Electrics Flashcards
Is a/c d.c
All dc aircraft
How many generators
4 ac gens,
How many batteries
2, main and apu
External dc
Just to start apu
What is dc power center
DCPC
Aft all ac, front all dc
All rectified at front
What is minimum gen capacity
Min 40kva per gen, upto 90kva for a few secs
What is apu gen
40kva in air 45 on grnd
What is apcp
What is EMS on electric control panel
For engineering isolates certain cab,s, do not leave on as will drain battery
How many ac busses
4 and 1 ac essential bus
What dc busses are there
Dc bus 1,
dc bus 2,
batt bus,
dc ess bus,
av batt direct bus,
dc emergency bus,
apu batt direct bus,
External power for zero degrees and below
Always ext power at freezing
Where is external power elec service panel
Aft of aircraft l/h side below baggage door
Where is apu shutoff
Outside aft elec service panel
Where do ems cdu 1 and 2 get info from
Complete system
P11
What do the EMS-CUD,S do
The electrical management system (EMS) consists of two electrical management system control display units (EMS CDUs), which interface with the battery master switch on the electrical control panel (overhead panel). The two identical EMS CDUs form part of the AC and DC electrical distribution. One EMS CDU is located on each pilot side panel. The EMS CDUs provide the operator with the status/remote control of certain circuit breakers, distribution contactors and switches, and the test facility for some circuits. They operate in two modes of operation, normal and maintenance mode.
What happens on power up
Power-Up The EMS CDUs show the PLEASE WAIT…. EPDS STARTUP IN PROGRESS message while it checks for correct ARINC 429 communications with all processor controlled power centers and distribution assemblies (PCDAs). The software shows in the lower left corner of the EMS CDUs an “S” character for a slave EMS CDU and an “M” character for a master EMS CDU. Initially, both EMS CDUs power up as slaves if all CBs are IN, or as master otherwise. An EMS CDU becomes master when key selections are made such as acknowledging a tripped breaker. Both EMS CDUs may be masters. If there have been no key selections, or the data displayed has not changed within 2 minutes of power-on or the last selection, the screen goes dark. The dark screen is a screen saver standby mode for the EMS CDUs.
What is displayed lower /left corner od EMS CDU
Master or slave icon-M-S
Aural warning test 1
AURAL WARNING TEST 1 AURAL WARNING TEST 2 Depress the AURAL WARNING TEST 1 (2) right display select key and note the following: • Aural warning test 1 (2) • “STALL” aural • Overspeed tone • Emergency descent (optional) • Triple chime tone (master warning) • “NO TAKEOFF” aural • “LEFT ENGINE FIRE” aural • “RIGHT ENGINE FIRE” aural • “APU FIRE” aural • “SMOKE” aural • “CABIN ALTITUDE” aural • “GEAR BAY OVERHEAT” aural • “LEFT REVERSER UNLOCKED” aural • “RIGHT REVERSER UNLOCKED” aural • “NORMAL BRAKE FAIL” aural • Single chime tone (any caution) • “GEAR” aural • Cavalry charge two times (autopilot) • “AUTOTHROTTLE” “AUTOTHROTTLE” aural • C-chord tone “ALTITUDE” aural • Double C-chord tone (vertical track alert) • Single chime (DH & MDA) • Trim clacker tone
What are extended functions
Extended Functions
Figure A26 The extended function mode (also known as diagnostic mode) allows access to special test, diagnostic, and configuration features of the electrical system. They are as follows: •
Signboard menu
•Data menu
•Special test modes The extended functions are only available with the aircraft on the ground. These functions are activated by depressing the CNTL function key, then depressing the lower left display key followed by the lower right display select key. Pressing the EMER CNTL function key aborts the extended function mode. Access to the extended function mode is inhibited in flight.
What is signboard menu
A24
Signboard Menu Figures A27, A28 and A29 All ARINC 429 data bus communication for the electrical power distribution system (EPDS) passes through the EMS CDUs. The EMS CDUs have the capability to display all ARINC data labels it receives in signboard data format. The signboard menu page automatically opens when the extended function mode is accessed. The signboard menu may be selected by depressing the STAT function key while in the extended function mode. The signboard data displayed for each received label is 16 bits of binary and status data. The operator is able to select between data received from each of the EPDS members, and from DAUs (1 and 2), or data to be transmitted to the DAUs (1 and 2), or the EPDS members.
