1. AVIATION 325
ELECTRICAL SYSTEM

2. Electrical System General Description Sources of Electrical Power
Power Distribution
Normal Conditions
Abnormal Conditions

3. General Description 14 Volt Dual Fed Split Bus Negative Ground
DC System

4. Sources of Electrical Power
Battery
External Power Unit
Alternators

5. Battery 12 Volt, 35 Amp-Hr Lead Acid Drains & Vents Recharge
Battery Bus
Battery Master Switch
Battery Contactor
Starter Contactors
Tie Bus (60 Amps)

6. External Power Receptacle
Location
Energizes
External Power Contactor
Starter Contactors
Tie Bus
Prior to Energizing
Battery Master Off
All Electrical Equipment Off

7. Alternators 14 Volts AC, 70 Amp Rectifier (AC to DC) Belt Driven
Alternator Field
Main Bus
5 Amps
Alternator Switch
Location

8. Alternators Alternator Control Unit Voltage Regulator
Over Voltage Relay
Load Sharing

9. Alternators An overvoltage relay if output exceeds 17 volts.
Voltage regulator maintains effective load sharing.
Location

10. System Monitors ALT Annunciator Light - ALT Switch Turned Off
Over Voltage Relay
Low Bus Annunciator less than 17.5 volts
Ammeter
Load Meter
Circuit Breakers

11. Power Distribution Battery Bus Tie Bus Main Bus Non-Essential Bus
Avionics Bus

12. Battery Bus Hot Wired Fuses Equipment Clock Flight Time Hour Meter
Maintenance Time Hour Meter
Heater Hour Meter

13. Power Distribution Tie Bus Main Bus Non Essential Bus
Essential Electrical Components
Tie Bus - Two 60 Amp Circuit Breakers
Non Essential Bus

14. Power Distribution
Avionics Bus #1
Avionics Bus #2
Radio Master

15. Circuit Breaker Panel

16. Circuit Breaker Panel

17. Abnormal Conditions Alternator Failure Circuit Breaker Over Voltage
Mechanical Failure
ALT Light

18. Abnormal Conditions Single Alternator Failure Alt Annunciator Light
Ammeter
Reduce Load
Dual Alternator Failure
Alt Annunciator
Lo Bus
Battery
Load Shedding

19. Electrical Failure Scenario
Okay,you loose your alternators, and you are flying on battery power alone. You’ve just departed on an IFR flight , but the weather is still VFR – you haven’t hit IMC yet. What do you do?
Turn back right?

20. Quiz
The over voltage relay will take its respective alternator offline if . . .
A. the electrical system’s voltage exceeds 17 volts.
B. the alternator’s output voltage exceeds 17 volts.

21. end