Which action is NOT used to close the hydraulic shutoff valves?

The action that is not used to close the hydraulic shutoff valves is the utilization of the throttle control. In aviation systems, hydraulic shutoff valves are typically closed for safety reasons, such as when there is a fire detected in the engine compartment.

Pressing the L/R Engine Fire Switch is designed to automatically close the hydraulic shutoff valves for the corresponding engine as part of the emergency response protocols. Similarly, using the L/R Hydraulic Valve Close Switch is a direct method to command the closure of these valves. Manual valve manipulation also allows an operator to close the valves directly in case automated systems are unavailable or not functioning.

In contrast, throttle control is primarily used to manage engine power and thrust; it does not have a function related to the closing of hydraulic shutoff valves. Instead, the throttle affects the aircraft's engine output rather than hydraulic systems, making it unrelated to valve operations.