2 Electrical System 28 Volt DC Negative Ground Dual Alternator Dual BatteryThe system provides uninterrupted power for the avionics, flight instrumentation, lighting, and other electrically operated and controlled systems during normal operation.
3 Components Alternator 1 100 Amp 28 Volts Gear driven Internally rectifiedSelf exciting (requires battery voltage for field excitation in order to start operating)Can power M1, M2, and Essential buses*Click on diagram above to see actual picture of component
4 Components Alternator 2 70 Amp 28.75 Volts Belt Driven Internally rectifiedSelf exciting (requires battery voltage for field excitation in order start operating)Can Power M2 and Essential BusCannot power M1 Bus*Click on diagram above to see actual picture of component
5 Components Battery 1 Aviation grade 12-cell 24-Volt 10 amp-hour Mounted on right firewallCharged by Alt 1 through Main Dist 1 BusCan supply power to M1, M2, and Essential Distribution Buses*Click on diagram above to see actual picture of component
6 Components Battery 2 Two 12 volt batteries in series = 24 volts total 7 amp-hourSealed lead acidLocated in the tail of the airplane below the parachute canisterCharged by Alt 1 or Alt 2 from a circuit breaker on the Essential Distribution BusPowers Essential Dist Bus only due to isolation diodes*Click on diagram above to see actual picture of component
7 Components Master control Unit (MCU) Controls: ALT 1, ALT 2, starter, landing light, external power and generation functionsProvides:ALT 1 and ALT 2 voltage regulation and overvoltage protectionExternal power reverse polarity protectionElectrical health annunciations to the Integrated Avionics System (PFD)*Click on diagram above to see actual picture of component
8 Components Isolation Diodes Electrical “check valves” or “one way street”Electricity can only flow in the direction of the arrowsPrevents ALT 2 from powering Main Dist Bus 1Prevent s BAT 2 from powering Main Dist Bus 1 and Main Dist Bus 2Check operation of diodes during preflight by turning only BAT 2 on and then verifying flap position light is out
9 Controls Electrical System Control Master Switches Rocker type electrical system master switches are located in front of the pilot on the bolster panel for easy access.Circuit Breaker PanelLocated on left side of center consoleAlternating gray collars on the CB panel provides easier recognition of circuit breakersCircuit breakers are re-settable (once)
11 Normal Operations ALT 1-28 volts Supplies power to M1 Charges BAT 1 Supplies power to M2 and Ess Bus because it operates at a higher voltageWater analogy- Think of higher voltage as higher pressure (water) running through the wires (pipes). The higher voltage (pressure) of ALT 2 prevents ALT 1 from powering M2 and Ess BusCharges BAT 2Diodes prevent ALT 2 from powering M1Click on diagram to see “normal” engine indications*Click on diagram above to see normal engine indications during flight
13 Abnormal Operations ALT 1 Failure Steady “ALT 1” on PFD Verify on MFD engine pageALT 1 (A)- 0ALT 2 (A) - NormalBATT 1 (A) discharging -5How long will it last?How to reduce drain on BATT 1?Ess (V)- ALT 2M1 (V)-Bat1M2 (V)- ALT 2
14 Abnormal Operations ALT 1 failure BAT 1 powers M1 items Landing lightAC COMPRCabin FanAC CONDYaw servoEVS Camera12V DC outlet (in armrest)MFD#1 – *MFD will be powered by ALT 2 through MFD#2 CBTurn off these items to reduce discharge of BATT 1 if ALT 1 failsALT 2 continues to power M2 and Ess Bus itemsComplete ALT 1 failure checklist to attempt reset of ALT 1
15 Abnormal Operations ALT 2 Failure Steady “ALT 2” on PFD Verify on MFD engine pageALT 1 (A)ALT 2 (A)- 0BATT 1 (A)ESS (V)-28M1 (V)- 28M2 (V)- 28ALT 1 will power all three main distribution buses after ALT 2 fails
16 Abnormal Operations ALT 2 Failure ALT 1 will power the entire electrical systemFollow ALT 2 failure checklist and try to reset ALT 2ALT 2 required for IFR flight
17 Ground Service Receptacle Allows connection of an External Power Unit for cold weather starting and maintenanceBAT 1 switch must be on to deliver power to systemBAT 1 must have power for the contactor to closeRecharging of BAT 1 should not be accomplished through use of an External Power UnitExternal Power Unit voltage must be regulated to no higher than 28 VDC
19 QuestionDuring the preflight check, why do we turn BAT 2 on only initially?Allows the pilot to check voltage (health) of BAT 2To verify the isolation diodes are operating correctly- flap light out
20 ScenarioDuring the preflight check with only BAT 2 on, you noticed the flap light was on. Would you still depart for your flight? Why or why not?The isolation diodes are not working correctly. ALT 2 would then try to power the entire electrical system. ALT 2 is 70 amps and not powerful enough to power Main BUS 1 itemsThe pilot would be unable to isolate items on the Essential Dist Bus in an emergency. BAT 2 would try to power Main Distribution Bus 1 and Main Distribution Bus 2
21 ScenarioLooking at your engine data in cruise, this is what you see. Has anything failed? What are you going to do?ALT 1 has failed. Perform ALT 1 failure checklist.
22 ScenarioLooking at your engine data in cruise, this is what you see. Has anything failed? What are you going to do?ALT 2 has failed. Perform ALT 2 failure checklist.
23 ScenarioLooking at your engine data in cruise, this is what you see. Has anything failed? What are you going to do?Nothing has failed, ALT 1 is still working because M1 is still at 28 V. All items on M1 bus are currently off, so ALT 1 (A) indicate low. Turn on your landing light, cabin fan, and ALT 1 amperage should increase.
24 ScenarioYou are 30 minutes out from your destination and you begin to smell something. After investigating you see white smoke rising from the circuit breaker panel.What is happening?What will you do?Will your procedure be different in VMC vs. IMC? Day vs. Night?Intent of Slide: Introduction to electrical fires and the situation it presents.Key Questions:How does the visual condition you are in factor in to the procedure you follow? VFR, stay VFRWhat instrumentation remains if you have no electrical power? – Standby Airspeed and AltimeterOther Considerations:Night flight – consider turning off ALT 1 and BAT 1 first and see if that fixes the problem. This will keep your essential bus powered if the problem was originally on the main bus.Compare Smoke and Fume Elimination vs. Cabin Fire in Flight checklists. – Determination of which checklist to use is based on whether the cause of the fire readily apparent.24