fligh safety and maintainence activities3 unit3.doc

7/29/2019 Fligh safety and maintainence activities3 unit3.doc

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Flight safety and

maintenance activities

Unit 3

Introduction:

Every year aircraft accidents cost great amount of money, aircraft and its

equipments and sometimes result in loss of precious human lives which include

passengers and trained aircrew. Hence it is necessary to protect the men and

material and use them judiciously. In this context the concept of flight safety or

aircraft accident prevention assumes its importance. The aim of flight safety is to

enhance the operational potential and efficiency of the aircraft industry.

The object of any safety effort is the identification and reduction of risk. Just

as in the other fields like highway traffic etc., provisions and procedures have been

made to reduce the risk of accident and promote flight safety. The successful

implementation of flight safety measures involves not only of safety among

personnel of all cadres but also their active participation and co-operation,

conspicuous and meticulous observance of aircraft accidents, both on the ground

and in the air.

(I)RELATIONSHIP BETWEEN MANITENANCE ACTIVITIES AND

FLIGHT SAFETY:

One of the major activities that are mainly oriented towards ensuring flight

safety is maintenance. The process of maintenance is broadly divisible in stages .

i .e, provisioning, holding, distributing and servicing. Every aspect of

maintenance included in this broad definition, has its own influence on Flight Safety.

To do this the man, the environment and the aircraft have to be investigated in

detail, and suitable procedures have to be laid down in the respective areas.


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(II) CRITICAL MAINTENANCE ACTIVITES: HAZARD AND SAFETY

PRECAUTIONS

(1)AIRCRAFT SERCIVING:

One of the important elements of aircraft servicing is the technician who

actually does the servicing. He should be professionally competent to carry out his

job and posses the necessary qualifications and skills. Though the technicians meet

these standards, he develops certain serious failings due to environmental factors.

Complacency or an easy going attitude and resorting to shortcuts in servicing are

two examples. It is necessary to eliminate such tendencies among technicians in

the interests of flight safety. Some other examples of undesirable habits which

affect critical technical activities are:

(a) Failing to consult servicing schedules/manuals before and duringservicing. Relying only on memory with regards to list of checks or steps

to be followed

(b) Resorting to shortcuts while replacing components in inaccessible parts of

aircraft.

(c) Using inappropriate tools or careless use of available tools.

(d) Showing disregard for cleanliness of working area by leaving tools and

parts laying about, not using suitable trays to keep dismantled parts etc,.

(2) BAY SERVICING:A considerable portion of maintenance of airborne equipment is carried out in

servicing bays. These bays will have all the facilities required to meet periodical or

scheduled bay-servicing. Adequate master process charts schedules or bay

servicing schedules are also made available here. The technician carrying out bay-

Servicing should invariably adhere to the detailed instructions pertaining to their

work, and avoid deviation from the laid down servicing procedures. The technician

must familiarize himself with principles and correct use of the test equipment

required for his work. He must maintain proper records of his actions as well as ofvarious readings. He must use the correct tools and test equipments and follow

correct technical practices. Failure to follow the laid down drill can result in sub

standard servicing and premature failure of airborne equipment leading to

accidents.

(3)SOME COMMON HAZARDS:


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Literally hundreds of occurrences under flight safety are caused by servicing

crew errors. A majority of them occur during first line and second line servicing of

aircrafts. The types of errors causing aircraft accidents/incidents over a period have

been analyzed and the potential hazard areas are identified. Some of the main

hazards are listed below:

ERRORS OF OMISSION AND COMMISION:(1)Failure to carryout laid down checks

(2) Failure to secure parts correctly

(3) Lapses of servicing due to haste of the technician

(4)Foreign Object Damage (FOD).

(5) Failure to take precautions especially involving explosives.

(6)Omission to complete refitment of parts after servicing.

(7)Unauthorized starting of engines.

(b)Professional errors(1)Incorrect servicing

(2)Incorrect fitment/installation of parts.

(3)Incorrect adjustments

(c) Inadvertent Errors(1)Wrong operation of controls.

(2)Reversal in fitment.

(3)Walking into air intake areas when engine running.

(d) Errors in ground handling of aircraft.

(e) Collision of ground vehicles (such as Refueller, Ground power units, Tow

tractors etc.) with the aircraft.

(f) Towing accidents

(4) Murphys law:

Murphys law states that if there is a possibility of an error being commited,

then someday someone will commit that error.


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For example, there are many subassemblies in various aircraft whose

fitments can be inadvertantly reversed by the technician. These are due to

connections, parts etc., looking exactly alike. In one instance the reverse fitment of

the tail rotor blade of a chetak helicopter resulted in the helicopter falling down and

getting seriously damaged. This happened when the pilot operated the rudder to

control a tendency for the helicopter to swing to onside. Thus there is a possibilityfor reverse fitting to take place. This is called a Murphy. Murphies should be

promptly reported to the supervisor in charge immediately so that a remedial action

can be taken to prevent a disastrous event.

(5)PRECAUTIONS:

In order to effectively contribute improved flight safety and reduce risk of

aircraft accidents technicians should ensure the following:

(i) Avoid casualness and easy-going attitude in carrying out servicing.

(ii) Acquire the requisite professional competence to carry out servicing.

(iii)Avoid resorting to shortcuts in servicing.

(iv) Follow meticulously the detailed steps laid down in the relevant servicing

schedules.

(v) Maintain the working area scrupulously clean at all times.

(vi) Account for each and every part dismantled during servicing until

completion of refitment.

(vii) Avoid littering of used material and discarded parts.

(viii) Observe precautions while moving around ther aircraft under servicing

and on Ground runs.

(ix) Avoid touching or operating controls or getting inside or rear of the

aircraft without authority.


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(III) TARMAC SAFETY

SOME AREAS OF TARMAC SAFETY WHICH ARE IMPORTANT ARE THE

FOLLOWING

(a) CRASH VEHICLES

These vehicles should be fully serviceable at all times. They should be run

sufficiently to ensure that their batteries are fully charged. This will avoid starting

problems at critical times when the crash vehicles are required.

(b) CRASH BARRIERS AND AIR FIELD LIGHTING:

These should be periodically serviced and documented.

(c) EMERGENCY POWER SUPPLIES

These are to be operated and maintained. Other standby generators

are also to be kept in serviceable condition.

(d) CRASH CLEARENCEThe crash crew should be familiar with the rescue operations of aircrew

and passengers when accident takes place.

(e) RUNWAY CLEARENCE AFTER TYRE FAILURE

This is a common occurrence but creates an emergency situation.

Jacking and towing equipments should be available at all times.

(f) GALE PRECAUTIONS

The general picketing, mooring and parking arrangements both

inside and outside hangars should be adequate. If picketing blocks are not

adequate, permanent mooring rings may have to be installed. These measures willreduce damage to aircraft during strong gales and storms.

(g) TURNAROUND CHECKS:

Accidents do occur during turnaround servicing of aircrafts. Correct

drills must be followed. Precautions to be strictly adhered while Refueling the

aircraft. Gas charging practices are to be correctly done. Wrong identification of

gas cylinders can be fatal.

