flight safety embraer emb-120 brasilia pilot training manual
TRANSCRIPT
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FlightSafety International, Inc.Marine Air Terminal, LaGuardia Airport
Flushing, New York 11371(718) 565-4100
www.flightsafety.com
FlightSafetyinternational
EMB-120 BrasiliaPILOT TRAINING MANUAL
VOLUME 2AIRCRAFT SYSTEMS
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Copyright 1995 by FlightSafety International, Inc.All rights reserved.
Printed in the United States of America.
Courses for the EMB-120 Brasilia are taught at the following FlightSafety Learning Centers:
Long Beach Learning CenterLong Beach Municipal Airport4330 Donald Douglas DriveLong Beach, California 90808Phone: (562) 938-0100Toll-Free: (800) 487-7670Fax: (562) 938-0110
Atlanta Learning Center1010 Toffie TerraceAtlanta, Georgia 30354Phone: (678) 365-2700Fax: (678) 365-2699
Paris Learning CenterBP 25, Zone d Aviation d AffairesBldg. 404 Aeroport duBourget93352 Le Bourget, CEDEX FrancePhone: (+33) (1) 49-92-1919Fax: (33) (1) 49-92-1892
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FOR TRAINING PURPOSES ONLY
FOR TRAINING PURPOSES ONLY
NOTICEThe material contained in this training manual is based on information obtained from theaircraft manufacturers Pilot Manuals and Maintenance Manuals. It is to be used forfamiliarization and training purposes only.
At the time of printing it contained then-current information. In the event of conflictbetween data provided herein and that in publications issued by the manufacturer or theFAA, that of the manufacturer or the FAA shall take precedence.
We at FlightSafety want you to have the best training possible. We welcome anysuggestions you might have for improving this manual or any other aspect of ourtraining program.
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CONTENTSChapter 1 AIRCRAFT GENERAL
Chapter 2 ELECTRICAL POWER SYSTEMS
Chapter 3 LIGHTING
Chapter 4 MASTER WARNING SYSTEM
Chapter 5 FUEL SYSTEM
Chapter 6 AUXILIARY POWER UNIT
Chapter 7 POWERPLANT
Chapter 8 FIRE PROTECTION
Chapter 9 PNEUMATICS
Chapter 10 ICE AND RAIN PROTECTION
Chapter 11 AIR CONDITIONING
Chapter 12 PRESSURIZATION
Chapter 13 HYDRAULIC POWER SYSTEMS
Chapter 14 LANDING GEAR AND BRAKES
Chapter 15 FLIGHT CONTROLS
Chapter 16 AVIONICS
Chapter 17 OXYGEN SYSTEMS
WALKAROUND
ANNUNCIATOR PANEL
INSTRUMENT PANEL POSTER
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Revision 4 1-i
CHAPTER 1AIRCRAFT GENERAL
CONTENTSPage
INTRODUCTION ................................................................................................................... 1-1
GENERAL............................................................................................................................... 1-2
STRUCTURES........................................................................................................................ 1-2
General ............................................................................................................................. 1-2
Cockpit ............................................................................................................................. 1-5
Cabin ................................................................................................................................ 1-9
Doors.............................................................................................................................. 1-13
EMERGENCY EQUIPMENT .............................................................................................. 1-17General........................................................................................................................... 1-17
Emergency Locator Transmitter .................................................................................... 1-17
Emergency Exits ............................................................................................................ 1-19
Emergency Lighting....................................................................................................... 1-19
SYSTEMS ............................................................................................................................. 1-19
Electrical Systems.......................................................................................................... 1-19
Fuel System.................................................................................................................... 1-20
Auxiliary Power Unit ..................................................................................................... 1-20
Powerplant ..................................................................................................................... 1-20
Fire Protection................................................................................................................ 1-20
Ice and Rain Protection.................................................................................................. 1-20
Air Conditioning and Pressurization.............................................................................. 1-21
Hydraulic System........................................................................................................... 1-21
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Landing Gear and Brakes .............................................................................................. 1-21
Flight Controls ............................................................................................................... 1-21
Avionics ......................................................................................................................... 1-21
Oxygen........................................................................................................................... 1-22
PUBLICATIONS................................................................................................................... 1-22
QUESTIONS......................................................................................................................... 1-24
EMB-120 PILOT TRAINING MANUAL
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Revision 4 1-iii
ILLUSTRATIONSFigure Title Page1-1 EMB 120 RT Brasilia ............................................................................................... 1-2
1-2 Exterior Three-View Drawing .................................................................................. 1-3
1-3 Turning Distance ...................................................................................................... 1-4
1-4 Danger Zones ........................................................................................................... 1-4
1-5 Cockpit Layout ......................................................................................................... 1-5
1-6 Overhead Panel......................................................................................................... 1-6
1-7 Windshield and Direct Vision Windows .................................................................. 1-7
1-8 Normal and Emergency Window Operation ............................................................ 1-7
1-9 Pilots Seats .............................................................................................................. 1-8
1-10 Observers Seat......................................................................................................... 1-8
1-11 Pedal Adjust Mechanism.......................................................................................... 1-81-12 Pilots Seat Adjustment ............................................................................................ 1-91-13 Passenger Configuration/Interior Layout (Typical) ............................................... 1-101-14 Attendants Station (Typical) ................................................................................. 1-111-15 Attendants Panel ................................................................................................... 1-12
1-16 Toilet....................................................................................................................... 1-12
1-17 Galley ..................................................................................................................... 1-12
1-18 Forward Door Controls .......................................................................................... 1-13
1-19 Door Warning Lights.............................................................................................. 1-13
1-21 Forward Entry Door Operation .............................................................................. 1-14
1-20 Forward Door Emergency Valve ............................................................................ 1-14
1-22 Cargo/Service Door Location ................................................................................ 1-15
1-23 Cargo Door Operation............................................................................................ 1-16
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1-24 Doors Warning Lights (Overhead Panel) ............................................................... 1-161-25 Standard Emergency Equipment Location............................................................. 1-17
1-26 Life Vest Location and Operation .......................................................................... 1-18
1-27 Hand Hold Rope Location and Use ....................................................................... 1-18
1-28 Emergency Exit Operation ..................................................................................... 1-19
EMB-120 PILOT TRAINING MANUAL
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INTRODUCTIONThis training manual provides a description of the major airframe and engine systemsinstalled in the EMB-120 Brasilia. The information contained herein is intended onlyas an instructional aid. This material does not supersede, nor is it meant to substitutefor, any of the manufacturers maintenance or operating manuals. The material presentedhas been prepared from current design data.
Chapter 1 covers the structural makeup of the airplane and gives an overview of the systems.
An annunciator section in this manual displays all annunciator and other light indica-tions and should be folded out for reference while reading this manual.
Review questions are contained at the end of most chapters. These questions are includedas a self-study aid, and the answers can be found in the appendix section.
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CHAPTER 1AIRCRAFT GENERAL
1-1FOR TRAINING PURPOSES ONLY
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GENERALThe EMB-120 Brasilia is certified in accor-dance w i th FAR Pa r t 25 a i rwor th ine s sstandards. It is designed for passenger andcargo transportation on typical commercialair carriers. There are three types: RT, ER,and FC.
The minimum crew requirements for operationsin the EMB-120 Brasilia are one pilot and onecopilot. The pilot-in-command must have aBrasilia type rating and meet the requirementsof FAR 61.58 for two-pilot operation. The copi-lot shall possess a multiengine rating and meetthe requirements of FAR 61.55.
STRUCTURESGENERALThe EMB-120 Brasilia (Figure 1-1) is an all-metal construction, pressurized, low-wingT-tail, monoplane. Two Pratt and WhitneyPW118 engines are mounted on the wing, sup-ported by a semimonocoque/tubular nacellestructure. The landing gear is the retractable,twin-wheel type.
Figure 1-2 shows a three-view drawing of theEMB-120 Brasil ia with the principal di-mensions. Figure 1-3 shows turning distance,and Figure 1-4 is a diagram of danger zones.
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Figure 1-1. EMB 120 RT Brasilia
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1-3FOR TRAINING PURPOSES ONLY
61.45 FT(18.73 M)
(20.00M)(6.98M) 65.62 FT
22.90 FT
(6.35
M)
20.8
4 FT
)
64.90 FT19.78 M
21.59 FT6.58 M
WINGTOTAL AREA...... 424.46 FT 2 (39.43 M 2)ROOT CHORD ............ 9.22 FT (2.81 M)MEAN AERODYNAMICCHORD ....................... 6.56 FT(2.00 M)ASPECT RATIO............................. 9.92
HORIZONTAL TAILTOTAL AREA..... 107.65 FT 2(10.00 M )2ROOT CHORD.............. 6.00 FT(1.83 M)TIP CHORD.................. 3.64 FT (1.11 M)ASPECT RATIO............................ 4.63
VERTICAL TAIL
TOTAL AREA........... 74.28 FT2 (6.90 M )ROOT CHORD............10.43 FT(3.18 M)TAPER RATIO............................... 0.65DORSAL FINAREA....................... 15.39 FT 2
(1.43 M ) 2FUSELAGEOUTSIDEDIAMETER................... 7.48 FT (2.28 M)
22.7
7 FT
6.94
M(
2
30.54 FT(9.31 M)
WING REARSPAR
MAC6.56 FT(2.00 M)
26.21 FT(7.99 M)
REFERENCEORIGIN LINE
Figure 1-2. Exterior Three-View Drawing
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EMB-120 PILOT TRAINING MANUAL
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61.85 FT(18.35 M)
50
51.71
FT
(4.08 M
)13
.39 FT
(15.76 M
)
47.07 FT(14.35 M)
35.76 FT
(10.90 M)29.89 FT(9.11 M)
APU EXHAUST27 FT RADIUS
AREA TO BECLEARED PRIORTO ENGINESTART
10 FT RADIUS
FULL THROTTLEVELOCITY FALLSBELOW 15 MPH
60 FT100 FT
Figure 1-3. Turning Distance
Figure 1-4. Danger Zones
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COCKPITGeneralThe general layout of the cockpit is shown inFigure 1-5. The overhead panel is shown inmore detail in Figure 1-6.
