Dornier 328Jet - Hydraulic Power - SmartCockpit - Airline …€¦ · · 2012-06-27Dornier 328Jet - Hydraulic Power Page 1. Feb 11/02 EFFECTIVITY : ALL 12–29–01–00 ... 1 2

Feb 11/02

EFFECTIVITY : ALL 12–29–01–00 Page 1

Hydraulic Power System Controls

Dornier 328Jet - Hydraulic Power

Page 1

Feb 11/02


MESSAGE (SYNOPTIC) WARN INHIBITLocation (COLOR)

WARNTONE CONDITION

1 2 3

HYD A PMP FAIL

CAS Field (AMBER)AC pump System A does not produce > 2160 PSI (180 bar) after 10second

X X

PMP FAILorAC pump System A does not operate in accordance with selected

HYDR Page (AMBER)switch position.

HYD A PMP INOPCAS Field (BLUE) AC power is not available at AC BUS 1 and 2

PMP INOPorAC main pump Sys. A switched OFF.

HYDR Page (BLUE)

HYD A PRSS HIGH System A pressure exceeds 3189 PSI (220 bar)

CAS Field (AMBER)for more than 2 seconds. X X

(ANALOG/DIGITAL) Analog scale expands to the high pressure direction.

HYDR Page (AMBER) Digital readout > 3189 PSI (220 bar).

HYD A PRSS LOW System A pressure drops below 1813 PSI (125 bar)

CAS Field (AMBER)for more than 1 second. X

(ANALOG/DIGITAL) Analog scale expands to the low pressure direction.

HYDR Page (AMBER) Digital readout < 1813 PSI (125 bar).

HYD A QTY FAIL

CAS Field (AMBER)X X

QTY FAILProximity switch has failed.

HYDR Page (AMBER)

HYD A QTY LOW

CAS Field (AMBER) Prximity switch is servicable and lw hydraulic fluid level in theX X

QTY LOW reservoire.

HYDR Page (AMBER)

Message inhibit logic: 1. WOW, Engines off and Electrical Bus Failure refer to section 12–31–17–042. Takeoff phase3. Landing phase

CAS Field and System Messages (Sheet 1 of 3)


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Feb 11/02



WARNTONE CONDITION

1 2 3

HYD A TEMP HIGH System A hydraulic fluid temperature exceeds 1020C for more than 1

CAS Field (AMBER)second orHydraulic System A AC pump overheated.

X X

PMP OVHT Hydraulic System A AC pump temperature switch indicates high motorHYDR Page (AMBER) temperature.

(ANALOG/DIGITAL)Analog scale reads > 1020C to < 1350C (amber).

HYDR Page (AMBER)

Analog scale reads > 102 C to < 135 C (amber).Analog scale reads > 1350C (red).

HYD B PMP FAIL≥

CAS Field (AMBER)

AC pump System B does not produce ≥ 2160 PSI (180 bar) after 10seconds.or

X X

PMP FAIL AC pump System B does not operate in accordance with selectedswitch position.

HYDR Page (AMBER)switch position.

HYD B PMP INOPCAS Field (BLUE) AC power is not available at AC BUS 1 and 2.

PMP INOPorAC main pump Sys. B switched OFF.

HYDR Page (BLUE)

HYD B PRSS HIGH System B pressure exceeds 3189 PSI (220 bar) for more than 2

CAS Field (AMBER)seconds. X

(ANALOG / DIGITAL) Analog scale expands to the high pressure direction.

HYDR Page (AMBER) Digital readout > 3189 PSI (220 bar).

HYD B PRSS LOW System B pressure drops below 1813 PSI (125 bar) for more than 1

CAS Field (AMBER)second. X

(ANALOG / DIGITAL) Analog scale expands to the low pressure direction.

HYDR Page (AMBER) Digital readout < 1813 PSI (125 bar).

HYD B QTY FAIL


QTY FAILProximity switch has failed.

HYDR Page (AMBER)

HYD B QTY LOW


QTY LOWProximity switch is serviceable and low hydraulic fluid in main reservoir.

HYDR Page (AMBER)




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Feb 11/02



WARNTONE CONDITION

1 2 3

HYD B TEMP HIGH System B hydraulic fluid temperature exceeds 1020C for more than 1

CAS Field (AMBER)second orHydraulic System B AC pump overheated.

