ELECTRICAL SYSTEM Flashcards
- What does IDG stand for?
Integrated drive generator
- How many IDG’s does this aircraft have?
Two
- Do the AC power sources normally operate paralleled or isolated?
Isolated
- What does BAT DISCHARGE light mean?
Excessive battery discharge
- What does TR UNIT light mean on the ground?
In flight?
Any TR has failed; TR 1 OR TR 2 and TR 3 have failed
- What does the ELEC light mean?
fault in DC or STBY power systems
- Will you see the ELEC light in flight?
No, It is a ground only light
- When is the ELEC light inhibited?
Inflight
- What is the normal IDG frequency?
400CPS
- What is the normal IDG voltage?
115volts
- What is the normal battery voltage?
24 (22-30voltrange)
- If under normal conditions the battery switch
is turned OFF, would the Battery Bus be powered?
No
- If under normal conditions the battery switch
is turned OFF, would the Switched Hot Battery Bus be powered?
No
- What does the STANDBY PWR OFF light
mean?
STBY AC, STBY DC, or Battery Bus are not powered
- What does the DRIVE light mean?
Low oil pressure in the IDG
- What items make up the Standby Power System?
Hot battery bus Switched hot battery bus Battery bus Standby AC Standby DC Static inverter
- With the standby power switch in BATT, what is available?
Hot battery bus Switched hot battery bus Battery bus Standby AC Standby DC Static inverter
- With the standby power switch in AUTO, what is available?
All busses
- With the standby power switch in OFF, what is
available?
Hot battery bus
Switched hot battery bus
Battery bus
- Can an IDG be automatically disconnected?
Yes, due to high oil temperature
- What is the covered Disconnect Switch used for?
When QRH procedure calls for a disconnect
- An illuminated GRD POWER AVAILABLE light means what?
Acceptable ground power is available
- What checks the incoming EXT PWR for
quality?
Bus power control unit
- Does the EXT PWR light have a bright blue/dim blue feature?
No
- When you connect external power to the
airplane electrical system, are both TB’s powered?
Yes
- If the APU is powering the TB’s and EXT PWR
is selected ON, how many busses will EXT power?
All
- What does a TRANSFER BUS OFF light mean?
Transfer bus not powered
- What does a GEN OFF BUS light mean?
IDG not supplying power to the TB
- What does a SOURCE OFF light mean?
Respective IDG not powering bus or previously selected source no longer
powering bus
- What does the BUS TRANSFER switch do?
Enables or disables autobus switching
- What does the APU GEN OFF BUS light mean?
APU GEN available but not powering any busses
- If the APU is supplying power to both TB’s and one APU GEN switch is moved to OFF, what happens?
That source off light illuminates and both transfer busses remain powered
- What happens in flight if an IDG fails?
Auto bus transfer allows other IDG to power failed side IDG’S TB
- How many TR’s are there?
Four (TR#1, TR#2, TR#3, and Battery Charger)
- What normally supplies power to the standby AC bus; if AC power is not available?
TB #1; inverter
- Is it possible to power one TB from EXT and
one TB from APU?
No
- Is it possible to power one TB from EXT or
APU and one TB from an IDG?
Yes
- Is ground service available without powering
all of the airplane busses?
Yes
- How is the ground service available without
powering all the a/c busses accomplished?

Ground service switch on fwd FA panel
- What happens if you takeoff with the APU powering both TB’s and the APU fails?
Auto connect to engine IDG’S one time only (flight only)
- For single generator operation, is load shedding automatic or manual?
Automatic
- Which components are shed automatically?
(Galley Switch Option) galleys on txfr bus 2, then galleys on txfr bus 1, then main bus #2, then main bus #1
(CAB/UTIL Switch Option) galleys and main bus on txfr bus #2, then galleys and main bus on txfr bus #1, then IFE busses
- In flight, if the APU is the only available power source do you have to manually load shed?
No
- How is the load shed when the APU is the only
power source?
(CAB/UTIL Switch Option) in flight, all galley and main busses are shed. If load still too high, the IFE busses are shed (Galley Switch Option) all galleys are shed first; if load is still too high, all main busses are shed
- On the ground, will the APU load shed?
The APU attempts to carry the full electrical load except during engine start
- Is load restoration automatic or manual?
Automatic
- Can you manually restore galley power? How?
maybe, cycle galley switch and see
- What would an IDG automatically disconnect
for?
High IDG oil temperature
- Can a disconnected IDG be reconnected in
flight?
No
- What normally powers:
DC BUS #1?
a. TR1, 2, and 3
- Normally, are DC BUS #1 and DC BUS #2 isolated?
No
- When are the main DC BUSSES isolated
automatically?
At glideslope intercept
- How can you isolate the DC BUSSES
manually?
Bus transfer switch off
- How long will a fully charged battery be able
to supply standby power?
30 minutes (single battery option)
1 hour (dual battery option)
- Does STANDBY POWER include one attempt
at starting the APU (fully charged battery)?
Yes (not recommended above FL250)
- What busses are powered by the battery after
loss of both generators?
Hot battery bus Switched hot battery bus Battery bus Standby AC Standby DC Static inverter
- What normally powers:
DC BUS #2?
a. TR1, 2, and 3
- What normally powers:
STBY AC BUS?
a. TB#1
- What normally powers:
STBY DC BUS?
a. TR1, or all TRs.
- What normally powers:
BATT BUS
a. TR#3
- What normally powers:
HBB
a. BATT CHG/TR
- What normally powers:
SHBB
a. BATT CHG/TR