Not the chinook helicopters but the ones with two propellers side by side. Instead of one big propeller there are two small ones.

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I think they are used by the military.

Military helicopters with two propellers. The ch 46 sea knight is used primarily by the navy and marines who use it to carry supplies conduct search and rescue sweeps anti sub oper. Its name chinook is from the native american chinook people of washington state. Usually a main rotor and a tail rotor.

It got its original design including the same engine transmission and rotor system from the huey. Two propellers are arranged one behind the other and power is transferred from the engine via a planetary gear or spur gear transmission. The boeing ch 47 chinook is an american twin engined tandem rotor heavy lift helicopter developed by american rotorcraft company vertol and manufactured by boeing vertol later known as boeing rotorcraft systems the ch 47 is among the heaviest lifting western helicopters.

The x3 has two propellers on the side of the craft thereby removing the need for a tail rotor and is being projected by airbus helicopter for the military s use in search and rescue special forces operations and troop transport. Boeing ch 47 chinook one rotor mounted in the front over the cockpit. The x4 is expected to replace the dauphin family in the four to six tonne class.

The failure of operation eagle claw during the iran hostage crisis in 1980. Aircraft equipped with contra rotating propellers also referred to as crp coaxial contra rotating propellers or high speed propellers apply the maximum power of usually a single piston or turboprop engine to drive two coaxial propellers in contra rotation. The bell boeing v 22 osprey is an american multi mission tiltrotor military aircraft with both vertical takeoff and landing and short takeoff and landing capabilities it is designed to combine the functionality of a conventional helicopter with the long range high speed cruise performance of a turboprop aircraft.

The cobra is a two blade single engine attack aircraft manufactured by bell. Contra rotating propellers are also known as counter rotating propellers although counter rotating. So i assume you meant 2 main rotors of same diameter.

All helicopters have 2 rotors. Simply googling your question would tell you about the ch 46 sea knight and the ch 47 chinook helicopters.