X X

PMP OVHT Hydraulic System B AC pump temperature switch indicates high motorHYDR Page (AMBER) temperature.

(ANALOG/DIGITAL)Analog scale reads > 1020C to < 1350C (amber).

HYDR Page (AMBER)

Analog scale reads > 102 C to < 135 C (amber).Analog scale reads > 1350C (red).

HYD STBY PMP CONTCAS Field (BLUE)

STBY selector set to CONT and DC pump running continuously.

CONTNOTE:HYD STBY PMP CONT is replaced by HYD STBY SYS FAIL when the

HYDR Page (BLUE) system pressure is < 1850 PSI (128 bar).

HYD STBY PMP FAIL

CAS Field (AMBER) DC pump does not operate in accordance with selected switch positionX X

FAILorFailure in the electrical part of the DC pump operational logic.

HYDR Page (AMBER)

HYD STBY PMP OFF

CAS Field (BLUE) STBY selector set to OFF.OFF

HYDR Page (BLUE)

ONSTBY selector set to AUTO, DC pump is running and the pressure isbelow 2990 PSI (206 bar).

HYDR Page (BLUE)NOTE:ON is replaced by STBY when the system pressure increased to 2990PSI ( 206 bar) and the DC pump had been switched off automatically.

STBYSTBY selector set to AUTO, DC pump not running and the pressure isabove 1850 PSI (128 bar).

HYDR Page (BLUE)

NOTE:STBY is replaced by ON when the system pressure droped down to <1850 PSI (128 bar) and the DC pump had been switched onautomatically.




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Feb 11/02


Indication/Messages on EICAS Display


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Feb 11/02


Indication/Messages on HYDR Page (Sheet 1 of 2)


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Feb 11/02


Indication/Messages on HYDR Page (Sheet 2 of 2)


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Feb 11/02


HYDRAULIC POWER SYSTEM

GeneralThe hydraulic system consists of two separate hydraulic circuits. They are designated assystem A and system B. A DC motor pump incorporated in system B provides energy asstandby. This section contains functional descriptions of all hydraulic consumer systems. Thecontrol and operation of the consumer systems is contained in the respective subsections of thismanual.The hydraulic system provides pressure to the following consumers:

– landing gear system extension and retraction – main landing gear wheel brake system – park brake accumulator system – nose wheel steering system – wing flaps system – roll spoiler system – ground spoiler system

Hydraulic systems A and B are not interconnected, each system comprises a hydraulic powerpack which generates the hydraulic pressure for its related consumer subsystems. System A and B main hydraulic pump each has a maximum delivery of 9.5 l/min (2.5US.gal/min) and rated working pressure of 3000 psi (207 bar).System B standby hydraulic pump has a rated delivery of 1.0 l/min (0.26 US.gal/min). Theworking pressure depends on the selected operational mode. It is in the AUTO mode between1850 psi (128 bar) and 2990 psi (206 bar).System and sub–system consumers are:

– System A supplies hydraulic pressure to the:

(a) Normal landing gear extension system(b) Outboard ground spoiler system(c) Alternate brake system

– System B supplies hydraulic pressure to the:

(a) Emergency landing gear extension system(b) Normal brake system(c) Nose wheel steering system(d) Park brake system(e) Flap system(f) Roll spoiler system(g) Inboard ground spoiler system.


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Hydraulic System Control PanelThe aircraft hydraulic system is controlled by a group of switches located on the OVERHEADPANEL. The SYSTEM – A push button located in the LH part of the HYD PWR panel controls thehydraulic pressure generated by a power pack which is installed in the LH landing gear fairing. The SYSTEM – B push button located in the RH part of the HYD PWR panel controls thehydraulic pressure generated by a power pack which is installed in the RH landing gear fairing. The rotary STBY switch located in the RH part of the HYD PWR panel controls the standbyhydraulic power which is part of system B.The ”BRK COV” push button located in the center of the HYD PWR panel, controls achangeover valve which allows manual selection of the normal or the alternate brake system.

