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Файл:Aircraft Maintenance. Учебное пособие
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UNIT 5. ELECTRICAL POWER
Primary DC power is supplied to the DC busses through transformer rectifier
units which are powered from the AC. TR-3 receives power from main bus 2 and
has a dual function. It is the primary power source for the battery bus and an alternate power source for both DC buss es 1 and 2. TR-2 is also a backup po wer
source for DC bus No.1 and TR-1 is also a backup power source for DC bus
No.2. The TR-3 disconnect relay automatically opens at glide slope capture. This
isolates the DC buss es during approa ch in orde r to prevent a s ingle failure fro m
effecting both navigation receivers and flight control computers. The TR-3 disconnect relay can be opened manually for smoke procedure with the BUS
TRANSFER SWITCH in OFF position. TR voltage range is 24 - 30 V. The battery bus has two possible sources of power: the battery or battery charger
through the hot battery bus or from TR-3. Under normal operating conditions, a
relay controlled by the battery switch connects th e TR-3 to the battery bus. If
TR-3 should fail the battery bus will automatically seek its power source from
the hot battery bus. Placing the Battery switch to OFF removes the ground for
the controlling relays and will cause the battery bus to lose power unless the
electrical standby power switch is in BAT position. With the electrical standby
power switch in BAT, the hot battery bus will power the battery bus regardless
of TR-3 output. The hot battery bus and the switched hot battery bus receive
power from the battery charger if a generator is operating or from the battery if
AC power is not available. The hot battery bus remains powered at all times. The
switched hot battery bus is powered when battery switch is in ON position. The
ground service bus is normally powered through generator bus 1. When the airplane is on the ground and external power is connected, pl acing the Gro und Se r-
vice Switch (located on the attendant’s panel) to ON will connect the ground
service bus directly to the external power source without energizing the other
airplane electrical busses. This bus contains most of the cabin lighting and other
equipment needed for cleaning.
Exercise 3. Answer the questions:
1. How is the Primary DC power supplied to the DC busses&
2. How do TR-2 TR-3 operate?
3. What does the battery bus have and how does it operate under normal operating conditions?
4. What does placing the Battery switch to OFF remove?
5. How does the hot battery bus operate?
6. What are the functions of ground service bus?
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AIRCRAFT MAINTENANCE
DC
a constant speed drive
AC
b revenue passenger-mile
APU
c variable speed constant frequency
TR
d direct current
RPM
e alternating current
CSD
f battery
BAT
g auxiliary power unit
VSCF
h Tyu-gata Ryokaku-ki
Exercise 4. Here are some common aircraft abbreviations. Match the
halves and translate them into Russian. Find the word-groups in the text
and translate the sentences.
Exercise 5. Look at the picture of an aircraft. Put the terms into the
right order. Translate them into Russian. Find the word-groups in the text
and translate the sentences.
GENERATOR NO. 2 (RH)
APU GENERATOR
LOAD CONTROL CENTER-LEFT (P18)
EXTERNAL POWER RECEPTACLE
GENERATOR NO. 1 (LH)
ELECTRONIC COMPARTMENT ACCESS DOOR
LOAD CONTROL CENTER-RIGHT (P6)
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UNIT 5. ELECTRICAL POWER
Text B
ELECTRICAL POWER CONTROL PANEL
DC Ammeter – амперметр постоянного тока
DC Voltmeter – вольтметр постоянного тока
DC Meter Selector Switch – переключатель счётчика электроэнергии постоянного тока
Frequency Meter – частотометр, измеритель частоты
AC Voltmeter – вольтметр переменного тока
AC Meter Selector Switch – переключатель счётчика электроэнергии переменного тока
Battery Switch – выключатель аккумулятора
Residual Volts Switch – переключатель остаточного напряжения
Low Oil Pressure Light (amber) – индикатор низкого давления масла (жел-
тый)
High Oil Temperature Light (amber)
– индикатор повышенной температуры
масла (желтый)
Standby Power Switch – запасный источник питания
Disconnect Switch – выключатель, разъединитель
DC Ammeter indicates current of source selected by the DC Meter Selector
Switch.