Specific customer requirements may causesome instruments and equipment to vary fromstandard configuration.
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OVERHEAD PANEL
FORWARD PANEL
PILOT'S CONSOLE CENTER CONSOLE
Figure 1-5. Cockpit Layout
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Figu
re 1
-6.
Ove
rhea
d Pa
nel
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Windshield and WindowsThe EMB 120 has two windshields and two di-rect vision windows (Figure 1-7). Only thewindshields are heated.
The direct vision windows may be partiallyopened dur ing normal opera t ion on theground. They may be totally removed in caseof loss of visibility through windshield or forc o c k p i t eva c u a t i o n . A W I N D OW N OT
CLOSED inscription, on the window frontframe, will be visible when the window is notclosed properly. Window operation is shownin Figure 1-8.
Crew SeatsThe pilots seats (Figure 1-9) are fixed to slidetracks which permit fore, aft, and lateral seatmovement. They are also equipped with a
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Figure 1-7. Windshield and Direct Vision Windows
21
43
PRESSING LOCK BUTTON, PULL HANDLEIN AND BACKWARD
WINDOW PARTIALLY OPEN
TO REMOVE WINDOW FROM ITS TRACKPULL IT UP AND INWARD
PULL DOWN EMERGENCY HANDLE ANDTURN IT
Figure 1-8. Normal and Emergency Window Operation
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height adjustment mechanism to lower or raisethe seat. The seats include quick-disconnectcombination lap belts and shoulder harnesswith inertial reels. Lateral seat movement ispossible only when the seat is in the full AFTposition.
Observers SeatA foldable jump seat (Figure 1-10), installed
in the floor at the cockpit entrance, may be usedfor an observer or a third crew member. Theobservers seat is provided with safety beltand inertia reel.
Pedal AdjustmentA mechanism under each pilots front panel(Figure 1-11), allows the pilots to adjust theirpedals for optimum position.
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INERTIAL SHOULDERHARNESS
BUCKLE
VERTICAL ADJUSTMENTCONTROL HANDLE
INERTIAL SHOULDERHARNESS LOCKING HANDLE
TRACKSHORIZONTALADJUSTMENTCONTROL HANDLE
ARMREST
PILOT'SPEDALS
COPILOT'SPEDALS
PEDAL ADJUSTMECHANISM
Figure 1-9. Pilot Seats
Figure 1-10. Observers Seat Figure 1-11. Pedal Adjust Mechanism
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Seat AdjustmentEach seat may be adjusted to position the pilotfor optimum control column operation usingthe alignment balls as shown in Figure 1-12.
This is accomplished by first moving the seatup or down until the pilots line of sight reachesthe same horizontal plane as the alignmentballs. Then, move the seat fore and aft so thatthe opposite white ball becomes aligned withthe black ball.
CABINFigure 1-13 shows typical passenger config-uration and internal layout.
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LINE O
F SIG
HT
FRONT VIEW
TOPVIEW
WHITE(2)
BLACK
Figure 1-12. Pilot Seat Adjustment
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Figure 1-13. Passenger Configuration/Interior Layout (Typical)
COPILOTSEAT
OBSERVERSEAT
TOILETPARTITION
ATTENDANT'SCABINET
TOILET CLOSET
SIDEPANEL
PASSENGERSEATS
REARPARTITION
CARGOCOMPARTMENTCLOSET
GALLEY
ATTENDANTSEAT
PILOTSEAT
COCKPIT
FRONTPARTITION
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Attendants StationThe attendants station, shown in Figure 1-14,is located next to the forward entry door. It isprovided with interphone, folding seat, fire ex-tinguisher, two life vests, and a flashlight.
The attendants panel (Figure 1-15) has con-trols for the emergency lights, cabin lights,cabin temperature, and forward entry door.
ToiletThe toilet, as seen in Figure 1-16, is locatedopposite the forward entry door. On some ear-lier aircraft the toilet may be located in the rearof the aircraft. The galley (Figure 1-17) is lo-cated just aft of the forward entry door.
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FIREEXTINGUISHER
FLASHLIGHT
ATTENDANT'SSEAT
(FOLDED IN)
ATTENDANT'SPANEL
ATTENDANT'SINTERPHONE
ATTENDANT'SCABINET
RH CLOSET
ATTENDANT'SPORTABLEOXYGEN CYLINDER
ATTENDANT'SSEAT IN POSITION
FOR USE
EXIT
EXIT
TOILET
TWO LIFEVESTS
Figure 1-14. Attendants Station (Typical)
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PUSHEXIT
CABIN TEMPADJUST KNOB
EMERGENCYLIGHTING SWITCH
COURTESY LIGHT SWITCH
PAX CABINLIGHT SWITCH
FWD DOORCONTROL
INTERCOMPHONE
SPARETOILET-ROLL
STOWAGE
TOWEL AND DRY/MOISTENED TISSUE
HOLDER
"RETURN TO YOURSEAT" WARNING
SIGN
HANDLE
TOILET-ROLLHOLDER
WASTEDISPOSAL
TOILET ASSEMBLYSHROUD
TOILET SEAT
PUSH-PULLBUTTON FORFLUSHINGTOILET BOWLLIQUIDDISINFECTANT
COVER
ASHTRAYS
Figure 1-15. Attendants Panel
Figure 1-16. Toilet Figure 1-17. Galley
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DOORSForward Entry DoorThe forward entry door, located just aft of thecockpit on the left side, incorporates foldingair stairs and is hinged at its lower edge.
In normal operation, the door is closed (raised)by two hydraulic door actuators, and opened(lowered) manually with hydraulic dampen-ing. With no hydraulic pumps operating, anaccumulator provides sufficient pressure forfour complete operations of the door. The doormay also be raised manually from outside bya ground attendant.
The door may be operated from either insideor outside the aircraft. The interior control islocated on the flight attendants panel just in-side the door, and the exterior control is on thefuselage at the lower left side of the door(Figure 1-18). Each control panel incorpo-rates a pushbutton which energizes a solenoidvalve, allowing hydraulic power to raise thedoor, and blue light that illuminates while thedoor is moving up. The interior control panelalso incorporates a circuit breaker.
With the door in the raised position it is thenclosed and locked by operation of either theinner or outer door handles.
When the forward door is not closed and lockedthe FORWARD light on the DOORS panel,shown in Figures 1-19 and 1-24, illuminates.
If the forward door actuator remains pressur-i z ed a f t e r c l o s ing , b lock ing t he doo rhydraulically, the FORWARD ACTUATORlight on the DOORS panel illuminates (Figures1-19 and 1-24). In this event, an emergencyvalve (Figure 1-20) is provided in the cockpitto allow the door to be lowered
Normal door operation from outside the air-craft is shown in Figure 1-21.
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Figure 1-19. Door Warning Lights
PRESSCLOSEDOOR
FWD DOOR
CONTROL IN TRANSIT
PRESSCLOSEDOOR
CONTROL IN TRANSIT
EXTERIOR FWD DOORCONTROL PANEL
FWD DOOR
INTERIOR FWD DOORCONTROL PANEL
2
DOORSWARNING
CAUTIONALARM
CANCEL
FORWARDACTUATOR
FOWARD
CARGO
SERVICE
DOORS
Figure 1-18. Forward Door Controls
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FORWARD DOOREMERGENCY VALVE
Figure 1-20. Forward Door Emergency Valve
TO OPEN PASSENGER/CREWENTRY DOORFROM THE OUTSIDE
PULLACTUATINGHANDLEOUTWARD
PULL DOOR
WAIT UNTIL DOOR ISFULLY LOWERED
OPENACCESSPANEL
DEPRESS DOORACTUATING BUTTON WAIT UNTIL DOOR
LIFTS UP TO ITS STOP
PUSH ANDLOCK DOOR
TO CLOSE PASSENGER/CREWENTRY DOORFROM THE OUTSIDE
Figure 1-21. Forward Entry Door Operation
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Cargo/Service DoorsLocation of the cargo and service doors isshown in Figure 1-22.
Cargo DoorOperation of the cargo door is shown inFigure 1-23. The initial opening (displace-ment of the door inward) and final closing(displacement of the door outward) are con-trolled by the external handle in the lowerhalf of the door. This handle is also re-sponsible for door locking.
