P-3 Electrical Procedures

  1. LOSS OF MEAC (indications and notes)
    • Indication: R HTR OUT, RAWS, Pilot Gyro flag, HSI off flags
    • Automatic switchover to FEAC for pilot and copilot red instrument lights, FDIs, and vertical gyro. Power sensed by Essential Indicating and lighting cont CB, power routed to the Attitude Ind and V. Gyro on FEAC.
    • If MEDC still powered, must pull power sensing CB on MEDC to regain SEAC when engine is selected.
    • Information displayed on the copilot FDI with Inertial 2 selected will be unreliable because of loss of synchro-excitation voltage. Standby Gyro shall be selected by both pilot and copilot
    • If the generator switch must be left in the OFF position because of a generator malfunction and the generator mechanical failure light is on (steady or intermittent), perform Emergency Shutdown procedure.
    • Cause: Primary Drive end bearing has failed (aux bearing is under a load).
    • H - uncover boost Handles
    • E - Essential bus monitoring switch off if lose generator
    • L - Lighting prepared: Utility lights and Flashlights
    • P - Proceed VFR if poss, if destination IFR consider VFR alt
    • L - Load closely monitored, Load monitoring with prop/emp
    • S - Secure all nonessential equipment and lights
    • D - Deice operations monitored, prop/emp not simultaneous
    • unless required by severity of icing conditions
    A tripped GEN 4 AUX CONT CB (FEDC) will disable gen 4 from assuming any part of the aircraft electrical load and does not cause the gen 4 OFF light to illuminate. Should an emergency occur resulting in the loss of either gen 2 or 3 at this time, the entire electrical load will be assumed by the remaining generator and load monitoring will be activated if the prop or emp deice systems are utilized.
  5. Operation with Failure of All Generators
    • H - boost handles pulled
    • E - Ess Bus Monitoring Switch OFF
    • L - Utility and flashlights as needed
    • P - Partial panel. Lost navaids, comms, flaps, deice. TIT by select
    • L - Land ASAP, considering Wx, Runway, Terrain for landing
    • E - Emergency landing gear ext with boost-out landing
    • A - Airbrakes available
    • D - No ground range until less than 125 knots (Caution)
    • 1. Generator switch - OFF
    • 2. Gen cont CB for respective generator (MEDC) pull and reset
    • 3. Gen switch - ON
    • Warning: A generator light that stays on steady may be indicative of a feeder fault, supervisory panel malfunction, generator flywheel diode malfunction, or gen bearing failure.
    • Note: If the generator light goes out momentarily and comes back on, the generator has a recurring malfunction.
    • 4. Generator switch - OFF
    • 5. Continue engine operation. The mission should be aborted
    • Note: Ensure GEN 4 AUX CONT and GEN 4 TRANS circuit breakers are set appropriately.
    • Tech: Check Big 4, Use restoring elect pwr for Bus Loss
  7. Use of APU in Flight
    • Loss of any two engine-driven generators. Alt < 20,000 feet, Airspeed < 225 knots.
    • M - monitor all nonessential equipment (to prevent overloading)
    • G - APU Gen switch - OFF
    • B - fuel Boost pump - ON (crossfeed if required)
    • A - In flight arm switch - ARMED
    • M - MDC powered? if not Boost out, pull TR3
    • S - APU start switch - START, release to ON
    • O - After APU RPM has stabilized, turn the APU gen switch
    • ON
    • T - TR3 reset, boost back on
  8. Partial load monitoring
    • Single engine-driven generator or APU only < 8000’
    • (APU and GEN 4 is single generator)
    • Propeller deice or empennage deice activated
    • Feeders - Bus A and Main DC electronic feeders
    • Heaters - side windshield heat, floor and wall heaters
    • Eaters - galley power
    • Feeders:
    • HF-2, UHF-2, ADF, Marker beacons, Autopilot, Radar, INS-2
    • Indications: Flashing RAWS (autopilot warning)
    • Copilot GYRO FLAG (INS-2)
  9. Full Load Monitoring
    • APU only, above 8000 feet
    • regardless of prop or emp deice
    • Feeders, Heaters, Eaters +
    • Hydraulic pump 1A
    • Empennage Deice
    • Can regain Empennage Deice with Override switch bust must manually monitor an equivalent load:
    • #1 and #2 Hydraulic pumps (boost out)
    • three fuel boost pumps
    • cabin exhaust fan
    • Monitor continues on descent thru 8000’ because of holding relay
    • unless both prop and emp deice are both turned off momentarily
    • Indications: RAWS warning, Hyd Press 1A, CP Gyro Flag
  10. GEN 2, 3, 4 OR APU GEN OFF light
    • Use reset procedure, or place associated BUS MONITORING switch on. If a generator light remains on steady throughout reset procedure, or goes out momentarily and comes back on, mission should be aborted
    • Tech: Check Big 4, look at engine. On ground, try shift up and down. Do not shut down and restart, may cover up a feeder fault. Can swap sup panel cables to troubleshoot sup panels – but run the chance of burning up another sup panel
  11. GEN light NOTES and CAUTIONS
    • Caution: Gen sup panels shall not be exchanged until appropriate maintenance actions are performed
    • Note: Ensure GEN 4 AUX CONT and GEN 4 TRANS cbs are set appropriately.
