Electrical Power Systems

Question 1

The Hawker is a primarily ___ aircraft.

Answer 1

DC

Question 2

HS-125 Electrical Bus Codes: What does P, X, and S signify?

Answer 2

P: DC power
X: AC power
S: Split-bus power

Question 3

What bus does the APU power?

Answer 3

The PS2 bus

Question 4

What provides power for some avionics and navigation equipment?

Answer 4

Two inverters providing 115-volt AC power

Question 5

What powers windshield heat, windscreen heat, and stall vane heat?

Answer 5

Two-engine driven alternators

Question 6

What do the alternators power?

Answer 6

Windshield heat, windscreen heat, stall vane heat

Question 7

Where are most of the electrical components located onboard?

Answer 7

Aft equipment bay

Question 8

Where is the one location besides the aft equipment bay electrical components may be found onboard?

Answer 8

The main distribution panel in the vestibule area

Question 9

How is power distributed onboard?

Answer 9

Through a split-bus system controlled via circuit breakers

Question 10

Where are the circuit breaker panels located?

Answer 10

One panel behind the head of the SIC, one larger panel in vestibule, and additional panels in the aft equipment bay

Question 11

What drives the electrical system onboard?

Answer 11

Two 28-volt, 300-amp (continuous, 400-amps for two minutes) starter-generators (with an additional starter-generator on the APU)

Question 12

What is the battery arrangement onboard?

Answer 12

Two main batteries (24-volt, 28 amp-hour lead-acid) and four additional smaller batteries

Question 13

Where are the batteries located and what are their function?

Answer 13

Aft equipment bay, primarily used to start APU/engines and provide emergency power

Question 14

What items are on the Hot Battery Bus? (VREF)

Answer 14

Voltmeter
Rear Equipment Bay Light
Entry/Vestibule Lights
reFueling Panel

Question 15

What are the batteries directly connected to?

Answer 15

The PE bus

Question 16

BATT switch ON:

Answer 16

Uses power from BATT 1 to close emergency contactors, connecting BATT 1 and BATT 2 to PE bus

Question 17

BATT switch EMERGENCY:

Answer 17

Closes emergency contactors, powers PE bus, batteries do NOT charge

Question 18

Why do we need fully charged batteries prior to takeoff?

Answer 18

Guarantees the minimum 30 minutes of electrical power in the case of an emergency

Question 19

What does the ISOLATE switch do?

Answer 19

Isolates the respective batteries from the system - it will neither be charged nor power anything

Question 20

EXT PWR switch ON:

Answer 20

Allows ground power units to power the electrical system

Question 21

EXT BATT switch CHG ON:

Answer 21

Allows onboard batteries to be charged from external ground power if available and EXT PWR is ON

Question 22

What is the voltmeter used for?

Answer 22

Allows monitoring of voltage on selected battery or bus

Question 23

How can you change what system you are monitoring on the voltmeter, and what systems/buses can be monitored?

Answer 23

Rotary switch under voltmeter - allows monitoring of BATT 1, BATT 2, PS1 bus, PS2 bus, PE bus, as well as an XFER position to check voltage of the 4 additional smaller batteries. Typically left in PE switch position.

Question 24

What is located on each engine and the APU, providing DC power to the aircraft?

Answer 24

A 28-volt, 300-amp starter-generator

Question 25

How are the starter-generators cooled?

Answer 25

Ram air inlets on the cowling for each engine

Question 26

How do starter-generators function?

Answer 26

Initially act as starters (for the engines and APU), then automatically switches to acting as a generator

Question 27

When does a starter-generator switchover to generating power?

Answer 27

Around 42.5% N2

Question 28

What are Generator Control Units? (GCU)

Answer 28

Provide output stabilization and load equalization - generators share the load through a bus-tie, and the GCUs ensure that the generators are carrying their half of the load and providing proper output

Question 29

What are the protections offered by a GCU?

Answer 29

Protection against reverse current flow, overvoltage, overexcitation (normal voltage is 28v)

Question 30

How do GCUs control generators?

Answer 30

Directly controlling Generator Line Contactors (GLC), which allows power from the generator into the aircraft electrical system and stabilizes bus bars at 28.5-volts

Question 31

What are bus-tie contactors?

Answer 31

Provides connection of the main bus bars (PS1 and PS2), allows load sharing to take place

Question 32

Are bus-tie contactors automatic?

Answer 32

NO, must be manually closed via the spring-loaded BUS TIE switch, when first starting the aircraft the bus-tie must be manually latched every time (however opens automatically)

Question 33

When would the bus-tie contactors automatically open?

Answer 33

In case of self-preservation due to under or over-voltage

Question 34

What voltage would cause the bus-tie contactor to open?