(h) GENERAL REPLENISHMENT PRACTICES

Correct replenishment practices should be followed in respect of

hydraulic fluids, oils and greases. Correct identification is essential. Periodic qualitycontrol checks of oils and greases are also important. Fluids should be clean and

free from dust and dirt as these can cause excessive internal wear and premature

failures of engines or equipments.


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(IV) FOREIGN OBJECT DAMAGE (FOD)Foreign object damage is one of the major causes of aircraft accidents. FOD

is not confined to engines only. Tools, nuts, Bolts and other miscellaneous items

left behind inaccessible places of the aircraft as a result of sloppy habits can cause

obstruction to control movements, shorting of electrical plugs etc. with catastrophic

results. A conscientious approach by all to eliminate this servicing lapse is essentialif accidents are too prevented.

There are certain basic precautions that can be adopted with success to

prevent foreign object damage to engines. FOD in engines take place by the entry

of foreign objects through the air intake when the maintenance is being undertaken.

The ready availability of a powerful flight for carrying out air intake inspection is an

important detail that should be ensured.

Foreign objects find their way into the airframe are also connected withnuts,bolts,washers and other parts removed during disassembly. They should be

counted and accounted for until they are refitted. Proper container should be used

for storing the removed parts. During subsequent assembly presence of surplus

parts should be viewed with as much as suspicion as deficiencies. The importance

of counting and daily accounting of tools should be a compulsory practice in every

servicing section. Daily issue and receipt of tools from a well managed tool-crib will

greatly assist FOD control. An independent check by a supervisor for loose articles

after maintenance in vulnerable areas, such as cockpit floors, control columns etc.

can be signed for on completion of major servicing activities. Finally the personal

relationships between the technician and the supervisor should be such that they

should feel free to report all accidental actions by which tools bolts etc. have been

inadvertently dropped into inaccessible areas without fear of retribution from

their supervisors.

No shortcuts should be adopted by the technicians during retrieval of objects

dropped into inaccessible areas or to the procedure laid down for a particular

servicing of the aircraft.

(V) TYPICAL OPERATIONAL HAZARDS

(1) Inadequate operations or weather briefing.

(2) Inadequate flight planning activities.

(3) Faulty maintenance and inspections.

(4) Inadequate aerodrome facilities like lighting, Radio aids crash rescue facilities

etc.


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(5) Hazardous fire prevention practices.

(6) Deficiencies of flight publications like charts, maps, handbooks, etc.

(7) Inadequate fire fighting equipments.

(8) Unsatisfactory radio procedures or ground control approach procedures andoperations.

(9) Poor radio transmission from air traffic control.

(10) Follow me jeep or wing walkers not available when parking aircrafts.

(11) Debris and other refuse materials on the taxi-track or parking areas.

AIRCRAFT GENERAL ENGINEERING AND MAINTENANCE

PRACTICES

Lesson Plan :2 SHOP SAFETY

(1) INTRODUCTIONMaintenance is carrying out certain actions which will extend the life of

manmade materials and machines. Safety is the precautionary measure to

prevent damage to the equipments and injury to the personnel involved in

maintenance activities. Hence maintenance safety is the set of disciplinary actions

to be observed during maintenance of aircraft and its associated equipments.

It is to be clearly understood that Flight Safety and Maintenance safety go

hand in hand together. Maintenance safety leads to Flight safety and then there

are additional responsibilities and precautions for Flight safety which concerns not

only the Pilot who flies the aircraft, but also other members involved in aircraft

flying such as maintenance team, airfield operators, Air traffic controller, other

aircrafts and their aircrew, the birds which share the sky along with aircrafts, the

weather conditions, the passengers (may include the terrorists and skyjackers) etc,.

(2) OBJECTS OF MAINTENANCE

(a) To extend the useful life of the materials.

(b) To ensure maximum availability of installed equipment and to

obtain the maximum possible profit on investment.

(c) To keep the equipments required for emergency use in serviceable

conditions (eg: Standby units, Fire fighting and Rescue equipments

etc.)


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(d) To ensure safety of personnel (group of persons) using the

machine.

(3) FORMS OF MAINTENANCE

(a)Planned maintenance

Preventive maintenance

Corrective maintenance

(b) Unplanned maintenance

Emergency maintenance

Breakdown maintenance

(c)Automatic maintenance: Provided in electronic equipments of

modern aircrafts known as Bite and MTN programs. Bite enables theautomatic sensing of failed components and the informations are

available in flight and after flight to the user. Identification of failed

LRU or PCB is easily done and change of LRUs or PCBs are possible

within a short period. MTN (maintenance) programs are stored in

modules and they can be used to carry out in-situ checks of Avionic

equipments without removing them from the aircraft. This short

durations check also enables the maintenance crew to identify the

faults in Avionic system easily. However individual LRUs are to be

tested in the test benches whenever needed.

EXAMPLES OF DIFFERENT TYPES OF MAINTENANCE:

Preventive maintenance

Daily inspections

Between flight inspections

Lubrications

Alignment Checks.

Topping up of fuel, oil, etc.

Corrective maintenance

1. Change of components after identification of faults

2. Change of components after life expiry


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3. Change of brake shoes

4. Change of aircraft tyres

5. Change of clutch plates etc.

Emergency Maintenance

1. Tyre brusts and tyre change

2. Undercarraige problems

3. Failure of engines

4. Brake failures etc.

Breakdown Maintenance:1. Tyre burst

2. Fuses blown down

(4) FACTORS AFFECTING MAINTENABLITY:1. DESIGN FACTORS

2. INSTALLATION FACTORS

3. OTHER FACTORS ETC.

(i) DESIGN FACTORSA. Reliability (capability of survival)

B. Interchangeability

C. Replaceability

D. Visibility

E. Acceptability

F. Repairability

G. Configuration(mode of arrangements)

(ii) INSTALLATION FACTORS:

A. Experience (by technical supervisors etc)

B. Training for technical supervisors


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C. Skill used by the technicians and others

D. Supervision of maintenance manual

(iii) OTHER FACTORS:

A. Environment (proper hanger with ventilation, lightening, water supply

etc.)

B. Manuals (maintenance manuals , workcard manuals, technical

manulals, wiring diagrams etc)

C. Equipments for overhaul (Tools and ground equipments)

D. Test equipments

E. Modification schedules

F. Available calibration

G. Testing facilities and techniques

(5) CAUSES FOR FAILURE OF AN AIRCRAFT OR AIRCRAFT COMPONENT

A. DEFICIENCY IN DESIGN: (wrong design not suiting to vehicle or

component)

B. DEFICIENCY IN MATERIAL: Cracks, Intercrystalline corrosion etc.

caused because of imperfect heat treatments.

C. ERRORS IN ASSEMBLY: While assembling the aircraft or

components errors by the manufacturer or purchaser.

D. IMPROPER SERVICE CONDITIONS: Abnormally severe conditions of

overloading, overspeeding, excessive temperatures etc. And also

other factors such as lack of scheduled maintenance, inspection

and regular monitoring.

E. INADEQUATE MAINTENANCE: In addition to scheduled maintenance

program, an aircraft may need more maintenance which is evolved

during the usage of an aircraft or aircraft components.