Brake Changeover (BRK COV) Switch/LightThe BRK COV Switch/Light controls the brake changeover valve which provides switchingbetween the normal brake system hydraulic supply (system A) and the alternate brake hydraulicsupply (system B). For further information, refer to: – Alternate Brake System – Normal Brake System – The main landing gear wheel brake system The alternate brake system is activated when the BRK COV push button is pressed in and theALT BRK caption is illuminated. The normal brake system is activated when the BRK COV push button is pressed out and theALT BRK caption is extinguished.


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Feb 11/02


Hydraulic Power System – Block Diagram


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Feb 11/02


SYSTEM A AND B HYDRAULIC POWER

Main Hydraulic System FunctionSystems A and B each generate main hydraulic power which is supplied to their respectivesub–system consumers. Systems A and B have an AC pump, a reservoir, a filter package, asystem accumulator and a pulsation damper. System B is also provided by a DC pump. The hydraulic fluid is drawn from the reservoir, pressurized by the AC pump and then routed viathe pulsation damper through a filter package to the respective consumer sub–systems. Therespective system pressure is smoothed by the system accumulator. The used hydraulic fluidfrom the consumer systems is subsequently routed back through return lines to the reservoirs tocomplete the hydraulic circuits.

System OperationWith electrical power available on the aircraft AC bus system, the AC pump operates when theassociated SYSTEM A or B push button is pressed and the OFF caption has extinguished. Thehydraulic power system can be controled via the overhead hydraulic control panel in the flightcompartment. The status and parameters of the hydraulic system are displayed and indicated inthe flight compartment on the HYD PWR section of the overhead panel and on the EICAShydraulic system page.

AC Pump Electrical Power SuppliesSystem A electrical power for the AC pump is normally supplied from AC BUS 1. Should ACBUS 1 fail, an automatic change over circuit switches to AC BUS 2 to maintain the electricalpower supply. System B electrical power for the AC pump is normally supplied from AC BUS 2. Should ACBUS 2 fail, an automatic change over circuit switches to AC BUS 1 to maintain the electricalpower supply.

AC PumpsThe AC pumps consists of an variable frequency AC electric motor and a variable displacementhydraulic pump. The AC electric motor is air cooled and supplied with 115/200 VAC from theaircraft bus system. The pump speed varies with the AC frequency and is directly propotional tothe engine speed.The AC hydraulic pumps have a rated discharge pressure of 3 000 psi.

Hydraulic ReservoirThe reservoir is unpressurized and stores hydraulic fluid for the AC pump.The fluid low level condition is continuously monitored by a proximity switch and a float mountedproximity target installed in the outboard wall of the reservoir. The proximity switch sends asignal to the EICAS if the fluid level falls to a low level. The hydraulic fluid level can also bevisually checked through a sight glass in the wall of the reservoir which has FULL and ADDmarks.The reservoir is replenished directly through a filler cap on the top of the reservoir. The filler capis self–locking and is equipped with a removable and cleanable filter screen.


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Filter PackageThe purpose of the filter packages is to filter out contaminants from the hydraulic fluid before itreaches the consumer systems and again as it returns from the systems to the reservoir. Thefilter packages contains the following components:

– pressure and return filters– system relief valve– check valves– inlet and outlet ports and ports for the pressure and temperature transducers and a pressure

switch for the DC motor pump control circuit.

System AccumulatorThe system accumulators are a conventional piston–type unit with a gas pressure gage and isprecharged with dry nitrogen, connected into the hydraulic system pressure line on the outletside of the filter package. The purpose of the accumulator is to cover peak demands anddampen pressure transients in the hydraulic system. The accumulator is constantly maintainedin a hydraulically charged condition during operation of the hydraulic system.

System Overpressure ProtectionEach hydraulic system is protected against excessive pressure by a relief valve installed in thefilter package. The relief valve is connected between the hydraulic pressure and return lines.Should the pressure in the pressure line increase to 3 480 psi, the relief valve opens and theexcess pressure is routed through the return line to the input side of the return filter.

Pulsation DamperThe Pulsation damper provides a tuned hydraulic volume to counteract noise emissions of theACMP and the associated tubing system.