When the cargo door is not closed and lockedthe CARGO l igh t on the DOORS pane l(Figures 1-19 and 1-24) illuminates.
Service DoorsThe service doors are the external doors whichprovide maintenance access to airplane sys-tems and equipment.
The controls rigging door is located on thefuselage beneath the cockpit providing accessto the fuselage pressurized compartment. Theelectronic compartment door is located insidethe nose landing gear compartment. The fuelcompartment doors are located under the wingoutboard of the right engine nacelle.
If any door is not closed and locked theSERVICE light on the DOORS panel (Figures 1-19 and 1-24) illuminates.
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CARGODOOR
FORWARDDOOR
ELECTRONICCOMPARTMENT
DOOR
CONTROLRIGGING
DOOR
REFUELINGCOMPARTMENT
DOORS
Figure 1-22. Cargo/Service Door Location
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TO OPEN:
PUSH THE DOOR
2 3
PULL THE ROPE
4TURN THE HANDLE
AND PUSH IN TO LOCK
5
PULL HANDLE OUTAND TURN
1
TO CLOSE:
DOORS
FORWARD DOOR LIGHT (RED)
ILLUMINATED - WHEN THE FORWARDDOOR IS NOT CLOSED AND LATCHED.
SERVICE DOOR LIGHT (RED)
ILLUMINATED - WHEN THE CONTROLRIGGING DOOR OR ELECTRONICCOMPARTMENT DOOR IS NOT CLOSEDAND LATCHED.
NOTE:FOR AIRPLANES POST-MOD. SB 120-031-0008 ORSN 120.046, 120.050, AND SUBSEQUENT, THE SERVICE LIGHT IS ILLUMINATED WHENEVER ANY REFUELING/DEFUELING SYSTEM DOOR IS OPEN.
FORWARD ACTUATOR LIGHT (RED)
ILLUMINATED - WHEN THE FORWARDDOOR ACTUATORS HYDRAULIC LINE
REMAINS PRESSURIZED AFTER DOORCLOSING. FOWARD ENTRY DOOR IS
HYDRAULICALLY BLOCKED.
CARGO DOOR LIGHT (RED)
ILLUMINATED - WHEN THE CARGO DOOR IS NOT CLOSED AND LATCHED
FORWARDACTUATOR
FORWARD
CARGO
SERVICE
Figure 1-23. Cargo Door Operation
Figure 1-24. Doors Warning Lights (Overhead Panel)
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EMERGENCY EQUIPMENTGENERALLocation of fire extinguishers, portable oxy-gen cylinders, oxygen masks, smoke goggles,escape ropes, and first aid kit is shown in Figure1-25. Emergency flashlights, though not shown,are also provided in the cockpit and cabin.
Passenger seat cushions can serve as a floata-tion device and are easily removable. Lifejackets for the attendant and observer are stowedin the attendants panel, and for the pilotsunder their seats (Figure 1-26). Escape ropelocation and use is shown in Figure 1-27.
EMERGENCY LOCATORTRANSMITTERAn Emergency Locator Transmitter (ELT) islocated in the dorsal fin (Figure 1-25). A re-mote switch on the copilots panel selectsei ther automat ic (ARM) or manual (ONRESET) activation. With the remote switch inthe ARM position, the ELT automaticallytransmits on 121.5 and 243.0 MHz when theairplane is subjected to a longitudinal decel-eration of 5 to 7 G.
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CREW PORTABLEOXYGEN CYLINDER(BEHIND COPILOT'S
SEAT)COCKPITESCAPE
ROPE
EMERGENCY EXITSELT
OXYGEN MASK(ON LATERALCONSOLES)
CRASHAXE
FIRE EXTINGUISHER(BEHIND PILOT'S SEAT)
FIRE EXTINGUISHER(BEHIND ATTENDANT'S SEAT)
BAG CONTAININGFULL FACE MASK
AND SMOKE GOGGLES
PORTABLEOXYGEN CYLINDER
(RIGHT CLOSET)
FIRST AID KIT(GALLEY)
PAX EMERGENCY ROPE
Figure 1-25. Standard Emergency Equipment Location
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4
JERK TO INFLATE. IF LIFEJACKET FAILS TO INFLATE,USE ORAL TUBE.
ORALTUBE
2
DON JACKET AND PUTSTRAPS AROUND BACK
3
BRING TO FRONT, MAKING SURE INFLA-TION TAB IS NOT UNDER WAIST STRAP.PROCEED TO SNAP ONTO "O-RING" ANDPULL SHORTENING TAB TO ADJUST.
1PILOT'S
SEAT
ATTENDANT'SSEAT
HAND HOLDROPES
REMOVE THE CARPETSTRAP (AIRPLANES
PRE-MOD SB 120-025-0081)
PASS ROPE AROUND SEATLEG (AIRPLANES POST-
MOD SB 120-025-0081 ORSN 120.035 AND ON)
OR
OR
SNAP HOOKONTO RING
1 2
3 4
Figure 1-26. Life Vest Location and Operation
Figure 1-27. Hand Hold Rope Location and Use
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EMERGENCY EXITSIn addition to each pilots direct vision window,there are three emergency exits in the cabin ofthe aircraft. Two are overwing exits on each sideof the fuselage and one is a floor level exit onthe right rear side. All are plug-type exits thatopen to the inside of the cabin from either in-side or outside the fuselage. Emergency exitoperation is shown in Figure 1-28.
EMERGENCY LIGHTINGEmergency lighting is provided internallyfor each emergency exit door, the mainentry door, and the aisle. External lightingilluminates the wing and ground in thevicinity of each exit.
The emergency lights and their operationare covered in Chapter Three, Lighting.
SYSTEMSELECTRICAL SYSTEMSTwo 400-amp, 28-volt DC starter-generators,one on each engine, are the primary source ofelectrical power. Two 150-amp, 28-volt DCgenerators, one each in the propeller reductiongearbox, supply power to essential circuits incase of a complete failure of the primary 28VDC sources.The airplane AC power is provided by twostatic inverters, one being a standby.A 24-volt nickel-cadmium battery is designedto assist each starter-generator during theengine starting cycle, and supply essentialloads in the event of complete generator/en-gine failure.
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1 2
3VALID FOR ALL EMERGENCY EXITS
REMOVE
Figure 1-28. Emergency Exit Operation
-
An emergency battery is available as a backupfor selected loads and to provide emergencypower for both the standby horizon and gen-erator control units (GCUs).A starter-generator installed on the APU, iden-tical to the main generators, is used to start theAPU. It may be used to provide electricalpower to all buses on the ground, and forstandby power in flight.
FUEL SYSTEMThe fuel system is made up of two tanks, onein each wing. Each wing tank is made up oftwo independent cells separated by the wheel-well. These inboard and outboard cells areinterconnected by tubes for gravity fuel trans-fer. Fuel is supplied to the engine by pumpsinstalled in a collector tank located in the low-est region of each inboard fuel cell. Each wingtank has a usable capacity of 437 US Gal.
Each engine is supplied independently fromits wing tank. A crossfeed line allows eitherwing tank to supply both engines simultane-ously. Gages for monitoring fuel flow and fuelquantity are located on the fuel managementpanel in the cockpit.
The aircraft may be gravity fueled using over-wing fillercaps, and manually defueled. Apressurized system is provided for faster fu-eling/defueling.
AUXILIARY POWER UNITThe APU, located in the tail cone, is a gas tur-bine engine used to supply pressurized air andelectrical power to the airplane.
POWERPLANTTwo Pratt and Whitney PW118 or PW118Aturboprop engines, both flat rated at 1800SHP, are mounted on the wings. The engine isa three-shaft, two-spool gas generator with afree power turbine.
Engine airflow is straight-through with airentering an intake below the propeller spinner,then through an S-duct to the engine. This S-duct provides inertial separation and protectionin the event of foreign object ingestion.
PropellerEach engine is equipped with a HamiltonSundstrand model 14 RF-9, four-blade, con-s t an t speed , r eve r s ib le , fu l l f ea the r ingpropeller. Automatic feathering and propellersynchronization systems are installed.
FIRE PROTECTIONFire detectors installed in the engine acces-sories section, wheelwell, pipe zones and APUcompartment provide fire or overheat warning.
The engine fire control panel, installed on thecenter glareshield panel, is provided with bot-tle discharge ability and INOP lights, shutoffvalve position indicators, fire warning lights,extinguishing handles, and a test button. TheAPU fire control panel on the overhead APUCONTROL panel, provides the means for APUfire detection and extinguishing.
A smoke detection system is installed for usewhen the a i rplane is conver ted to cargoconfiguration.
ICE AND RAIN PROTECTIONAn electrical anti-icing system protects the leftand right windshields, pitot/static tubes, staticports, angle of attack, and side slip sensors.
Electrical deicing system protects the pro-peller blades to permit unrestricted operationinto known icing conditions. The wings, sta-bilizers, vertical fin, and engine air inlets areprotected by inflatable deicers.
The rain removal system consists of two in-dependent two-speed wipers, one on eachwindshield.
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AIR CONDITIONING ANDPRESSURIZATIONThe air-conditioning and pressurization sys-tem provides conditioned pressurized air to thecockpit and passenger cabin. The system is op-erated using bleed air from either the enginesor the APU.
