The main transmission reduces the input RPM to the output RPM for the, main rotor, tail rotor, and accessories.

• A. Engines
• B. Nacelles, Antennas
• C. Main rotor, Tail rotor, and Accessories
• D. Hyd Pumps, Gearbox

Answer: (C)

The main idea is that the helicopter’s powertrain lowers engine speed to a level appropriate for turning the rotor blades and powering other systems. Engines run at high RPMs, but the rotors need a slower, high-torque output to generate lift and maintain control. The main transmission does this reduction and, in doing so, also drives the tail rotor and various accessories (like hydraulic pumps and generators) from the same gear system. This setup ensures the main rotor and tail rotor turn at the correct speeds while keeping essential systems powered. The other options don’t fit because engines don’t inherently reduce RPM, and nacelles or antennas aren’t the driven loads here; the phrase that includes the main rotor, tail rotor, and accessories captures exactly what the transmission feeds.