    • Note: If the APU Gen Cont cb is out, APU GEN OFF light will be on. Automatic load monitoring above 8,000ft will be disabled, however, the generator will assume the load.
  12. Run-around Feeder Failure
    Tech: Loose that priority for busses. ie if Gen #2 feeder pops, Gen 4 will power FEAC. If Gen 4 feeder pops, just lose that backup.
  13. Run around relay failures
    • Relay #1: Pull run-around feeders #2 and #4. MEAC will be powered by Bus A, FEAC will be powered by Gen 3
    • Relay #2: Pull run-around feeders #2, #4 & #3. MEAC and FEAC will be powered by Bus A with no backup
  14. Essential AC Bus Relay Failure
    • #1: Essential Bus Monitoring Switch OFF will remove ground. Pull ESS BUS CB on Bus A to remove power. MEAC will be lost
    • Monitor: ESS BUS MON switch OFF to remove ground, Pull GEN #2, #4, #3 feeders to remove power. MEAC will be lost, FEAC powered by Bus A with no backup
    • #2: Pull GEN #2, #4, #3 feeders and ESS BUS CB on BUS A to remove power. MEAC and FEAC will be lost
  15. Transformer Rectifier Overheat Light ON
    • TR overheated (150?C).
    • Pull respective CB
    • No. 3 in flight station (MEAC)
    • No 1 on MLC (Bus A – 1 Lower)
    • No 2 on MLC (Bus B – 3 Lower)
    • Tech: Ensure other TR is carrying a load or anticipate a bus loss on MDC/EMDC. Can check CB for other TR if no load.
  16. EXTERNAL PWR AVAILABLE light ON (neon)
    • Indicates that electrical power is connected to the aircraft
    • Light will glow whether on not external power is selected
    • Tech: With thumbs up from the lineman, place external power switch on. May need to reset to get power.
  17. EXTERNAL PWR AVAILABLE light ON (neon) but no power into aircraft
    • R – Reset the external power switch
    • U – Check nosegear uplock position
    • B – Check Battery condition
    • E – Check external power control circuit breaker (GOB)
    • R – Check No. 4 Runaround Feeder CB
    • B – Battery
    • E – External power reset
    • E – External power CB (GOB)
    • N – Nosegear uplock
    • 4 – No. 4 runaround feeder CB
  18. External power available light ON partial power into aircraft
    • Check:
    • 3 – TR-3 CB
    • 2 – Essential DC Feeder #2 (MEDC)
    • 1 – MEAC Ganged CB (behind copilot)
    • Switch – MEAC Buss Monitoring Switch
  19. Buss Loss (technique)
    • Bus A – Copilot select Stby Gyro
    • Bus B – Uncover Boost handles (loss of 1A and 2)
    • On ground – secure ground AC (refer fans inop)
    • Use restoring electrical power checklist to cleanup
    • LOSS of SEDC – Cycle TDs!!
  20. RACK OVERHEAT light ON (135?F)
    • Initiate fire of unknown origin procedures. Locate overheated electronics bay(s) by illuminated individual bay overheat lights(s). Provide required cooling or secure equipment as necessary.