Page 12

System A Hydraulic Power – Schematic


Page 13

System B with Standby Hydraulic Power – Schematic


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Feb 11/02


SYSTEM B WITH DC MOTOR PUMP OPERATION

Standby System FunctionThe purpose of the standby system is to provide energy for filling up the park brake accumulatorwhen no AC power is aviallable. It produces only low fluid flow which can be used for restrictedoperation of the consumers of system B in case of an AC motor pump failure. The standbyhydraulic DC driven pump is installed in the RH landing gear fairing adjacent to the system Bcomponents. It consists of an electrical DC constant speed motor and a fixed displacement geartype pump. The DC standby pump draws hydraulic fluid from the system B reservoir and supplies hydraulicfluid at a reduced volume and pressure to the hydraulic system B filter package. The AC pumppressure line to the filter package has a check valve installed to prevent reverse flow to the ACpump. Two redundant check valves ( one in the filter package and one in the DC pump)prevent reverse flow through the DC pump when the AC pump operates.

DC Pump OperationThe DC pump can be switched OFF or controlled automatically (AUTO) or continuously (CONT)by the STBY rotary switch located in the HYD PWR system control panel.

AUTO Mode– In this mode, the DC pump is armed when the STBY switch is set to AUTO. The DC pump

will start automatically if system B pressure falls to approximately 1 850 psi. The DC standbypump will stop automatically when system B pressure increases to approximately 2 990 psi.

CONT Mode– Continuous operation of the DC pump is selected when the STBY switch is set to CONT. In

this mode the DC pump will run without stopping until deselected (OFF/AUTO). Thisoperational mode is forbidden except explicitly adressed in the AFM to cover failure cases.

OFF Mode– The DC pump is disabled when the STBY switch is set to the OFF position.

The operation of the hydraulic system is monitored by the indicating system. The status andparameters are displayed on the EICAS hydraulic system page.

DC Pump Electrical Power SuppliesWith the STBY switch set to the respective operational mode, electrical power for operation ofthe DC standby pump motor is supplied from DC BUS 1 and the ESS BUS. The DC pump can also be supplied with electrical power for a limited time from either batteryNo.1 or 2.


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SYSTEM A CONSUMERS

GeneralSystem A hydraulic pressure is generated by a power pack that is installed in the LH landinggear fairing and is controlled by the SYSTEM – A push button.The system A consumers are:

– outboard ground spoilers– landing gear (Normal operation)– alternate brakes and anti–skid control.

The system A hydraulic consumers are monitored by the indicating system. The status andparameters are displayedand indicated on the EICAS hydraulic system page.

Outboard Ground SpoilersThe LH and RH outboard ground spoilers are electro–hydraulically controlled and are eachoperated by a hydraulic actuator. The hydraulic actuator for each outboard ground spoiler iscontrolled by two solenoid operated valves.When all parameters such as thrust lever settings, main wheel WOW and main wheel spin–upare fulfilled, the solenoid operated valves energize and hydraulic fluid from system A is appliedto the extension ports of the actuators. The actuators extend to deploy the respective outboardground spoilers.When any parameter is not longer fulfilled or the ground spoilers are switched off, the solenoidoperated valves de–energize and hydraulic fluid from system A is applied to the retract ports ofthe actuators. The actuators retract, lock and stow the respective outboard ground spoilers.


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Dual Ground Spoiler Control – Schematic


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Feb 11/02


Landing Gear (Normal Operation)Under normal operating conditions the landing gear is extended and retracted by hydraulicpower from system A of the hydraulic system. Gear selection is made by a gear control leverlocated on the instrument panel.

Gear RetractionWhen the gear control lever is selected UP, the up solenoid of the selector valve energizes.When the landing gear system logic and all parameters are fulfilled, hydraulic pressure fromsystem A is simultaneously applied to:

– downlock release actuator of each gear leg– gear retract chamber of each gear actuator– despin circuit of the wheel brake system.

The main gear actuator retracts the associated gear leg and the nose gear actuator extends toretract the nose gear leg. The return fluid from each gear actuator is forced through restrictorswhich prevent the gear legs from slamming into the uplocks. When the gear legs have fully retracted and uplocked, the solenoid of the UP selectordeenergizes. This closes off the pressure line from the hydraulic system A and connects thegear extend and retract lines to the hydraulic system return line.

Gear ExtensionWhen the gear control lever is selected DN, the down solenoid of the selector valve energizes.When the landing gear system logic and all parameters are fulfilled, hydraulic pressure fromsystem A is simultaneously applied to:

– main hydraulic cylinder of each gear uplock– gear extend chamber of each gear actuator.