The cockpit and passenger cabin are suppliedby separate air ducting with cross-connectingcapabilities. Temperature of the two zones isindependently controlled.
The cabin pressure control, designed to main-tain a 7 psi cabin/ambient pressure differential,maintains the cabin at sea level pressure up toan altitude of 16,800 ft. Control is accom-p l i shed by an e l ec t ropneuma t i c va lve(automatic mode) or by a pneumatic valve(manual mode).
HYDRAULIC SYSTEMHydraulic power is provided by two indepen-dent systems. Each system is powered by amain pump, driven by the left or right propellergearbox. DC powered electrical pumps providebackup pressure for each system. Two pres-surized hydraulic reservoirs are arranged sothat leakage in either of the systems will notaffect operation of the other. Each hydraulicreservoir is equipped with transmitters andswitches that display system status on the HY-DRAULIC POWER PANEL located on thecockpit overhead panel.
LANDING GEAR AND BRAKESThe landing gear is a conventional tricycle,dual-wheel, forward retracting type.
Three modes are provided for operation of thelanding gear:
Normal hydraulic retraction and extension Alternate electrical override extension Emergency free-fall extension with man-
ual release of the uplocks.
Nosewheel steering is controlled through asteering handle on the pilots left console.Limited nosewheel steering is available withthe rudder pedals.
A normal brake system is actuated by con-ventional means through the pilot or copilotrudder pedals and controlled by a dual anti-skidsystem.
An emergency brake sys tem is ac tuatedthrough a handle and control valve. Pressureto the brakes is proportional to handle dis-placement.
FLIGHT CONTROLSFlight controls are operated by conventionalcontrol wheels, columns, and rudder pedals forpilot and copilot. They are normally inter-connec t ed and j o in t l y ope ra t ed . I n anemergency, control wheels and columns maybe disconnected between the pilot and copi-lot, rendering the airplane controllable byeither. Pedals are independently adjustable, al-lowing comfortable operation.
The elevators and ailerons are mechanicallyactuated. The rudder is hydraulically actu-ated with a mechanical back-up.
The flaps, divided into three panels per wing,are hydraulically actuated.
Elevator and aileron trim is by mechanical ac-tuators to trim tabs. Rudder trim is hydraulic.
AVIONICSFlight instrumentsConventional air data instruments (airspeed,altimeter, and vertical speed indicator) areprovided with separate pitot/static sources forpilot and copilot.
An independent standby attitude indicator onthe center panel, and a standby compass inthe top of the windshield center post, provideback-up attitude and heading information.
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NavigationThe navigation system includes the followingequipment:
Electronic flight instrument system(EFIS)
Two independent attitude and headingreference systems (AHRS)
Two radiomagnetic indicators (RMI) Two distance measuring equipment
(DME) systems Two VHF/NAV(VOR/ILS/MB) radios Two ATC transponders One automatic direction finder (ADF) One radio altimeter system
The EFIS displays consist of two electronic at-t i t ude d i r ec to r i nd i ca to r s (EADI) , twoelectronic horizontal situation indicators(EHSI), and a multifunction display (MFD).The EADI and EHSI are color cathode-raytube displays.
The AHRS provides attitude and heading sig-nals to the EFIS and autopilot/flight director;pitch and roll angle to the weather radar; andturn rate and normal acceleration data to theautopilot, if required.
Radar is displayed on the multifunction displayand each EHSI when in the ARC or map mode.
AutoflightThe autoflight system is a fully integratedthree-axis dual flight control system includ-ing manual electric trim. It is divided into twogeneral systems:
Flight director system Autopilot system
Available functions include heading, altitude andairspeed control, VOR/ILS approach coupling,glide-slope operation, and go-around mode.
CommunicationThe communication system includes:
Interphone for communication betweenpersonnel in the cockpit, and flight crewmembers and cabin/ramp personnel
Passenger address system for commu-nication between flight crew membersand passengers
VHF for air-to-air and air-to-groundcommunication.
The airplane is equipped with a cockpit voicerecorder.
OXYGENThe airplane is equipped with a conventionalgaseous oxygen system. One oxygen cylin-der supplies low-pressure oxygen to both thecrew and passenger systems. The crew systemconsists of three quick-donning masks. Thepassenger system consists of continuous flowmasks in dispensing units, installed in theaisle ceiling. The units open automatically,when cabin altitude exceeds 14,000 feet, ormanually by a switch installed on the controlstand in the cockpit.
Other related equipment includes portableoxygen cylinders, smoke goggles, and fullface masks.
PUBLICATIONSThe FAA-approved Airplane Flight Manual(AFM) is a required flight item. It contains thelimitations, operating procedures, performancedata pertinent to takeoffs and landings, andweight and balance data. It does not containenroute performance information. The AFMalways takes precedence over any other pub-lication.
The EMB 120 Operating Manual contains ex-panded descriptions of the airplane systemsand operating procedures. It contains enrouteflight planning information as well as sometakeoff and landing performance information.
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The EMB120 check l i s t (QRH QuickReferrence Handbook) contains abbreviatedope ra t i ng p rocedu re s and abb rev i a t edperformance data. If any doubt exists or if theconditions are not covered by the checklist, theAFM must be consulted.
The EMB 120 Weight and Balance Manualcontains detailed infomation in the form oftables and diagrams. However, it is not requiredto be in the airplane as the basic empty weightand moment and means of determining thecenter-of-gravity location are all containedin the AFM.
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1. The EMB 120 is certified under:A. FAR Part 25B. FAR Part 61C. FAR Part 91D. Brazilian CAA Paragraph 7
2. The EMB 120 has how many generators?A. 2B. 3C. 4D. 5
3. The EMB 120 forward entry door may be:A. Raised and lowered electricallyB. Raised and lowered manuallyC. Raised hydraulicallylowered man-
uallyD. Both B and C
4. The EMB 120 direct vision windows maybe removed by the crew.A. TrueB. False
5. If the main entry door is not securelyclosed and locked:A. An alarm will sound at the flight at-
tendants station.B. A door open light will illuminate in
the cockpit.C. A door solenoid will prevent engine
start.D. There is no indication of this situation.
6. How many cycles can the forward entrydoor be operated without recharging itsaccumulator?A. 1B. 2C. 3D. 4
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CHAPTER 2ELECTRICAL POWER SYSTEMS
CONTENTSPage
INTRODUCTION ................................................................................................................... 2-1
GENERAL............................................................................................................................... 2-1
DC POWER............................................................................................................................. 2-2
Components ..................................................................................................................... 2-2
Distribution ...................................................................................................................... 2-6
Control and Monitoring ................................................................................................... 2-9
AC POWER........................................................................................................................... 2-12
Components ................................................................................................................... 2-12
Distribution .................................................................................................................... 2-12
Control and Monitoring ................................................................................................. 2-12
ELECTRICAL SYSTEM OPERATION............................................................................... 2-12
Normal Mode................................................................................................................. 2-15
Emergency Mode ........................................................................................................... 2-20
Overcurrent Protection................................................................................................... 2-22
PRE MOD SB 120-024-00051 ELECTRICAL SYSTEM DIFFERENCES ........................ 2-29
ELECTRICAL CONTROL PANEL SUMMARY ................................................................ 2-37
QUESTIONS......................................................................................................................... 2-39
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ILLUSTRATIONSFigure Title Page2-1 Electrical Component Location................................................................................ 2-2
2-2 Battery Location....................................................................................................... 2-2
2-3 Battery Temperature Gage........................................................................................ 2-3
2-4 Backup Battery Switch............................................................................................. 2-4
2-5 External Power Receptacle....................................................................................... 2-5
2-6 Power Select Switch ................................................................................................. 2-5
2-7 Central DC Power Distribution ................................................................................ 2-6
2-8 Auxiliary DC Power System .................................................................................... 2-7
2-9 Backup DC Power System ....................................................................................... 2-8
2-10 Radio Master System................................................................................................ 2-9
2-11 Electrical Control PanelDC System ................................................................... 2-11
2-12 AC Power System .................................................................................................. 2-13
2-13 Electrical Power System......................................................................................... 2-14
2-14 Electrical System ConfigurationBattery Only.................................................... 2-16
2-15 Electrical System ConfigurationExternal Power................................................ 2-17
2-16 Electrical System ConfigurationAPU Generator ............................................... 2-18
2-17 Electrical System ConfigurationSingle Engine.................................................. 2-19
2-18 Emergency ModeBoth Main Generatorsand One Auxiliary Generator Failure..................................................................... 2-21
2-19 Emergency ModeTotal Generator Failure .......................................................... 2-23
2-20 Overcurrent Case 1: Short Circuit, Central DC Bus............................................... 2-24
2-21 Overcurrent Case 2: Short Circuit, Relay Box DC Bus 1 ...................................... 2-26
2-22 Overcurrent Case 3: Short Circuit, Relay Box DC Bus 2 ...................................... 2-28
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2-23 Circuit-Breaker Panel............................................................................................. 2-35
2-24 Electrical Control Panel ......................................................................................... 2-36
TABLETable Title Page2-1 Electrical Bus Equipment Distribution................................................................... 2-30
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2-1
INTRODUCTIONThis chapter provides a description of the EMB-120 Brasilia Mod SB 120-024-0008 electrical powersystem; (Pre Mod differences are covered in the final section.) Included is information on the DCand AC systems. The DC system consists of storage, generation, distribution, and system mon-itoring. The AC system consists of generation, distribution, and system monitoring. Provision ismade for a limited supply of power during emergency conditions in flight, and for connection ofan external power unit while on the ground.
