What are the three sections of the transmission?

• A. Accessory gearbox, reduction gearbox (main case) and mast and bell housing (upper case)
• B. Inner case, outer case and shaft case
• C. Locking case, main case and upper case
• D. Main transmission, engine gearbox and tail gearbox

Answer: (A)

The correct answer focuses on the specific components that make up the transmission system in the TH-73A helicopter. The transmission is a crucial part of the helicopter's drivetrain, tasked with transferring power from the engine to the rotor system while adapting for speed and torque.

In this context, the accessory gearbox serves essential functions such as supplying power to various systems and components, including hydraulic pumps and electrical generators. The reduction gearbox, or main case, functions to decrease the rotor speed from the engine to the appropriate levels for efficient rotor operation. Additionally, the mast and bell housing, or upper case, plays a critical role in supporting the rotor system and maintaining alignment and stability.

Together, these components ensure that the power generated by the engine is effectively and safely transmitted to the rotor blades, enabling flight. Understanding these sections is vital for maintaining and troubleshooting the helicopter's operational systems.