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Atlas 767 > Electrical > Flashcards

Electrical Flashcards

1
Q

Describe the Electrical System (FCOM)

A
  • AC and DC Power is generated and distributed automatically.
  • Faults are detected and isolated automatically as well.
  • AC is the main source of airplane electrical power.
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2
Q

What are the AC Power Sources?

A

L and R Engine IDGs (Main Source)
APU (Main Source)
EXT PWR (Ground Ops)
HDG (Back-up for Dual Main AC Bus Fail / ETOPS)

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3
Q

Describe IDG operation.

A
  • Switch Normally Kept ON
  • Automatically Controlled Priority Source for Main AC BUS.
  • When connected, previous source is auto disconnected.
  • Can be disconnected with the switch, or EXT PWR ON.
  • OFF displays anytime the Gen Control Breaker is OPEN.
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4
Q

What does an Illuminated DRIVE light indicate, what should accompany it, and what should the pilot do?

A
  • IDG High Oil Temp or IDG Low Oil Pressure.
  • L or R GEN DRIVE EICAS message.
  • Pull QRH. Pushing DRIVE DISC disconnects the IDG from the N2 rotor.
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5
Q

Describe the APU GEN.

A
  • Identical to the Engine IDGs.
  • Can supply all NECESSARY power for the A/C.
  • Connected to both Main AC Busses.
  • Connected to the Ground Handling Bus, and a backup for the Ground Service Bus.
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6
Q

When does the APU GEN OFF light illuminate?

A
  • When the APU is operating and the GEN SWITCH is selected OFF, or
  • FAULT.
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7
Q

What does an EXT PWR AVAIL light indicate?

A
  • Adequate
  • Voltage
  • Frequency
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8
Q

What happens when you push the EXT PWR switch ON?

A
  • External Power connects to both main busses.

- IDGs and APU disconnected from busses.

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9
Q

What are the three main components of the BUS TIE System?

A
  1. The AC BUS TIE breakers
  2. The DC BUS TIE.
  3. The Fight Instrument TX Busses.
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10
Q

What are the three functions of the Bus Tie System?

A
  1. Automatically Reconfigure Electrical System in case of a PWR Source FAIL.
  2. Automatically Isolate a FAULT.
  3. Automatically Prevent Paralleling Power Sources.
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11
Q

When would a BUS TIE switch ISLN light illuminate?

A
  • Bus Tie OPEN due to
  • Fault, or
  • Selected OPEN.
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12
Q

When would a L/R BUS OFF light illuminate?

A
  • Whenever the L/R Main AC Bus is not powered.
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13
Q

What is the Source order for powering the Main AC Busses?

A
  • Respective IDG
  • APU GEN
  • Opposite IDG
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14
Q

What Busses provide FIRE DETECT and PROTECT?

A

DETECT - Battery Bus

PROTECT - Hot Battery Bus

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15
Q

When, Why, and What is shed for an OVERLOAD?

A
  • When the Captain does his B4 Start Flow,
  • HYD and FUEL Pumps are selected, and there is normally only one power source (APU), and therefore,
  • The C2 ELEC HYD Pump and Galley Loads are shed.
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16
Q

When, Why, and What is shed for an ENG START?

A
  • When GRND is selected and yet increases the load more,
  • The Utility Bus and the L ELEC DMND Pump Shed.
  • For the Second Engine Start, the On-Side Galley Load is Shed.
17
Q

What is shed if a GEN is lost?

A
  • Only “Non-Normal” Shedding Condition
  • Shed system armed when Thrust Levers are advanced.
  • Galley First, then Utility, then individual equipment items.
18
Q

How is the HDG Powered?

What does it power?

A
  • Powered by the Center Air Demand Pump.
  • 4 AC Busses - L/R TX, CA FLT INST TX, STBY AC
  • 3 DC Busses - STBY DC, BATT, HOT BATT
  • Available instruments will generally be those with “Standby” in their name; L of Alternate Gear, except EICAS and Autobrakes.
19
Q

What is available with Battery Power only?