    • Cause: rack overheat condition, MDC failure. ASH-33 (DMTS) will cause a rack overheat indication when the system is initially turned on, or will illuminate continuously when a loss of airflow is detected.
    • Tech: Have IFT check the tape drive and switch.
  21. Gen Off Light Probably Cause
    • Generator failure
    • off frequency
    • overvoltage
    • undervoltage
    • feeder fault
    • supervisory panel failure,
    • transfer relay 2 or 3 failure, or
    • associated bus monitoring switch OFF.
  22. MEAC (SOF) Loads
    • Instrument Bus #1 and #2
    • 28 Volt FWD Lighting Bus (R Heater Out Light)
    • Electronics
    • Aux Vent Actuator TD Control
    • EFDI – FEAC backup SHP
    • EHSI – No Backup Stanby Gyro
    • Fuel Crossfeed Windshield Wipers
    • Fuel Quantity Indicators Windshield Heat
    • Ice Detector Xfmr Rectifier #3
    • Landing Lights
    • Oil Cooler Flap Control
    • RAWS 1 and 2
  23. 28 Volt FWD Lighting Bus
    • RH Pitot Heater
    • C/B Panel Red Edge Lights
    • Dome and Reading Lights
    • Taxi Lights
    • Wheel Well Lights
    • Wing and Tail Lights
  24. MEAC Elecronics (SOF)
    • GPS
    • HF-1
    • RINU
    • TACAN
    • UHF-1
    • VHF (ARC-101)
    • VOR-1 and 2 (ARN-87)
  25. Instrument Bus #1 (MEAC)
    • Bleed Air Manifold Pressure Indicator
    • Left EDC Air Pressure Indicator
    • Flap Position Indicator
    • Hydraulic Pressure Indicator #1 System
    • Normal Brake Pressure Indicator
    • Oil Cooler Flap Position Indicator (#1 and #4)
    • Oil Pressure Indicator (#1 and #4)
  26. Instrument Bus #2 (MEAC)
    • Right EDC Pressure Indicator
    • Fuel Crossfeed Manifold Pressure
    • Hydraulic Pressure #2 System
    • Emergency Brake Pressure
    • Oil Cooler Flap Position (#2 and #3)
    • Oil Pressure Indication (#2 and #3)
  27. BUS A (SOF Loads)
    • Parting Strips (Emp Deice)
    • Feather Motors (#2, #3 primary; Alternate for #1 and #4)
    • FWD Fuel Transfer Pump
    • Fuel Boost Pumps #1 and #3
    • Fuel Dump Pump
    • Fuel Flow Indicator
    • Fuel Qty Panel (fueling panel)
    • Hyd Pump #1
    • INS-2
    • Prop Sync
    • Side Windshield Heat
    • TR #1
  28. Electronic Feeders (Bus A) SOF items
    • F-2
    • UHF-2
    • UHF-DF
    • Autopilot
  29. FEAC
    • Pitot Heater (LH)
    • Outflow Valve
    • Standby Gyro (backup Power)
    • Standby Attitude Indicator (p-nut gyro)
    • FDI (backup Power)
    • IFF Transponder
    • Radar Altimeter
    • Essential Lighter (backup Power)
  30. Bus B
    • Aft fuel transfer pump
    • Cabin exhaust fan
    • Emp Deice (Cycling strips)
    • Feather Pumps (#1 and #4)
    • Fuel Boos Pumps (#2 and #4)
    • Heat Exchanger Fans
    • Hyd pumps #1A and #2
    • Prop Deice Power
    • Strobe Lights
    • TR #2
    • Floor and Wall Heaters, Galley Power
  31. Transfer Relay 2a
    • Connects Gen 2 to Bus A
    • #2 Sup panel ACR
  32. Transfer Relay 2b
    • Connects alternate generator to Bus A
    • Bus A cont - MEDC
  33. Transfer Relay 3a
    • Connects Gen 3 to Bus B
    • #3 Sup panel ACR
  34. Transfer Relay 3b
    • Connects alternate generator to Bus B
    • Bus B cont - MEDC
  35. Transfer Relay 4
    • External power priority over Gen #4
    • EXT PWR cont - GOB
  36. Transfer RElay 5
