What is the primary purpose of the transmission?

• A. Increase engine RPM
• B. Reduce engine RPM, change direction of drive
• C. Stabilize flight controls
• D. Maximize engine power output

Answer: (B)

The primary purpose of the transmission in the TH-73 helicopter is to reduce engine RPM and change the direction of drive. The transmission is a crucial component that connects the engine to the rotor system and is responsible for managing the engine's power output.

In a helicopter, the engine operates at a higher RPM than what is needed for the rotor blades to turn effectively at safe operating speeds. Hence, the transmission reduces this engine RPM to a more suitable level for rotor operation, allowing for optimal performance during various flight conditions. Additionally, the transmission can change the direction of drive to facilitate the proper rotation of the main rotor and tail rotor, which is essential for controlling the helicopter's flight direction and stability.

This function is vital for flight safety and efficiency, as it enables the helicopter to fly smoothly while maintaining sufficient power and control.