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incorporates the shutoff and selection features into a single valve. Large aircraft fuel systems have numerous valves. Most simply open and close and are known by different names related to their location and function in the fuel system (e.g., shutoff valve, transfer valve, crossfeed valve). Fuel valves can be manually operated, solenoid operated, or operated by electric motor. 

A feature of all aircraft fuel valves is a means for positively identifying the position of the valve at all times. Hand- 

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operated valves accomplish this through the use of detents into which a spring-loaded pin or similar protrusion locates when the valve is set in each position. Combined with labels and a directional handle, this makes it easy to identify by feel and by sight that the valve is in the desired position. [Figure 14-38]  Motor- and solenoid-operated valves use position annunciator lights to indicate valve position in addition to the switch position. Flight management system (FMS) fuel pages also display the position of the fuel valves graphically in diagrams called up on the flat screen monitors. [Figure 14-39]  Note that many valves have an exterior position handle, or lever, that indicates valve position. When maintenance personnel directly observe the valve, it can be manually positioned by the technician using this same lever. [Figure 14-40] 

## Hand-Operated Valves 

There are three basic types of hand-operated valves used in aircraft fuel systems. The cone-type valve and the poppet- type valve are commonly used in light general aviation aircraft as fuel selector valves. Gate valves are used on 

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