DC Voltmeter indicates voltage of source selected by the DC Meter Selector
Switch.
DC Meter Selector Switch selects DC source for DC Voltmeter and DC Amme-
ter.
Frequency Meter reads frequency of source selected by the AC Meter Selector
Switch.
AC Voltmeter
• Indicates (Scale Range100130 V) AC voltage selected by AC Meter Selec-
tor Switch.
• Indicates (Scale Range 030 V) Residual Voltage of the selected Generator
when the RESID VOLTS switch is pushed.
AC Meter Selector Switch selects the AC source for the AC Volt Meter and
Frequency Meter. The position Test is for further measuring purpose.
83
AIRCRAFT MAINTENANCE
Battery Switch
• ON (guarded position): With No. 2 AC Main Bus powered TR 3 provides
power to the Battery Bus. If No. 2 AC Main Bus is not powered, the Battery
Bus receives the power via Hot Battery Bus
• OFF: Battery Bus and Switched HOT Battery Bus are deenergized and Ex-
ternal Power will be tripped from the airplane.
Galley Power Switch
• ON: The galleys are powered when the Generator Busses are energized.
• OFF: The galleys are deenergized.
Residual Volts Switch push to read residual voltage of Generator selected by
AC Meter Selector Switch. The Generator Control Relay (Field Relay) must
be tripped by the respective Generator Switch when the Engine is running.
Caution: If respective GCR has not tripped, AC Voltmeter could be damaged.
Low Oil Pressure Light (amber) illuminates when the respective CSD/VSCF
oil pressure is below 120 PSI. Simultaneously, the Master Caution Warning
with ELEC Annunciator comes on.
High Oil Temperature Light (amber) illuminates when CSD/VSCF oil tem-
perature exceeds 157°C. Simultaneously, the Master Caution Warning with
ELEC Annunciator comes on.
Standby Power Switch
• AUTO (guarded position):
During normal operation DC Standby Bus is powered by DC Bus No. 1, AC
Standby Bus is powered by the 115 Volt AC Transfer Bus No. 1.
If either power source fails, the following switching will occur:
- In Air: Battery Bus will be automatically connected to the DC Standby Bus
and the Battery to the Static Inverter in order to supply the AC Standby Bus.
- On Ground: No automatic transfer switching will occur. The Standby Busses are deenergized.
• OFF (unguarded center position)
The Standby Busses are deenergized.
• BAT (unguarded position)
The Battery Bus supplies the DC Standby Bus and Static Invert er supplies the
AC Standby Bus regardless of the BAT Switch position.
Standby Power OFF Light (amber) illuminates when the AC Standby Bus is
not powered.
84
UNIT 5. ELECTRICAL POWER
1 Static Inverter
A reads frequency of source
2 AC Meter Selector Switch
B indicates voltage of source
3 The Battery Bus
C disconnects the respective CSD from
Engine actuation
4 DC Ammeter
D selects DC source for DC Voltmeter
and DC Ammeter
5 Battery Switch
E reads residual voltage of Generator
6 Frequency Meter
F supplies the AC Standby Bus
7 Standby Power OFF Light
G illuminates when the AC Standby
Bus is not powered.
8 DC Meter Selector Switch
H selects the AC source
9 High Oil Temperature Light
I illuminates when the respective
CSD/VSCF oil pressure is below
120
10 AC Voltmeter
K indicates current of source
11 Disconnect Switc h
L supplies the DC Standby Bus
12 Residual Volts Switch
M Indicates AC voltage and Residual
Voltage
13 Low Oil Pressure Light
N illuminates when CSD/VSCF oil
temperature exceeds 157°C.
14 DC Voltmeter
O provides power to the Battery Bus
1 indicate
А нажимать
2 damage
B получать
Disconnect Switch (guarded and safetied) disconnects the respective CSD from
Engine actuation (VSCF will be disconnected electrical only).
