What components are involved in the nose gear up system?

The nose gear up system primarily involves components that work to retract the nose landing gear into the aircraft fuselage when in flight. The selector valve and actuating cylinders are crucial to this process.

The selector valve is responsible for directing hydraulic fluid to the actuating cylinders, allowing them to extend or retract the landing gear. The actuating cylinders, which are hydraulic or pneumatic devices, physically move the landing gear mechanism. When the pilot commands the retraction, the selector valve activates, and hydraulic pressure is applied to the actuating cylinders, causing the nose gear to retract.

The other options do not pertain to the nose gear up system. Fuel systems and engines are related to aircraft propulsion and operation, crash sensors and alarms are safety mechanisms that alert the crew of potential dangers, and landing gear and control surfaces, while related to aviation, do not specifically address the operation of the nose gear up system.