Initially the gear legs drop out by gravity and the nose leg extension is also assisted byaerodynamic forces. The main gear actuator extends the associated gear leg and the nose gearactuator retracts to extend the nose gear leg. The hydraulic pressure applied to each gearactuator provides the power to drive the main gear side struts and the nose gear downlock strutinto their over–center downlock position. The return fluid from each gear actuator is forcedthrough a restrictor which slows the gear extension speed and prevents detrimental structuralforces.When the gear legs have fully extended and downlocked, the solenoid of the DN selector is deenergized. This closes off the pressure line from the hydraulic system A and connects thegear extend and retract lines to the hydraulic system return line.


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Landing Gear (Normal Operation) System – Schematic


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Alternate Brake SystemThe alternate and normal main gear wheel brake systems each provide identical brakingperformance at the main wheels. The alternate brake system is supplied by hydraulic system Aand is automatically or manually selected via the brake changeover valve. Automatic selectionoccurs when a pressure loss is detected in the normal brake hydraulic supply from system B.Manual selection is used if there is a failure or degradation of the normal antiskid system.Manual control is via the BRK COV switch on the HYD PWR panel, when the switch is pushedthe ALTBRK caption in the switch comes on.With alternate brakes selected, hydraulic pressure from system A is supplied to the wheelbrakes via the brake changeover valve. When the brake pedal is pressed, the related hydraulic brake master cylinders actuated. Theresulting hydraulic pressure is applied to the alternate brake metering unit. The metering valveregulates the high fluid pressure from hydraulic system A into a controlled output pressurewhich is applied to:

– LH/RH alternate dual servo valve manifold– normal brake shuttle valve and fuse assembly– main gear wheel disk brake unit.

The brake metering valve controls the brake performance in accordance with the amount offorce applied to the Captains or First Officers LH/RH rudder pedals. Differential braking isachieved by applying a different amount of toe pressure to the LH or RH rudder pedals.After takeoff, hydraulic pressure from the gear retraction circuit is applied to a wheel despin porton the alternate brake metering unit as the gear retracts. This automatically applies hydraulicpressure to the disk brake unit of each main gear wheel to stop rotation of all main wheelsbefore they enter the wheel wells.For further information on the braking system, refer to Section 12–32–00–00 LANDING GEAR.

Alternate Anti–Skid ControlThe alternate brake system has an independent antiskid control unit (ASCU) which providesmain gear wheel antiskid control, touch down protection and locked wheel protection. When the inboard or outboard wheel speed sensor at any main gear wheel detects a suddenreduction in wheel speed, the applicable wheel speed sensor sends a signal to the ASCU. TheASCU sends a signal to operate the associated control valve in the alternate dual servo valvemanifold which reduces or dumps the hydraulic pressure to the disk brake unit. This allows theapplicable wheel to come up to its correct rotation speed in relation to aircraft ground speed.Therefore, the control valves provide antiskid, touchdown and locked wheel protection whichprevents flattening or bursting the tires on touchdown or during the landing run. The anti–skid control function provides optimum braking performance at the main gear wheelsand prevents skidding. The antiskid control is disabled when the increasing ground referencespeed is less than 25kts and when the decreasing ground reference speed is less than 7kts.The touch down protection function allows the main gear wheels to spin up for 3 seconds aftertouch down should any of the brake pedals be inadvertently pressed during this phase.


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The locked wheel protection function detects when the speed of one main gear wheel is lessthan 30% of the other. This function allows the slower or locked main gear wheel to spin up tospeed. The locked wheel protection function is disabled when the locked main wheel exceeds70% of the other main wheel reference speed.The alternate ASCU is interfaced with the flight control system through inputs from the wheelspeed sensors. When the main gear wheel speed is more than 45 kts, the ASCU produces acontrolling signal to enable automatic deployment of the outboard ground spoilers.


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Alternate Brake and Anti–Skid Control Systems – Schematic


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Feb 11/02


SYSTEM B CONSUMERS

GeneralSystem B hydraulic pressure is generated by a power pack that is installed in the RH landinggear fairing. System B supply is controlled by the SYSTEM – B push buttom and the standbysupply is controlled by the STBY rotary switch. The system B consumers are:

– The normal brakes and anti–skid control– The parking brake– The emergency landing gear extension– The nose wheel steering– The flaps– The roll spoilers– The inboard ground spoilers.