Caution: Actuating is allowed only when Engine is running.
Exercise 6. Here are some common aircraft terms. Match the words with
the definitions and translate them into Russian.
PSI
Exercise 7. Here are some common verbs from the text. Match the
halves and translate them into Russian. Find the words in the text and
translate the sentences.
85
AIRCRAFT MAINTENANCE
3 power
C выбирать
4 trip
D обеспечивать
5 connect
E включать
6 select
F показывать
7 energize
G включаться
8 push
H превышать
9 disconnect
I повредить
10 receive
J снабжать энергией
11 illuminate
K выключать
12 deenergize
L обеспечивать
13 provide
M функционировать
14 supply
N отключать
15 run
O рассоединять
16 exceed
P соединять
AC Generator with CSD
AC Generator/VSCF (Variable Speed Constant Frequency)
GENERAL
Annunciator Lights
Generator Control Unit
Generator Manual Controls
Generator Breaker
Generator Control Relay (GCR)
Exercise 8. Read the texts about AC Generation. Match the titles with the
texts. Translate them.
AC GENERATION
1. The ac generation system consists of generators, manual controls, generator
control relays (GCR), generator control units (GCU), main power circuit
breakers (GB) and annunciator lights.
2. A rotating electromagnetic field causes the output voltage - three phase electrical power at 115 volts and a constant frequency of 400 Hz- to be induced
in the stationary generator armature. The engine-driven generators are driv-
86
UNIT 5. ELECTRICAL POWER
110
Nose 3-phase position contactors magnet position tripping engine
bulkhead
en by CSD’s. A complete generator assembly consists of an AC exciter generator, a rotating rectifier and a main generator.
3. It is interchangeable with the CSD and generator assembly. It gets power
from a variable speed shaft on the accessory gearbox on the engine. It converts this to three phase electrical power at 115 volts and a constant frequency of 400 Hz.
4. Manual controls and monitoring devices for the electrical power system are
on the forward overhead panel P5. The switches for latching contactors are
momentary. There is an AC ammeter for each engine. The ac voltmeter and
frequency meter monitor various systems as determined by the selector
switches below the meters.
5. The GCR, located in the generator control unit, energizes the generator field.
The GCR and the generator field circuit are normally closed. The GCR’s
may be opened or closed by the GEN switches on the pilot’s forward overhead panel P5 or opened by signals from the GCU protection circuits.
6. The purpose of it is to provide excitation, control and protection functions
for the generator system. The three GCU’s are located in the right front of
the P6 panel. Each of the GCU’s (and also the bus protection panel - BPP)
contains a transformer rectifier unit (TRU). The TRU converts the 3-phase
ac power to 28 volt dc power for the control and protection circuits during
normal system operation. If the ac power is not available or the TRU has
failed, the power for the control and protection circuits is available from the
switched hot battery bus. With the battery switch in ON position the
switched hot battery bus is connected to the three GCU‘s and the BPP as a
back-up power for each of the TR units.
7. They connect the 115 volt ac, 400 Hz, 3-phase po wer to the distribu tion sy stem from the engine and APU generators.
8. They indicate the situation of the ac system and the genera- tors.
Exercise 9. Read the texts about generator breaker. Put the words into
the texts. Translate the texts.
GENERATOR BREAKER
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AIRCRAFT MAINTENANCE
Protection wheel deenergizes polarity aft spring auxiliary removing energizing
magnet operation
2236
Panel coil generator circuit breaker panel light blue amber leads connector position bottom removed prior
Purpose
The two (1) generator breakers connect 115 volt ac, 400 Hz, (2) power to the dis-
tribution system from the engine generators.
Location
The two engine generator breakers are located on either side of a (3) attached to
the right outboard side of the (4) wheel well.
Physical Description
The breaker has a dc coil for closing and (5). A permanent (6) assists closing and
holds it in the closed (7) The breaker has 6 main 115 volt ac contacts and 20 auxiliary contacts. The auxiliary contacts are used to control the positions of APU
(8) breakers and external power (9), and for indicating lights in the (10) compartment.
