expect. Loss of the alternator or generator causes the loadmeter to indicate zero. incorporated to prevent excessive voltage  which may damage the electrical components. The bus bar serves to distribute the current to the various electrical com- ponents of the helicopter. Electrical switches are used to select electrical compo- nents. Power may be supplied directly to the component or to a relay  which in turn provides power to the  component. Relays are used when high current and/or heavy electrical cables are required for a particular com- ponent  which may exceed the capacity of the switch. A battery is mainly used for starting the engine. In addition  it permits limited operation of electrical components  such as radios and lights  without the engine running. The battery is also a valuable source of standby or emergency electrical power in the event of alternator or generator failure. Circuit breakers or fuses are used to protect various electrical components from overload. A circuit breaker pops out when its respective component is overloaded. The circuit breaker may be reset by pushing it back in  unless a short or the overload still exists. In this case  the circuit breaker continues to pop  indicating an elec- trical malfunction. A fuse simply burns out when it is overloaded and needs to be replaced. Manufacturers usually provide a holder for spare fuses in the event one has to be replaced in flight. Caution lights on the instru- ment panel may be installed to show the malfunction of an electrical component. An ammeter or loadmeter is used to monitor the electrical current within the system. The ammeter reflects current flowing to and from the battery. A charging ammeter indicates that the battery is being charged. This is normal after an engine start since the battery power used in starting is being replaced. After the battery is charged  the ammeter should sta- bilize near zero since the alternator or generator is supplying the electrical needs of the system. A dis- charging ammeter means the electrical load is exceeding the output of the alternator or generator  and the battery is helping to supply electrical power. This may mean the alternator or generator is mal- functioning  or the electrical load is excessive. A loadmeter displays the load placed on the alternator or generator by the electrical equipment. The RFM for a particular helicopter shows the normal load to Most helicopters  other than smaller piston powered helicopters  incorporate the use of hydraulic actuators to overcome high control forces. [Figure 5-13] A typi- cal hydraulic system consists of actuators  also called 5-9 Figure 5-13. A typical hydraulic system for helicopters in the light to medium range is shown here. HYDRAULICS Pressure Return Supply ScupperGLYPH<.notdef> Drain Vent Reservoir Pump PressureGLYPH<.notdef> RegulatorGLYPH<.notdef> Valve QuickGLYPH<.notdef> Disconnects Filter SolenoidGLYPH<.notdef> Valve ServoGLYPH<.notdef> Actuator GLYPH<.notdef> LateralGLYPH<.notdef> Cyclic ServoGLYPH<.notdef> Actuator GLYPH<.notdef> Fore andGLYPH<.notdef> AftGLYPH<.notdef> Cyclic ServoGLYPH<.notdef> Actuator GLYPH<.notdef> Collective PilotGLYPH<.notdef> Input RotorGLYPH<.notdef> Control