HI.XI.B.K6

From the FAA library

• Helicopter Flying Handbookp. 4-11
  Chapter 4: Helicopter Components, Sections, and Systems › Transmission System › Dual Tachometers

  Main Rotor Transmission The primary purpose of the main rotor transmission is to reduce engine output rpm to optimum rotor rpm. This reduction is different for the various helicopters. As an example, suppose the engine rpm of a specific helicopter ... rotor speed of 450 rpm would require a 6:1 reduction. A 9:1 reduction would mean the rotor would turn at 300 rpm. Dual Tachometers Most helicopters use a dual-needle tachometer or a vertical scale instrument to show…

• Helicopter Flying Handbookp. 11-2
  Chapter 11: Helicopter Emergencies and Hazards › Autorotation

  Therefore, autorotative descents at very low or very high airspeeds are more critical than those performed at the minimum rate of descent airspeed. Refer to the height/velocity diagram discussion in Chapter 7, Helicopter Performance. Each type of helicopter ... specific airspeed and rotor rpm at which a power-off glide is most efficient. The specific airspeed is somewhat different for each type of helicopter, but certain factors affect all configurations in the same manner. In general, rotor rpm maintained…

• Helicopter Flying Handbookp. 11-16
  Chapter 11: Helicopter Emergencies and Hazards › Low Rotor RPM and Rotor Stall

  Other causes of a power-on low rotor rpm condition include the pilot rolling the throttle the wrong way in helicopters not equipped with a governor or a governor failure in helicopters so equipped. As the rpm decreases, the amount ... horsepower the engine can produce also decreases. Engine horsepower is directly proportional to its rpm, so a 10 percent loss in rpm due to overpitching, or one of the other scenarios above, will result in a 10 percent loss…

• 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…

• Pilot's Handbook of Aeronautical Knowledgep. 5-23
  Chapter 5: Aerodynamics of Flight › Aerodynamic Forces in Flight Maneuvers › Forces in Turns

  that the vertical component of lift must be equal to the weight to maintain altitude. At a given airspeed, the rate at which an aircraft turns depends upon the magnitude of the horizontal component of lift. It is found that ... horizontal component of lift is proportional to the angle of bank—that is, it increases or decreases respectively as the angle of bank increases or decreases. As the angle of bank is increased, the horizontal component of lift increases, thereby…