The drive system consists of two of which type of gearboxes?

The drive system's primary function is to convert engine power into usable drive to the rotor system, and this is accomplished through specific types of gearboxes designed for that purpose. Proprotor gearboxes are integral to the operation of rotorcraft, specifically in managing the distribution of power from the engines to the rotors while also controlling critical aspects such as speed, torque, and direction of rotation.

Proprotor gearboxes are designed to handle the unique demands of rotor systems, including the varying operating conditions they encounter during different flight profiles. Their construction allows for the absorption of loads from the rotors, which is essential for maintaining stability and ensuring efficient operation.

In contrast, transmission gearboxes typically refer to systems used in various vehicles, and while they may share some functional similarities with proprotor gearboxes, they are not specifically tailored for rotorcraft applications. Control gearboxes may be involved in adjusting rotor position or other control mechanisms but are not directly involved in the primary drive system. Electric gearboxes, while relevant in electric drive systems, do not relate directly to the traditional rotor systems found in conventional rotorcraft. Thus, proprotor gearboxes stand out as the correct answer, reflecting their vital role in the specific dynamics and requirements of rotorcraft operation.