Special test modes
Virgin start will wipe all data from aircraft
Virgin Start The virgin start option forces the selected assembly to perform a “virgin start” at the next power application. Virgin start option initialization causes all of the assemblies CBs to change to OUT status. Each circuit breaker must be manually reset.
What are discreet inputs
Discrete Inputs Figure A35 Various cockpit control switches and discrete inputs from some LRUs are routed directly into both EMS CDUs to allow operation of aircraft systems loads that are directly controlled by the electrical system, i.e. landing lights. EMS CDU 1 SYSTEM CIRCUIT BREAKER SYS STAT TEST CNTL PAGE NEXT PAGE PREV BUS BUS BRT CONT EMER Discrete Inputs PCDA BUS The state of the discrete inputs is placed directly onto the PCDA BUS to be broadcast to all power center and distribution assemblies. The assemblies monitor the state of these switches that are used as variables in the logic equations to determine the output state of controlled loads.
How is power system divided
The AC power distribution system is subdivided into: • Primary power distribution • Secondary power distribution The primary and secondary power distributions are controlled by the AC power center (ACPC) installed in the baggage compartment. For primary power distribution, the ACPC connects the output of the AC power generation system to four primary AC buses. These four primary AC buses are located in the ACPC.
What bare the components
COMPONENTS;
Primary AC power supply consists of the following components:
Variable frequency generators (VFGs)
Line current transformer assemblies (LCTAs)
Generator line contactors (GLCs)
Generator control units (GCUs) Electrical control panel
What is power
115/200v ac
Most gpu,s are 45kva
5000 series needs70kva
What is LCTA
There are four line current transformer assemblies (LCTAs) located at the bottom of the ACPC (one per generator). They provide the GCUs with the current draw from the ACPC main AC buses.
HOW MANY BUSSES
8 officially
EHP meaning
Electrical hydraulic pump
Do generators have own oil supply
Each generator is cooled and lubricated by its own self-contained oil system. The generator shaft is designed to shear, if ever an oil starvation resulted in a seized generator.
Outboard number generator
What is GLC 4
AC bus 4
Where is LCTA situated
Back of aircraft opposite baggage door
How many LCTS,s
4,; 1 per GLC
How many GCU,s
5 including apu GCU
What is kva for each gen
40kva continuous
What happens if 1 and 4 gens replaced
They have a different phase rotation, check phase rotation to colour on posts
What happens if oil temp is too high
Oil discharged via thermal release
What is main terminal block
Main Terminal Block Figure B6 The main terminal block has four stud connections designated: T1, T2, T3, G. The feeders to the ACPC are connected here. The neutral lead is designed to prevent accidental connection to a phase stud. The studs are covered with a removable cover. Since the generators rotate in different directions depending on their position, the phase output differs. Phase rotation of generator 1 and 4 is A, B, C at T1, T2, T3. Phase rotation of generator 2 and 3 is C, B, A at T1, T2, and T3. Phase rotation is corrected by switching A and C phase of generators 2 and 3 at the ACPC.
What does GCU do
B16
Generator Control Units Figures B13 and B14
Each generator interfaces with its respective generator control unit (GCU). The GCU performs the following functions: • Monitors generator operating parameters • Controls generator field excitation • Interfaces with the AC power center (ACPC) via analog/discrete signals and RS-422 data bus • Interface with the DAU, via ARINC 429 data bus, for EICAS and CAIMS The GCUs are located in the baggage compartment near the ACPC. GCUs 1 and 4 are mounted above the ACPC, GCUs 2, 3, and APU are stacked in that order from bottom to top directly aft of the ACPC.
On power-up, the GCU receives power from the BATT BUS for power on built-in test (PBIT), initialization and fault protection. Once the engine starts rotating, the generator PMG power output is sufficient to power up the GCU. If both power sources are available, the PMG power takes precedence over the BATT BUS. Once powered, the GCU protection circuits monitor parameters from the generator, the ACPC and the fire pull handle (refer to table B1). If one of the parameters exceeds the trip value, the GCU turns off the generator by removing the main excitation field (MEF).