Normal Brake SystemThe consumers of hydraulic system B are monitored by the indicating system. The status andparameters are displayed on the HYD PWR section of the overhead panel and on the EICAS. The normal and alternate main gear wheel brake systems provide identical braking performanceat the main wheels. In normal operating conditions,the brakes are controlled by the normalbrake system. In this state the brakes are automatically supplied via the brake changeovervalve with hydraulic pressure from the system B.Hydraulic pressure from system B is supplied to the wheel brakes via the brake changeovervalve. The resulting hydraulic pressure is applied to an associated metering valve in the normalbrake metering unit. The metering valve regulates the high fluid pressure from hydraulic systemB into a controlled output pressure which is applied to:

– the LH/RH normal dual servo valve manifold– the park brake shuttle valve and fuse assembly– the main gear wheel disk brake unit.

Therefore the brake metering valve controls the brake performance in accordance with theamount of force applied to the Captains or First Officers LH/RH rudder pedals. Differentialbraking is achieved by applying a different amount of toe pressure to the LH or RH rudderpedals.After takeoff, hydraulic pressure from the gear retraction circuit is applied to a wheel despin porton the normal brake metering unit as the gear retracts. This automatically applies hydraulicpressure to the disk brake unit of each main gear wheel to stop rotation of all main wheelsbefore they enter the wheel wells.For further information on the braking system, refer to Section 12–32–00–00 LANDING GEAR.


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Normal Anti–Skid ControlThe normal brake system has an independent anti–skid control unit (ASCU) which providesmain gear wheel anti–skid control, touch down protection and locked wheel protection. When the inboard or outboard wheel speed sensor at any main gear wheel detects a suddenreduction in wheel speed, the applicable sensor sends a signal to the ASCU. The ASCU sendsa signal to operate the associated control valve in the normal dual servo valve manifold whichreduces or dumps the hydraulic pressure to the disk brake unit. This allows the applicable wheelto come up to its correct rotation speed in relation to aircraft ground speed. Therefore, thecontrol valves provide anti–skid, touchdown and locked wheel protection which preventsflattening or bursting the tires on touchdown or during the landing run. The anti–skid control function provides optimum braking performance at the main gear wheelsand prevents skidding. The anti–skid control is disabled when the increasing ground referencespeed is less than 20kts and when the decreasing ground reference speed is less than 7kts.The touch down protection function allows the main gear wheels to spin up to speed for 3seconds after touch down should any of the brake pedals be inadvertently pressed during thisphase.The locked wheel protection function detects when the speed of one main gear wheel is lessthan 30% of the other. This function allows the slower or locked main gear wheel to spin up tospeed. The locked wheel protection function is disabled when the locked main wheel exceeds70% of the other main wheel reference speed.The normal ASCU is interfaced with the flight control system through inputs from the wheelspeed sensors. When the main gear wheel speed is more than 45 kts, the ASCU produces acontrolling signal to enable automatic deployment of the inboard ground spoilers. In addition theASCU also receives brake temperature signals from sensors installed on each disk brake unit.The temperature data is diplayed on the EICAS.


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Normal Brake and Anti–Skid Control Systems – Schematic


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Feb 11/02


Park Brakes

GeneralThe park brake system is used to apply the wheel brakes when the aircraft is parked and give alimited emergency braking function in the event of failure of the normal and alternate brakesystem.The park brake system uses hydraulic power from System B through the park brakeaccumulator. The accumulator is maintained at system pressure when System B is operational.If System B is not operational, there are at least six full applications of the park brake systemavailable from the fully charged accumulator.

A pressure switch installed in the park brake pressure line monitors the brake system and thestatus is displayed on the EICAS.

Park BrakeTo set park brake, the park brake handle must be pulled to the stop in the center pedestal. Fromthis position, the handle must be lifted against spring force and pulled further aft and thenreleased into the detend. The brake is released by lifting the handle out of the detend andmoving it to its maximum forward position.

