ELECTRICAL_MAIN PANEL

Question 1

METERING PANEL - LED DISPLAY

Answer 1

• powered WHEN BATT Switch is turned ON
• DC data on left - AMPS (top) VOLT (bottom)
• AC data on right - CPS FREQ (top) VOLTS (bottom right) AMPS (bottom center)

DC AMPS: (top left) - STBY PWR and BAT BUS positions will NOT show AMPS

Question 2

BATT DISCHARGE Light

What does this light mean? (1sp)

Is it ever normal to see that light?

Answer 2

[1sp - excessive battery discharge.

(b) it could be if we started the APU on batt power because the battery charger is not working]

Illuminated (Amber):

• with BAT switch ON - it detects excessive battery discharge

Notes.

• could mean a failed battery charger
• will illuminate a MC & ELECT caution (except during an APU battery start)
• you will get this light during APU battery start (high discharge)
• will NOT get this light during APU AC start (#1 AC transfer bus powered)
• GROUND CREW CALL HORN - will sound a continuous sound 2 minutes after condition is detected

Question 3

TR UNIT Light

What is the TR Unit light mean? (1sp)

Answer 3

[1sp - if on the ground, it means that any of the 3 TRs fail, if it comes on in flight it means that either TR 1 or TR2 & 3 have failed]

Illuminated (amber):

• Ground: ANY TR has failed.
• Air: TR 1 failed OR TR 2 AND TR 3 failed.

Question 4

ELEC Light

What does the ELEC light illuminated mean? (1sp)

Answer 4

[1sp - means we have a DC system or the standby system electrical fault.]

Illuminated (Amber):

• fault exists in either - DC system OR Standby Power system
• works ONLY on GROUND

To see the BITE message - press the MAINT button

Question 5

MAINT Button

Answer 5

Notes.

• works ONLY on the ground.
• connects to BITE for ELECT light fault analysis
• if a fault exists it will show on LED display
• if an ‘I’ follows the fault message - that means it intermittant

This is a MAINT ONLY button.

Question 6

DC METER Selector

Answer 6

Notes.

• each position EXCEPT TEST is related to a DC power source or bus
• BAT: shows volts/amps (load) of the battery (or battery charger) if operating
• BAT BUS or STBY PWR: only shows VOLTAGE (since these are not SOURCES of power)
• TR 1 & TR 2: indication is taken from the respective DC BUS and amps come from the respective TR which is different than TR 3 which shows BOTH volts AND amps from TR 3
• TEST - used by MAINT
• BAT (and Aux BAT): amps are normally 0 (means full battery - not charging)

Question 7

BAT Switch

• 2 positions -

OFF

ON

How many batteries do we have installed? (1sp)

How many volts is the battery? (1sp)

DC system voltage?

TRU output voltage?

Min voltage for APU start?

Answer 7

[1sp - normally 1 with an option for 2

(b) 24 v
(c) 28 v
(d) also 28v - TRU output
(e) 23v

OFF:

• removes power from: (with NORMAL power sources available)
  
  • BATT Bus AND
  • SWITCHED Hot Bat Bus
• removes power from: (when BATT is ONLY source of power)
  
  • BATT BUS
  • SWITCHED HBB
  • AC & DC STANDBY BUSES
  • STATIC INVERTER

ON: (guarded)

• powers the SWITCHED HBB
• energizes relays to provide auto switch of standby system to BATT power with loss of normal power

Question 8

AC METER Selector

Answer 8

Notes.

• 7 positions
• each position EXCEPT TEST is related to an AC power SOURCE or BUS
• shows AC Volts / Amps (load) / or output FREQ on display
• Will only show VOLTS and FREQ in these positions: STBY PWR, GRD PWR, INV (no AMPS)
• Normally 115 +/- 5 V and 400 cps +/- 10
• TEST position: used by maint

Question 9

CAB UTIL Switch

• 2 positions -

OFF

ON

Answer 9

ON:

• powers galley and cabin equip systems
  
  • all 115vac galley busses
  • RECIRC fans
  • door heaters & drain masts
  • lav water heaters
  • LOGO LIGHTS
  • potable water compressor

OFF: removes power to the above

Question 10

IFE/PASS SEAT Power Switch

Answer 10

ON:

• supplies power to componets of the pax seats and inflight entertainment (and other power systems)
• 115vac audio & video equipment
• cabin telphone equipment
• 28vdc video equipment and pax seat electronic outlets
• ACARS Printer

OFF: removes electrical power from the above items.