Answer 34

When voltage reaches 29.5±0.5 volts or 24.5±0.5 volts

Question 35

What allows for load sharing between the main bus bars?

Answer 35

An equalizing circuit

Question 36

Generator Close Switches are located where?

Answer 36

The electrical services panel

Question 37

Generator Control Switch to CLOSE:

Answer 37

Connects the respective generator to electrical system IF the GCU allows it

Question 38

Generator Control Switch to TRIP:

Answer 38

Opens circuit, removing generator power from system; may happen automatically for self-preservation, may be moved manually to disconnect generators if needed

Question 39

What are the ammeters for?

Answer 39

Dual purpose (may indicate loads on two different things), indicate load on respective generators for engines, range from 0-450 amps

Question 40

Where is the ammeter for the APU generator?

Answer 40

APU Control Panel

Question 41

What does the BATT pushbutton do when pressed?

Answer 41

Connects ammeters to batteries to show the charge rate of the batteries

Question 42

What should the charge rate of the batteries be less than prior to takeoff?

Answer 42

The charge rate of the batteries should be below 20 amps prior to takeoff

Question 43

What is shown if the BATT pushbutton is not pressed down when checking amperage?

Answer 43

The system or generator amperage is read instead

Question 44

What does the 0-40 pushbutton do when pressed?

Answer 44

Rescales the ammeter from 0-450 amps to 0-40 amps for easier reading when checking battery amperage

Question 45

How long does it typically take after engine start for the batteries to have an acceptable charge rate for takeoff?

Answer 45

Around 5-7 minutes after engine start

Question 46

Where is the external power port located on the Hawker?

Answer 46

Right side fuselage, underneath the engine pylon

Question 47

What connector is used for Ground Power Units?

Answer 47

Standard 3-pin, 28 volt DC-power receptacle

Question 48

If using a GPU for engine start, what are the limitations of the GPU?

Answer 48

The GPU output capability must be 42kW (with a short term capability of 28-volts, 1500-amps), and a current limiter rated at 1,100-amps

Question 49

What GPU is capable of powering the onboard systems?

Answer 49

A standard 28-volt battery cart

Question 50

What happens if you attempt engine start with too weak of a power cart?

Answer 50

May damage electrical system onboard

Question 51

In the cockpit, how is GPU power turned on and controlled?

Answer 51

Only the EXT PWR switched to ON - BATT switch does not need to be ON for electrical power to be supplied

Question 52

How is AC power supplied onboard?

Answer 52

Two inverters in aft equipment bay - single-phase, 115-volt, 400Hz AC powering avionics and some navigation equipment

Question 53

How do the inverters power the XS buses?

Answer 53

INV 1 normally powers XS1, INV 2 normally powers XS2, one inverter can power BOTH XS1 and XS2

Question 54

How does the distribution of AC power work?

Answer 54

Automatic distribution, INV 1/2 switches provide manual control of inverters

Question 55

How are the inverters started?

Answer 55

INV 1/2 switch must be held momentarily in START position (spring-loaded switch)

Question 56

Maximum Battery Amps Before Takeoff (B1 and B2)

Answer 56

20 amps

Question 57

Starter Limits

Answer 57

30 seconds on, 1 minute off. 30 seconds on, 1 minute off. 30 seconds on, 30 minutes off.

Question 58

What is the maximum continuous generator load?

Answer 58

300-amps (transient load of 400-amps is permitted for two minutes maximum), active monitoring required

Question 59

Can you reset tripped circuit breakers?

Answer 59

NO, unless deemed necessary for the safety of flight. If a reset is followed through with, only ONE attempt is allowed

Question 60

What is the minimum battery voltage?

Answer 60

23 volts

Question 61

What does a WHITE circuit breaker mean?

Answer 61

Unswitched PE function

Question 62

What does a RED circuit breaker mean?

Answer 62

Related to the fire suppression system

Question 63

What does a YELLOW circuit breaker mean?

Answer 63

Electric Pitch Trim

Question 64

The batteries will maintain essential service during a dual generator failure for:

Answer 64

30 minutes maximum

Question 65

When a generator is offline and the GEN FAIL and ELECT ^ annunciators are illuminated, the generator can be reinstated by:

Answer 65

Positioning the GEN switch to CLOSE for five seconds then releasing it

Question 66

The battery-charging rate can be monitored by:

Answer 66

Depressing the BATT ammeter pushbutton

Question 67

For engine starting, the ground power unit must produce

Answer 67

28 volts, 1,500 amps with 1,100-amp current limiter

Question 68

Circuit breakers protecting unstitched PE circuits are marked to ease isolation in the event of smoke or fire with:

Answer 68

A white background

Question 69

When either the BATT 1 CNTCTR or BATT 2 CNTCTR annunciator illuminates, it indicates that the respective:

Answer 69

Battery contactor or emergency contractor is open