GENERALThe primary electrical power for the EMB-120Brasilia is 28 VDC. Two main and two auxiliarygenerators are the primary power sources. Secondarysources that may be utilized are: an external powersource; the auxiliary power unit (APU) generator;or the aircrafts nickel-cadmium battery. An addi-tional battery supplies backup power to essential instru-ments and the standby horizon.
Distribution of DC power is primarily via twogroups of buses, normally connected by a tie bus (thecentral DC bus). Each group of buses may be iso-lated from the central DC bus and powered by itsrespective generator. In flight, three buses are nor-mally connected to the auxiliary generators. Theemergency buses, normally connected to the rightmain generator, may be switched automatically ormanually to other power sources in the event of maingenerator power loss.
#1 SE
RVO
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EM
BATT
HOT
BAT O
FF
ACGE
N
#1 DC
GEN
#1 EN
G
OIL PL
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CHAPTER 2ELECTRICAL POWER SYSTEMS
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AC electrical power is provided by either of two 250-VA, 400 Hz static inverters which convert 28 VDCpower into 115 and 26 VAC. In normal operation,inverter No.1 powers the four AC buses, withinverter No.2 as standby power.
DC POWERCOMPONENTSMany of the electrical system components are locat-ed in the nose of the aircraft (Figure 2-1). They areaccessible through either the electronic compartmentdoor inside the nose landing gear compartment, or indi-vidual panels on the outside of the aircraft.
BatteriesThere are two batteries installed on the EMB 120: A24-VDC, 36 ampere-hour, nickel-cadmium mainbattery, and a 24-VDC, 5 ampere-hour, sealed lead-acid, backup battery. Both are located in the nose of
the aircraft and accessible through a panel just forwardof the cockpit on the left side (Figure 2-2).In flight, forced airflow is provided to the batterycompartment to ensure suitable ventilation for themain battery.
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APUFIREWALL
APU GEN
APU ELECTRONICCONTROL UNIT
PRESSUREFRAME
PRESSUREFRAME
LEGENDMAIN GENERATORSMAIN GENERATORAPU GENERATORAUXILIARY GENERATOREXTERNAL POWER
EXTERNALPOWER
BATTERY
FIREWALLGEN 1
FIREWALLGEN 2
AUX GEN 1
AUX GEN 2
AUX GEN 1 GCUGEN 1 GCU
AUXILIARYRELAY BOX
AUX GEN 2 GCUGEN 2 GCUAPU GEN GCU
DC 1 RELAY BOX
DC 2 RELAY BOX
BATTERYRELAY BOX
INVERTERS
BATTERY
EMERGENCYBATTERY
Figure 2-2. Battery Location
Figure 2-1. Electrical Component Location
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Revision 4 2-3
Main BatteryThe main battery is connected in parallel with themain generators. It is designed to power each gen-erator during the engine starting cycle when exter-nal power is not available. It will also supplyessential loads for approximately 30 minutes in theevent of loss of all generators.
The battery is always connected to the hot battery bus.
Positioning the PWR SELECT switch to BATT ener-gizes the battery contactor closed, connecting thebattery to the central DC bus. The battery contac-tor is provided with a protective device that openswhen the current from the central DC bus to the bat-tery exceeds 500 amps.
On the ground with the battery as the only powersource, a safety circuit inhibits power to the recir-culation fans, gasper fan, and ground cooling fans.
Battery Temperature Monitoring System. Abattery temperature monitoring system is used to warnthe crew of a battery overheat condition.
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BATTERYOVERHEATTEST BUTTON
Figure 2-3. Battery Temperature Gage
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A gage on the cockpit overhead electrical panel(Figure 2-3), displays battery temperature in thefollowing ranges:
15 to 60C . . . . . . . . . . . . . . . . Green arc
60 to 70C . . . . . . . . . . . . . . . Yellow arc
70 to 85C . . . . . . . . . . . . . . . . . . Red arc
If the battery temperature exceeds 70C, the Bat-tery voice warning sounds, the BATT OVER-HEAT light on the multiple alarm panel illuminates,and the master WARNING lights flash.
The system incorporates two individual tempera-ture sensing elements in the battery case. One pro-vides a signal for the gage and the other a signal forthe warning system.
To test the sensing system, press and hold the bat-tery overheat test button on the battery temperaturegage. Heating elements heat the two sensors, caus-ing the temperature indication to rise. When the tem-perature reaches 70C, the alarm and warningsare triggered. Release the test button.
After the test button is released, the temperature willcontinue to rise briefly. It should then decrease andthe alarm and warnings stop. Holding the test but-ton beyond the warning activation point may cause
damage to the sensing elements.
During the test the two sensors are heated by sep-arate heating elements. This may cause a variationbetween the warning activation and the gage tem-perature. Minor differences are not a problem.
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Figure 2-4. Backup Battery Switch
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Backup Battery
The primary purpose of the backup battery is to pro-vide an uninterrupted source of power to the stand-by artificial horizon should the normal powersupply fail.
Its secondary purpose is to provide a stabilizedpower supply to sensitive electronic components dur-ing power transients such as engine starts.
The backup battery is controlled by a three-position(OFFARMTEST) switch on the center panel(Figure 2-4). The normal in-flight position for thisswitch is ARM.
Starter-GeneratorsWith one installed in each engine, two 28-VDC, 400-amp (600-amp during start) engine-driven starter-generators are the primary power source for theelectrical system. They may be connected inde-pendently or in parallel to the main distribution buses.
During engine start, the starter-generators act asmotors and are powered by the central DC busthrough the respective engine start contactor. At50% NH, (high-pressure compressor speed) whenthe starting cycle is completed, the generatorcontrol unit (GCU) automatically opens the enginestart contactor allowing the starter-generator to oper-ate as a generator.
The engine-driven starter-generators are connect-ed to the aircraft electrical system by the maingenerator contactors. The GCUs command the
Figure 2-5. External Power Receptacle
Figure 2-6. Power Select Switch
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Revision 42-6
closure of these contactors when the main gener-ator switches, on the overhead electrical panel, arepositioned to ON.
Auxiliary GeneratorsTwo 28-VDC, 150-amp generators, each drivenby its respective propeller reduction gearbox, sup-ply power to the auxiliary power system.
The auxiliary generators are not connected to the
aircraft electrical system unless the propeller speed(NP) is greater than 70%.
APU Starter-GeneratorThe APU starter-generator is identical to the mainstarter-generators.
When the APU turbine reaches 95% rpm, theAPU generator is able to provide its nominalelectrical power output.
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EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RELAY BOXEMERGENCY DC BUS 2
RELAY BOXEMERGENCY DC BUS 1
RELAY BOX DC BUS 2
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2ENGINE
STARTCONTACTOR 2
ENGINESTART
CONTACTOR 1 APUSTARTCONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
EXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUSBUS TIE
CONTACTOR2
BUS TIECONTACTOR
1
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR
1
EMERGENCYBUS
CONTACTOR
DC BUS 2
DC BUS 1
RELAY BOX DC BUS 1
EMERGENCYBUS
CONTACTOR 2
Figure 2-7. Central DC Power Distribution
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2-7
The main purpose of the APU generator is to sub-stitute for the external power unit on the ground. Itmay also be used in parallel with the battery to powera starter-generator during engine start.
In flight, if required, the APU generator may be usedin parallel with the main generators.
External PowerAn external power unit may be connected to the air-craft DC system through a receptacle located justaft of the battery compartment panel (Figure 2-5).Placing the PWR SELECT switch on the overheadelectrical control panel (Figure 2-6) to the EXTPWR position closes the external power contac-tor, allowing the external source to power thecentral DC bus.
A protective circuit prevents the APU generator andthe external power source from simultaneouslysupplying the central DC bus; priority is external
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AUXILIARY DC BUS
RELAY BOXDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
BUS 3 RELAY
RELAY BOX DC EMERGENCY BUS 2RELAY BOX DC EMERGENCY BUS 1
Figure 2-8. Auxiliary DC Power System
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Revision 42-8
power. A similar circuit also prevents the maingenerator and the external power source fromsimultaneously supplying the central DC bus; pri-ority in this case is the main generator.
An overvoltage relay protects the central DC bus ifexternal power exceeds 32 VDC. In this condition, theexternal power contactor will open, disconnecting theexternal power from the central DC bus.
The external power voltage may be monitored on
the left voltammeter by setting the voltammeter selec-tor to the CENTRAL BUS/APU GEN position.
DISTRIBUTIONCentral DC SystemDirect current is distributed throughout the air-craft as shown in Figure 2-7.