1121
Access
Access to the breakers is gained by (11) the forward and (12) access panels from
the right inner wall in the nose (13) well.
Power
Power supply for (14) of the breaker is 28 volt dc.
Control
The closing and tripping signals for the breakers are from the P5-4 panel, gener ator control units and the bus (15) panel.
Operation
Application of 28 volt dc to close, allows mo mentary (16) of the coil. When the
breaker closes, the coil (17) through the auxiliary contact and the breaker is held
closed by the permanent (18). Application of 28 volt dc to trip, reverses the (19)
of the coil and the contactor opens assisted by the (20). The coil deenergizes
through the (21) contact.
88
UNIT 5. ELECTRICAL POWER
1 GEN OFF BUS light
A illuminates if both the normal and alternate coil
The bus transfer relay being in the center or neutral
position is an indicatio n of loss of power to the
transfer bus.
2 BUS OFF light
B illuminates if both APU generator breakers are
open. It is an indication that the APU is operating and over 95% RPM or after APU shut
down, but the APU generator is not pow
ering
either generator bus.
3 APU GEN OFF BUS
light
C illuminates if its respective generator breaker is
open. It is an indication that the generator is not
powering the respective generator bus.
4 TRANSFER BUS OFF
D illuminates if its respective engine generator
breaker, APU GB and external power con -
tactor are open. For generator, it is an indication
of loss of power to the generator bus and main
bus.
Monitor
The (22) position is monitored by the (23) BUS OFF and (24) GEN OFF BUS
lights on the P5-4 (25).
Maintenance Practices
The breaker is (26) by disconnecting the six ac power (27) and an electrical (28)
for the (29) and auxiliary contacts. Power must be off (30) to removal of the
breaker.
Differences APU/Engine (31) breakers
• the APU generator breakers are located in the (32) of P6 panel
• access to the breakers is gained by opening (33) breaker panels P6-11 and
P6-12 at the bottom of P6 (34).
• the breaker contacts (35) is indicated by the blue APU GEN OFF BUS (36)
on the P5-4 panel.
Exercise 10. Read the texts about AC power annunciator lights. Match
the lights with their functions. Translate the texts.
AC POWER ANNUNCIATOR LIGHTS
of the bus transfer relay are relaxed.
light
89
AIRCRAFT MAINTENANCE
SUPPLEMENTARY READING
Skimming a text
Exercise 11. Read how to skim a text and try to do the task.
Skimming a text is a fast reading technique to look for main ideas in a text.
Skimming is used to obtain the gist (the overall sense) of a text.
Do the following tasks:
- read the title, subtitles and subheading to find out what the text is about;
- look at the illustrations to give you further information about the topic;
- read the first and last sentence of each paragraph;
- don't read every word or every sentence; let your eyes skim over the text,
taking in key words;
- continue to think about the meaning of the text.
INFORMATION PROCESSING
Working in aviation requi res operatives (pilots, controllers, airside safety, etc.) to
take in information from a multitude of sources, assess this information, prioritise it, and use it to make decisions and take actions. This complete process from
sensing information (whether it is aural , visual, mental, kinaesthetic, gustative or
olfactory) through to taking action is referred to as “human information pro-
cessing”, or information processing for short. So, information processing refers
to the ability of the operator to process the type and amount of information within the required timeframe, and to do so in an effective manner that leads to suitable responses. Information processing capabilities vary from person to person,
day to day, place to place and task to task. It is particularly affected by age,
health, stress, different environments, workplace cultures, experience levels, interpersonal relationships, distractions, and in particular, by its own limitations.
These limitations can be substantial and will be explained later in this Article.
Knowing how our information processing capabilities can be limited is important
in designing and delegating tasks to ensure that the information processing re quirements fall within the capabilities o f employees and colleagues (i.e. within
their memory, attention and decision-making capabilities) such that the following are minimised:
Failure to see information
Misunderstanding inform atio n
Handling the information incorrectly
Forgetting the information.
Reacting inappropriately
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