Questions tagged [contra-rotating]

Use for contra-rotating propellers and coaxial rotors.

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What are the expected vibration frequencies in a co-axial rotor system with contra-rotating propellers?

I am trying to understand the frequency spectrum of a co-axial rotor system. Form now i have a RC helicopter with two sets of three gear systems arranged in parallel, The number of teeth are 7,23,27) ...
6
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2answers
111 views

Do the blades of the rear disk have different geometry to the blades of the front disk on a contra-rotating assembly?

If my understanding is correct, the air flow is accelerated by the front propeller toward the rear propeller in a contra-rotating prop assembly. Therefore, the rear disk would be receiving air at ...
12
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2answers
797 views

Why don't NK-12 powered contra-rotating propellers turn in equal rpm?

The Kuznetsov NK-12 is a Soviet turboprop engine of the 1950s, designed by the Kuznetsov design bureau. The NK-12 drives two large four-bladed contra-rotating propellers, 5.6 m (18 ft) diameter (NK-...
6
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5answers
674 views

Do contra-rotating propellers have the same RPM?

Image source Here is a contra-rotating propeller. The front propeller rotates counterclockwise while the back propeller rotates clockwise. My questions are: Do they rotate at the same speed (RPM)? ...
4
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4answers
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Are there disadvantages of coaxial rotor on attack helicopters?

My question stems from the fact that, although this is a very fierce looking, and formidable aircraft with a very powerful engine, Ka-52 Alligator has not seen many export success. Its export is very ...
24
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8answers
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What is the purpose of having contra-rotating props on an aircraft?

Why do planes, like the famous XF-11 and the Tu-95, have contra-rotating props? What is their purpose? Image credit: Mike Freer / Touchdown-Aviation / Wikimedia