Chapter 5: Electrical

Question 1

IDG (Integrated Drive Generator)

Answer 1

115 VAC, 40 kVA, 400 Hz, 3-phase
Constant Speed Drive coupled to an electrical generator, controlled by GCU (Generator Control Unit)
EICAS message and Amber Light on Associated IDG if:
Oil temperature > 335 F +/- 10 F
Oil pressure < 140 psi +/- 25 psi
Automatic Disconnect if oil temperature > 366 F
Manual Disconnect: Hold “DISC” for 1 second (NOT more than 3 seconds)
Cannot reconnect after disconnection

Question 2

APU (Auxillary Power Unit)

Answer 2

115 VAC, 40 kVA, 400 Hz, 3-phase

Can provide pneumatic power for ECS and engine starts

Question 3

RAT (Ram Air Turbine)

Answer 3

115 VAC, 15 kVA, 400 Hz, 3-phase
Powers AC ESS BUS
Takes 8 seconds to spin up to speed
Must be > 130 KIAS

Question 4

Batteries

Answer 4

NiCd (Nickel-Cadmium) or LSA (Lead Solid Acid)
22.8 VDC, 27A, 27 Ah
Max Temperature:  70 C
Lower than 22V => Need to be recharged
Lower than 21V => Call maintenance

Question 5

TRU (Transformer Rectifier Unit)

Answer 5

Converts 115 VAC to 28 VDC

Rated for 300 A

Question 6

Electrical Emergency

Answer 6

AC power sources are not powering AC busses

Batteries only last 10 minutes

Question 7

Source Priority

Answer 7

Respective IDG
APU
AC GPU
Opposite IDG

Question 8

DC GPU Voltage Limits

Answer 8

24-32 VDC

Question 9

SPDA Locations

Answer 9

SPDA 1: Forward Electronics Bay

SPDA 2: Center Electronics Bay

Question 10

HOT BATT BUS 1 Components

Answer 10

• Courtesy/Service Lights Forward
• DC Ceiling Lights
• Engine 1 Oil Level Indication
• Engine 1A Fire Extinguish
• Engine 2A Fire Extinguish
• Engine Fuel SOV 1
• Hydraulic SOV 1

Question 11

HOT BATT BUS 2 Components

Answer 11

• Engine 2 Oil Indication
• Engine 1B Fire Extinguish
• Engine 2B Fire Extinguish
• Engine Fuel SOV 2
• Hydraulic SOV 2
• Panel Refuel 3
• Water and Waste System Controller PWR 3
• CMC

Question 12

STBY AC BUS Components

Answer 12

Engine 1 Exciter 1A

Engine 2 Exciter 2A

Question 13

AC ESS BUS Components

Answer 13

AC Fuel Pump 2A
ACMP 3A
SF-ACE 1 Flap Ch 1 AC Feed
SF-ACE 2 Slat Ch 2 AC Feed

Question 14

Electrical System Distribution

Answer 14

Power Source => AC/DC Busses => SPDA => Components

SPDA has built-in circuit breakers
MAUs can define complex logic for specific components
Some components have alternate direct connection to AC/DC Bus for redundancy in case of SPDA/MAU failure

Question 15

Load Shed

Answer 15

When power demands exceed system limit, SPDA commands load shedding of:

• Galleys
• Righthand windshield heating

Question 16

MAU 1 Power Source and Location

Answer 16

Forward E-Bay

1/2 (Ch A) DC ESS BUS 1
3 (Ch B) DC BUS 1

Question 17

MAU 2 Power Source and Location

Answer 17

Forward E-bay

1 (Ch A) DC BUS 2
2 (Ch B) DC ESS BUS 2/DC BUS 2

Question 18

MAU 3 Power Source and Location

Answer 18

Center E-Bay

1 (Ch A) DC ESS BUS 2
2 (Ch B) DC BUS 2