A

Busses: HOT, BATT, STBY AC and DC.

- STBY Attitude Indicator, Air Speed, Altimeter and CA DMI

20
Q

General Description of the Electrical System.

A
  • Four Power Sources
  • Two Sides (L/R)
  • Each side - Main AC, Utility (non-essential high power), Instrument Transfer, and DC Busses.
  • Bus Tie System Tries to run each side separately, but can use any one source to power both sides.
  • STBY and BATT busses normally powered by Left Side, but if there’s no PWR there, then through the HOT Bus.
  • Load Shedding gets rid of high power non-essential items during peak demands - utility busses, HYD and FUEL pumps, Galley Stuff.
  • Isolates systems for independent power sources during autoland.
21
Q

How could you power the airplane service outlets, some galley power, most cabin lighting, and the battery chargers with EXT PWR?
The Entire Aircraft?

A
  • Check AVAIL Light indicating acceptable voltage and frequency; This means the GRND SERVC Bus is powered.
  • The Bus Switch ON, on the FA Panel next to 1L door will then power the GROUND SERVICE Bus via the GROUND HANDLING BUS.
  • If you then select external power ON, then the entire aircraft will be powered (and the GND SRV Bus will switch back to the R MAIN AC Bus.)
22
Q

Describe a Single Source Shed.

A
  • Before Engine Start, with one AC Source (usually APU) selecting all the HYD and FUEL Pumps ON will cause the #2 C HYD Pump to shed. (PRESS light)
23
Q

Describe an Engine Start Load Shed.

A
  • Moving the ENG START SELECTOR to GND will shed both utility busses, and as a result, the RECIRC FAN INOP lights illuminate.
  • GND also opens the Start Valve (VALVE in-tx flash) the APU goes to high flow (inc in duct press) arms selected ignition, and closes the engine bleed air valve, if opened.
  • The Center Fuel Pumps will show PRESS (inhibited) until their associated engine is at 50% N2.
  • The IDG will trigger the GEN BREAKER CLSD and the OFF Light Extinguishes, the R AC BUS TIE BREAKER OPENs to isolate the two sides. The #2 C ELEC HYD Pump comes back on because we have two sources, and the Center Boost Pumps because we have adequate power.
24
Q

Walking into a cold dark airplane, what is the first step in powering the aircraft?

A
  • Battery Switchlight ON and STBY PWR AUTO.
  • This powers the HOT, BATT, and STBY Busses.
  • STBY ADI, AI, ALT, ENG Indications, L VHF, L VOR, C ILS
25
Q

If no other power is AVAIL before starting the APU, what indications do you see as you start the APU?

A
  • Check ELEC HYD Pumps OFF, and APU Bleed OFF.
  • APU Selector ON.
  • FAULT light flashes as APU Fuel Valve OPENS.
  • (The APU Inlet Doors Open, and the L DC APU Fuel Pump pumps)
  • (Powered by Ship Battery)
26
Q

What could FAULT the APU Start Sequence?

A
  • Low Oil Pressure
  • High EGT
  • Overspeed.
  • Cranking Limits?
27
Q

What is special about the transfer busses?

A

they have ETOPS stuff.

28
Q

Talk me through from a cold dark airplane to all 14 buses being powered.

A
  • Hot battery bus - fire protection, APU Fuel valve, refueling System, RAT and LG Manual Drop, IRS emergency power, and parking break valve.
  • Turn on Batery Switch, you get discharge light and stby bus off lights are off. Now battery and hot bus are powered. add stby instruments and fire protection.
  • Turn STBY Switch to AUTO - Now, HOT, BATT, and 2 STBY Lights - STBY OFF Lights go off.
  • Establish Power - EXT PWR AVAIL? - Acceptable Power? - Now have ground handling (Auto Fuel, Cargo Doors and Lights) and could have ground service bus.
  • Accept External Bus - now all busses are powered.

Atlas 767 (14 decks)

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