Electric Power Systems Review Questions

Question 1

When will the battery contactor automatically open?

Why does it automatically open?

Answer 1

If the battery voltage drops to less than 14 VDC for more than 10 seconds with the airplane on the ground.
This prevents the battery from being depleted at low volts.

Question 2

How many volts do the main batteries have? What duration of electrical power do they provide?

Answer 2

24VDC
Minimum of 30 minutes (27 or 28 amp/hour batteries)
Minimum of 1 hour (38 amp/hour batteries)

Question 3

What is the power duration of a fully charged emergency battery?

Answer 3

1 hour

Question 4

Where can the emergency battery voltage be checked?

Answer 4

By viewing the EMER-V on the EICAS/MFD SUMRY page or EMER BUS VOLTS on the EICAS/MFD ELEC systems schematic prior to applying GPU, APU, or engine GEN power.

Question 5

How long should you wait to power on the EMER BATT after turning on both main batteries? Why?

Answer 5

About 5 seconds.
It prevents power transients from interrupting the built-in-tests. Sometimes, the pax masks will deploy if EMER BATT is pressed too soon.

Question 6

How many generators are on the Lear 45? Where are they located?

Answer 6

3 total generators

One engine driven for each main engine and one APU generator.

Question 7

What is each engine GEN rated at?

Answer 7

30VDC (regulated to 28VDC) and limited to 300 AMPs.

Question 8

What engine speed will the DEEC’s automatically bring the engine GEN online (if not using GPU)?

Answer 8

approx. 95% of N1 IDLE (if not in MANUAL mode)

Question 9

How are the engine GEN’s cooled?

Answer 9

Air is routed from a scoop on the engine nacelle to the generator. Cooling on the ground is provided by a fan mounted on the generator shaft.

Question 10

What are some of the functions of the Generator Control Unit (GCU)?

Answer 10

• Voltage Regulation
• Generator Current Limiting
• Automatic Starter Cutoff
• Overvoltage Protection
• Overspeed (Runaway) Protection

Question 11

What are the different ways the airplanes main batteries can be charged?

Answer 11

GPU
APU
Left or Right Generator

Question 12

Normally, the two generator busses act independently; however, they are automatically tied when?

Answer 12

During engine start.

Following a single generator failure.

Question 13

Which of the following busses are automatically isolated from the main electrical system during engine starting to prevent possible voltage spike damage?

Answer 13

1. Emergency battery, Essential and Essential Avionics Busses.
2. Main Avionics Busses

Question 14

What does illumination of the white EMER BATT light on the CWP indicate?

Answer 14

The emergency battery is turned on and is discharging.

Question 15

How is an alternator failure indicated?

Answer 15

Windshield heat will be inoperative.

Question 16

“EMER” will illuminate in the emergency battery switch during start when using what?

Answer 16

The GPU

Question 17

Can the APU be used to power the electrical system on the ground in conjunction with an engine generator?

Answer 17

Yes, of course.

Question 18

In flight, at what amperage will the amp display on the EICAS SUMRY page change color from white to amber?

Answer 18

Above 300 amps

Question 19

If the left generator fails in flight, what will the left essential VOLTS show on the EICAS SUMRY page?

Answer 19

It will show the voltage of the operating generator.

Question 20

What indications will the crew have of a generator failure.

Answer 20

1. The Master Caution lights with flash.
2. An “OFF” annunciation will illuminate on the corresponding generator switch.
3. A flashing amber L or R GEN FAIL message will appear on the CAS.