Where are GCU,s located
Aft fuselage next to power management unit, opp baggage door
What kva is apu
It is rated at 45 kVA during ground operations and 40 kVA continuous duty during flight conditions.
How does apu know its on the ground
WOW input is received by the GCU to change its load rating from 40 kVA to 45 kVA when on the ground. The GCU also gives load parameters to the APU full authority digital engine control (FADEC) for fuel adjustments, depending on generator load.
Where is line contractor for apu
In primary power sub assy, ACPC at back of aircraft
Are batteries being charged in ground service mode
Yes both batteries are being charged
What is EMI gasket
On the ACPC cover has to be removed to change cards, its on this cover
What are ACPC cards hooked up to
EMS CDU
Can EMS CDU inhibit the contractor operation
Using the EMS CDUs, the crew can monitor the contactor position and inhibits its operation. The EMS CDUs also receive discrete input from the ACMP switches (hydraulic control panel), which is forwarded to the secondary logic card along with the contactor inhibit command.
What are important busses
AC BUS 1 AND 4
HOW MANY transformers does the DC SYSTEM USE
4
Where are tru, sited
The DC power conversion system consists of four transformer rectifier units (TRUs) located in the forward equipment compartment.
What are the properties of the tru,s
Four transformer rectifier units convert variable frequency AC power (115/200 VAC 3 ∅, 324-596 Hz) to 28-VDC power. All four TRUs are located in the forward equipment compartment. Each TRU is rated at: 150 A continuous, 180 A for 5 minutes and 240 A for 5 seconds. Since the total estimated load on the aircraft is 329 A, any three TRUs are capable of supplying the entire load. An internal AC-powered fan cools each TRU. The fan has a blade spinning detection function that outputs a FAN FAIL discrete signal to the DCPC logic subassembly. Each TRU is equipped with an EMI filter, AC-DC converter, DC filter capacitors, interface balance transformer and a bleed discharge output filter. Each TRU is powered from a different AC bus, located in the cockpit circuit breaker panel (CCBP). Each TRU output is connected to one of four primary DC buses via their TRU contactors, located in the DCPC.
How many battery chargers
1 per battery , 2 total
Where is apu battery
The nicad APU battery is located in the AFT equipment compartment and is rated at 25.2 VDC, 42 ampere-hours (Ah). The APU battery is connected directly to the APU BATT DIR BUS located in the APU start contactor assembly (ASCA).
Where is avionics battery
The nicad avionics battery is located in the forward equipment compartment and is rated at 24 VDC, 25 Ah. The avionics battery is connected directly to the AV BATT DIR BUS located in the DCPC.
What does ASCA MEAN
The APU start contactor assembly (ASCA) contains the electrical feed components that operate the APU battery system. It is normally powered by the APU battery but can also be powered by the external DC system.
How many primary logic cards
Three primary logic cards, located in the ACPC control and logic subassembly, receive power availability information from the EPQM and control the APU/EPCL as well as the generator transfer contactors to allow the incoming AC to supply the ACPC AC buses.
Where is the cabin feeder card located
DC Cabin Feed Relay (K11)
The DC cabin feeder card, located in the DC power center (DCPC), contains two solid-state power controllers (SSPCs) and a cabin feed relay K11. Normally (not in ground service mode), DC BUS 2 supplies its cabin feed SSPC directly while DC BUS1 supplies its cabin feed SSPC via relay K11. This relay is energized by the DCPC primary logic cards to allow DC BUS 2 to power both cabin feed SSPCs when in the ground service mode.
