Tandem rotors

tandem rotortandem-rotorTandemTandem roterTandem rotor helicopterTandem-rotor craft
Tandem rotor helicopters have two large horizontal rotor assemblies mounted one in front of the other.wikipedia
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Helicopter

helicoptersrotorcraftchopper
Tandem rotor helicopters have two large horizontal rotor assemblies mounted one in front of the other.
Tandem rotor helicopters are also in widespread use due to their greater payload capacity.

Nicolas Florine

Nikolay Florin
The first successful tandem rotor helicopter was built by Nicolas Florine in 1927.
He built the first tandem rotor helicopter to fly freely in 1933.

Coaxial rotors

coaxial rotorcoaxialco-axial
This is commonly accomplished by a tail rotor, coaxial rotors, and the NOTAR systems.
Common alternatives are single-rotor helicopters or tandem rotor arrangements.

Tail rotor

tailanti-torque rotortail rotor blades
This is commonly accomplished by a tail rotor, coaxial rotors, and the NOTAR systems.
Tandem / Transverse rotors: to use two non-overlapping main rotors which turn in opposite directions, so that the torque created by one rotor cancels out the torque created by the other. Such a design is commonly seen on heavy lift helicopters like the tandem rotored CH-47 Chinook and effectively with the tiltrotor configuration V-22 Osprey.

Piasecki H-21

H-21CH-21CH-21 Shawnee
Piasecki H-21 (1949)
The Piasecki H-21 Workhorse/Shawnee is an American helicopter, the fourth of a line of tandem rotor helicopters designed and built by Piasecki Helicopter (later Boeing Vertol).

Piasecki HRP Rescuer

HRP-1Piasecki HRP-1 RescuerHRP
HRP Rescuer (1945)
The Piasecki HRP Rescuer (also called Harp) was a United States tandem-rotor transport or rescue helicopter designed by Frank Piasecki and built by Piasecki Helicopter.

Piasecki HUP Retriever

Piasecki HUP-3 RetrieverPiasecki HUP-1Piasecki HUP-2 Retriever
Piasecki PV-14 (1948)
The Piasecki HUP Retriever/H-25 Army Mule was a compact single radial engine, twin overlapping tandem rotor utility helicopter developed by the Piasecki Helicopter Corporation of Morton, Pennsylvania.

Bristol Belvedere

BelvedereBelvedere HC.1Belvedere helicopter
Bristol Belvedere (1952)
The Bristol Type 192 Belvedere is a British twin-engine, tandem rotor military helicopter built by the Bristol Aeroplane Company.

Yakovlev Yak-24

Yak-24Yak-24 "Horse
Yakovlev Yak-24 (1952)
The Yakovlev Yak-24 (NATO reporting name "Horse") is a Soviet twin-engine, tandem rotor, transport helicopter developed by Yakovlev in the 1950s.

Piasecki H-16 Transporter

H-16Piasecki PV-15 H-16 TransporterPiasecki XH/YH-16 Transporter
Piasecki H-16 (1953)
The Piasecki H-16 Transporter (company designation PV-15) was a tandem-rotor transport or rescue helicopter designed by Frank Piasecki and built by Piasecki Helicopter.

Boeing Vertol CH-46 Sea Knight

CH-46 Sea KnightCH-46CH-46E Sea Knight
Boeing Vertol 107-II (1958)
The Boeing Vertol CH-46 Sea Knight is a medium-lift tandem-rotor transport helicopter powered by twin turboshaft engines.

Boeing CH-47 Chinook

ChinookCH-47 ChinookCH-47
CH-47 Chinook (1961) - most-produced tandem-rotor helicopter (over 1,200 built)
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).

NOTAR

jet effluxno tail rotor
This is commonly accomplished by a tail rotor, coaxial rotors, and the NOTAR systems.
Tandem rotors

Helicopter flight controls

cycliccollective pitchhelicopter pilot
Tandem rotor designs achieve yaw by applying opposite left and right cyclic to each rotor, effectively pulling both ends of the helicopter in opposite directions.
Tandem-rotor craft (like a Boeing CH-47 Chinook) also employ two rotors spinning in opposite directions–termed counter-rotation when it occurs from two separate points on the same airframe–but have the rotors on separate drive shafts through masts at the nose and tail.

Filper Research Beta

Filper Helicopter
Filper Helicopter (1965)
The Filper Research Beta series of 100A/200A/300/400A variants was an American tandem rotor helicopter program.

Boeing Model 360

Boeing Model 360 (1987)
The Boeing Model 360 was an American experimental medium-lift tandem rotor cargo helicopter developed privately by Boeing to demonstrate advanced helicopter technology.

Bell HSL

HSL
Bell HSL (1953)
The Bell HSL (Model 61) was an American 1950s anti-submarine warfare (ASW) helicopter built by the Bell Helicopter company, the only tandem rotor type designed by Bell.

Disk loading

disc loadingwing-disc loading
Tandem rotor helicopters tend to have a lower disk loading than single rotor helicopters.

Rotorcraft

rotary-wingrotary-wing aircraftrotary wing
Rotorcraft
TandemOne in front of the other.

Tiltrotor

tilt-rotortilt rotortiltrotor aircraft
Tiltrotor
In vertical flight, the tiltrotor uses controls very similar to a twin or tandem-rotor helicopter.

Intermeshing rotors

synchropterintermeshing rotorintermeshed contrarotating twin rotor
Intermeshing rotors
Tandem rotors

Transverse rotors

Transversetransverse-mounted rotortwin transverse rotored
Transverse rotors
Tandem rotors

Vertical and horizontal

verticalhorizontalhorizontal plane
Tandem rotor helicopters have two large horizontal rotor assemblies mounted one in front of the other.

Aircraft principal axes

pitchyawroll
Single rotor helicopters need a mechanism to neutralize the yawing movement produced by the single large rotor.

Helicopter rotor

rotorrotor bladerotors
Tandem rotor helicopters have two large horizontal rotor assemblies mounted one in front of the other.