AE 703-AIRFRAME MAINTENANCE AND REPAIR

AE 703-AIRFRAME MAINTENANCE AND REPAIR

OBJECTIVE OF AIRFRAME REPAIR:

THE PRIMARY OBJECTIVE OF AIRFRAME REPAIR IT TO RESTORE THE DAMAGED PARTS TO THEIR ORIGINAL CONDITION.IF DAMAGED PART CAN BE REPAIRED ITS PURPOSE OR FUNCTION MUST BEFULLY UNDERSTOOD .1.TO RESTORE TO ORIGINAL STRENGTH2.ORIGINAL CONTOUR3.MINIMUM WEIGHT4.ORIGINAL SHAPE

DAMAGE CLASSIFICATION:

•NEGLIGIBLE DAMAGE•PATCH REPAIRABLE DAMAGE•DAMAGE REPAIR BY INSERTION•DAMAGE REQUIRING REPLACEMENT

NON DESTRUCTIVE INSPECTION(NDI):

1.VISUAL INSPECTION2.DYE PENETRANT INSPECTION3.FLUORESCENT PENETRATION INSPECTION4.MAGNETIC PARTICLE INSPECTION5.RADIOLOGICAL (X RAY) INSPECTION6.EDDY CURRENT INSPECTION

GUIDELINES FOR RIVET REPAIR DESIGN:

1.RIVET REPLACEMENT2.RIVET DIAMETER3.RIVET SPACING4.REPAIR WIDTH

RIVET REPAIR DESIGN:(GENERAL,APPLIED,CALCULATED)

1.DETERMINATION OF THE RIVET DIAMETER2.DETERMINATION OF NUMBER OF RIVETS3.DETERMINATION OF RIVET SPACING AND LAYOUT

WELDING

WELDING IS A PROCESS USED FOR JOINING METAL PARTS BY EITHER FUSION OR FORGING.

TYPESFORGE WELDINGFUSION WEDING

TYPES OF FUSION WELDING:•OXYACETYLENE WELDING•ELECTRIC ARC WELDING•ELECTRIC RESISTANCE WELDING•INERT GAS ARC WELDING

INERT GAS ARC WELDING:

TYPES:

1.TUNGSTEN INERT GAS WELDING(TIG)TIG USES TUNGSTEN ELECTRODE WHICH IS NON COSUMABLE

2.METAL INERT GAS WELDING(MIG)MIG USES METAL ELECTRODE WHICH IS CONSUMABLE

3.PLASMA ARC WELDINGPLASMA ARC WELDING THE GAS GETS IONIZED AFTER THE PASSAGE OF ELECTRIC CURRENT.THIS RESULTS IN HIGH TEMPERATURE.

TYPES OF WELD JOINTS:

•BUTT JOINTS•TEE JOINTS•LAP JOINTS•EDGE JOINT•CORNER JOINTS•FLANGE BUTT JOINTS

Welding Jigs.Welding jigs are specialized devices which enable the components to be easily and rapidly setup and held.

Jigs are stationery while fixtures rotate usually on trunions about vertical and horizontal axis.

It should be 1. rigid and strong to stand without deforming.2. simple to operate, yet it must be accurate.

3. Designed such that it is not possible to put the work in it in the wrong way.

4. Faced with wear resistant material to stand continual wear.

Welding FixturesA welding fixture serves the same purposes as

welding jig, but in addition, it permits the changing of the position during actual welding so as to place the welds in plane convenient

to the operator at all times. This increases welding speed

CharacteristicsSupporting, clamping grounding, imparting movement

Fixture classificationThose that act on the work being weldedThose that act on the welding equipment

Maintenance of Electric resistance welding eqptWeekly•Inspect electrical connections•Clean electrode holders and exterior.•Clean transformer with low pr hose•If noisy stop operation &tighten bolts.

Monthly•Flush cooling system to wash out dirt and rust particles•Check air system for leaks and faults,valves•Clean cables,sockets,swtiches•Tighten loose electrical connections, replace worn wires and insulation

Three monthly/Quarterly

1.Check cooling hoses for rust and damage2.Run a test on sequencer timer using oscilloscope3.Inspect entire air system

Annually1.Clean transformer with secondaries2.Replace the hoses of air if reqd3.Clean machining cabinet and paint if necessary4.Check excess wear in all moving parts.5.Clean controlsConsult manufacturer in case of doubts

ELCETRIC ARC WELDING –DC

WEEKLYMONTHLYYEARLY

GAS WELDING

DAILYMONTHLY

The main source of synthetic plastics is crude oil.

Coal and natural gas are also used.

Petrol, paraffin, lubricating oils and high petroleum gases are bi-products, produced during the refining of crude oil.

These gases are broken down into monomers. Monomers are chemical substances consisting of a single molecule.

A process called Polymerisation occurs when thousands of monomers are linked together. The compounds formed as called polymers.

Combining the element carbon with one or more other elements such as oxygen, hydrogen, chlorine, fluorine and nitrogen makes most polymers.

ADVANTAGE OF PLASTICS1.PLASTICS ARE USED IN PLACE OF GLASS FOR WINDOWS BECAUSETHEY ARE LIGHT IN WT AND NO REDUCTION IN CLARITY.

2.RESISTANT TO BREAKING THAN GLASS.

3.POOR CONDUCTOR OF HEAT AND PROVIDES SOME LEVEL OF THERMAL INSULATION.

