The main transmission case (RGB) is a ___-stage reduction gear box.

• A. Single
• B. Two
• C. Three
• D. Four

Answer: (B)

The main transmission case, also known as the reduction gearbox (RGB), is classified as a two-stage reduction gearbox in the context of the TH-73A helicopter. The two-stage design is essential for reducing the high rotational speeds of the engine to a more manageable speed for the rotor system, allowing for efficient power transfer while maintaining optimal performance and reliability.

In a two-stage reduction gearbox, the gear ratio is achieved in two separate stages, which helps to distribute the stress and heat more effectively during operation. This design reduces the size and weight of the gearbox while still ensuring it can handle the power requirements of the helicopter. It also contributes to smoother operation and can enhance the overall safety and durability of the transmission system.

Understanding this mechanism is crucial for those working with the TH-73A, as it emphasizes the importance of the gearbox in the helicopter's propulsion system and helps clarify how various components interact to achieve desired flight characteristics.