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Tail rotor turning direction

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Tail rotor turning direction

Old 31st May 2022, 18:48
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Tail rotor turning direction

Hi everyone.

In the most of the types, the tail rotor turns in such a way that the blades closer to the main rotor downwash go upwards, slashing into it. This is true for the most of the helos and makes sense to me specially in forward flight as of 20-30 kt where the tail rotor disc should get more effective as it is washed by the main rotor. Just like with ETL, where the main rotor becomes more efficient as the advancing blades slash into the air.

I was wondering why in a few types the tail rotor turns in such a way that the blades closer to the induced flow go downwards (thus escaping from it) like in Robinsons, S300, MD500, OH-23 and a very few more.

Thank you!
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Old 31st May 2022, 21:49
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Robinsons, S300, MD500, OH-23 and a very few more.
Designed in 50s, 60s and 70s.

I think they got smarter in more recent times. Even Bell designed the flip-flop tail mod for the 50s Huey, moving it from downwards on the left side to upwards on the right side.
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Old 31st May 2022, 23:12
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The Lynx tail rotor direction was reversed on later models, quoted reason was to reduce vibration. The “top” blade was chopping forwards on earlier models but later versions had it moving backwards.
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Old 31st May 2022, 23:35
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Yup, pretty much everyone figured out tail rotors should kick rocks into the fuselage... at least that's how I remember it. I'm sure the more correct answer is the advancing blade should be in cleaner air and not advancing into the wake of the main rotor in forward flight.
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Old 1st Jun 2022, 01:14
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If I recall correctly, the R22's tailrotor spins in the "less effective direction" because the gearbox needed to spin it the other way would have been too big and heavy. The R44 on the other hand, does spin the other way.
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Old 1st Jun 2022, 01:16
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The tail rotor is more efficient if it is turning in the opposite direction of the main rotor tip vortex. The earlier designs did not take that into effect. Bell flopped the T/R on the 212/UH-1N so they would not have to redesign the gear box to rotate the "correct" way. The Bell aircraft which were designed from the mid-sixties on (206, 222, 407, etc) had gearboxes that turned the proper direction. The AH-1G had an MWO that flopped the T/R with mods starting in 1970.
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Old 1st Jun 2022, 09:57
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After many years in service, CFS (H) at Tern Hill 'discovered that it was possible to fit the Whirlwind tail rotor the wrong way round ! Subsequent preflight was to include checking that the lower t/r blade 'matched' the aerodynamic profile of the tail pylon. ... and, yes, the rotation was into the main rotor.
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Old 1st Jun 2022, 10:06
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As in “retreating” blade at the top.
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Old 2nd Jun 2022, 00:50
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it was possible to fit the Whirlwind tail rotor the wrong way round
And on the Huey, one reportedly flew for some 70 hours with comments of high freq vibes before an alert lad walking down the flight line noted that something didn't look quite right when compared to the other aircraft in the line.
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Old 2nd Jun 2022, 06:17
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Seen a Schweizer nee Hughes 300 with the tail rotor blades on backwards, 300 "B" blades an a 300 "C", H500 "C" with a "D pitch link opposite the correct "C" version (different length) - nobody mentioned anything undue from the "cyclic attendant" department although the 500 sounded in bit funny when it turned up..............
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Old 7th Jun 2022, 02:08
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Originally Posted by Robbiee View Post
If I recall correctly, the R22's tailrotor spins in the "less effective direction" because the gearbox needed to spin it the other way would have been too big and heavy. The R44 on the other hand, does spin the other way.
​​​​​​
Yes, Tim Tucker mentions this during the Robinson safety course, along with the length limitations on the first R22 tail rotor blades - they couldn't be any longer than the width of Frank's kitchen oven!
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