When the park brake handle is pulled the park brake valve opens and allows hydraulic pressurefrom the park brake accumulator to flow to the park brake shuttle valve manifold of the normalbrake system. This pressure causes the normal shuttle valves within the park brake manifold toclose off the hydraulic supply from the alternate shuttle valves and braking system. This allowsthe pressure from the park brake accumulator to flow directly to the four wheel brake units.

Emergency brakingTo apply emergency braking the park brake handle is pulled. The handle activates the samesystem components as used in the operation of the park brake.The brake efficiency achieved is proportional to the force applied to the brake handle. Becausethe rudder pedal toe brakes and the alternate brake meetering and antiskid control units areby–passed, differential braking and antiskid protection are not available.

Park Brake AccumulatorThe park brake accumulator is a conventional piston–type unit with a gas pressure gage and itis precharged with dry nitrogen. It is connected into the hydraulic system pressure line and ismonitored by a pressure switch. The purpose of the accumulator is to store sufficient pressure to operate the wheel brakes forparking the A/C for a limited time.The accumulator is constantly maintained in a hydraulically charged condition during operationof the hydraulic system. The accumulator state of charge is displayed on the EICAS.


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Park Brake System – Schematic


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Emergency Landing Gear ExtensionWhen the gear is being extended using the emergency extension system, the main and nosegear actuators move with their associated gear legs. To prevent a hydraulic lock, thedisplacement of fluid from these actuators is routed back through return line of hydraulic systemB. This is controlled automatically by the bypass valve of the emergency extension system. The system is activated when the emergency landing gear extend lever is pulled through thedetent to the end position which simultaneously operates the emergency extension and bypassvalves. This lets hydraulic pressure from system B through to the extension valve via tworestrictor valves. The restrictor valves decrease the hydraulic pressure, which decreases thespeed of operation of the uplocks and the assist actuators. This prevents damage to the uplockand downlock mechanisms. From the extension valve the hydraulic pressure goes through theemergency gear extension line (EMERG) to the auxiliary hydraulic cylinder of each main andnose gear uplock and to the LH and RH MLG downlock assist actuators. With each gear uplock hook released and open, the main and nose gear legs drop out bygravity.Simultaneously hydraulic pressure is applied to the MLG downlock assist actuators to drive themain gear side struts into their overcenter downlock position.The nose gear is downlocked by gravity which is assisted by aerodynamic–forces acting on theleg that drives the strut into the overcenter downlock position.


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D1–

FCO

M–1

2–00

62–0

01

Emergency Landing Gear Extension – Schematic


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Feb 11/02


Nose Wheel Steering

GeneralThe aircraft nose wheels can be steered on the ground by an electrically controlled,hydraulically powered nose wheel steering (NWS) system. Steering is achieved either bycommand signals from the rudder pedals which give a maximum nose wheel deflection of +/–10degrees or from a hand control unit which provides a maximum nose wheel deflection of +/–60degrees. There are two modes of operation of the NWS system, which are set by the NWSHIGH switch. If the switch is pushed in (high mode on) both the rudder pedals and the handcontrol unit give control inputs to the NWS system. With the switch pushed out (high mode off)only the rudder pedals give control inputs to the NWS system. The NWS system is disabledwhen the landing gear is retracted.With the landing gear extended, the NWS system is reenabled 0.5 seconds after the aircrafttouches down (NLG WOW). The steering command signals from the rudder pedals to the NWSsystem can be disabled by pressing a pedal disconnect push button on the hand control unit. At the discretion of the flight crew, the NWS system can be disabled by pressing the NWSswitch/light located in the instrument panel.

Steering System FunctionWith the NWS system enabled, steering command signals from the potentiometer of the rudderpedals and/or from the hand control unit are sent to the Electronic Control Unit (ECU). Thesteering command signals from the pedals and/or hand control unit are compared by the ECUwith the signals sent from the feedback potentiometers on the steering actuator. As long as the nose wheels have not reached the desired LH or RH steering angle, as dictatedby the rudder pedals and/or hand control unit, the ECU sends a discrete signal to a servo valve.This valve controls the flow control valves which direct the flow of hydraulic pressure to eitherthe LH or RH hydraulic cylinder in the steering actuator. When hydraulic pressure is applied to the applicable LH or RH hydraulic cylinder, it operates arack that rotates a pinion and turns the nose gear leg and wheels to the desired LH or RHsteering angle.This process is constantly repeated until the signal from the feedback potentiometers nulls thesteering command signal and the desired nose wheel steering angle is reached.The status of the NWS system is displayed on the EICAS.


