Introduction:
This assignment mainly talks about the hydraulic system within an aircraft. The hydraulic system in an aircraft is use for operating various services such as landing gear, wheel brakes and power flight controls etc. Each system has its hydraulic circuit within the system. These independent circuits are linked to the normal pressure and return lines of the hydraulic power circuit. A full power hydraulic system consists of the next;
A power or delivery circuit,
A range of service circuits,
Emergency circuits.
Below is the diagram of basic hydraulic system;
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Task Two:
Pump:
Pump provides pressurise hydraulic fluid to the machine by comprising the fluid which comes from the reservoir. Pump can pressurise the fluid up to 5000 psi. is determined by different pumps.
Pressure Reducing Valve:
The Pressure Reducing valve reduces the machine output pressure to a pressure ideal for operating a particular system or component.
Pressure Relief Valve:
Whenever there is certainly excessive pressure in the machine the pressure relief valve reliefs the excess pressure.
Reservoir:
The function of reservoir in the hydraulic system is to store the hydraulic fluid and provides the hydraulic fluid to the pump which in turn provides pressurise fluid to the system. The reservoir also pressurise the fluid up to 40psi in order never to get cavitation.
Motor:
The function of Motor is to assist in engaging the pump and also help in starting the machine.
Strainer:
Strainer is a filter. It filters out the dirt before the fluid would go to the pump. You will find high and low pressures strainers, normally the ruthless strainer want the pump and low pressure are prior to the pump.
Task Three:
B767
HYDRAULICS SYSTEMS
INTRODUCTION:
This airplane has three independent hydraulics systems that happen to be;
Left Hydraulic system
This hydraulics system powers the;
Flight controls
Left side engine Thrust reversal
It includes;
Reservoir,
Engine Driven pump, and
Electric motor driven pump
Right Hydraulic system
This system is comparable to Left hydraulic system and it involves same;
Reservoir,
Engine driven pump, and
Electric motor driven pump
This system powers the;
Flight controls,
Right side engine Thrust reversal,
Normal brakes, and
Pitch enhancement
Centre hydraulics system
The system consists of;
Reservoir,
Two Electric motor driven pumps,
An Air driven demand pump, and
RAT (Ram Air Turbine) pump
It powers the;
Flight controls,
Nose wheel steering,
Flaps and slats,
Alternate brakes,
Landing gear,
Hydraulic driven generator, and
Tail skid
So basically the hydraulic system of this aircraft powers the;
Flight controls,
Leading edge slats,
Trailing edge flaps,
Landing gear,
Wheel brakes,
Nose wheel steering,
Autopilot servos,
Thrust reversals, and
Tail skid
Flight control system components are distributed so that any hydraulic system can offer sufficient airplane controllability. All hydraulic reservoirs supplies fluid to pumps and these pumps pressurized the system and the reservoirs are pressurized by bleed air system.
Below figure shows three independent system what they consist of and what they power. In addition, it display there switches in the cockpit.
HYDRAULIC SYSTEM SCHEMATICS
FLUID SUPPLY
Hydraulic fluid comes to each pump from a reservoir. Reservoirs are pressurized from bleed air system.
There is fluid quantity measured device in every the reservoirs which provides information on EICAS status display. When RF illuminates on the EICAS status page then the reservoirs requires refilling prior to dispatch. Valid only once airplane is on ground with both engines shutdown or after landing with flaps up during taxi-in. As shown in figure below;
The QTY (1) light illuminates and the EICAS advisory message e. g. L HYD QTY displays which means that left side reservoir fluid quantity is low. SYS PRESS (2) illuminates when the system pressure is less.
ENGINE DRIVEN PUMP:
The primary hydraulic system pump is engine driven pump. As there are two engines on this aircraft it has two engines driven pump left and right. It runs with the engine and pressurized the machine.
When the pump output pressure is low the primary pump PRESS light illuminates on the hydraulic overhead panel and a warning display on the EICAS e. g. (if it is right side) R HYD PRIM PUMP. When the pump temperature is high OVHT light illuminates on the hydraulic overhead panel and again a warning display on the EICAS e. g. (if it's left side) L PRIM HYD OVHT
ELECTRIC MOTOR DRIVEN PRIMARY PUMP:
The two centre electric motor driven primary pumps are identical left and right systems electric motor driven pumps. The C2 pump may be load shed automatically to reduce electrical loads. As you can plainly see the figure above it has also the same PRESS low pressure and over heat OVHT warnings on hydraulic overhead panel. The associated EICAS messages for low output pressure C HYD PRIM 1 or C HYD PRIM 2 as well as for over heat C HYD 1 OVHT or C HYD 2 OVHT.
