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Direction of Torque


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Which way does the Hind want to twist from main rotor torque? Huey wants to go right so you give left pedal, Mi-8 wants to go left so you give right pedal, but both have left-hand tail rotor in game. The hind is also on the left, so is that a huey left or a hip left?

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I thought the mi-8 was always a clockwise rotating main rotor.

they just reversed the side of the tail rotor because it became a more efficient puller instead of a pusher type fan.

why the tail rotor on the mi-17 and mi-24 is the opposite side. to the older mi-8's

torque is the same direction.

you just have more authority with the puller.

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The increase in tail rotor effectiveness does not come from pusher/puller but rather from benefitting from main rotor airflow over the tail rotor blades. That is, the tail rotor is a lot more effective when the lower half of the tail rotor spins forward into the main rotor downwash. On the older Mi-8 versions (prior to Mi-8M/Mi-8MT) the lower half of the tail rotor spun away from the main rotor downwash. To increase effectiveness, the tail rotor gearbox and the entire tail rotor assembly was simply "flipped" to the other side, changing the direction of rotation and greatly increasing effectiveness without any parts or major design changes.


The Mi-8 always had a clockwise-spinning main rotor and therefore always used right pedal to counter torque as power was applied, regardless of which side the tail rotor was on.

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thanks for that alpha. interesting. so you are getting two bonuses from the swap. the more efficient puller and the synergy between the blades rotation and the main rotor.

I always wondered why the original mi-8 had a pusher. 

because they worked out pullers are more efficient a long time ago.

hence why every war bird worth the name has a puller.

even though it comes with the real downside of you having to shoot through the blades.


looking at the mi-28 that seems to have a pusher too... if its clockwise rotating.

I wonder why?

i mean you usually have a reason for using the less efficient pusher config.

like sea planes. they used pushers because it keeps the blades away from the sea and waves, on take-off and landing. they mounted the engine high and pointing backwards.

but they didn't need the speed.


it just seems like free efficiency wasted so there has to be a reason? less stress on the tail rotor head? pushing it into the tail boom rather than pulling away from it?


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7 hours ago, Sacarino111 said:


A far as I know, soviet machines mostly have an oposite turning direction than the occidental ones, no matter planes or hellos. you can see this if you fly the Huey and then  the MI8.The direction of the tail rotor is a mistery to me....




It has a clockwise rotating rotor, so the torque will yaw the body to the left, you have to add right anti-torque to counteract it.


What side the tail rotor is mounted on doesn't really matter - in the Hip it's on the left hand side, configured as a puller, because it was found to work better than being mounted on the right side, configured as a pusher.

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  • 2 weeks later...

Just clarification on tail rotor design (for those who care)


1.  Fwd blade is travelling with rotor downwash in first generation. (Decreased efficiency - Think reduced relative airspeed)

2. Fwd blade is travelling against rotor downwash in second generation.  (Increased efficiency - Think increased relative airspeed)


Hopefully makes sense.  If not, stick your hand out the window of your car while it's moving and swing it with the direction of relative airflow, then try it the other way.


Not sure about Mi-8 designer philosophy, but I know if I wanted a simple solution without having to redesign the gearbox.... turn it around and it spins the other way.  Cheap and easy.


Although a very simplified explanation given above, I thought I could add some additional in depth reading for anyone interested in the study conducted by Lt Col Ellin - Royal Navy, Defense Research Agency which is quoted in many helicopter dynamics textbooks.  He describes the testing they conducted of Lynx tail rotor designs (in both the above configurations) and is written in such a way for a person to read without having to understand a complex series of equations.


Edited by pbishop
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