F. RELIABILITY: of an aircraft or a component is found from the

following:

CONDITION MONITORING (TO IMPROVE THE DESIGN): It is the

process of collecting failure data for the aircraft as well as for

the component

SERVICE HISTORY: By properly maintaining the service records

such as aircraft servicing form, Aircraft logbooks, component log


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book etc, the history of servicing carried out on an aircraft on a

particular component can be traced out for analysis.

FROM THESE FACTORS THE FOLLOWING CAN BE DETERMINED:

Life of an aircraft or a component

Operational reactions

Failure rate

Maintenance schedules

Programs

Provisioning of spares

(7) SAFETY:Safety can be categorized as personnel safety and aircraft and equipment

safety.

(a) SAFETY OF PERSONNEL: Safety of personnel involves in safeguarding the

persons from external and internal injuries when servicing aircraft and its

equipments.

EXTERNAL INJURIES TO THE PERSONNELS ARE CAUSED OUT OF THEFOLLOWING:

A. Heavy weights

B. Tools

C. Protruding parts and sharp edges of the aircraft and its components

D. Opened panels, doors and canopies.

E. Brake failure of aircraft and ground vehicles and equipments.

F. Electricity and electrical installations

G. Heat, fire and irritant lights

H. Fuel ,oil and other toxic liquids

I. Corrosion


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J. Slippery grounds,platforms,aircraft wing surfaces and fuselage

surfaces

K. Cryogenics such as LOX, Liquid nitrogen etc.

L. Explosion due to overpressures, detonators, cartridges, etc.

INTERNAL INJURIES ARE CAUSED BY:

TOXIC OR POISONOUS GASES, FUMES, SMOKE ETC.

PENETRATING PAINTS, OILS ETC.

RADIATION

SAFETY OF AIRCRAFT AND EQUIPMENTS INVOLVES THE

FOLLOWING HAZARDS: IMPROPER HANDLING SUCH AS DROPPING,JARRING,HAMMERING ,USING

NO CUSHIONS ETC. AND ALSO NOT FOLLOWING PRECAUTIONS WHILE

TOWING

Use of improper tools such as pressure gauges, torque wrenches

etc.

Not using appropriate cleaning materials, cleaning agents not using

blanking when cleaning, painting.

Power supplies

Fire

Accumulated oils, fuels and gases etc.

Temperature effects on LOX, sensitive compasses etc.

Not using the specified fuels, oils, gases, etc.

Birds, animals, snakes, wasps, etc.

By untrained persons, no supervisors etc.

Brake failure if aircraft and other vehicles such as refuellers,charging trolleys, GPUs etc.

SHOP SAFETY: AIRCRAFT HANGARShop includes all the workplaces involved in maintenance of aircraft.

Aircraft hanger is a place is parked during storm conditions and storage. Many of


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the servicing inspections and maintenance activities are carried out inside the

hangar during 1st line, 2nd line, 3re line and 4th line of maintenance. These are

hangars meant only for painting the aircrafts. As these hangars have provisions for

required electrical power supplies for both aircraft and ground equipments, it is

required to follow the safety rules and precautions with regard to the usage of these

power supplies high pressure charging trolleys, mobile groundpower(electrical)units using petrol, Diesel oxygen charging trolleys ,oxygen purging

trolleys, oil storage, tool crib, Supply stores, Grinders, Test benches using high

pressure hydraulic system or pneumatic system, portable mobile lightening

equipments, hydraulic trolleys, Air conditioning trolleys, Spray guns, vacuum

cleaners Jacks, Cranes, support/Storage trolleys, Work platforms, Storage racks,

Standby generator ram etc.

HAZARDOUS MATERIALSHazardous materials that are present in the aircraft hanger can be classified

as chemical agents, Physical hazards and biological hazards

LIST OF COMMONLY FOUND HAZARDOUS MATERIALS IN AN

AVIONIC ENVIRONMENT:

1. Aircraft liquids

Gasolines

Jet fuels

Hydraulic fluids

Brake fluids

Anti-ice additives

2. Gases

Freon

Nitrogen

Oxygen

Halons

3.Others

Alcohols

Methanol


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Battery acids

Glycol

Baking soda

Degreasers

Disinfectants

SQUIBS (a small fire work)

(2)AIRCRAFT SERVICING

(A)LUBRICANTS

Dry lubricants

Spray lubricants

Greases

(B)SOLVENTS AND CLEANERS

Methyl ethyl ketone

Toluene

Engine cleaners

Carburetor cleaners

PAINTS AND PRIMERS:

Paints strippers

Primers

Doping products

Shellac dissolved in alcohol-Varnish

Lacquers

Enamels

Explosives

(D)ADHESIVES

Fibre glass resins

Gasket adhesives


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Rubber adhesives

(3)COMPONENT SHOPS

(A)INSPECTION

Liquid penetrants

Dye penetrants

(B)WELDING

Argon gas

Hydrogen gas

Oxygen gas

Acetylene gas

Fluxes and pastes

OTHER

Compressed air

Glass beads

Blurring and thinner

Quenching fluids

Muriatic acid

Locking compounds

Anti-seiging compounds

Mineral spirits

Cutting fluids

Soldering fluxes

(1)CHEMICAL AGENTS

The chemical agents in an aircraft industry can be brought under the

following categories: Flammable and corrosives, toxic, reactive. The acronym

FACTOR will help to remember the classes of chemical agents. The two outside

letters of the acronym FACTOR, F and R (flammable and reactive) become

hazardous primarily after some outside event, condition or substance interacts with

them. For example the necessary components for a fire to occur are fuel, oxygen


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and heat. Oxygen is the outside agents. Reactive when combined with certain

materials are capable of generating heat and or gases, causing an explosion. The

inside letters of the acronym C and T (corrosive toxins) on the other hand, act

directly on the human body when exposure occurs. Exposing the skin, eyes, and

the other mucous membranes (such as the nose) to these elements can cause

varying degrees of harm. Toxic agents cause poisoning. Aviation maintenancetechnicians should be particularly concerned when using toxic agents, because the

ultimate effects of toxic poisoning to become apparent; because the toxic poisons

are capable of using the blood stream to move through the body, the cause-and-

effect relationship may not be easily recognized.

EXAMPLES OF

(I)FLAMMABLE OR COMBUSTIBLE MATERIALS: Fuels, paint-

related products, alcohols, acetone, toluene, and somemetal filings.

(II)CORROSIVES: Battery acids, metal cleaning solutions, bases etc.

(III)TOXINS:

Solvents and thinners for blurring (such as dykern)

Paints

Ketone

Adhesives

Solids such as metal dust or asbestos

Machine lubricants, cutting fluids and oils

Gases such as carbon id oxide or nitrogen

Polymers, epoxies and plastics

Sensitizers such as epoxy systems

Carcinogens

(IV)PHYSICAL HAZARDS

X-Rays

Microwaves


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Beta or gamma rays, invisible laser beams

High frequency (ultra sonic sound waves) not detectable by human senses.

Compressed liquids and gases such as welding oxygen and acetylene\, aviators

breathing oxygen, nitrogen and hydraulic accumulators-detectable by human

values senses.