Each main generator is normally connected to the
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VSUSTANDBYHORIZON BACKUP
BATTERYRELAY
BACKUP BATTERY
BACKUPBATT
SWITCH
OFFTEST
ARM
NORM
AUX GEN 1/2 GCUGEN 1/2 GCU
EMERGEMERGENCY
SWITCHING RELAY
EMERGENCYDC BUS 2
EMERGENCYDC BUS 1
STBY HORIZ EMERG BUS
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
DC BUS 1 EMERG DC BUS 1 EMERG DC BUS 2 DC BUS 2
AURAL WARNING AHRS 1 NH AND T6 ENG 1 INDICATIONS RCCBs FOR: L HYD AUX PUMP
L PROP HEATERRECIRC FAN 1L WSHLD DEICEGASPER FANTAXI LIGHTL GRND COOL FAN
AHRS 2 NH AND T6 ENG 2 INDICATIONS RCCBs FOR: R HYD AUX PUMP
R PROP HEATERRECIRC FAN 2R LDG LIGHTR WSHLD DEICER GRND COOL FAN
EEC 1 IGNITION LIGHT 1 RCCB FOR L AUX FEATHER PUMP
CLOCK/CHRONO EEC 2 IGNITION LIGHT 2 RCCBs FOR: R AUX FEATHER PUMP
L LDG LIGHT
Figure 2-9. Backup DC Power System
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central DC bus, which functions as a tie bus. Thisallows either generator to supply the entire air-craft electrical load.
The battery is always connected directly to thehot battery bus. During normal operation, the powersource energizing the central DC bus powers the hotbattery bus and charges the battery.
EMB-120 PILOT TRAINING MANUAL
RELAY BOXEMERGENCYDC BUS 1
RELAY BOXEMERGENCY
DC BUS 2
RELAYBOXDC BUS 1
RELAY BOXDC BUS 2
DC BUS 2
RADIO MASTERDC BUS 2A
RADIO MASTERDC BUS 2B
RADIO MASTERDC BUS 2C
ON
OFFNORMAL
RADIO MASTER
AHRS 2 DC
1 2AUXGCUs
ON
ON
OFF
OFF
EMERGENCYRADIO MASTER
NORMALRADIO MASTER
RADIO MASTEREMERG DC BUS 1
RADIO MASTERDC BUS 1A
RADIO MASTERDC BUS 1B
RADIO MASTERDC BUS 1C
AHRS 1 DCRMI 2
1 2 AUXGCUs
Figure 2-10. Radio Master System
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Auxiliary DC SystemWhen propeller speed (NP) reaches 70%, the aux-iliary generator control unit (GCU) connects the aux-iliary generator to the auxiliary DC bus (Figure 2-8).(The auxiliary generators are the only power sourcefor the auxiliary DC bus.)When powered, the auxiliary DC bus, energizes arelay that shifts the bus 3 contactor, switching bothrelay box DC bus 3 and DC bus 3 from relay boxDC bus 2 to the auxiliary DC bus.
When NP drops below 70%, the auxiliary GCU dis-connects the generator from the auxiliary DC bus. Ifthe auxiliary DC bus loses power (both auxiliarygenerators below 70%), both relay box DC bus 3 andDC bus 3 switch back to relay box DC bus 2.
The auxiliary GCUs also switch the primary nav-igation equipment (AHRS 1, AHRS 2, RMI 2,and radio master DC bus 1A and 2C) to the emer-gency buses.
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Figure 2-11. Electrical Control PanelDC System
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Backup DC Power SystemThe backup power system (Figure 2-9) consists ofthe backup battery, the BACKUP BATT switchon the center panel, and the following buses:
Backup DC bus 1
Backup DC bus 2
Backup emergency DC bus 1
Backup emergency DC bus 2
Standby horizon emergency bus
Through one-way diodes, each backup bus is joint-ly connected to essential instruments normallypowered by one of the four main DC buses (DC bus1, DC bus 2, emergency DC bus 1, emergency DCbus 2).The backup battery system operates in the normalmode whenever the BACKUP BATT switch is in theARM position (and the electrical DC system isoperating in the normal mode). In this mode, all fivebuses are in a powered, standby status. The back-up battery is charged by emergency DC bus 2, andthe standby attitude indicator is powered by emer-gency DC bus 1.
If the voltage on any of the four main DC buses dropsbelow the voltage of their respective backup buses,power will be supplied to essential instrumentsthrough the backup buses.
The backup bus circuit breakers are all rated oneamp higher than the corresponding main DC buscircuit breakers. As a result, the main bus circuitbreakers on the overhead panel open before the back-up bus circuit breakers. This feature assists faultdetection by the pilot.
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RADIO MASTERDC BUS 2C EMERGENCYDC BUS 1
DC BUS 2
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL 1
TRANSFERCONTROL 2
115-VACESSENTIAL BUS
26-VACESSENTIAL BUS
115-VACEMERGENCY BUS
26-VACEMERGENCY BUS
INVERTERNO. 2INVERTER
NO. 1
Figure 2-12. AC Power System
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EM
B-1
20
PILO
T T
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ININ
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UA
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TRAIN
ING PU
RPOSES ON
LYR
evision 4
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL 1
TRANSFERCONTROL 2
115-VACESSENTIAL BUS
26-VACESSENTIAL BUS
115-VACEMERGENCY BUS
26-VACEMERGENCY BUS
VSUSTANDBYHORIZON
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
BACKUPBATTERYRELAY
BACKUP BATTERYBACKUP
BATTSWITCH
OFFTEST
ARM
NORM
50
35
80
200 225 200
15
200
80
35
EMERGEMERGENCY
SWITCHING RELAY
AUXILIARY DC BUS
RELAY BOXDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
BUS 3 RELAY
EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RELAY BOXEMERGENCY DC BUS 2
RELAY BOXEMERGENCY DC BUS 1
RELAY BOX DC BUS 2
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2
ENGINESTARTCONTACTOR
ENGINESTART
CONTACTOR APUSTART
CONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
RADIO MASTERDC BUS 2A
RADIO MASTERDC BUS 2B
RADIO MASTERDC BUS 2C
ON
OFFNORMAL
RADIO MASTER
AHRS 2 DC
1 2AUXGCUsEXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUSBUS TIE
CONTACTOR2
BUS TIECONTACTOR
1
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR
1
EMERGENCYBUS
CONTACTOR 1 EMERGENCYBUSCONTACTOR 2
ON
ON
OFF
OFF
EMERGENCYRADIO MASTER
NORMALRADIO MASTER
RADIO MASTEREMERG DC BUS 1
RADIO MASTERDC BUS 1A
RADIO MASTERDC BUS 1B
RADIO MASTERDC BUS 1C
AHRS 1 DCRMI 2
1 2 AUXGCUs
LEFT MAIN DC GENERATOR
RIGHT MAIN DC GENERATOR
APU GENERATOR
AUXILIARY GENERATORS
EXTERNAL POWER
AC (INVERTER NO. 1)STANDBY AC (INVERTER NO. 2)MAIN BATTERY
BACKUP BATTERY
STBY HORIZ EMERG BUS
INVERTERNO. 2INVERTER
NO. 1
DC BUS 2
DC BUS 1
RELAY BOX DC BUS 1
LEGEND
Figure 2-13. Electrical Power System
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Radio Master SystemDuring the engine starting cycle, bus voltage tran-sients may cause damage to communication and nav-igation instruments. To avoid this, the radio masterswitches allow the pilot to turn off the avionics dur-ing engine start.
There are two radio master switches, onelabeled EMERG and the other labeled NORMAL(Figure 2-10).The radio master system consists of the radio mas-ter switches, six normal radio master buses, and oneemergency radio master bus.
With both radio master switches in the ON position,the three corresponding relays are deenergized.This connects DC power to the radio master system.
When the switches are in the OFF position, the relaysare energized and power is removed from the radiomaster system.
CONTROL AND MONITORINGControl of the DC electrical system is accom-plished automatically through the five generator con-trol units (GCUs), and manually by switch positionon the overhead electrical control panel.
Monitoring of the electrical system is through thegages and indicator lights on the overhead electri-cal control panel.
GCUsThe main/APU starter-generators and the auxiliarygenerator are controlled by individual GCUs. Thesemultifunction units also provide electrical faultprotection.
