Questions tagged [contra-rotating]

Use for contra-rotating propellers and coaxial rotors.

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What is the meaning of "Contra-Rotating Propeller Increases Efficiency"? How is it calculated?

This picture is taken from here. In that video is mentioned that contra-rotating propeller increases efficiency up to 6-16%. Regardless of the number that could be vary from one airplane to another, ...
AirCraft Lover's user avatar
1 vote
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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) ...
Nilesh Naik's user avatar
6 votes
2 answers

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 ...
Whiskeyjar Joe's user avatar
16 votes
2 answers

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-...
Jpe61's user avatar
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7 votes
5 answers

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)? ...
AirCraft Lover's user avatar
6 votes
4 answers

Are there disadvantages of coaxial rotor on attack helicopters?

Although the Ka-52 Alligator is a very fierce-looking and formidable aircraft with very powerful engines, it has not seen much export success. Its export is very limited, as only Egypt uses this type ...
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25 votes
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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
Madhav Sudarshan's user avatar