(3)PHYSICAL HAZARDS:

Biological hazards are transmitted in the form of a droplets or spores and

enter the body through contact with contaminated objects or individuals. An

aviations maintenance technician is likely to be exposed to biological hazards when

working on cargo aircraft or in a cargo (baggage) compartment where breakage or

leakage of biologically hazardous material has occurred.

(III)SAFETY MEASURES

Chemical hazards can be avoided by using protective clothing such as apron,

Respirator, face shield, goggles and sometimes protective foot wears. Physical

hazards can be avoided by clearly marking the areas where this exposure exists.

Biological hazards are avoided by the properly documenting the transportation of

such materials and avoiding exposure to such materials

MSDS (Material Safety Data sheet)A material Safety data sheet is a document provided by the material

manufacturer or subsequent material processor that contains information related to

the material hazard includes safe handling and disposal procedures

LABELLING:All hazardous materials should have identifying labels adhered to them. As a

general rule, these labels should never be remarked. The most common

standardized hazardous materials identification placard used today is of NFPA

(national fire protection association). The pleading system uses far diamonds a

particular type of hazard is present. The top three diamonds follow a numbering

system from one to 4 indicating the degree of hazard.

The top diamond specifies the relative fire hazard interms of flash points from

1 to 4. The left side diamond specifies the health hazard and the right side diamond

indicates the degree so the reactivity of the material. The bottom most diamond

indicates any specific hazard such as corrosive or does not use water precautionsetc.

The diamond coding system may also use different colors to segregate each

type of hazard.


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The Health hazard diamond is blue

The flammability diamond is red

The reactivity diamond is yellow

The specific hazard diamond is white

Aviation maintenance technician working confined, poorly ventilated areas

should use appropriate precaution if NFPA health hazard is code greater than

0(1, 2, 3, 4). Those who are working on hot brakes should beware of the relative

fire hazard code.

Aviation maintenance technician must be aware of the hazards of materialsused in aircraft industries and also he should know how to dispose these

materials. Generators of hazardous materials should maintain records regarding

hazardous waste material and also the records of disposals of such materials.

Prior to using a hazardous material the aviation maintenance technician should

evaluate the types of accidental releases that might occur and prepare for them.

A review of the MSDS prior to the usage is advised.

The aviation maintenance technician should be concerned first with personal

safety. If AN ACCIDENTYAL RELEASE might have determinate effect to other

individuals, a means of notification should be established containment is the

next priority to avoid accidental releases of hazardous materials. For example ifthe hazardous materials are in a tank how the drain could be quickly plugged.

These questions may have answers with a little imagination. Any hazardous

material release should be reported by the aviation maintenance technician to

his supervisor to take necessary follow up steps.

(IV)SAFETY PRECAUTIONBS TO BE TAKEN IN AIRCRAFT HANGAR:

The safety precautions adapted should prevent as far as possible any injury

to personnel or damage to property. There are a number of risks to be

considered such as those caused FIRE, ACIDS, MACHINES, ELECTRICITY,

COMPRESSED/EXPLOSIVE GASES, and CRYOGENICS etc. In an aircraft hangar a

list of general safety precautions should be summarized and posted on the

hangar notice board and also attention drawn to special risks by means of

suitable notices placed near the danger points. There are Flight Safety posters

with cartoon type pictures posted on the walls at suitable places to illustrate

right and wrong practices in aircraft maintenance with cautionary captions.

Though some of the precautions may appear elementary, it should be

remembered that many accidents are the result of over confidence. In all cases


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of personnel injury, first and treatment should be given immediately, and proper

medical attention obtained as soon as possible. Hence every hangar should

have a first aid kit which is replenished periodically and every aircraft industry or

a complex should have a medical inspection room with a trained doctor within

the complex and also an ambulance for emergency.

Some of the precautions to be observed in aircraft hangar to prevent

accidents with regard to fire, electricity, and other environmental factors are

discussed below:

(1)FIRE PRECAUTIONS

(I)WASTE:

Receptacles containing waste paper and oily rags, or rags impregnated with

spirit, dope, varnish and paint are prolific sources of fire and it is desirable that

metal containers are only used; these substances should be separated from

rubbish. Smoking is prohibited in aircraft hangars. Attention is drawn to thepossibility of spontaneous combustion caused by the tight packing of oil rags, in

containers. All waste oil and combustible rubbish should be burned in safe place

or otherwise carefully disposed off.

(II)CLEANING

The use of petrol is only permitted for such special purposes as cleaning

magnetos during overhaul. Containers used to hold petrol should be clearly

marked PETROL. Petrol should not be used in cleaning engine tanks (or) mixed

with paraffin. On no account should petrol or any other inflammable liquid bepoured down a drain, as this may cause a serious explosion. Processes involving

the use of heat or naked flames should be undertaken only at a safe distance

from all inflammable material or vapour.

(III)MAGNESIUM ALLOYS:

The working of magnesium alloys etc requires special care in order to reduce

the risk of fire, because under certain conditions these materials are readily

combustible. When machining these metals fine cuts to be avoided, the tools

used should be sharp with generous clearance and low cutting speeds employed.

When grinding, special wheels should be kept for use on these metals and they

should be clearly marked for identification purposes; metal particles should notbe allowed to accumulate or remain on the clothing as a precaution, rubber

apron is recommended for the user of operators. Prior to dressing the wheels

they should be free from metal dust. During hand furnishing processes glass

paper should be used in preference to emery cloth. To extinguish a fire

involving magnesium alloys, dry sand or earth should be applied to smother the

flames, alternatively dry cast iron cuttings may be used of available in sufficient


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quantities; water should not be used for this purpose as hydrogen gas is

generated when water comes in to contact with these metals when burning and

combustion is there by accelerated

(IV) Use special type of inspection lamps for petrol tank inspection and tank

repairs.

(V)If acid is kept in containers, these must be tightly closed. A good supply of

sand and shovel should always be tightly closed. A good supply of sand and

shovel should always be available for use in emergency.

(VI)DOPING: Fabric covered aircraft components that have been doped should

not be dusted or brushed until the metal parts have been earthed. Care should

be taken when employing electric water heaters or any electrical equipment in

the vicinity of dope shops in order to minimize the risk of fire.

(2)ELECTRICAL PRECAUTIONS:Precautions should be taken to guard against the possibility of accidents

where electric lights and power system are installed. Particularly when the

supply current at a voltage exceeding 110 volts a.c or 250 volts d.c. In instances

where the voltage is 440 volts or over, notices should be displayed, clearly

marked high voltage main switches should be clearly marked so that they are

readily located in an emergency.

(I)ELECTRICAL WIRES:

Do not use water on electrical wires on fire; use c02 fire extinguishers as far

as possible or dry chemical powders. It is always advised to put off the main

switch, if possible, in case of fire in the electrical fittings.

(II)EARTHINGS

All electrical equipments, portable or otherwise connected to the aircraft

hanger supply should be earthed properly.

(iii)DEFECTS:

All flexible wires, extension cables switches and plug connections etc. Should

be examined frequently for defects. Loose connections should be tightened by

authorized personnel and any defective parts to be replaced without delay.

(iv)OIL ON RUBBER INSULATIONS:

Rubber components should be kept free from oil; otherwise the insulating

properties will become impaired. In the case of unavoidable contact, the oil should

be wiped off immediately and French chalk applied to the portion of the c able

affected.