Functions of the starter-generator GCUs are asfollows:
Initiates start cycle:
Closes start contactor
Energizes ignition circuit
Energizes return solenoid to empty draincollector (EPA) tank
Allows up to 600 amps for generator-aided cross start
Provides overspeed protection in eventof sheared shaft
Cancels start cycle at 50% RPM:
Opens start contactor
Deenergizes ignition circuit
Deenergizes EPA return solenoid
Enables the generator function
Regulates generator output between 26 and30 VDC (Normal 28.5 VDC)
Overvoltage protection (> 32 VDC) Overcurrent protection (> 400 amps) Reverse current protection
Generator field over excitation protection
Paralleling protection (maintains generatorloads within 10%)
2-15FOR TRAINING PURPOSES ONLYRevision 4
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2-16FOR
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115-VAC ESS
26-ESS AC
115-VAC EM
26-VAC EM
VSUSTBYHORIZ
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
BACKUPBATTERYRELAY
BACKUP BATTERYBACKUP
BATTSWITCH
OFFTEST
ARM
NORM
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL1
TRANSFERCONTROL2
50
35
80
200 225 200
15
200
80
35
EMERGEMERGENCY
SWITCHING RELAY
AUXILIARY DC BUS
RBDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
BUS 3 RELAY
EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RBEMERGENCY DC BUS 2
RBEMERGENCY DC BUS 1
RB DC BUS 2
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2
ENGINESTARTCONTACTOR
ENGINESTART
CONTACTOR APUSTART
CONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
RMDC BUS 2A
RMDC BUS 2B
RMDC BUS 2C
ON
OFFNORMAL
RM
AHRS 2 DC
1 2AUXGCUsEXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUSBUS TIE
CONTACTOR2
BUS TIECONTACTOR
1
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR
1
EMERGENCYBUS
CONTACTOR 1
ON
ON
OFF
OFF
EMERGENCYRM
NORMALRM
RMEMERG DC BUS 1
RMDC BUS 1A
RMDC BUS 1B
RMDC BUS 1C
AHRS 1 DCRMI 2
1 2 AUXGCUs
STBY HORIZ EMERG BUS
DC BUS 2
DC BUS 1
RB DC BUS 1
INV 2INV 1
AC (INV 1)
STANDBY AC (INV 2)
MAIN BATTERY
BACKUP BATTERY
LEGEND
EMERGENCYBUS
CONTACTOR 2
Figure 2-14. Electrical System ConfigurationBattery Only
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115-VAC ESS
26-ESS AC
115-VAC EM
26-VAC EM
VSUSTBYHORIZ
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
BACKUPBATTERYRELAY
BACKUP BATTERYBACKUP
BATTSWITCH
OFFTEST
ARM
NORM
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL1
TRANSFERCONTROL2
50
35
80
200 225 200
15
200
80
35
EMERGEMERGENCY
SWITCHING RELAY
AUXILIARY DC BUS
RBDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
BUS 3 RELAY
EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RBEMERGENCY DC BUS 2
RBEMERGENCY DC BUS 1
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2
ENGINESTARTCONTACTOR
ENGINESTART
CONTACTOR APUSTART
CONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
RMDC BUS 2A
RMDC BUS 2B
RMDC BUS 2C
ON
OFFNORMAL
RM
AHRS 2 DC
1 2AUXGCUsEXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUS
BUS TIECONTACTOR
2
BUS TIECONTACTOR
1
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR
1
EMERGENCYBUS
CONTACTOR 1
ON
ON
OFF
OFF
EMERGENCYRM
NORMALRM
RMEMERG DC BUS 1
RMDC BUS 1A
RMDC BUS 1B
RMDC BUS 1C
AHRS 1 DCRMI 2
1 2 AUXGCUs
STBY HORIZ EMERG BUS
DC BUS 2
DC BUS 1
RB DC BUS 1
INV 2INV 1
AC (INV 1)
STANDBY AC (INV 2)
MAIN BATTERY
BACKUP BATTERY
EXT PWR
LEGEND
RB DC BUS 2
EMERGENCYBUS
CONTACTOR 2
Figure 2-15. Electrical System ConfigurationExternal Power
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2-18FOR
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evision 4
115-VAC ESS
26-ESS AC
115-VAC EM
26-VAC EM
VSUSTBYHORIZ
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
BACKUPBATTERYRELAY
BACKUP BATTERYBACKUP
BATTSWITCH
OFFTEST
ARM
NORM
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL1
TRANSFERCONTROL2
50
35
80
200 225 200
15
200
80
35
EMERGEMERGENCY
SWITCHING RELAY
AUXILIARY DC BUS
RBDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
BUS 3 RELAY
EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RBEMERGENCY DC BUS 2
RBEMERGENCY DC BUS 1
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2
ENGINESTARTCONTACTOR
ENGINESTART
CONTACTOR APUSTART
CONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
RMDC BUS 2A
RMDC BUS 2B
RMDC BUS 2C
ON
OFFNORMAL
RM
AHRS 2 DC
1 2AUXGCUsEXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUSBUS TIE
CONTACTOR2
BUS TIECONTACTOR
1
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR
1
EMERGENCYBUS
CONTACTOR 1
ON
ON
OFF
OFF
EMERGENCYRM
NORMALRM
RMEMERG DC BUS 1
RMDC BUS 1A
RMDC BUS 1B
RMDC BUS 1C
AHRS 1 DCRMI 2
1 2 AUXGCUs
STBY HORIZ EMERG BUS
DC BUS 2
DC BUS 1
RB DC BUS 1
INV 2INV 1
AC (INV 1)
STANDBY AC (INV 2)
MAIN BATTERY
BACKUP BATTERY
APU GEN
LEGEND
RB DC BUS 2
EMERGENCYBUS
CONTACTOR 2
Figure 2-16. Electrical System ConfigurationAPU Generator
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115-VAC ESS
26-ESS AC
115-VAC EM
26-VAC EM
VSUSTBYHORIZ
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
BACKUPBATTERYRELAY
BACKUP BATTERYBACKUP
BATTSWITCH
OFFTEST
ARM
NORM
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL1
TRANSFERCONTROL2
50
35
80
200 225 200
15
200
80
35
EMERGEMERGENCY
SWITCHING RELAY
AUXILIARY DC BUS
RBDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
BUS 3 RELAY
EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RBEMERGENCY DC BUS 2
RBEMERGENCY DC BUS 1
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2
ENGINESTARTCONTACTOR
ENGINESTART
CONTACTOR APUSTART
CONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
RMDC BUS 2A
RMDC BUS 2B
RMDC BUS 2C
ON
OFFNORMAL
RM
AHRS 2 DC
1 2AUXGCUsEXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUS
BUS TIECONTACTOR
2
BUS TIECONTACTOR
1
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR
1
EMERGENCYBUS
CONTACTOR 1
ON
ON
OFF
OFF
EMERGENCYRM
NORMALRM
RMEMERG DC BUS 1
RMDC BUS 1A
RMDC BUS 1B
RMDC BUS 1C
AHRS 1 DCRMI 2
1 2 AUXGCUs
STBY HORIZ EMERG BUS
DC BUS 2
DC BUS 1
RB DC BUS 1
INV 2INV 1
AC (INV 1)
STANDBY AC (INV 2)
MAIN BATTERY
BACKUP BATTERY
AUXILIARY GENERATOR
R MAIN DC GEN
LEGEND
RB DC BUS 2
EMERGENCYBUS
CONTACTOR 2
Figure 2-17. Electrical System ConfigurationSingle Engine
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Revision 42-20
Functions of the auxiliary generator GCUs are asfollows:
At 70% propeller RPM:
Connects generator to auxiliary DC bus
Switches relay box DC bus 3 and DC bus3 from relay box DC bus 2 to auxiliaryDC bus
Voltage regulation same as main generators
Overvoltage protection (> 32.5 VDC) Undervoltage protection (< 23 1 VDC) Overcurrent protection (220 amps) Field excitation protection same as main
generators
Paralleling same as main generators
Underspeed protection when propeller speeddrops below 70%
Electrical Control PanelThe DC electrical system is monitored on the over-head electrical control panel (Figure 2-11) by twovoltammeters, the battery temperature gage, and thefollowing annunciator warning lights:
GEN OFF BUS (left and right main generators) BUS 1 OFF
BUS 2 OFF
EMERG BUS OFF
CENTRAL BUS OFF
BATTERY OFF BUS
AUX GEN OFF BUS (left and right auxil-iary generators)
TRANSFER FAIL
A voltammeter selector switch permits monitoringof the volts and amps of each main generator, theauxiliary DC bus, main battery, central bus, and APUgenerator.
AC POWERCOMPONENTSInvertersThe alternating current system (Figure 2-12) con-sists of two independently powered inverters locat-ed in the nose section of the aircraft and accessiblethrough the electronic compartment door in thenose wheel well. Each inverter produces 115- and26-VAC, 400-Hz power.
Normally both inverters are energized, but only oneis used to power the AC buses. Inverter No. 1, pow-ered from DC bus 2, is the primary AC power source.
Inverter No. 2, powered from emergency DC bus1, is kept in a powered backup status for invert-er No. 1.
Transfer Control RelaysTwo transfer control relays direct the output ofthe inverters to the appropriate AC buses.
Transfer control relay 1 is powered by the 115-VACoutput of inverter No. 1. Transfer control relay 2is powered by DC bus 2 (the power source forinverter No. 1) and radio master DC bus 2C.
