11.8 Flashcards
Uses of electrical power
Electrical heating
Lighting
Mechanical power
Electronic devices
Lighting equipment is used where
Cockpit
Cabin area
Outside
Why light cockpit
Illuminate panels , maps , instruments
Why light outside aircraft
Visability to other aircraft
Illuminate ground during take off/ landing
2 electrical power subsystems
Generation subsystem
Distribution subsystem
How is ac power generated
By engines during flight
How is ac generated in an emergency
By hydraulic motor or propeller
How many generators per engine for ac supply
1 per engine
787 has 2
How do you convert ac to dc
TRU
How is ac voltage distributed
115v at 400hz
How many phases is ac voltage generated
3
% of energy supply ac consumers need
95
What are the ac voltage consumers
Heating
Lighting
Mechanical equipment
How many sources does dc voltage come from
2
What are the sources of dc voltage
Tru - convert 115v ac to 28v dc
Nickel cadmium Battery - gives 24v dc
% of energy dc consumers use
5%
What are dc consumers
Electrical equipment
Control and monitoring
What are the dc generators
Alternators and starter generator
What do batteries do in dc
Provide power for emergency distribution, apu starting and engine start
Power distribution parts
Main , essential , emergency
What is essential power distribution for
Allow safe flying
What is emergency power distribution for
Safe landing
What does a bus do
Connects power source to electrical consumer
How many ac buses
3 main buses , one for each phase
What does load shedding do
Improves reliability of power relays
How is manual load shedding done
Via push button
What’s auto load shedding used for
Prevent overload or detect overload of generators
Where is emergency power available
Aircraft battery , power for 30 minutes
Where does dc voltage go in emergency power
24v dc to dc bus
Where does ac voltage go in emergency power
115v ac after static inverter to ac emergency bus
where does dc voltage go in emergency power
28v dc via tru to dc bus
3 disrupter components
power relays
circuit breakers
current transformers
boeing emergency power switching
via switch
where are fuses used
high current devices, easiest method of overcurrent protection
airbus emergency power switching
push button
how does a fuse or cb work
prevents currents higher then maximum allowed for cross section of wire
relays for AC
contactors &
breakers
purpose of a fuse or cb
prevent overheating and fire due to short circuit
AC line to nuetral voltage
115v
why are cb’s replacing fuses
reset quickly and have manual on/off switches for deactivation
AC line to line voltage
200v
whats a orange colour cb
pulled by flight crew
whats a grey collar cb
pulled during maintainece
purpose of csd’s
add or subtract speed
whats a red safety clip cb
prevent cb from closing
whats a red safety tag cb
used during ground maintenance
advantages to 3 phase ac generation
2 different voltage levels without additional equipment needed
when monitoring what are the green knobs for
essential systems
what do you do in low speed range
increase speed
what do you do in high speed range
decrease speed
what’s the low speed region operation
overdrive
what’s the high speed region operation
underdrive
whats straight drive used for
acceleration & deceleration
how is DC power generated
via the TRU
how many busses per TRU
1
what does the TRU do
convert 115v AC into 28v DC
purpose of battery
emergency power & apu starter motor power
how many batteries do aircraft use
1,2, or 3
whats the most common battery type
nickel cadmium
advantage of nickel cadmium batteries
less maintenance costs & low temperature performance
what does workshop check for in batteries and when
check for good battery condition , checked every 2000 operating hours
nickel cadmium saftey tips
special care when charging and discharging , don’t discharge battery under 22v
what are lithium ion batteries used for
large amount of power in a short period and high energy tasks such as jet engine start up
how many cells doe a lithium ion battery have
8 cells which produce 28v dc at 75amp
what makes lithium ion better then nickel cadmium
30% lighter , improved power quality, compact
how is ground power supplied
1 external source or 1 apu generator
ground power supply for large aircraft
2 or 4 external power sources and up to 2 APU generators
how many pins in a receptacle
6
4 thick pins , 2 shorter thinner pins
what does holding strap do
supports weight of cable
how is towing power supplied
only using aircraft battery
why cant you carry too many apu starts immediately after each other
battery cell overheats and reduces electrolyte level and can melt plastic separator