ELECTRIC MOTOR DRIVEN DEMAND PUMP:
An electric motor driven demand pump has an additional hydraulic power either on demand or consistently for periods of high system demand. The demand pump also offers a backup hydraulic power source for the engine driven primary pumps.
To reduce electrical load, the electric demand pump is inhibited on the floor during engine start of either engine, when only 1 power generator is operating. The demand pump PRESS and SYS PRESS lights illuminates when starting engines on the floor. As shown in the figure below the overhead hydraulic panel with warnings. The warnings will also display on the EICAS e. g. R HYD DEM PUMP.
AIR DRIVEN DEMAND PUMP:
An air driven demand pump also provides additional hydraulic power either on demand or consistently for periods of high system demand. This pump provides the backup hydraulic power for electric motor driven primary pumps. As shown in picture above it shows the warnings on the hydraulic panel PRESS when it's low pressure and OVHT when the pump come over heat. The warning may also be observed in EICAS.
RAT (RAM AIR TURBINE) PUMP:
This pump is used in emergency conditions it provides hydraulic capacity to the flight control part of the centre hydraulic system. The RAT provides sufficient hydraulic power at the speed above 130 knots. In flight, the RAT deploys automatically when both engine fails. The RAT is inhibited from auto deployment on the floor.
The RAT can be deployed manually by pushing the RAT switch. The UNLKD light illuminates and the EICAS advisory message RAT UNLOCKED displays when the RAT is not stowed and locked. After the RAT is producing the pressure the PRESS lights illuminates. The SYS PRESS light illuminated if RAT is merely the source of centre system pressure. Once the RAT is deployed then it cannot be stowed in flight.
SYSTEM PRESSURE INDICATIONS:
The SYS PRESS lights illuminates and the EICAS caution message e. g. ( for left hydraulic system) L HYD SYS PRESS when the left side hydraulic system pressure is low same for the right side and centre system.
HYDRAULIC DRIVEN GENERATOR:
Hydraulic driven generator is automatically powered by the centre system when electrical power is lost from both main AC buses. The centre air demand pump then operates continuously to ensure sufficient hydraulic pressure to operate a vehicle the generator.
HYDRAULIC PANEL:
System Pressure (SYS PRESS) Lights:
Illuminated (amber) - system pressure is low.
Reservoir Low Quantity (QTY) Lights:
Illuminated (amber) - reservoir quantity is low.
Left/Right Engine (L/R ENG) Primary Pump Switches:
ON - the engine driven hydraulic pump pressurized when engine rotates.
OFF (ON not visible) - the engine driven hydraulic pump is switched off and depressurized.
Pump Pressure Lights (PRESS) :
Illuminated amber - Pump output pressure is low.
Pump Overheat (OVHT) Lights:
Illuminated amber - pump temperature is high.
Centre 1/2 Electric (C1/2 ELEC) Primary Pump Switches:
ON - the electric motor driven pump pressurized the centre hydraulic system.
OFF - the electric motor driven pump is switched off and is not pressurizing the machine.
Left/Right Electric and Centre Air ( L/R ELEC and C AIR) Demand Pump Selectors:
ON - continuous operation
AUTO
Left/Right electric pumps operate when engine pump pressure is low.
Centre air demand pump operates when both centre electric pump pressure is low.
Centre AIR demand pump operates when heavy load items are selected.
OFF - Pumps are turned off
LANDING GEAR:
Introduction:
The airplane has two main landing gear and single nose gear. The nose gear is a steerable with two wheel unit. Each main gear has four wheels in tandem pairs.
Hydraulic power for retraction, extension, and steering comes by the centre hydraulic system. An alternative extension system is also provided.
Below is the schematic of the landing gear system;
Air Ground Sensing System:
The air ground sensing system receives air ground logic signals from tilt sensors situated on each main landing gear. These signals are being used to configure the airplane system to the correct air or ground status.
A nose air ground system receives signals from nose gear strut compression sensors. These signals are for controlling stall warning and portions of the caution and warning system.
LANDING GEAR UNDER NORMAL OPERATION:
The landing gears are normally managed by the landing gear lever.
On the bottom, the lever is held in DN position by an computerized lever lock managed by the primary gear tilt sensor.
The lever lock can manually overridden by pushing and holding the landing gear lever LOCK OVRD switch. In flight, the lever lock is automatically released through air ground sensing of main gear tilt sensor.
