transport category aircraft as shutoff valves. While many are  motor operated, there are several applications in which gate  valves are hand operated.  A cone valve, also called a plug valve, consists of a machined  valve housing into which a rotatable brass or nylon cone  is set. The cone is manually rotated by the pilot with an  attached handle. Passageways are machined through the  cone so that, as it is rotated, fuel can flow from the selected  source to the engine. This occurs when the passageway  aligns with the desired fuel input port machined into the  housing.  Figure 14-41  shows a cross sectional view of a cone  valve. The cone can also be rotated to a position so that the  passageway(s) does not align with any fuel input port. This  is the fuel OFF position of the valve.  Selector valves are also commonly the poppet type. As the  handle is rotated in this valve, a cam on the attached shaft lifts  the poppet off the seat of the desired port being selected. At  the same time, spring-assisted poppets close off the ports that  are not selected. Detents lock the valve into position when  the cam pushes a poppet fully off of its seat. There is also a  positive detent when the cam engages none of the poppets,  which is the OFF position of the valve.  [Figure 14-42]  Note  that a similar mechanism is use in some selector valves, but  balls are used instead of poppets.  14-26 Figure 14-42.  The internal mechanism of a poppet-type fuel  selector valve.  Figure 14-40.  This motor-operated gate valve has a red position  indicating lever that can be used by maintenance personnel to  identify the position of the valve. The lever can be moved by the  technician to position the valve. Figure 14-39.  The graphic depiction of the fuel system on this  electronic centralized aircraft monitor (ECAM) fuel page includes  valve position information. Figure 14-41.  A cone valve is open when the bored cone aligns the  inlet and the outlet ports. It shuts off the flow when the un-bored  portion of the cone is aligned with the inlet port(s).  Poppet Valves Cone Valves Cam moved by selector valve handle From reserve tank From tank 1 From tank 2 To main strainer Detent plate Valve housing Inlet port Bored  passageway Brass cone Outlet port