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(V)CARBONDUST:

The brush gear of rotary equipment should be periodically and any carbon

dust that has accumulated carefully removed, otherwise sparking and current

leakage may occur.

(VI)FUSES:

When a fuse is blown off the current supply is to be cut off before

attempting to do any repair and the fuse is blown off the current supply is to be of

correct amperage. Fuse box cares should be replaced on completions of the repair

work

(VII)HEATING APPARATUS:

Electrical heating apparatus such as soldering iron, immersion heater etc.

should be switched off immediately after use. Use correct stands for keeping

soldering iron when it is hot.

(VIII)OVERHEATING:

Air cooled motors should have a free flow of air; no obstructions on the air

ducts. Overheating may be caused because using an underrated wire for heavy

currents. When there is any sign of overheating the causes should be immediately

investigated and remedial measures to be taken.

BUILDING AND EQUIPMENT:I. Under no circumstances the facility for charging nickel-cadmium

battery is to be used for charging lead- acid batteries and vice versa.

And also ensure that the ventilation arrangements of both charging

rooms should not cause cross contamination.

II. Buildings and rooms used for the purpose of charging batteries should

be well lit and cool, and fumes which may be present during the

servicing and charging operations.

III. The floor surface should be of a material which is impervious to acid

and alkali, has non- slip qualities and is quick drying and able to bewashed, down easily. Examples of such materials are dustless

concrete, bituminous compound or tiling.

IV. Adequate and suitable drainage should be provided for washing down

purposes.


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V. Because of fire risks, it is strongly recommended that doors should be

fitted so that they open outwards thus facilitating easy evacuation

from the building in the event of fire.

VI. To permit free and easy movement of batteries, steps and thresholds

should where possible be eliminated. If however different levels areunavoidable they should be linked by inclines.

2. WATER SUPPLY:

I. At least one tap in each room where battery charging is carried out

should be connected to a mains fresh water supply. Sinks and draining

boards and a hot water supply should also be provided.

3. LIGHTING:

The level of lighting within the charging rooms should be sufficient to enable

the level of the electrolyte in individual cells of batteries to be easily determined

without additional lightening. To prevent accidental ignition of gases all electrical

fittings, should be of a spark proof design.

4. VENTILATION:

Hydrogen is given off at all stages of lead-acid battery serving; highest

concentration being at the end of the charging cycle. Hydrogen is also produced

when the nickel cadmium batteries reach the fully charged state i.e., at the

overcharge point and for a 24 hour period thereafter. Heavy corrosive fumes are

also emitted when mixing of electrolytes takes place. Therefore a ventilation

system is required which is capable of extracting all gases and fumes, whether

heavier or lighter than air.

5. TEMPERATURE

(a)ELECTROLYTE TEMPERATURE:

Environmental temperatures exceeding 27c for lead acid batteries and 21 c

for nickel batteries impose time penalties in reaching the fully charged state and

may also be deleterious to the batteries. The temperature of battery charging

rooms should therefore be maintained at a temperature consistent with specified

limitations and with a free air flow around each battery or cell.

6. CHARGING BOARDS AND BENCHES:

Charging board consists of a pair of terminals to which the rectified a.c supplyis connected together with a number of pairs of output terminals to which the

batteries are connected for charging. All the output circuits are internally

connected in parallel. Charging board should be mounted directly above the rear of

the benches. Battery connecting cables should be well insulated and should be of a

sufficient capacity to carry the charging current required. The free end of the

cables should be fitted with the suitable connectors (i.e. crocodile lips) power should


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be switched off while connecting and disconnecting these output cables to the

terminals.

The height of the charging benches should be such that the lifting strain of

the batteries is minimum and visual inspection of the batteries by the charging

personnel are more effective (approximately 20 above the ground). The surface ofthe charging battery should be resistance to acid and alkali and should facilitate

cleaning.

7. POWER SUPPLIESTransformer /rectifiers which normally provide rectified a.c. for charging

board supplies should be sited in a fume free dry and cool position, preferably in a

separate room, located as near as possible to the charging boards. Charging

boards which require 240 volts mains supply, should be supplied from a ring main

system

8. STORAGE:

(a)Batteries:Incoming unserviceable batteries and the outgoing serviceable batteries to

be kept separately. If possible unserviceable batteries also can be segregated as

the batteries walling for initial charging, batteries waiting for minor repairs and

batteries waiting for routine servicing. Batteries waiting for issue (outgoing) should

be also segregated as lead acid batteries and Nickel-cadmium batteries and kept in

separate rooms.

(b)ELECTROLYTE:

The handling and storage of electrolyte materials should always be inaccordance with the manufacturers recommendations. Glass earthenware or lead

lined wooden containers are suitable for the storage of lead acid battery electrolyte

(sulphuric acid). Plain iron, glass and earthenware containers are suitable for

nickel-cadmium battery electrolyte (potassium hydroxide). Galvanized containers

or containers with soldered seams must not be used. Each container should be

clearly marked as to its contents and should be stored accordingly. Electrolytes

(waste or surplus) should be disposed only after neutralizing them. Neutralizing

agents for sulphuric acid are 1.Saturated solution of sodium bicarbonate

2.Ammonium powder 3. Borax powder neutralizing agents on acid or alkali which is

spilled on the floor they should be soaked with sawdust and then be removed andburied. The containers of neutralizing agents are also to be clearly marked and

stored properly.

Avoid storing of mixed electrolytes. All mixing vessels mixing rods etc.

should be clearly marked as acid only and Alkali only. Sulphuric acid containers

should be kept tightly when not in use to prevent contamination. Potassium

hydroxide is supplied in solid form contained steel drums. Once the drum has been


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opened the contents are liable to carbondi oxide contamination. Hence the entire

contents are liable to carbondi oxide contamination. Hence the entire contents

should be mixed as soon as drum has been opened. Any unused mixture should be

stored in a stoppered glass container.

De-mineralized and distilled water are generally supplied in carboys andshould be stored separately from the electrolytes. Carboys should be clearly

marked and firmly stoppered. Only the water containers used for topping up

should be kept in the charging room and stoppers should be immediately fitted

after filling the topping up containers.

The renewal of electrolyte of lead acid batteries is done whenever S.G. falls

below the normal value sulphation takes place, alkali contamination etc. The

renewal of electrolyte of alkaline batteries

9. PROTECTION:

To prevent the risk of burns, personal items such as rings, metal watches,watch straps, bracelets, long neck chains to be removed to avoid contact with

connecting links and terminals.

Naked lights, non-safety matches and automatic lighters should not be taken

into battery charging rooms.

Fire extinguishers of the co2 type and buckets of sand should be placed at

strategic points inside the building for use in the event of any chemical fires.