Landing Gear Retraction:
When the landing gear lever is put to UP, the tilted landing gear begins to retract. The landing gear doors open and the apparatus retract to up position. Automatic wheel braking occurs during gear retraction. The landing gear lever is located in the OFF position to depressurize the landing gear system.
Landing Gear Extension:
When the landing gear level is moved to DN, the landing gear door opens, the apparatus are unlocked, and the apparatus and DOORS light illuminates.
The gears are hydraulically powered to the down and lock position. The down locks are powered to the lock position, all hydraulically actuated gear door close, and the primary gear trucks hydraulically tilt to the flight position.
When all gears are down and locked, the gear down light illuminates and the apparatus and DOOR light extinguish.
Landing Gear Alternative Extension:
The alternative landing gear extension system uses an electric motor to trip the fasten for every gear. Selecting DN on the ALTN GEAR EXTEND switch releases all the door and gear up locks, the landing gear then free fall to the down and locked position.
TASK FOUR:
Introduction:
The Workplace (Health, Safety and Welfare) Regulations 1992 cover a wide range of basic health, safety and welfare issues and apply to most workplaces (with the exception of those workplaces involving construction focus on construction sites, those in or on a ship, or those beneath ground at a mine). They are amended by the Quarries Regulations 1999, the Health and Safety (Miscellaneous Amendments) Regulations 2002, the task at Height Regulations 2005, and the Construction (Design and Management) Regulations 2007.
These Regulations aim to ensure that workplaces meet the health, safety and welfare needs of all members of your workforce, including people who have disabilities. Many of the Regulations require things to be suitable.
Followings are the Health insurance and safety regulations that ought to be followed in the working place;
HEALTH:
Ventilation
Workplaces need to be adequately ventilated. Fresh, climate should be drawn from a source outside the workplace, uncontaminated by discharges from flues, chimneys or other process outlets, and be circulated through the workrooms. Ventilation also needs to remove and dilute warm, humid air and provide air movement gives a feeling of freshness without causing a draught. When the workplace contains process or heating equipment or other resources of dust, fumes or vapours, more oxygen will be had a need to provide adequate ventilation. Windows or other openings might provide sufficient ventilation but, where necessary, mechanical ventilation systems should be provided and regularly maintained.
Temperatures in indoor workplaces
Environmental factors (such as humidity and sources of heat at work) incorporate with personal factors (such as the clothing a worker is wearing and exactly how challenging their work is) to influence what's called someone's 'thermal comfort'. Individual personal preference helps it be difficult to specify a thermal environment which satisfies everyone. For workplaces where the activity is mainly sedentary, for example offices, the temperature should normally be at least 16 C. If work involves hard physical work it should be at least 13 C (unless other laws require lower temperatures).
Work in hot or cold environment
This includes risk to workers' health from working in the hot or cold environment must consider both personal and environmental factors. Personal factors include body activity, the total amount and kind of clothing, and duration of exposure. Environmental factors include ambient temperature and radiant heat; if the work is outside, sunlight, wind velocity and the occurrence of rain or snow.
Lighting:
Lighting should be sufficient to enable people to work and move about safely. Lighting and light fittings shouldn't create any hazard. Automatic emergency lighting, powered by an unbiased source, should be provided where sudden loss of light would make a risk.
Cleanliness and waste material
Every workplace and the furniture, furnishings and fittings should be kept clean and it should be possible to keep carefully the surfaces of floors, walls and ceilings clean. Cleaning and the removal of waste should be completed as necessary by an effective method. Waste should be stored in suitable receptacles.
Room dimensions and space:
Workrooms must have enough free space to allow visitors to move about easily.
Workstations and seating:
Workstations should be suited to the people with them and for the task they are doing. People should be able to leave workstations swiftly within an emergency. If work can or must be done sitting, seats that are suitable for the individuals using them as well as for the work they actually should be provided. Seating should give adequate support for the lower back, and footrests should be provided for staff who cannot place their feet flat on to the floor.
SAFETY:
Maintenance:
The workplace, and certain equipment, devices and systems should be maintained in efficient working order (efficient for health, safety and welfare). Such maintenance is necessary for mechanical ventilation systems; equipment and devices which would cause a risk to health, safety or welfare when a fault occurred; and equipment and devices intended to prevent or reduce hazard.
The condition of the buildings needs to be monitored to ensure they have appropriate stability and solidity for his or her use. This includes risks from the normal running of the task process (e. g. vibration, floor loadings) and foreseeable risks (e. g. fire in a cylinder store).