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Nose Wheel Steering – Schematic


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Flaps SystemThe flaps are electrically controlled and hydraulically powered. Each flap is driven by a single hydraulicactuator which is installed on the trailing edge of the wing. The position of the flaps is selected by a flapcontrol switch located on the center pedestal. The selected flap position on the flap control switch is sensed by two integral rotary transducers whichsend flap position command signals to the flap control unit (FCU). The FCU decodes the flap commandsignals and generates control signals which are sent to the control valve manifold that subsequentlyoperate the flap actuators. The FCU also receives flap position signals from feedback sensors in the flapactuators. The FCU uses these position feedback signals:

– to stop flap movement when the flap position agrees with the selection on the flap control switch– to monitor the flap symmetry– to send flap position signals, flap control fail signals and, should the condition occur, flap asymmetry signals to the EICAS for indication purposes.

The control valve manifold is the hydraulic control element of the flap control system. It is installed in theupper fuselage fairing on the LH side.The FCU is the electrical control element of the flap system operation of the flap control. It is installed inthe LH avionic rack. The FCU continuously controls and monitors the flap system and the flap positionand status is displayed on the EICAS.To ensure symmetrical flap movement, the LH and RH flaps are interconnected by a synchronizationtorque shaft.


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Flaps System – Schematic


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Roll SpoilersThe LH and the RH roll spoiler are controlled by roll command inputs to the aileron controllinkage which subsequently controls the hydraulically driven spoiler. The aileron control linkageis designed so that it does not start to deflect the spoiler until the associated aileron updeflection has reached 4o.The system consists of the following LH and RH components:

– a hinge mounted roll spoiler located on the upper wing surface forward of the outboard flap section– a hydraulic actuator located on the rear wing spar– a spool valve which is an integral component of the actuator cylinder– a position sensor which is an integral component of the actuator piston rod.

The roll spoiler is driven by a hydraulic actuator which is a double–acting hydraulic cylinder thatis connected to the hydraulic system B by its pressure and return line ports. When a LH or RHroll command input is made through the aileron control linkage, the deflection of the associatedLH or RH roll spoiler is controlled by the actuator integral spool valve. The spool of the valvecontrols the direction of hydraulic fluid flow to the piston rod extend and retract cylinderchambers of the actuator. Depending on the position of the spool, the actuator piston rod either extends or retracts, or ishydraulically locked in a required position. The movement of the piston rod drives the spoiler inthe required direction. As the spoiler approaches its required deflection angle, a mechanicalfeedback signal from the actuator piston operates the spool which closes off the hydraulicsupply to the cylinder chamber and the actuator is now hydraulically locked until the next rollcommand is given.The actuator is equipped with a break–out device. The device allows the command input leverto move freely after application of an overriding force in the case of a control valve jam. Thisensures that the aileron controls are not jammed by a jammed control valve.A position sensor is integrated into each spoiler actuator. The sensors send spoiler positioninformation to the electronic indicating, caution and advisory system EICAS. The position of theroll spoilers is displayed on the EICAS.


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Roll Spoilers – Schematic


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Inboard Ground SpoilersThe LH and RH inboard ground spoilers are electro–hydraulically controlled and are eachoperated by a hydraulic actuator. The hydraulic actuator for each inboard ground spoiler iscontrolled by two solenoid operated valves. When all parameters such as thrust lever settings, WOW and main wheel spin–up are fulfilled,the solenoid operated valves energize and hydraulic fluid from system B is applied to theextension ports of the actuators. The actuators extend to deploy the respective inboard groundspoilers.When the inboard ground spoilers are no longer required or a parameter is no longer fulfilled,the solenoid operated valves de–energize and hydraulic fluid from system B is applied to theretract port of the actuators. The actuators retract, lock and stow the respective inboard groundspoilers.


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Dornier 328Jet - Hydraulic Power - SmartCockpit - Airline …€¦ · · 2012-06-27Dornier 328Jet - Hydraulic Power Page 1. Feb 11/02 EFFECTIVITY : ALL 12–29–01–00 ... 1 2