Electrics

AC Power Source

Three integrated engine-driven generators mounted on engines 1, 2, and 3.

Generator Control Units (GCU)

Each Integrated Drive Generator (IDG) has a corresponding GCU.

If the GCU is tripped manually it cannot what?

Be auto-reset.

A manual reset command (BTB manual reset) is required to restart the generator.

This is due to the engines needing to be shutdown for maintance to manually reset it.

Distribution

Each IDG connects through a generator control breaker to its own load bus.

Load buses are interconnected through a bus tie breaker (BTB) to the synchronizing bus.

Parallel Operation

The bus tie breaker (BTB) allows parallel operation of generators.

AC Power Supply

The AC system supplies AC power to all AC-Powered systems.

It also supplies AC power to two transformer rectifiers (TRs) for conversion to DC Power.

On-Ground Power Sources

On the ground, if IDGs are not operating, AC power can be supplied by: Onboard Auxiliary Power Unit (APU) and External power cart.

Bus Power Control Unit (BPCU)

The BPCU is the central control unit responsible for managing power distribution.

It allows for the safe addition of external or APU power through the synchronizing bus.

External Power Receptacle Door

If the external power receptacle door is open, the APU cannot be connected to the synchronizing bus.

Direct Current (DC) System

Power comes from two TR’s that are the primary source of DC power for the aircraft.

Backup Source of DC power

The main aircraft battery or APU battery through the battery bus.

Batteries

Batteries can provide backup power to the system.

APU battery - power to the APU.

Main Battery - power to the aircraft.

Batteries also supply power to the battery bus and are wired so that either may supply power to the aircraft DC system.

TR Buses

The two TR buses distribute power from the two TR units to various airplane DC loads.

Copilot Instrument Power System (CIPS)

Consists of one hydraulically-powered generator and a 28 Volt TR.

The GCU controls all what?

Generator functions and protection features.

TR’s convert what?

AC power to DC for distribution to DC operated equipment.

Switched DC Bus

Receives primary power from TR bus No 1 when the battery power switch is in normal.

Battery bus

Distributes power from the main and/or APU batteries.

Battery Chargers

Located with the batteries in the Latrine

Main Battery

Recieves input power from No 3 gen

APU Battery

Receives input power from No 2 general

What if power is unavailable for the CIPS?

It can be supplied by the main power system.

This system is normally independent of the aircraft electrical system.

If main AC power is unavailable?

The CIPS will supply power to the copilot's instruments.

TR supplies DC power to what?

The connected loads.

TR’s convert what?

AC to DC

Where can In find the TR’s?

They are acessible throught the door in the crew entry chute.

When will the BTB remain closed?

At all times unless opened manually or a fault exists

What are the electrically powered units in the A/R system?

A/R line calve, hydraulic valve & the signal amp

The A/R electrical system operates on power recieved from what?

28 volt DC system

What does the A/R Master Switch control on Jets Prior to 57-1460?

Only the power flow to the signal amp to the A/R control circuits

What does the A/R Master Switch control on Jets 57-1460 and on?

All electrical equipment in the boom operator compartment except for fuel dumping, the alarm bell, and communication equipment