170 Electrical

  1. How many networks make up the electrical system on the airplane? Why?
    • 2 independent networks

    • Redundancy and fault isolation
  2. What happens if a power generating source fails?
    Bus ties automatically connect to provide no system degradation
  3. What components power the AC system?
    • • 2 Integrated Drive Generators (IDG)
    • • Auxiliary Power Unit (APU)
    • • Inverter
    • • Ram Air Turbine (RAT)
    • • AC GPU receptacle
  4. What components power the DC system?
    • • 2 NiCad batteries
    • • 3 Transformer Rectifier Units (TRU)
    • • DC GPU receptacle
  5. How does the IDG maintain a stable power output?
    A Constant Speed Drive (CSD) attaches the IDG to the AGB (Accessory Gear Box)
  6. What monitors and controls the IDG’s?
    Each has a Generator Control Unit (GCU)
  7. Can one IDG supply the entire electrical system?
  8. What will cause the amber IDG light on the overhead panel to illuminate?
    • • High oil temperature
    • • Low oil pressure
  9. If an IDG is manually disconnected can it be reconnected by the flight crew?
    No. This is a maintenance function
  10. What is the primary purpose of the AC generators?
    • • To power the AC BUSSES and AC ESS BUS which…
    • • Power the 3 Transformer Rectifier Units (TRU) 1, 2, and ESS
  11. What is the purpose of the Transformer Rectifier Units?
    To convert 115 VAC to 28 VDC
  12. Can the APU replace a failed IDG?
  13. What is the AC electrical system‘s priority?
    • • Onside (IDG)
    • • Inside (APU)
    • • Outside (GPU)
    • • Cross-Side (Other IDG)
    • Note: The airplane uses an onboard AC power source before an external AC source
  14. How is it known that an AC GPU is hooked up to the airplane and ready to provide electricity?
    • GPU button displays AVAIL and the GPU icon is presented on the electrical synoptic page

    • Once the GPU button is pushed in, the button will display IN USE provided another AC power source is notavailable
  15. What does it mean if the AC GPU is plugged in and the outside GPU panel button displays IN USE?
    • • Ground service bus is in use
    • • Cockpit GPU button will display AVAIL even though the ground service bus is in use
  16. If the airplane is using the AC GPU and the APU is started what should the pilot be sure to do?
    Deselect the GPU button before the next GPU connection
  17. Deselect the GPU button before the next GPU connection
    Any AC Power Source
  18. How long will the aircraft’s batteries last with no recharging?
    10 minutes
  19. What is the purpose of the DC GPU receptacle?
    • For APU start when batteries < 22.5 VDC, or

    • If battery temp is < -20°C
  20. What is the minimum battery temp for APU start?
  21. What is the minimum battery voltage to close the battery bus-ties?
    18 volts
  22. What battery is used for the APU start?
    • BATT 2 powers the APU Start Bus

    • BATT 1 powers the FADEC & EICAS for monitoring
  23. What is the purpose of the Inverter?
    Converts 28 VDC from the batteries to 115 VAC to power the AC STANDBY BUS when an AC source is notavailable
  24. What is on the AC STANDBY BUS?
    Engine exciters 1A and 2A
  25. What powers the Ram Air Turbine (RAT)?
    Airflow turns the RAT propeller which spins the turbine inside
  26. When will the RAT deploy?
    • Automatically deploys if AC BUSSES are not powered

    • Manually by pilot
  27. How long after deployment before the RAT will supply power?
    8 seconds
  28. Is there a total loss of power during the 8 second RAT deployment?
    No. Batteries supply power to the DC ESS BUSSES and AC STANDBY BUS
  29. What does the RAT power?
  30. What is minimum airspeed for the RAT?
    • 130 kts

    • Load shedding occurs below this speed
  31. When is the RAT icon displayed on the electrical synoptic page?
    When the RAT is deployed
  32. What manages the electrical system?
    • 4 Integrated Control Centers (ICC)

    • 2 Secondary Power Distribution Assemblies (SPDA)
  33. What is an ICC?
    An electrical control device, which provides power distribution and protection for electrical loads
  34. What is an SPDA?
    An electrical load-management unit (powered by the ICC’s) that distributes electrical loads to aircraft systems according to distribution logic
  35. Can the flight crew reset the ICC and SPDA remote electronic CBs?
    • ICC CB’s can only be reset by maintenance on the ground

    • SPDA CB’s can be reset via the MCDU
  36. DC HOT BAT BUS 1
    Battery 1

    Courtesy / service lights fwd

    DC ceiling lights

    Engine 1 oil level ind

    Engine 1A fire extinguish

    Engine 2A fire extinguish

    Engine fuel shutoff valve 1

    Hydr sys sov 1
  37. DC HOT BAT BUS 2
    Battery 2


    Engine 1B fire extunguish

    Engine 2 oil level indication

    Engine 2B fire extinguish

    Engine fuel shutoff valve 2

    Hydr sys sov 2

    Panel refuel 3

    Water and waste system controller pwr 3
  38. AC ESS BUS
    AC fuel pump 2A

    Hydr motor pump 3A

    SF-Ace 1 flap channel 1 ac feed

    SF-ace 2 slat channel 2 ac feed
    Engine 1 exciter 1A

    Engine 2 exciter 2A
  40. ICC are?
    Integrated control center - collect and confirm the power is safe and then sends it to the SPDA

    Provides power distribution and protection for the airplane electrical loads

    Line replaceable units which is plug and play like a computer's motherboard
  41. SPDA
    Secondary power distribution assembly

    Receives power from the ICCs and distributes the power to the airplane systems

    The SPDA works as a circuit breaker or relay interfacing the electrical buses with the airplane systems and components.
  42. MAU
    Modular avionics assembly

    The airplane systems that require a complex logic for the normal operation are connected to the MAUs which have the ability to process various inputs and define either on/off or open/close status for a specific system

    Monitors aircraft systems
  43. Items on the MAU
    • Auto Pilot
    • Air Data Application
    • Auto Throttle
    • Data Aquistion
    • Display Control Functions
    • Flight Director
    • Flight Management System
    • GPS
    • Monitor/Warning System
    • Stall Protection/Warning
    • Windshear Guidance
  44. Items located in the forward electronics compartment
    • MAU 1 and 2
    • SPDA 1
    • EICC
    • Battery 1
    • 2 P-ACE
    • 1 S-ACE
  45. Items located in the mid or center electronics compartment
    • MAU 3
    • LICC
    • RICC
    • SPDA 2
    • 2 SF-ACE
    • 2 S-ACE
  46. Items located at the rear electronic compartment
Card Set
170 Electrical
170 Electrical