The Rotor Brake Control has a specific configuration. When in the ON position, what does it prohibit?

When the Rotor Brake Control is in the ON position, it specifically prohibits the movement of Engine Control Levers (ECLs) past the crank position. This design is crucial for safety, as it ensures that the engines cannot be inadvertently engaged while the rotor brake is applied, which could lead to unintended rotor motion and result in an accident or injury. The control system is engineered to prevent any action that could compromise the safety of the pre-flight checks or preparations involving the rotor system.

The other options, while they present significant considerations, do not specifically relate to the direct function of the Rotor Brake Control in the ON position. For example, the state of the engine startup is not directly affected by the rotor brake in this context, as starting procedures may still be followed depending on the aircraft system's configuration or operational guidelines, mitigating confusion during engine operations.