10. TOOLS AND TEST EQUIPMENTS USED IN BATTERY CHARGING ROOMS:

In addition to the general engineering hand tools, the following specialized

items are to be available in battery charging rooms

Hydrometers(for measuring s.g of electrolytes)

Thermometers (to measure the temperature of electrolytes)

Battery kits(supplied by battery manufacturers)

Capacity test(to test the ampere fan of the battery)

Leakage tester (for lead acid batteries)

Filler pumps(to transfer liquids from one container to another small

container)

Calibrated test equipments such as:

o Insulation resistance tester

o Universal test meter


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o Digital voltmeter

CAUTION:To prevent contamination between the two types of aircraft batteries, two

sets of equipments should be held each being contained in separate cupboards and

clearly marked acid only or alkaline only as appropriate to the applicationwherever possible tools and equipments comprising the sets should be of insulating

materials.

RADIO WORKSHOPS: SHOP SAFETYRadio workshops can be categorized into two groups, namely those which are

established as an adjacent to an approved maintenance organization of an airline

solely to maintain that companys equipment and those which are setup

independently by organizations other than an airline, and which, generally, are

more expensive and have a much wider scope especially in respect of overhaulfacilities.

An airline workshop may also include approved electrical and instrument

workshops capable of handling such items as rotary transformers for which the

radio workshop may not be equipped.

An airline radio workshop handles the following:

a) Operating checks on equipment prior to installation in aircraft

b) Verification of reported defects.

c) Storage of serviceable equipments removed from aircraft undergoing

extensive servicing checks.

d) Servicing of racks, cable harnesses, aerials and other associated items during

the general courage of maintenance.

II.ELECTRICAL AND RADIO INTERFACE:Radio workshops situated on airports and close to hangers, air traffic control

buildings ground radio stations and electrical installations will inevitable be

subjected to a considerable amount of radio and or electrical interference, sufficient

at times to seriously affect the testing of sensitive receivers. The tuning and testingof transmitters at the workshop may also cause interference to the other

installations around them. Hence, incoming and outgoing can be dealt with by

adequate filtering of all the power supplies and by the provision of screened of

aerial cables and made-up artificial aerials, or by operation of transmitter inside

screened cages. Engineers must listeners on the transmitter frequency before

switching on and announce the identity of the workshop.


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(III)PREMISES:(1)Corrugated type of roofing should be avoided; if not possible, false ceiling

roofs can be fitted

(2) Here should be no dust in the air caused by engine run-ups, by dope or

paint spraying operations.

(3)No unacceptable electrical interference should be present in the radio test

area.

(4)The overall lighting intensity should be commensurate with the work to be

done; the lighting may be of fluorescent type.

(5)The workshop building should not be proving to dampness and should be

heated, [preferably by electricity or steam hot water central heating. The use of

solid fuel or oil heaters is not recommended.

(6)The workshop and its furnishings should be constructed of materials whichassist the maintenance of a clean environment. Concrete and unpolished wood

floors should be cared or sealed and painted so as to minimize dust.

(7)Accommodation separate from the radio workshop

should be provided for the following

Quartile and boarded stores. (Note: special precautions are necessary

for the storage and handling of magnetrons and radioactive valves.

Magnetrons should be stored in cupboards Remote from any

equipment instruments and components, which may be an affected by

a strong magnetic field).

A store for items of equipment, test panels, instruments, etc, not

immediately required.

Battery compartment

Office equipments, including record system

Stripping and cleaning bay

(8)MAIN WORKSHOP SHOULD HAVE THE FOLLOWING:

A ZONE FOR RACKS AND CUPBOARDS IN WHICH UNDESIRABLE RADIO

EQUIPMENTS CAN BE STORED

A ZONE FOR BENCHES SUITABLE FOR WORKING, INSPECTION AND

TESTING.

A ZONE FOR CERRVED DUST-FREE BENCHES FOR INSTRUMENT

ASSEMBLY


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A SONE FOR TECHNICAL MANUALS, BULLETINS, SPECIFICATIONS,

MODIFICATIONLEAFLETS AND DRAWINGS.

A STORAGE ZONE FOR FLUIDS, LUBRICANTS, PASTES, VANISHES AND

GENERAL STORES.

A ZONE FOR THE POSSESSIONS OF THE STAFF PERSONNEL.

(iii)TEST BENCHES

If there are several test benches with a common power supply each

bench should have an independent control of dc power supply with a

voltmeter and ammeter. An earth rail of substantial cross section and

having a very low resistance to earth should be provided in addition to

240 volts ac main supply earth.

AC mains wiring should be run through metal conduits (now days

plastic conduits) and provided with 3-pen outlets.

Individual power supplies, from a central source, to each bench should

be protected by circuit breakers or fuses but power supplies should be

protected by circuit breakers or fuses but power supplies other than

A.C. main supply can be protected on raised shelves to permit ease of

adjustment.

There should be storage space in the test benches for storing different

type of connecting harnesses(when different type of equipments aretested)

(IV)POWER SUPPLIES:The following power supplies are needed in a most radio workshops.

240 volts, 50 Hz, single phase a.c. supply c for lighting, heating mains

rectifiers, test equipments. This supply should be wired throughout in

screened conduit.)

A 15 volt or 30 volts D.C. supply regulated at source under varying

loads, the current capacity of the cables being determined by the size

of the workshop. These supplies can be obtained from a series of

secondary batteries of sufficient capacity and may be charged by main

rectifiers. The output should be ripple free and should be faltered to

exclude noise and to reduce transient voltage peaks liable to damage


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the most sensitive equipment, e.g. transistors, integgrated circuits,

and equipments wiring.

19 volts D.C. stabilized supply for testing certain equipment this best

supplied by individual precision supply units.

A 200 volt, 400 Hz, three phase regulated, supply, wired to the

benches in screened cable to provide the following precision a.c.

supplies.

(A) 200volt 400 Hz 3phase

(b) 115volts 400Hz 1 phase

26 volts, 400 Hz 1 phase

Note: Frequencies is required to monitor the frequency within +or 3Hz. As an

alternative method of supply, individual static invertors can be wired benches as

required.

(V)ANCILLARY SUPPLIES:

Compressed air supply to blowout the dust from the inaccessible areas

of components

Vacuum cleaner with a small flexible hose to remove dust from the test

equipments and sub assemblies in the workshop

Test installations

Power unit test rigs.

(VI)SPECIALISED EQUIPMENT TESTING:Air borne equipments such as VOR/ILS, DME, Transponders, Doppler radar,

Weather radar etc are to be tested at specially designed bench positions in order to

and radio interference with other equipments being tested at other positions.

(A) Certification of radio equipments:To enable certification of radio equipment after carrying out repair,

modification and test the following are necessary in radio workshops as per

equipment overhaul manual:

1. Test installations with appropriate harness

2. Test equipments which are periodically calibrated and certified along with

appropriate technical tools


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3. Tools, lubricants, solvents and accessories as specified in overhaul manual

along with the procedures and caution while using them.

RADIO INSTRUMENTSRadio instruments means those instruments which operate independently of

non-radio aids and flight systems(e.g. Radio magnetic compass) There should beseparate work bench for dismantling inspection, reassembly and testing of radio

instruments. The bench should have a dust proof enclosure in the form of a

detachable or hinged cover of laminated glass with a gap at the front sufficient for

the operator to insert his hands for assembly and sealing work.

In order to keep the enclosures slightly at higher pressure than the ambient

pressure, use filtered and dry compressed air supply. Use covered trays for storing

of exposed parts. Manufacturers special instructions are to be followed in case of

hermetically sealed instruments.