Floor:
The surfaces should not have holes or be uneven or slippery, and really should be kept free of obstructions and from any article or substance which may cause a person to slide, trip or fall. Criteria for defects such as subsidence, unevenness, pot holes, assortment of surface water, cracks and ruts should be determined and set, and maintenance systems developed to attempt repair when these limits are exceeded.
Windows:
Open able windows, skylights and ventilators should be capable of being opened, closed or adjusted Safely and, when open, should not pose any undue risk to anyone.
FATIGUE TESTING MACHINE:
Fatigue testing machine ensure that you determines the useful working life of an element which is subjected to repeated load. Fatigue testing machine applies pre-defined loads or alternating loads to the sample component and records fatigue life indicated by the number of cycles required to product failure.
Followings are the health and safety problems with fatigue testing machine;
As Fatigue-testing machines produce heavy vibration so it takes a strong foundation.
Safety guidelines provided by the metal fatigue-testing equipment manufacturers should be followed prior to starting a fatigue test.
Proper controls and accessories should be installed for fatigue-testing machine to avoid accidents.
Task Five:
Maintenance Procedure for Landing Gear:
Landing Gear is the most rugged part of the aircraft and should be maintain properly in order not have accidents.
In order to raise the life time and minimising the accidents regularly inception should be produced for inspecting the landing gear as a result of force hitting the runway after landing stresses the entire system no matter how gentle the landing is.
Following is the procedure to keep the landing gear;
Place the aircraft on jacks in the approved manner as detailed in the manufacturers maintenance manual.
Interconnect a manual pump (filled with a one gallon reservoir and a 3000 p. s. i. pressure gauge) in to the system at the service tee fitting. This fitting is located downstream of the pump check valve.
Deactivate the pump and motor by disconnecting the plug on the pressure switch.
Disconnect the pressure relief valve and the thermal relief valve from the machine and cap from the lines.
Disconnect the accumulator from the machine and cap off the line.
Pressurise the system to 3000 p. s. i.
When the pressure reaches 3000 p. s. i. , the system must remain within 50 p. s. i. of the pressure for just one minute without additional pumping.
Reconnect the THERMAL relief valve and pressurise the system until the valve opens. The cracking pressure of the valve should be 2200 + or - 50 p. s. i. *
With the gear doors disconnected, select 'gear up' and retract using the hand pump. Take the gear up slowly and check the flex lines for clearance and signs of chafing.
When the gear reaches the up position, raise the pressure to 3000 p. s. i. The system must again remain within 50 p. s. i. of the pressure for one minute.
Pull the 5 amp L/G control breaker, reconnect the pressure switch plug and reset the 5 amp breaker. Extend the gear with the normal system.
Reconnect the pressure relief valve and pressurise the system before valve opens. The cracking pressure because of this valve is the same as the thermal relief valve, 2200 + or - 50 p. s. i. *
Disconnect manual pump from service tee and cap tee.
Check emergency nitrogen bottle is charged to 1500 p. s. i.
With gear in down position and system pressurised, open manual nitrogen valve in the cockpit and look for leaks between the valve and the actuators. Maximum leakage rate, 50 p. s. i. in ten minutes.
Close the manual nitrogen valve and bleed from the pressure in the emergency system by loosening the line at the bleed valve in the nose wheel well. Prior to re-connecting the line, be sure the bleed valve is open. Blow air gently into the bleed valve fitting and check the most notable of the valve for a flow of air.
Charge the accumulator to 1250 p. s. i. Re-connect to the machine.
Recharge the emergency nitrogen bottle to 1500 p. s. i.
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Tasks
Yes
No
Jack is placed on right position
Aircraft is put on jack according to maintenance manual
Connect manual pump in to the system at service tee fitting. Fill it to 1 gallon reservoir with 3000 psi.
Pump De-activated
Pressure relief valve and thermal valve dis-connected
Accumulator dis-connected
Pressurise till 3000 psi
System remain at 50 psi for a minute
Thermal relief valve re-connected and system pressurise until the valve opens
Gear doors dis-connected
Gear up selected
Retract using the hand pump and check the flex lines for clearance and signs of chafing.
On the gear reaches the up position, boost the pressure to 3000 p. s. i. The system must again remain within 50 p. s. i. of the pressure for one minute.
System remained within 50 p. s. i. for just one minute.
5 amp L/G control breaker pulled.
Pressure switch plug reconnected and reset the 5 amp breaker reset
Gear extended with the standard system.
Pressure relief valve reconnected and pressurise the system before valve opens
Manual Pump dis-connected
Emergence Bottle check
Leakage check between your valve & actuator
Emergency system check
Emergency Bottler recharge to 1500 psi.