What happens when external power is supplied to aircraft
External AC power is applied to the aircraft by connecting the external AC power cart to the aircraft AC power receptacle and energizing the cart power contactor. The contactor is energized by depressing the cart momentary ON switch. Once the cart power contactor is energized, external AC power is fed to the ACPC APU/EPLC. Inside the ACPC, EM 3 redirects AC power directly to the EXT AC TRU and through fuses to the EPQM. The EXT AC TRU converts the 115 VAC, 3Ø to 28 VDC. The DC power is fed to ACPC contactor coils (through EM 1 and 2), external AC panel lights (C/B), external AC interlock (C/B to EPQM) and K27 relay. The EPQM receives interlock power from the EXT AC TRU and monitors the external AC power quality through EM 3 fuses and the two LCTAs. At this point, the EPQM is powered and determines if the power quality is within specified parameters (voltage, frequency, current and phase rotation). If the power quality is good, the EPQM sends 28-VDC interlock power through pin F of the AC power receptacle, to keep the external AC power cart power contactor energized. At that moment, the ground personnel can release the cart momentary ON switch. Simultaneously, the EPQM illuminates the AVAIL legends of the EXT AC PBA (electrical control panel) and the EXT AC annunciator (aft service control panel). External AC power can be applied to the aircraft in two modes; ground service mode or normal mode. Under ground service mode, only the systems required for cabin operation are powered. In the normal mode, the whole aircraft is powered.
How many ac busses are there
4 plus ac ess bus
How many line current transformer assys
Line Current Transformer Assemblies Figure B43
Six 3 ∅ current transformer assemblies are located at the bottom of the primary power subassembly. They monitor the three phases of power input from the AC power sources, including external AC. From left to right, the sources monitored are:
•VFG 4
•VFG 3
•VFG 1
•VFG 2
•APU GEN
•Externa l AC All VFGs and APU LCTAs report to their respective GCUs, and the external AC LCTA reports to the EPQM, located in the ACPC control and logic subassembly.
What are the primary logic cards
Primary Logic Cards
Figures B44 and B46
Three primary logic cards interface with the GCUs and the EPQM for AC power source availability and bus fault information. They also monitor the GLCs, GTCs and the APU/EPLC positions via the status contacts, and provide contactor control for primary bus distribution (the GLCs are monitored and controlled by the GCUs but they are also monitored by the primary logic cards for distribution information). The primary logic cards work on a voting system where two cards must agree before an action is carried out. The distribution logic is built into each card, and primary distribution is carried out, even if ARINC 429 data bus communication is lost.
What are secondary logic cards
Secondary Logic Cards Figures B44 and B46 Four secondary logic cards monitor and control the AC bus feed, the electrical hydraulic pump (EHP) and cabin feed contactors for the respective AC bus. The combination of contactor, current sensor and the control functions of the secondary logic card is referred to as a “smart contactor” logic. The secondary logic cards interface with the EPQM for secondary load control under external power conditions. The secondary logic cards are also the point of connection for the thermal circuit breaker status lines and the cockpit switches for the hydraulic pumps, associated with an AC bus. Primary AC bus voltage sensing is also handled by the secondary logic cards.
Where are current sensors
What comprises emergency AC power supply
The emergency AC power supply system consists of a ram air turbine (RAT) system and associated control/distribution components. The RAT system is used to supply emergency hydraulic power to no. 3 hydraulic system and emergency AC power to the AC ESS BUS. The RAT is installed on the right of the lower nose forward fuselage in the RAT compartment. The RAT can be deployed throughout the A/C flight envelope. The deployment can be automatic or manual. The RAT can only be stowed, by technicians, when the A/C is on the ground. The RAT generator is rated at 9 kVA, 115/200 VAC, 3 ∅, over a frequency range of 325 to 475 Hz. The RAT GCU monitors and controls the output power of the RAT generator. The generator output is fed, through the RAT line contactor, to the AC ESS BUS located in the cockpit circuit breaker panel (CCBP). The electrical control panel provides reset and override functions for the RAT system using the RAT generator control switch (guarded PBA). A RAT system test can be carried out from the EMS CDUs.
What components in emergency ac supply
COMPONENTS
The emergency AC power supply system consists of the following components:
• Ram air turbine (RAT)
• RAT generator control unit (RAT GCU)
• Deployment actuator • Retraction pump
• Uplock mechanism
• Manual release cable
• RAT line contactor (RATLC)
• Electrical control panel
How many pins for dispatch
6 including rat lockout pin
What is priority on rat
Hydraulic pump
What deploy signal does rat com from
SPDA1
What do ADC1 AND ADC3 supply
How is the RAT re-stowed
Retraction Pump
Figure B20
Located in the upper avionics compartment above the RAT compartment, the retraction pump consists of a pump, a two-position selector valve (ARM/STOW), a retraction pump handle and a reservoir with a sight gauge and a fluid fill port. Selecting the STOW position on the selector valve ports fluid to the retract side of the deployment actuator. Once the RAT is engaged in the uplock, the selector valve is moved to the ARM position.
