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Wikipedia

Tandem-rotor aircraft

April 08, 2024

A tandem-rotor aircraft is an aircraft with two large helicopter rotor assemblies mounted one in front of the other in the horizontal plane.

Boeing Vertol CH-46 Sea Knight
Animation

Currently this configuration is mainly used for large cargo helicopters.[1]

Design edit

Single-rotor helicopters need a mechanism to neutralize the yawing movement produced by the single large rotor. This is commonly accomplished by a tail rotor, coaxial rotors, and the NOTAR systems. Tandem-rotor helicopters, however, use counter-rotating rotors, with each cancelling out the other's torque. Therefore, all of the power from the engines can be used for lift, whereas a single-rotor helicopter uses some of the engine power to counter the torque.[1] An alternative is to mount two rotors in a coaxial configuration. The first successful tandem-rotor helicopter was built by Nicolas Florine in 1927.

Advantages of the tandem rotor system are a larger center of gravity range and good longitudinal stability. Disadvantages of the tandem rotor system are a complex transmission[1] and the need for two large rotors.

The two rotors are linked by a transmission that ensures the rotors are synchronized and do not hit each other, even during an engine failure.[2]

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. To achieve pitch, opposite collective is applied to each rotor; decreasing the lift produced at one end, while increasing lift at the opposite end, effectively tilting the helicopter forward or back.[3]

Tandem-rotor helicopters have the advantage of being able to hold more weight with shorter blades, since there are two sets. However, the rear rotor works in the aerodynamic shadow of the front rotor, which reduces its efficiency. This loss can be minimized by increasing the distance between the two rotor hubs, and by elevating one hub over the other.[4][5] Tandem-rotor helicopters tend to have a lower disk loading than single-rotor helicopters.[6]

Tandem-rotor helicopters typically require less power to hover and achieve low-speed flight as compared to single-rotor helicopters. Both configurations typically require the same power to achieve high-speed flight.[7]

Examples edit

 
Columbia Helicopters Boeing Vertol 107-II and Boeing 234
 
A Piasecki H-21B in the early 1960s
 
A Yakovlev Yak-24 at Central Air Force Museum

See also edit

References edit

  1. ^ a b c . Archived from the original on 2014-02-18. Retrieved 2017-12-03.
  2. ^ Art of the helicopter by John Watkinson, p. 13
  3. ^ "US Army FM 3-04.203 Fundamentals of Flight; page 1-33, para 1-81, 1-82" (PDF).
  4. ^ Principles of helicopter aerodynamics by J. Gordon Leishman p. 73.
  5. ^ Rotary Wing Aerodynamics, W.Z. Stepniewski, p. 197.
  6. ^ Rotary Wing Aerodynamics, W.Z. Stepniewski, p. 185
  7. ^ Rotary Wing Aerodynamics, W.Z. Stepniewski, p. 200.

April 08, 2024
tandem, rotor, aircraft, tandem, rotor, aircraft, aircraft, with, large, helicopter, rotor, assemblies, mounted, front, other, horizontal, plane, boeing, vertol, knightanimationcurrently, this, configuration, mainly, used, large, cargo, helicopters, contents, . A tandem rotor aircraft is an aircraft with two large helicopter rotor assemblies mounted one in front of the other in the horizontal plane Boeing Vertol CH 46 Sea KnightAnimationCurrently this configuration is mainly used for large cargo helicopters 1 Contents 1 Design 2 Examples 3 See also 4 ReferencesDesign editSingle rotor helicopters need a mechanism to neutralize the yawing movement produced by the single large rotor This is commonly accomplished by a tail rotor coaxial rotors and the NOTAR systems Tandem rotor helicopters however use counter rotating rotors with each cancelling out the other s torque Therefore all of the power from the engines can be used for lift whereas a single rotor helicopter uses some of the engine power to counter the torque 1 An alternative is to mount two rotors in a coaxial configuration The first successful tandem rotor helicopter was built by Nicolas Florine in 1927 Advantages of the tandem rotor system are a larger center of gravity range and good longitudinal stability Disadvantages of the tandem rotor system are a complex transmission 1 and the need for two large rotors The two rotors are linked by a transmission that ensures the rotors are synchronized and do not hit each other even during an engine failure 2 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 To achieve pitch opposite collective is applied to each rotor decreasing the lift produced at one end while increasing lift at the opposite end effectively tilting the helicopter forward or back 3 Tandem rotor helicopters have the advantage of being able to hold more weight with shorter blades since there are two sets However the rear rotor works in the aerodynamic shadow of the front rotor which reduces its efficiency This loss can be minimized by increasing the distance between the two rotor hubs and by elevating one hub over the other 4 5 Tandem rotor helicopters tend to have a lower disk loading than single rotor helicopters 6 Tandem rotor helicopters typically require less power to hover and achieve low speed flight as compared to single rotor helicopters Both configurations typically require the same power to achieve high speed flight 7 Examples edit nbsp Columbia Helicopters Boeing Vertol 107 II and Boeing 234 nbsp A Piasecki H 21B in the early 1960s nbsp A Yakovlev Yak 24 at Central Air Force MuseumBell HSL 1953 Boeing CH 47 Chinook 1961 most produced tandem rotor helicopter over 1 200 built Boeing Model 360 1987 Boeing Vertol 107 II 1958 Boeing Vertol CH 46 Sea Knight 1960 military version of Vertol 107 II Boeing Vertol XCH 62 1970s not completed Boeing Vertol Model 234 1981 Bristol Belvedere 1958 Bristol Type 173 1952 Chu CJC 3 1952 Filper Beta 200 1966 Filper Beta 400 1967 Filper Helicopter 1965 HERC JOV 3 1948 Jovair Sedan 4A 1963 McCulloch MC 4 1951 Piasecki H 16 1953 Piasecki H 21 1949 Piasecki H 25 HUP Retriever 1952 Piasecki HRP Rescuer 1945 Piasecki PV 14 1948 Rotorcraft XR 11 1947 Yakovlev Yak 24 1952 See also editCoaxial rotor aircraft Intermeshing rotor helicopter Rotorcraft Tiltrotor Transverse rotor aircraftReferences edit a b c FM 1 514 CHPTR 3 Rotor System Operation Archived from the original on 2014 02 18 Retrieved 2017 12 03 Art of the helicopter by John Watkinson p 13 US Army FM 3 04 203 Fundamentals of Flight page 1 33 para 1 81 1 82 PDF Principles of helicopter aerodynamics by J Gordon Leishman p 73 Rotary Wing Aerodynamics W Z Stepniewski p 197 Rotary Wing Aerodynamics W Z Stepniewski p 185 Rotary Wing Aerodynamics W Z Stepniewski p 200 Retrieved from https en wikipedia org w index php title Tandem rotor aircraft amp oldid 1180680455, wikipedia, wiki, book, books, library,

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