(VIII)DOCUMENTATION AND RECORDS:The minimum required documentation and records are listed below:

Worksheets

Performance sheets

Modification records

Certification of compliance(along with worksheet or performance

sheet)

Status identification rags or labels (such as cat B, cat c, cat D etc.)

Records of all tests and calibrations made on test equipments

(IX)TEST EQUIPMENTS

The following are the technical manuals to be available in a radio workshop:

Civil air worthiness requirements sections AandR.

Civil aircraft inspection procedures

Technical manuals for the test equipments

Maintenance, overhaul and repair manuals for the aircraft equipments

Spare parts catalogues

Modification leaflets and bulletins

Amendment records(time to time in order to update the manuals)


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LESSON PLAN NO: 06

INTRODUCTION:

The aircraft system components belonging to electronic, instrumentation and

mechanical systems require higher reliability. One of the causes of failure of an

aircraft component is contamination. Hence it is necessary to control the

contamination in all its forms. The technique to control the contamination are to be

applied to selected areas of aircraft operating organizations where the

manufacturing organizations and to selected areas of aircraft operating

organizations where the manufacturing processes, overhauling processes and

testing processes are done. Such selected areas are called as CLEAN ROOMS.

SOURCES OF CONTAMINATION:

Any substance that causes failure or malfunctioning of a component is a

contaminant. The substance (particles) may be in any form and may come from

any source.

AIR:

The air which continuously surrounds the components may be considered as

contamination store house containing dirt and dust particles, organic and inorganic

vapors.

MANUFACTURING PROCESS:

Contaminants are produced during all manufacturing processes. Examples

are as follows;

(a) Sward resulting from machining operation.

(b) particles forced into the surface during pressing or heating process

ASSEMBLY:

DURING THE ASSEMBLY a component the following are the possibilities of

introducing contamination:

Soldering processes

Use of adhesives

While joining threaded portions

Glinding, lapping or honing operation


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Deformation of surfaces such as bolt head, nut surface, screw head

etc.

STORAGE AND TRANSIT:

Improperly cleaned containers or covers in which components are

stored for transit

Containers which are not hermetically sealed are subjected to a

breathing cycle as the temperature of the container varies and during

the intake portion of the cycle, the entering air may carry particles

from the surrounding air.

Movement of packed containers during transit may dislodge loose

particles or new particles by abrasion.

COMPONENT CLEANING PROCESS:

The contamination can take place during improper cleaning processes of dry

cleaning or wet cleaning.

(VI)PERSONAL ACTIVITY OR PERSONNEL ACTIVITY:

(a)The act of walking or other body movements

(b) Brushing off of particles

shedding of skin and hair particles

(d)Exhaled air which contains moisture and acidic

(e)Perspiration from the skin

CONTROL OF CONTAMINATION:

Control of contamination is affected in two ways:-

By establishing a clean room which will provide a clean

atmosphere and working condition

By adopting rigid routines by the personnel working within the

area of the clean rooms.

CLEAN ROOMS:

SIZE OF CONTAMINANTS:

The conventional unit is micrometer or microns. The filtration system of a

clean room should control the contaminant particles of 0.5 microns and above.


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CLASSIFICATION OF AIR CLEANILINESS:

Air cleanliness is classified as No: 1, 2, 3 and 4 depending upon the number

of contaminant particles contained in a cubic meter of air. As per the classes they

are periodically checked i.e. class 1 daily, class2 weekly, class3 monthly, three

monthly.

CLASSIFICATION OF CLEAN ROOMS:

The cleanliness achieved by the clean room is dependent on the air handling

systems capacity to purge the room of contaminant particles. This includes not

only effectiveness of the filters and the number of air changes per hour but also the

distribution of the air within the room. There are two main methods of distributing

air into clean rooms namely, (a) CONVENTIONAL CLEAN ROOMS and (b)

UNIDIRECTIONAL FLOW CLEAN ROOMS.

CONVENTIONAL CLEAN ROOMS:Conventional clean rooms are based on recognized air-conditioning

techniques. The conditioned air is highly filtered and distributed through ceiling-

mounted diffuser outlets and then exhausted from return air ducts located near the

floor around the periphery of the room. In addition to direct emission from the

diffuser outlets, spreading of conditioned air throughout the room is obtained by

secondary mixing of the air caused by thermal effects of warm and cool air

currents.

UNIDIRECTIONAL FLOW CLEAN ROOMS:These rooms have been developed from the conventional type clean

room and are designed to overcome three primary deficienciesassociated with it; lack of self- cleanup facilities to effect contamination

brought in by personnel and equipment, non-uniformity of the airflow

patterns and the requirement of rigid control of personnel. In this

clean rooms, air is introduced through a large filtered diffuser area

moves through the room and is exhausted through an outlet opposite

to the diffuser and of equally large area. Such an arrangement ensures

that the air in a straight or unidirectional flow. The outlet is connected

to return air ducts thus permitting recycling of the air.

ENVIRONMENT AND COMFORT:The temperature humidity and pressure characteristics of the air

passing through the air handling system is controlled to establish an

environment suitable for work process to be carried out in a clean

room personnel.


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(a)TEMPERATURE AND HUMIDITY:

A Suitable temperature for working conditions is 20 to +or-2 c.

Humidity is controlled and maintained at a relative humidity of 35 to

50% for all classes of clean rooms, contained workstations and clean

boxes.

(b)PRESSURE:

Clean rooms are always slightly pressurized in order to maintain

the required out flow of air under closed working conditions and to

prevent entry of contaminant airborne particles when entryways or

doors are opened.

Unidirectional flow rooms should normally have an air velocity of

0.45 +or- 0.1 m/sec. For horizontal flow rooms and 0.30+-0.05m/sec

for vertical flow rooms. Air pressure for conventional flow rooms

should be such that the number of air changes, including re-circulated

air, should not normally be less than 20 per hour, except for class 4rooms where not less than 10 changes per hour may be acceptable.

5. AIR HANDLING SYSTEMS:

The primary function of an air handling system is to control the

level of airborne contaminant particles by consulting filtering and re-

circulating air. The arrangement consists of fans, ducting for inlet and

exhaust air and an air filtration system. Fans are electrically-operated

type designed to deliver a constant air flow rate through the clean

room as the filter non-flaking and corrosion resistant (stainless steel

and aluminum) filtration system consists of prefiltering and final

filtering stages. Pre- filtering is carried out at the inlet stage and finalfiltering at the inlet to the cleaning room stage. Filters are made up of

glass fibre and asbestos. The final stage filters are known as HEPA(i.

High efficiency particle air filters).

6. MAINTENANCE OF CLEAN ROOMS:

In order to maintain the clean rooms to the necessary standards

the following good housekeeping practices and monitoring of the air

handling system are to be practiced.

CLEANING:

Rooms to be cleaned when there is no work process. Vacuumcleaners, wet sponges and cellulose mops, detergents and high grade

plastic buckets can be used for cleaning. If ladders are needed, they

should be made up of anodized aluminum material. Care should be

taken that these equipments used for cleaning do not bring

contamination along with them when they are brought for cleaning


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MONITORING OF CLEAN ROOMS:

CONTAMINATION MONITORING:

Samples of air at different periods to be taken to check the

contamination level.