FOR TRAINING PURPOSES ONLY
EMB-120 PILOT TRAINING MANUAL
FlightSafety international
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115-VAC ESS
26-ESS AC
115-VAC EM
26-VAC EM
VSUSTBYHORIZ
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
BACKUPBATTERYRELAY
BACKUP BATTERY
BACKUPBATT
SWITCH
OFFTEST
ARM
NORM
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL1
TRANSFERCONTROL2
50
35
80
200 200
15
200
80
35
EMERG
EMERGENCYSWITCHING RELAY
AUXILIARY DC BUS
RBDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RBEMERGENCY DC BUS 2
RBEMERGENCY DC BUS 1
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2
ENGINESTARTCONTACTOR
APUSTART
CONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
RMDC BUS 2A
RMDC BUS 2B
RMDC BUS 2C
ON
OFFNORMAL
RM
AHRS 2 DC
1 2AUXGCUsEXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUS
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
ON
ON
OFF
OFF
EMERGENCYRM
NORMALRM
RMEMERG DC BUS 1
RMDC BUS 1A
RMDC BUS 1B
RMDC BUS 1C
AHRS 1 DCRMI 2
1 2 AUXGCUs
STBY HORIZ EMERG BUS
DC BUS 2
DC BUS 1
RB DC BUS 1
INV 2INV 1
RB DC BUS 2
BUS 3 RELAY
BUS TIECONTACTOR
1
EMERGENCYBUS
CONTACTOR 1
BUS TIECONTACTOR
2
ENGINESTART
CONTACTOR
225
MAIN GENERATORCONTACTOR
1
MAIN BATTERY
BACKUP BATTERY
GCU
EMERGENCY
STANDBY AC (INV 2)
AUXILIARY GENERATORS
LEGEND
EMERGENCYBUS
CONTACTOR 2
Figure 2-18. Emergency ModeBoth Main Generators and One Auxiliary Generator Failure
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EMB-120 PILOT TRAINING MANUAL
FlightSafety international
DISTRIBUTIONThe 115/26-VAC inverter output is distributed to fourbuses: two 26-VAC (essential and emergency)and two 115-VAC (essential and emergency) buses.In the event of inverter No. 1 failure, the loss of 115-VAC output causes the transfer control relay toautomatically switch the four AC buses to invert-er No. 2. (A failure of only the 26-VAC output ofinverter No. 1 does not lead to automatic systemtransfer; thus, it is necessary to manually deenergizeinverter No.1. This condition is indicated by theillumination of both essential and emergency 26VAC BUS OFF lights).
CONTROL AND MONITORINGEach inverter is controlled by its respective switchon the electrical panel (Figure 2-12). An INOPannunciator light illuminates in the event of invert-er failure or if the switch is turned off. Each AC bushas an annunciator light to indicate loss of powerto that bus.
ELECTRICAL SYSTEMOPERATIONThere are two modes of operation for the aircraft elec-trical system:
Normal
Emergency
The normal configuration for the aircraft electricalsystem is the normal mode.
Under normal operating conditions and if bothmain generators fail while operating in the normalmode, the system automatically switches, after a 2second delay to the emergency mode.
The electrical system may be manually switched tothe emergency mode by positioning the guarded elec-trical emergency switch to EMERG.
NORMAL MODEBefore Engine StartPrior to engine start, the battery or external powersupplies electrical power to all DC buses (except theauxiliary DC bus) and to both inverters (Figures 2-14 and 2-15). If the APU is available and provid-ed the PWR SELECT switch is set to BATT, the APUgenerator will supply the same buses and charge thebattery (Figure 2-16).
Takeoff and Normal FlightWhen NP reaches 70%, the auxiliary GCUs connectthe auxiliary generators to the auxiliary DC bus.
Once the auxiliary DC bus is powered the bus 3contactor shifts, switching relay box DC bus 3and DC bus 3 from relay box DC bus 2 to the aux-iliary DC bus.
The auxiliary GCUs also switch the primary nav-igation equipment (AHRS 1, AHRS 2, RMI 2,and radio master DC buses 1A and 2C) to theemergency DC buses.
The main generators continue to power the remain-ing buses and charge the battery.
Normal electrical system configuration (NP >70%), is shown in Figure 2-13.
2-22 FOR TRAINING PURPOSES ONLY Revision 4
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115-VAC ESS
26-ESS AC
115-VAC EM
26-VAC EM
VSUSTBYHORIZ
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
BACKUPBATTERYRELAY
BACKUP BATTERY
BACKUPBATT
SWITCH
OFFTEST
ARM
NORM
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL1
TRANSFERCONTROL2
50
35
80
200 200
15
200
80
35
EMERGEMERGENCY
SWITCHING RELAY
AUXILIARY DC BUS
RBDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RBEMERGENCY DC BUS 2
RBEMERGENCY DC BUS 1
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2
ENGINESTARTCONTACTOR
APUSTART
CONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
RMDC BUS 2A
RMDC BUS 2B
RMDC BUS 2C
ON
OFFNORMAL
RM
AHRS 2 DC
1 2AUXGCUsEXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUS
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
ON
ON
OFF
OFF
EMERGENCYRM
NORMALRM
RMEMERG DC BUS 1
RMDC BUS 1A
RMDC BUS 1B
RMDC BUS 1C
AHRS 1 DCRMI 2
STBY HORIZ EMERG BUS
DC BUS 2
DC BUS 1
RB DC BUS 1
INV 2INV 1
RB DC BUS 2
BUS 3 RELAY
BUS TIECONTACTOR
1
EMERGENCYBUS
CONTACTOR 1
BUS TIECONTACTOR
2
ENGINESTART
CONTACTOR
225
MAIN GENERATORCONTACTOR
1
BACKUP BATTERY
GCU
EMERGENCY
MAIN BATTERY
STANDBY AC (INV 2)LEGEND
AUXGCUs
2 1
EMERGENCYBUS
CONTACTOR 2
Figure 2-19. Emergency ModeTotal Generator Failure
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115-VAC ESS
26-ESS AC
115-VAC EM
26-VAC EM
VSUSTBYHORIZ
BACKUP DC BUS 1 BACKUP EMERG DC BUS 1 BACKUP EMERG DC BUS 2 BACKUP DC BUS 2
BACKUPBATTERYRELAY
BACKUP BATTERY
BACKUPBATT
SWITCH
OFFTEST
ARM
NORM
115 VAC26 VAC
115 VAC26 VAC
TRANSFERCONTROL1
TRANSFERCONTROL2
50
35
80
200200
15
200
80
35
EMERGEMERGENCY
SWITCHING RELAY
AUXILIARY DC BUS
RBDC BUS 3
DC BUS 3AUXILIARYTRANSFER
RELAY
EMERGENCYSWITCHING
RELAYAUX GENCONTACTOR1
AUX GENCONTACTOR
2
AUX GEN 1 AUX GEN 2
EMERGENCY DC BUS 2EMERGENCY DC BUS 1
RBEMERGENCY DC BUS 2
RBEMERGENCY DC BUS 1
RIGHT ENGINESTARTER-GENERATOR
MAIN GENERATORCONTACTOR2
ENGINESTARTCONTACTOR
APUSTART
CONTACTOR
EMERGENCYBATTERYCONTACTOR
BATTERYCONTACTOR
HOT BATTERY BUS
MAINBATTERY
RMDC BUS 2A
RMDC BUS 2B
RMDC BUS 2C
ON
OFFNORMAL
RM
AHRS 2 DC
1 2AUXGCUsEXTERNALPOWER
EXT POWERCONTACTOR
CENTRAL DC BUS
APUGENERATORCONTACTOR
APUSTARTER-GENERATOR
LEFT ENGINESTARTER-GENERATOR
ON
ON
OFF
OFF
EMERGENCYRM
NORMALRM
RMEMERG DC BUS 1
RMDC BUS 1A
RMDC BUS 1B
RMDC BUS 1C
AHRS 1 DCRMI 2
STBY HORIZ EMERG BUS
DC BUS 2
DC BUS 1
RB DC BUS 1
INV 2INV 1
RB DC BUS 2
BUS 3 RELAY
BUS TIECONTACTOR
1
EMERGENCYBUS
CONTACTOR 1
BUS TIECONTACTOR
2
ENGINESTART
CONTACTOR
225
MAIN GENERATORCONTACTOR
1
AUXILIARY GENERATORS
AC (INV 1)
R MAIN DC GEN
L MAIN DC GEN
BACKUP BATTERY
GCU
MAIN BATTERY
STANDBY AC (INV 2)LEGEND
AUXGCUs
2 1
EMERGENCYBUS
CONTACTOR 2
Figure 2-20. Overcurrent Case 1: Short Circuit, Central DC Bus
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Revision 4 2-25FOR TRAINING PURPOSES ONLY
EMB-120 PILOT TRAINING MANUAL
FlightSafety international
Single-Engine FlightThe electrical power distribution for single-engineflight (Figure 2-17) is the same as the normal flightconfiguration.
The DC load on the remaining main generatorshould be reduced to 400 amps if the APU gener-ator is not available.
The remaining auxiliary generator continues tosupply the loads of the auxiliary DC bus, relaybox DC bus 3 and DC bus 3 with no restriction.
EMERGENCY MODEThe electrical system may be switched to the emer-gency mode of operation manually; or it mayswitch automatically with the loss of both main gen-erators (after a 2-second delay).For the switch to occur automatically, the follow-ing conditions must be met:
At least one main generator switch ON
PWR SELECT switch in BATT
Both main generators loss (Line con-tactors open)
NOTETo prevent a reset to the normal modeafter an automatic switch to the emergen-cy mode, select EMERG on the electricalemergency switch prior to turning both maingenerators switches OFF.
In the emergency mode:
The emergency bus contactor opens, dis-connecting the emergency DC buses from relaybox DC bus 2.
The auxiliary transfer relay shifts, connect-ing the emergency DC buses to the auxiliaryDC bus.
The battery contactor opens, disconnectingthe battery from the central DC bus.
The emergency battery contactor closes,connecting the battery to the emergency DCbuses.
The backup battery relay is deenergized,disconnecting the backup buses from thebackup battery.
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