Hey, can anyone help me with this circuit picture, how does this electric circuit relate to the aircraft pic?


Can anyone tell me how each item relates to the other???

How could it be used on a typical aircraft system???????

please can someone help me out??? Explanations would be nice.


4 Answers

  • 1 decade ago
    Favorite Answer


    4 - Grounds

    1 - 12VDC Battery

    2 - Switches

    1 – Lamp

    1 – Bus Bar

    2 – CB’s

    1 – Motor

    1- Relay

    You have a battery, once the battery switch is closed the bus bar is hot (electrified). This will be indicated by the lamp on the bottom of the drawing. Then you have 2 CB’s and this are here to protect the wires (not the equipment). The second switch is used to energize (pull) the relay. This is done because the motor draws too much power (amps) and if you weren’t using a relay, the size of the switch and the gauge of the wires will be too large for the cockpit, not to mention the weight added. So instead you will use a .5 to 5 amp switch with a .5 to 5 amp breaker with wire between 10 to 16 AWG to energize the relay which will be located close to the motor. Once the relay closes the motor will be energized.

    By the drawing you can tell this is a large motor, like a starter an electric pump or even an air conditioner, because the use of the relay. Smaller motors like cockpit fans or avionic fans they are very small compared to a starter or an electric pump so the use of a relay is not necessary.

  • al b
    Lv 5
    1 decade ago

    this is a drawing showing a typical starter setup, using the airframe as common ground (-). The vertical component in the centre is your (+) positive bus from which everything draws it's power, It is hooked up to a battery, centre horizontal to the left and is activated by slecting the "master switch" shown in the "off" position between the battery and the buss, At the bottom of the bus, running horizontally to the left, is a light bulb that illuminates when the master switch is "on" and the "Bus" is "Hot" usually this is just a reminder to the pilot so the battery doesn't go flat when he isn't using the airplane. Running horizontally in the centre of the bus to the right, is the starter switch circuit. the first component is a circuit breaker, followed by a switch which must be "made" to complete the circuit which activateds a solenoid (the next component), to send power to the starter. the switch here is shown in the off position. At the top of the buss, headed right horizontally is the starter power circuit, it goes from the (+) bus, through the circuit breaker, to the solenoid switch, When the solenoid switch is closed ( by pushing the starter button) the power proceeds to the motor, making it turn.

    I hope this answers your question. This same cicuit could be any one of a number of systems, but usually the starter circuit is the only one that uses a solinoid to activate the motor.

  • 1 decade ago

    What you have pictured is an electric motor that is energized by a battery direct switch via a relay. An indicator light shows that the switch is selected on. Since the switch is not shown as a momentary connection (as in a starter, perhaps the diagram is too simple), one application could be a limited duty boost pump. On a DC9, a dc start pump is used to supply fuel pressure during APU start (or an engine start without an AC cart). When the ac generators come on line, the start pump is selected off. I flew a Piper Cherokee that had a similar arrangement, boost pump on during take-off and landing.

  • Anonymous
    1 decade ago

    A starter and a light telling the main bus is energized.

    Many turbine starters are not momentary contact.

    A boost pump is run direct from the switch on most light aircraft, but some use relays on larger aircraft.

    Notably missing is the master contacter between the batteries and the bus; it just shows a switch.

    Source(s): Certified aircraft mechanic
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