swash plate and the rotating swash plate. [Figure 5-8] The stationary swash plate is mounted around the main rotor mast and connected to the cyclic and collective controls by a series of pushrods. It is restrained from rotating but is able to tilt in all directions and move verti- cally. The rotating swash plate is mounted to the sta- tionary swash plate by means of a bearing and is allowed to rotate with the main rotor mast. Both swash plates tilt and slide up and down as one unit. The rotat- ing swash plate is connected to the pitch horns by the pitch links. The fuel system in a helicopter is made up of two groups of components: the fuel supply system and the engine fuel control system. The supply system consists of a fuel tank or tanks, fuel quantity gauges, a shut-off valve, fuel filter, a fuel line to the engine, and possibly a primer and fuel pumps. [Figure 5-9] Most non-gravity feed fuel systems contain both an electric pump and a mechanical engine driven pump. The electrical pump is used to maintain positive fuel pressure to the engine pump and also serves as a backup in the event of mechanical pump failure. The electrical pump is controlled by a switch in the cockpit. The engine driven pump is the primary pump that sup- plies fuel to the engine and operates any time the engine is running. flow to the engine in the event of an emergency or fire. The shut-off valve remains in the open position for all normal operations. A fuel filter removes moisture and other sediment from the fuel before it reaches the engine. These contami- nants are usually heavier than fuel and settle to the bot- tom of the fuel filter sump where they can be drained out by the pilot. The fuel tanks are usually mounted to the airframe as close as possible to the center of gravity. This way, as fuel is burned off, there is a negligible effect on the cen- ter of gravity. A drain valve located on the bottom of the fuel tank allows the pilot to drain water and sedi- ment that may have collected in the tank. A fuel vent prevents the formation of a vacuum in the tank, and an overflow drain allows for fuel to expand without rup- turing the tank. A fuel quantity gauge located on the pilot’s instrument panel shows the amount of fuel measured by a sensing unit inside the tank. Some gauges show tank capacity in both gallons and pounds. Some fuel systems contain a small hand-operated pump called a primer. A primer allows fuel to be pumped directly into the intake port of the cylinders prior to engine start. The primer is useful in cold weather when fuel in the carburetor is difficult to vaporize. The purpose of the fuel control system is to bring out- side air into the engine, mix it with fuel in the proper proportion, and deliver it to the combustion chamber. The fuel travels from the fuel tank through a shut-off valve, which provides a means to completely stop fuel 5-6 ENGINE FUEL CONTROL SYSTEM FUEL SUPPLY SYSTEM FUEL SYSTEMS Figure 5-9. A typical gravity feed fuel system, in a helicopter with a reciprocating engine, contains the components shown here. Figure 5-8. Collective and cyclic control inputs are transmit- ted to the stationary swash plate by control rods causing it to tilt or to slide vertically. The pitch links attached from the rotating swash plate to the pitch horns on the rotor hub transmit these movements to the blades. StationaryGLYPH<.notdef> SwashGLYPH<.notdef> Plate PitchGLYPH<.notdef> Link RotatingGLYPH<.notdef> SwashGLYPH<.notdef> Plate ControlGLYPH<.notdef> Rod Throttle Low LevelGLYPH<.notdef> WarningGLYPH<.notdef> Light Vent Fuel QuantityGLYPH<.notdef> Gauge MixtureGLYPH<.notdef> Control FuelGLYPH<.notdef> Shutoff Primer Tank Valve Carburetor FuelGLYPH<.notdef> Strainer Primer NozzleGLYPH<.notdef> at Cylinder