Why 14 sec before rat deployment
Gives crew time to re cycle generators
What happens when rat deployed
Generator Control and Distribution Figures B25, B26, B27 and B28 Once the RAT is deployed, its speed is controlled automatically by the RAT spinner which uses a spring-loaded governor to control the blade angle. Generator control and distribution is performed by the RAT GCU. It controls generator operating parameters and the RATLC which connects the RAT generator output to the AC ESS BUS. The generator operating parameters are monitored for: • Overvoltage trip 124 VAC • Underfrequency < 324 Hz • Feeder fault If any of the above parameters should occur, the GCU deenergizes the RATLC as well as the generator field excitation. The RATLC is also deenergized if the aircraft speed is below 147 knots or if the RAT GEN PBA is selected and AC BUS 4 has regained AC power. The RAT GCU reconnects the RAT GEN to the AC ESS BUS by energizing the RATLC, if the aircraft speed increases above 152 knots.
Does rat charge batteries
No, too much load
What is CCBC
Cabin circuit breaker panel
What hydraulic system is rat connected to
System 3
What is dc power emergency override
alternate DC power distribution (ADCPD)
The DC power emergency override system consists of a DC emergency override switch and five alternate DC power distribution (ADCPD) boxes, located in the cockpit and the baggage compartment. OVRD NORM The purpose of the DC power emergency override system is to reroute essential TRU 1 and essential TRU 2 output power directly to the four SPDAs, bypassing the DCPC. The DC power emergency override switch is manually selected by the crew in the event of a total loss of the DCPC control and logic functions.
What are ADCPD box 1 and 2
ADCPD Box No. 1 and 2
Figures C40, C41 and C45
The ADCPD box no. 1 and 2 are located in the cockpit, under the center instrument panel. Box no. 1 contains two diodes and a relay (K53). The diodes prevent reverse current flow between the two battery direct buses. Relay K53 is controlled by the DC emergency override switch. In the deenergized position, relay K53 connects essential TRU 1 output to the DCPC. In the energized position, K53 reroutes essential TRU 1 output to ADCPD box no. 3 which redirects the TRU output directly to the four SPDAs. Box no. 2 contains a single relay (K52) which is controlled by the DC emergency override switch. In the deenergized position, relay K52 connects essential TRU 2 output to the DCPC. In the energized position, K52 reroutes essential TRU 2 output to ADCPD box no. 4 which redirects the TRU output directly to the four SPDAs.
What are ADCPD boxes 3 and 4
ADCPD Box No. 3 and 4
Figures C40, C41 and C45
The ADCPD boxes no. 3 and 4 are located in the cockpit, under the left and right side consoles. Both boxes contain four circuit breakers and two relays each. The circuit breakers provide load protection when the essential TRUs are connected to the SPDAs. The relays are controlled by the DC emergency override switch. In the deenergized position, the relays connect the DCPC outputs to the SPDAs. In the energized position, the relays connect the essential TRU outputs from the ADCPD box 1 and 2 to the four SPDAs. ADCPD box no. 3 is used for essential TRU 1 and ADCPD box no. 4 is used for essential TRU 2.
ADCPD box 5
ADCPD Box No. 5
Figures C40 and C45
ADCPD box no. 5 is located in the baggage compartment on the right side and is mounted on the generator control units (GCUs) mounting frame. The box consists of a single relay (K51) which is continuously energized, through a terminal module containing five diodes, when the battery master switch (BMS) is selected in the ON position. Once energized, the relay provides 28 VDC from the APU BATT DIR BUS to the ACPC control power D (ACPC CTL PWR D). This 28 VDC is used to power the ACPC internal power supplies (microprocessor cards and the AC/DC converter card), allowing the ACPC to remain operational.