    • Connects Gen 2 to Bus B
    • Gen 4 trans - MEDC
  37. Transfer RElay 6
    • Connects Gen 3 to Bus A
    • Gen 4 trans - MEDC
  38. Transfer Relay 7
    • Gen 4 priority over the APU
    • Gen 4 aux cont - FEDC
  39. FEDC Loads:
    • command Bell, Utility lights, Gen 4 aux cont, GOB, Pitchlock reset, Inverter relay, IFF emergency cont, INS 1+2 (RINU), Turn rate gyro (pilot), Stby Att Ind (EFDS)

    • FEAC Loads:
    • (POSSFIRE)
    • Pilots pitot heater, Outflow valve, Standby gyro, Standby Attitude indicator, FDI backup, IFF transponder, Radar altimeter, ESS lighting (red instrument) backup
  40. AC + DC Feeder loads:
    • (HUAMARI)
    • HF #2, UHF #2, Autopilot, Marker beakons, ADF, Radar, INS #2
  41. Start DC loads:
    • (STAFFIP)
    • Start cont, Tds, engine and fuselage bleed-Air valves, Fuel Shutoff valves, Fuel and ignition cont, Inverter, Primer cont
  42. MDC Loads:
    • Ground air sensing, Rack overheat, Accelerator counter, flap Brake, Electronic Feeders (HUAMARI), Dump Pump cont, load Monitoring, Transfer valves
  43. Gen 2 Off light means?
    Gen 2 not powering Bus A
  44. GOB in flight:
    Inflight Arm switch, Pull GOB power relay CB, drop gear
  45. Priority Bus A
    • (GEGAG)
    • Gen 2, Ext pwr, Gen 4, APU, Gen 3
  46. Priority Bus B
    • (GEGAG)
    • Gen 3, Ext pwr, Gen 4, APU, Gen 2
  47. Priority MEAC
    • (AGEGAG)
    • Bus A, Gen 2, Ext pwr, Gen 4, APU, Gen 3
  48. Priority FEAC
    • (GEGAGA)
    • Gen 2, Ext pwr, Gen 4, APU, Gen 3, Bus A
  49. Power and backup for FEDC
    MEDC thru blocking diode #2 / Battery
  50. Power source MDC
    TR 1 on Bus A, TR 2 on Bus B
  51. Power source for MEDC
    TR 3 on MEAC, EMDC thru blocking diode #1
  52. Power source for SEDC
    MEDC (ESS Feeder #3), FEDC thru inverter power relay
  53. Power source for SEAC
    MEAC, SEDC thru inverter
  54. Power source for Apu ess
    MEDC (with power sensing relay), GOB
  55. Generator characteristics:
    • 115V, 3 Phase, 400 Hz.
    • Cooled by internal fan.
    • 60 KVA for APU
    • 90KVA for engine driven in flight due to ram air.
    • Mechanical Air SOV positioned by E-handle.
  56. 3 sub-generators:
    PMG, exciter generator, main generator.
  57. Gen control switch
    energizes GCR with voltage from PMG and allows excitation current from voltage regulator to the excitation generator. Sup panel senses correct voltage and energizes ACR to allow gen to power bus.
  58. Generator protection:
    • Over-voltage (inverse time delay relay)
    • Undervoltage (4 seconds to allow branch protection to operate)
    • Off frequency (only under freq by solid state sup panels, gen off at 109% manually)
    • Feeder fault (differential current transformers monitor current leaving gen vs that arriving at MLC, protects against shorts to aircraft.
    • All four deenergize both GCR and ACR.
  59. Battery:
    • 24V, 31Amper-hour.
    • Used for starting APU, allow external power, emergency source of electrical power.
    • Can power FEDC, GOB, Apu ess, SEDC and SEAC (thru inverter).
    • Charged by MEDC through blocking diode #2 (which prevents FEDC from powering MEDC)
  60. Transformer rectifiers:
    transforms 120VAC to 27VAC then rectifies 27VAC to 27VDC.
  61. TR overheat
    at 150C due to failure of internal fan.
