PH.I.G.K1d

From the FAA library

• Helicopter Flying Handbookp. 4-10
  Chapter 4: Helicopter Components, Sections, and Systems › Transmission System

  Transmission System The transmission system transfers power from the engine to the main rotor, tail rotor, and other accessories during normal flight conditions. The main components of the transmission system are the main rotor transmission, tail rotor drive system, clutch ... freewheeling unit. The freewheeling unit or autorotative clutch allows the main rotor transmission to drive the tail rotor drive shaft during autorotation. In some helicopter designs, such as the Bell BH-206, the freewheeling unit is located in the accessory…

• Helicopter Flying Handbookp. 4-8
  Chapter 4: Helicopter Components, Sections, and Systems › Antitorque Drive Systems

  Antitorque Drive Systems The antitorque drive system consists of an antitorque drive shaft and a antitorque gearbox mounted at the end of the tail boom. The drive shaft may consist of one long shaft or a series of shorter shafts ... connected at both ends with flexible couplings. This allows the drive shaft to flex with the tail boom. The tail rotor gearbox provides a right-angle drive for the tail rotor and may also include gearing to adjust the output…

• 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 ... instead of a drive shaft. A failure of the drive shaft 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…

• Helicopter Flying Handbookp. 4-7
  Chapter 4: Helicopter Components, Sections, and Systems › Antitorque System

  maintain directional control whenever the main rotor torque changes, or to make heading changes while hovering. Most helicopters drive the tail rotor shaft from the transmission to ensure tail rotor rotation (and hence control) in the event that the engine ... quits. Usually, negative antitorque thrust is needed in autorotations to overcome transmission friction. Figure 4-12. Freewheeling unit in normal drive position and freewheeling position. Note that in the top example, the engine output shaft (inner part) drives the rotor…

• Helicopter Flying Handbookp. 4-12
  Chapter 4: Helicopter Components, Sections, and Systems › Transmission System › Belt Drive Clutch

  Belt Drive Clutch Some helicopters utilize a belt drive to transmit power from the engine to the transmission. A belt drive consists of a lower pulley attached to the engine, an upper pulley attached to the transmission input shaft ... aircraft utilize a clutch for starting. This allows the engine to be started without requiring power to turn the transmission. One advantage this concept has is that without a load on the engine starting may be accomplished with minimal throttle…

• Helicopter Flying Handbookp. 4-13
  Chapter 4: Helicopter Components, Sections, and Systems › Transmission System › Centrifugal Clutch

  springs hold the shoes in, so there is no contact with the outer drum, which is attached to the transmission input shaft. As engine speed increases, centrifugal force causes the clutch shoes to move outward and begin sliding against ... outer drum. The transmission input shaft begins to rotate, causing the rotor to turn slowly at first, but increasing as the friction increases between the clutch shoes and transmission drum. As rotor speed increases, the rotor tachometer needle shows…