western helicopters from many different manufacturers.) $\endgroup$
    – Party Ark
    Aug 28, 2018 at 12:04
  • $\begingroup$ Not necessarily. The tail rotor on the Blackhawk is on the right $\endgroup$
    – DeepSpace
    Aug 28, 2018 at 12:42
  • $\begingroup$ note also that the rotors of the two copters in the question spin in the same direction. $\endgroup$
    – Federico
    Aug 28, 2018 at 12:47
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    $\begingroup$ @DeepSpace East versus west? Surely they spin one way in the northern hemisphere and the opposite way in the south! ;-) $\endgroup$
    – David Richerby
    Jul 22, 2019 at 20:34

2 Answers 2

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It's hard to say the design rational used for all helicopter manufacturers. Push vs pull doesn't seem to be very important.

One example is the Bell UH-1 Huey (Left side Pull). When Bell modified the design for civilian use 205, 212, 412, 214, they put the TR on the (RH side Push). When asked about the reasoning for the original Huey/205 change, Bell engineers explained that they found better TR effectiveness with rotation of forward blade climbing, as the interaction with wake and vortices of the main rotor was more favorable in this configuration.

Now look at the AH-1 Cobra Gunship variants. Bell switched sides at least twice. Left on early models, switched to right on later 2 blade models (AH-1W). Back to Left side for the 4 blade AH-1Z. While on opposite sides, the AH-1W and AH-1Z are both forward blade climbing.

Sikorsky? S-76(Left - Climbing) H-60(Right - Climbing) H-53(Left - Climbing). One could speculate that the higher the TR is mounted, the more this rational comes into play.

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Location of the tail rotor is the result of mainly:

  • Tractor or pusher type: blow against the vertical fin or away from it. If against the vertical fin, there is a beneficial pseudo ground effect on the tail rotor. The pusher type has the vertical fin slowing down the inflow, which produces a pseudo ceiling influence which is beneficial as well
  • Rotation direction of the main rotor.

Ray Prouty (In Helicopter Performance, Stability and Control) has this to say about pusher/puller:

The tail rotor can be installed either as a pusher or as a tractor.Test results...show that the pusher is more efficient since it is less interfered with by the vertical fin. Nevertheless, there may be reasons for using the tractor installation. For example, on the Sikorsky UH-60, the designers decided to tilt the tail rotor shaft to take advantage of a vertical component of tail rotor thrust. To obtain adequate clearances as a pusher, the tail rotor shaft would have had to be very long. As a tractor, the installation was much lighter and compact.

enter image description here

Data on the effects of pusher/puller can be found in Leishman (Principles of Helicopter Aerodynamics), showing that the interference effect is most beneficial if the obstruction is not in the high energy flow. It also shows that with USA helicopters, the pusher is on the left side and the tractor on the right. For European helicopters this is the other way around since the main rotor turns the other way.

The two helicopters in the OP have no vertical fin, and then the decision is basically arbitrary.

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