FH.XI.B.K3

From the FAA library

• Helicopter Flying Handbookp. 1-4
  Chapter 1: Introduction to the Helicopter › Rotor System › Tandem Rotor

  Tandem Rotor Tandem rotor (sometimes referred to as dual rotor) helicopters have two large horizontal rotor assemblies, instead of one main assembly and a smaller tail rotor. [Figure 1-6] Single rotor helicopters need a tail rotor to neutralize ... twisting momentum produced by the single large rotor. Tandem rotor helicopters, however, use counter-rotating rotors, each canceling out the other’s torque. Counter-rotating rotor blades will not collide with and destroy each other if they flex into…

• Helicopter Flying Handbookp. 2-15
  Chapter 2: Aerodynamics of Flight › Hovering Flight › Translating Tendency (Drift)

  Translating Tendency (Drift) During hovering flight, a single main rotor helicopter tends to move in the direction of tail rotor thrust. This lateral (or sideward) movement is called translating tendency. [Figure 2-27] To counteract this tendency, one or more ... following features may be used. All examples are for a counterclockwise rotating main rotor disk. Figure 2-27. A tail rotor is designed to produce thrust in a direction opposite torque. The thrust produced by the tail rotor is sufficient…

• Helicopter Flying Handbookp. 11-21
  Chapter 11: Helicopter Emergencies and Hazards › Recovery Technique (Uncontrolled Right Yaw) › Main Drive Shaft or Clutch Failure

  Main Drive Shaft or Clutch Failure The main drive shaft, located between the engine and the main rotor transmission, provides engine power to the main rotor transmission. In some helicopters, particularly those with piston engines, a drive belt is used ... clutch or belt has the same effect as an engine failure because power is no longer provided to the main rotor and an autorotation must be initiated. There are a few differences, however, that need to be taken into consideration…

• Helicopter Flying Handbookp. 2-25
  Chapter 2: Aerodynamics of Flight › Turning Flight

  Figure 2-45. Forces acting on the helicopter during turning flight. Autorotation is the state of flight where the main rotor disk of a helicopter is being turned by the action of air moving up through the rotor rather than ... engine power driving the rotor. In normal, powered flight, air is drawn into the main rotor disk from above and exhausted downward, but during autorotation, air moves up into the rotor disk from below as the helicopter descends. Autorotation…

• Helicopter Flying Handbookp. 4-6
  Chapter 4: Helicopter Components, Sections, and Systems › Main Rotor System › Tandem Rotor

  metal-to-metal contact of older bearings and the need for lubrication is eliminated in this design. Tandem Rotor Tandem rotor (sometimes referred to as dual rotor) helicopters have two large horizontal rotor assemblies; a twin rotor system, instead ... main assembly, and a smaller tail rotor. [Figure 4-10] Single rotor helicopters need an anti-torque system to neutralize the twisting momentum produced by the single large rotor. Tandem rotor helicopters, however, use counter-rotating rotors, with each canceling…

• Helicopter Flying Handbookp. 11-18
  Chapter 11: Helicopter Emergencies and Hazards › System Malfunctions › Loss of Tail Rotor Effectiveness (LTE)

  catastrophic. LTE is an aerodynamic condition and is the result of a control margin deficiency in the tail rotor. It can affect all single-rotor helicopters that utilize a tail rotor. The design of main and tail rotor blades ... will not nullify the phenomenon entirely. Translational lift is obtained by any amount of clean air through the main rotor disk. Chapter 2, Aerodynamics of Flight, discusses translational lift with respect to the main rotor blade, explaining that the more…