  62. Load meter
    0-1 on MLC and MEDC panel.
  63. Inverter:
    • DC motor driving single phase alternator.
    • Powered by SEDC with inverter/battery test or engine selected with MEDC not powered (or power sensing CB out).
    • Provides TIT indications during battery start/shutdown, all generators lost in flight, or MEAC source lost.
  64. External power:
    • APU gen unavailable.
    • Monitor receives power from Ext Pwr CB on GOB thru external power switch.
    • Monitor ensures proper phase, voltage and frequency and then energizes transfer relay #4.
    • Ensure ext power switch is off prior to connecting or disconnecting ground power.
  65. Transfer relays:
    Ensure a source of power to Bus A and Bus B, and establish a priority.
  66. Gen #4 control aux relay:
    • Energized by Gen 4 transfer CB on MEDC to allow transfer relays #5 and #6 to be energized.
    • Power is routed thru the de-energized ACR on the APU sup panel.
  67. Run-around relays:
    Provide MEAC and FEAC alternate sources of power and establish a priority for the generators.
  68. Run-around feeders:
    Protect the rest of the electrical system from malfunctions in the run-around relays or the essential AC buses.
  69. Essential AC bus relays:
    • allow Bus A to power MEAC as its first priority and FEAC as its last priority with run-around relays.
    • Also allows manual monitoring of MEAC.
  70. Starting APU in flight:
    • Monitor non-essential loads, Gen switch-OFF, Boost pump-ON, inflight Arm, Apu-Start, Gen switch-ON (100%).
    • (My Good BASO)
  71. Starting APU with loss of MDC and MEDC still powered:
    • Monitor loads, Gen - OFF, Inflight Arm, Boost out (set V)
    • Pull TR3, Apu - Start, Gen - ON, reset TR3 and Boost back on.
  72. Why pull TR3 to start APU with loss of MDC?:
    • APU electrical starter off EMDC when MEDC powered.
    • Will not start with loss of MDC.
    • Cannot pull power sensing because APU starter will pull current from MEDC through blocking diode #2
    • potentially blowing the diode and removing the normal power source to FEDC.
    • Battery would be depleted by FEDC and GOB.
  73. Loss of MEAC:
    • FEAC powers Vertical Gyro, FDI, Red inst lights
    • CP FDI unreliable, both pilots select STBY Gyro
    • With MEDC still powered: Pull pwr sensing cb for TIT
  74. Gen Mech Warning
    If generator switch is off due to Gen Malfunction and get GEN MECH light, steady or intermittent - E-Handle
    • Disables Gen 4 from assuming a load with no Gen 4 Off light
    • if Gen 2 or 3 lost, entire load assumed by remaining generator
    • Load monitoring will occur with prop/emp deice selected
    • Gen off light will be on
    • Generator will assume a load
    • Load monitoring is disabled
    • H - uncover boost Handles
    • E - Essential bus monitoring switch off if loose generator
    • L - Lighting prepared: Utility lights and Flashlights
    • P - Proceed VFR if possible, if destination IFR consider VFR alt
    • L - Load closely monitored, Load monitoring with prop/emp deice
    • S - Secure all nonessential equipment and lights
    • D - Deice operations monitored, prop/emp not simultaneous
  78. Partial Load Monitoring
    • Single engine driven generator or APU only below 8000’
    • (Gen 4 + APU is single generator)
    • Prop and/or Emp deice selected
    • Lose: Bus A and MDC electronic feeders (HULAMARI)
    • Galley power
    • Radient heaters
    • Side windshield heat
    • Do single generator precautions
  79. Full Load Monitoring
    • APU only above 8000’
    • without manual actuation of any switches
    • Lose: Partial load monitoring loads
    • Empennage deice system
    • Hydraulic pump 1A
    • Continues on descent thru 8000’ unless both prop and emp are turned off
    • Can regain emp deice by monitoring an equivalent load and activating the
    • EMP De-ice monitor switch - OVRD.
  80. Emp Deice Equivalent load:
    Three boost pumps, Hyd pumps 1 and 2, Cabin exhaust fan.
Card Set
P-3 Electrical Procedures
Electrical Procedures