B737 Electrical System

The engine integrated drive generators (lDGs): Are three-phase, 115 volt, 400 cycle direct current. Adjust varying generator speeds throughout normal range of operation. Allow the generator to maintain a constant speed throughout the normal operating range of the engine. Have an integral electro-mechanical disconnect device that does not provide complete mechanical isolation of the IDG.

AC Transfer busses. Supply power to the 115V AC main busses. Cannot be powered by both external power and APU power at the same time. Can be paralleling sources of power. Both A and B.

In flight, if an engine generator is no longer supplying power, the BTBs automatically close to allow the other engine generator to supply both transfer busses through the tie bus and BTBs. True. False.

During cruise, one engine-driven generator drops offline and the BUS TRANSFER switch is in the AUTO position, what indications will the pilot see on the failed side. A TRANSFER BUS OFF light and a GEN OFF BUS light illuminate. SOURCE OFF and GEN OFF BUS lights illuminate and the TRANSFER BUS OFF light remains extinguished. Illumination of the fuel pump, probe heat, and hydraulic pump lights. D. Both Band C. Both Band C.

Under which of the following conditions will the Cross Bus Tie Relay automatically open isolating DC bus 1 from DC bus 2?. An engine-driven generator drops offline. The bus transfer switch is positioned to OFF. At glide slope capture, during a F/D or autopilot ILS approach. Both Band C.

With the STANDBY POWER switch in the AUTO position, the loss of all normal AC electrical power causes the battery to power the standby loads: Only in flight. Only on the ground. Both in the air and on the ground. None of the above.

AC amperage can be observed on the AC ammeter for the source by the AC meters selectors. True. False.

Illumination of the amber BAT DISCHARGE light indicates. The battery is being overcharged. Excessive battery discharge is detected with the battery switch ON. Battery discharge when the DC meter is in the BAT position with the battery switch ON. That the battery bus is not being powered.

The TR UNIT amber light will illuminate in flight if: Any TR unit fails. TR1 fails. TR2 and TR3 fails. Both B and C.

The ELEC amber light will illuminate on the ground if. A fault exists in the AC or standby power system. A fault exists in the DC or standby power system. A fault exists in the AC, DC or the standby power system. A fault exists in the AC power system only.

Illumination of the amber Generator Drive (DRIVE) light indicates low oil pressure caused by which of the following?. IDG failure. IDG disconnected through generator drive DISCONNECT switch. IDG automatic disconnect due to high oil pressure. Both A and B.

) Illumination of the blue GRD POWER AVAILABLE light indicates. External ground power is connected and meets airplane power quality standards. External ground power is connected; however, no airplane power quality is assured. External ground power is connected and the AC GRD SERVICE BUS 1 is automatically powered. External ground power is connected and both AC GROUND SERVICE BUSSES are automatically powered.

The SOURCE OFF light will illuminate when: No source has been manually selected to power the related transfer bus. The manually selected source has been disconnected. Both transfer busses are being powered if a source has been selected to power the opposite transfer bus. All of the above.

) Illumination of the GEN OFF BUS light indicates: The related main bus is not powered. The related transfer bus is not powered. The IDG is not supplying power to the related transfer bus. The APU is running and not powering a bus.

The APU generator can meet the following conditions: The APU electrical load maximum altitude is 17,000 ft. The APU bleed and electrical load maximum altitude is 10,000 ft. The APU electrical load maximum altitude is 41,000 ft. Both Band C.

Illumination of the STANBY POWER OFF light indicates one or more of the following busses are unpowered. The AC standby bus. The DC standby bus. The battery bus. All of the above.

Both AC transfer busses can be powered simultaneously by: A single IDG on the ground or in flight. The APU generator while on the ground or in flight. The APU and external power. Both A and B.

When takeoffs are made with the APU powering both transfer busses: One transfer bus will disconnect automatically after lift-off. If the APU is either shut-down or fails, the engine generators are automatically connected to their related transfer busses. The generators will NOT automatically come online if the APU is either shut down or fails. Both transfer busses will automatically disconnect after lift-off.

The Battery powers the following DC busses. The hot battery bus. The switch hot battery bus. The battery bus. The DC standby bus. All of the above.

The GRD PWR switch when momentarily moved to the ON position and ground power is available: Removes previously connected power from DC transfer buses. Connects ground power to AC Main busses if power quality is correct. Disconnects ground power from AC transfer busses,. Connects ground power to AC transfer busses if power quality is correct.

One basic principle of operation for the B737 electrical system is. All generator bus sources can be automatically connected by the Standby Power System. There is no paralleling of the AC sources of power. There is no paralleling of any power source. An AC power source may be used in parallel with a DC power source.

Which equipment will be powered when the only source of electrical power ar-e the main and auxiliary battery. Standby compass light. Engine shut off valves. Standby instruments. All of the above.

When the STANDBY POWER switch is OFF. The STANDBY PWR OFF light will be illuminated. The AC standby bus, static inverter, and DC standby bus powered. The AC standby bus is powered by the battery through static inverter. The static inverter provides 28 volt DC power to Transfer Bus No. 1.

The 115 volt AC Standby Bus is powered by: The 115 volt AC Transfer Bus No. 1 under normal conditions. The battery bus through the static inverter under normal conditions. The battery through the static inverter with a failure of both engine-driven and APU generators. Both A and C.

Two fully charged batteries can provide: Maximum of 60 min. Maximum of 90 min. Minimum of 60 min. Minimum of 90 min.