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Comment by ahh | Hacker News Reader

What about the Tu-95? It's famously loud due to (says Wikipedia) supersonic propeller tips. Do you know why they're still effective?

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I am convinced that if you were to dimple the propeller (tips) such as a golf ball is pitted, you would reduce this effect.

Further, if you wer to dimple/convex in an alternating pattern the leading edge of any aero ... efficiencies would increase.

Micro-dimples are better.

Understand the eddys, as Da vinci would say....

The Tu-95’s props are paired for counter-rotational torque balance. The second prop does not add additional thrust.

The supersonic speed was the question, not the contrarotation.

Well, samstave's original question was one of adding power with an inline stack. As I understood it, that isn't the purpose for he Tu-95's pair of props since they share a power source. The below explanation [0] has some interesting analysis based on Russian language documentation about how torque is divided between the prop pairs. Additionally the paper linked from the Wikipedia contra-rotating prop page "Analysis of a contra-rotating propeller driven transport aircraft" [1] has a great section on fuel savings, which probably has contributed to the Tu-95's success.

Thus, the front prop gets almost 20% more torque than the rear prop.

0. https://aviation.stackexchange.com/questions/74787/why-dont-...

1. https://www.rcgroups.com/forums/showatt.php?attachmentid=281...

Thank you all TIL so much.

I believe they're sacrificing efficiency for performance.

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