HUMIDITY MONITORING:

By using conventional wet and dry bulb thermometers and

psychometric charts humidity level can be checked, 40% level in

desired.

PRESSURE MONITORING:

Clean room should always be slightly pressurized. Hence the

pressure inside and outside the room to be measured using single U

type manometer or differential pressure gauge calibrated in mm

water .

LESSON PLAN NO: 7

CLEAN ROOM FURNISHINGS, GARMENTTS AND

PERSONNEL HYGINE:

LAYOUT OF CLEAN ROOMS:

The unidirectional clean rooms will have the following areas

devoted:-

Personal cleaning

Parts cleaning

Additional support rooms such as offices lunch rooms etc.

Conventional clean rooms need not have air showers in personnel cleaning area and

also more space is allotted for working area. Personnel cleaning area and also more

space are allotted for working area. Personnel cleaning rooms provide lockers for

outdoor clothing, air showers and wash-up area. Parts cleaning area provides

cleaning machines and washing facilities to decontaminate the tools, aircraft parts,equipments and material before they are taken into the working area.

2. CONSTRUCTION OF CLEAN ROOMS:

Construction of clean rooms involves the application of specifically developed

techniques such as:

Noise and vibration control


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Shear resistant floors

Walls which do not chip or flake.

Ceilings which provide adequate sealing and less impact

Lighting to provide light intensity of 3000 lux at work bench

Utilities such as water, electrical power, vacuum and compress air

supplies.

3. CLEAN ROOM FURNISHES:

Work benches, chairs and contgainers for component parts require careful

selection of materials and design. The main structure work of benches and chairs

should be metals such as stainless steel, melamine decorative laminate type

material.

4. CLEAN ROOM GARMENTS:Clean room products can be readily contaminated by particles from clothing

such as smocks, overalls, caps, hoods, shoes etc. Hence they should be designed to

provide maximum comfort and also prevent the transfer of contamination. The

materials used can be man-made fibers which are non-flammable, limited-linting

and negligible electrostatic generation. In addition, shoes can be covered with shoe

covers and gloves can be worn on hands. Fingerstalls can also be used whenever

possible. The garments are to be periodically dry cleaned and stored in lockers

ready for use. The garments are to be periodically dry-cleaned and stored in

lockers ready for use. The garments to be packed and sealed when they are

transported after cleaning and drying.

5. CLEAN WORK STATIONS:

These are work benches specially designed to incorporate their on fultered air

supply systems. They may be utilized in a clean room, in addition to benches or

tables based on conventional patterns, or in an uncontrolled environment.

Individuals switches for lighting units and fans are located at convenient points.

They have the glass panels which can be opened and closed. Some benches will

have the glass panels which can be opened and closed. Some benches will have

glove box i.e. arm ports with the attached gloves.

6. CLEAN ROOM OPERATION:In addition to the air handling system, the contamination level in a clean

room is kept at an acceptable level by two other methods namely

Limiting the contamination entering the room and

Limiting the contamination generated within the room. Both these

methods controlled by the personnel selected for clean room


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operations. The contaminations entering the room are limited by the

wearing of proper garments, personnel cleaning parts and equipments

cleaning etc. The contamination generated is limited by restricting the

movement proper work techniques.

PERSONNEL SELECTION:The selection of personnel for clean room involves both physical and

human factors. Physical factors:

Allergies to synthetic fibers

Allergies to solvents

Nasal discharge

Skin shedding

Flaking

Dandruff

Acidity in hands

Severe nervous conditions such as itching, scratching or

claustrophobia... Human factors are manual dexterity, visual

acuity, patience concern for detail, attitude toward repetitive

operations and reaction to the rigid disciplines.

PERSONAL HYGINE:The development of personal hygiene is of great importance in clean room

operations.

Personnel with colds temporary coughing and sneezing should be assigned to

temporary jobs outside the clean rooms. Personnel having received severe sun

burn also to be prevented from entering into clean rooms because peeling of skin

may contaminate the components.

ENTRY PROCEDURES:

Clean rooms are restricted areas. Only the authorized personnel should enter

into these rooms. The procedure to be adopted is governed by the type of clean

room. Typical activities associated with entry procedures are as follows:

Removal of outdoor clothing such as overcoats and raincoats and

stowage in the lockers provided in the dirty or in controlled area.

Checking clothes and shoes for visible contamination such as mud,

sand, etc. Removal of such contamination.


37/39

Washing of face and hands using foot-controlled wash strands, liquid

soap dispensers and air driers.

Passing through air showers and air locks to ensure adequate air

scrubbing.

Walking over sticky or tacky mats

Changing into requisite clean room garments. In connection with

unidirectional flow clean room operations, charging is done in the

uncontaminated section of the change room adjacent to the clean

room. In conventional clean rooms changing is done in area located at

the dirty end of the clean rooms.

GENERAL RULES FOR OPERATION:The following are the general rules which should be enforced to assist in the

successful operation of clean rooms:

PERSONAL ACTIVITIES:

Hand should be washed often and finger nails kept clean.

The specified clothing should always be worn in the approval manner.

Personal items such as keys, coins, cigarettes, matches, pencils,

handkerchiefs, and combs should be deposited in lockers prior to

changing into clean room garments. Valuable items such as trouser

pockets provided they are not removed inside the clean room

Food stuffs should not to be taken into a clean room.

Smoking is strictly forbidden.

The wearing of jeweler such as large rings, bracelets, watches,

necklaces, ear rings, lockets etc should be avoided.

Nervous mannerisms such as scratching the head, rubbing of hands or

similar actions should be avoided.

Movement of personnel should be restricted as much as possible to

prevent stirring settled particles on the clean room floor. This appliesparticularly to conventional clean rooms.

Solvent contact with hands should be avoided as many solvents

remove natural skin oils causing excessive skin peeling or flaking.

Female personnel should not wear or apply fingernail polish or

cosmetics in a clean room.


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Visitors or clean room maintenance personnel must be authorized to

enter a clean room and must follow the specified entry procedures.

WORK ACTIVITIES:

1. All tools including personal tool kits should be kept clean and in good

condition and should undergo cleaning processes in accordance with aperiodic cleaning schedule. Tools not essential to specific work

processes should be excluded from tool kits.

2. Paper materials should not be allowed in a clean room unless the

paper is plastic-coated or covered, sprayed to prevent linting or is a

special limited linting paper. Papers should not be subjected to

excessive shuffling, handling, rolling or bending as they can generate

excessive amounts of small particles under these conditions.

3. Pencils and erasers are not allowed. All writing should be with ball

point pens.

4. Parts of components should be kept in their individual contgainers until

ready for assembly. They should not be left exposed on a work bench

or station.

5. Containers and any component parts surplus to requirements should

be always returned to a parts cleaning area for cleaning and re-use.

6. Metal objects such as wire clippings and solder splashes should be

deposited in waste boxes at the end of each process.

7. Where cleaning of parts is to be carried out inside a clean room, thetype of cleaning equipment and its location within the room should be

carefully selected.

SUBMITTED BY

SATHEESH KUMAR,

JAASIM,

KATHIRVEL MOORTHY.


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