Thermosetting Thermosetting plastics are plastic compounds that require application Of heat to set up properly or harden.Once these materials have set ,further appn of heat does not allow themto be formed in a controllable manner. Any further heating normallyResults in deformation or structural weakening. It is permanently hardening.It hardens permanently after one application of heat and presure.The molecules of thermosetting plastics are heavily cross linked.They form a Rigid molecular structure.Ex.Bakelite,melamine resign,polymer resign,epoxy resign

The molecules of thermosetting plastics are heavily cross-linked. They form a rigid molecular structure.

The molecules in thermoplastics sit end-to-end and side-by-side.

Although they soften when heated the first time, which allows them to be shaped they become permanently stiff and solid and cannot be reshaped.

Thermoplastics remain rigid and non-flexible even at high temperatures. Polyester resin and urea formaldehyde are examples of thermosetting plastics.

Cross-linked molecules

THERMOPLASTICSIT HAS THE PROPERTY OF SOFTENING WHEN HEATED AND HARDENINGAND BECOMING RIGID AGAIN WHEN COOLED.THEMOPLASTIC CAN BE REMELTED AND COOLED TIME AFTER TIME WITHOUT UNDERGOING ANY APPRECIABLE CHEMICAL CHANGE.

1.WHEN HEATED MOLECULES MOVE APART WHICH INCREASES THE DISTANCE BETWEEN THEM,BECOMING UNTANGLED.THIS ALLOWS TO BECOME SOFT WHEN HEATED SO THAT THEY CAN BE BENT TO ALL TYPE OF SHPES.2.THE PROCESS OF HEATING,SHAPING,REHEATING AND REFORMINGCAN BE REPEATED MANY TIMES.3.THERMOPLASTICS ARE THEREFORE RECYCLABE.Eg TEFLON,POLYCARBONATE,POLYSTER,POLYETHYLENE,POLYVINYL CHLORIDE.

There are a wide range of thermoplastics, some that are rigid and some that are extremely flexible.

The molecules of thermoplastics are in lines or long chains with very few entanglements. When heat is applied the molecules move apart, which increases the distance between them, causing them to become untangled. This allows them to become soft when heated so that they can be bent into all sorts of shapes.

When they are left to cool the chains of molecules cool, take their former position and the plastic becomes stiff and hard again. The process of heating, shaping, reheating and reforming can be repeated many times.

Long chain molecules

Plastic are easily formed materials.

The advantage to the manufacturer is that plastic products can be mass-produced and require less skilled staff.

Plastics require little or no finishing, painting, polishing etc. Plastic is referred to as a self-finishing material. Particular finishes can be achieved at relatively low cost.

Plastics can be easily printed, decorated or painted.

Plastics are corrosion resistant, and generally waterproof although certain types of plastics such as UPVC can become brittle and it is possible for the sun’s rays to cause the colour of the plastic to fade. It becomes bleached.

Plastics are lighter than metals, giving deeper sections for a given weight, and hence stronger sections.

It was first used to make aircraft canopies. It is ten times more impact resistant than glass.

Image: Perspex top of a container

TYPES OF CLEAR PLASTICS:

1.ACRYLICS

2CELLULOSE ACETATES

CEMENTING OF PLASTICS:MANY THERMOPLASTICS CAN BE FASTENED TOGETHER TO FORM STRONG BONDS USING CHEMICAL ADHESIVES OR SOLVENTS.

ANNEALING OF PLASTICS:PURPOSE:1.IT RELIVES INTERNAL STRESSES.2.PROVIDES GREATER DIMENSIONAL STABILITY3.IT IMPROVES PLASTIC RESISTANCE TO CRAZING

COMPOSITE INSPECTION(NDI)

1. ACOUSTIC EMISSION2. HOLOGRAPHY3. ULTRASONICS4. X AND N RAYS5. THERMOGRAPHY6. RING TESTS

RIGGING:IT IS ALIGHNMENT OF AIRCRAFT PARTS OR SECTIONS TO OBTAIN PROPER FLIGHT CHARACTERISTICS.A CERTAIN AMOUNT OF RIGGING IS NECESSARY DURING THE ASSEMBLY OF AN AIRCRAFT AND AFTERFINAL ASSEMBLY.THERE IS OVERLAP BETWEEN THE ASSEMBLYOPERATION AND RIGGING OPERATION.

HELICOPTER FLIGHT CONTROLSIT CONTROLS:

1.MOVEMENT ABOUT THE THREE AXES OF THE AIRCRAFT

2.THE ENGINE POWER

3.THE ROTOR SYSTEM LIFT.

THE CONTROL CONSISTS OF CYCLIC CONTROL,ANTITORQUECONTROLS,THROTTLE AND COLLECTIVE CONTROL

RIGGING OF HELICOPTERSMAIN ROTOR IS CONTROLLED BY TWO PRINCIPAL SYSTEMS,THE COLLECTIVE PITCH CONTROL AND CYCLIC PITCH CONTROL

THE COLLECTIVE PITCH CONTROL CHANGES PITCH ON ALL BLADESOF THE MAIN ROTOR SIMUTANEOUSLY.COLLECTIVE PITCH IS ADJUSTEDBY RAISING OR LOWERING THE COLLECTIVE PITCH LEVER.

THE CYCLIC PITCH CONTROL IS EMPLOYED TO CHANGE THE PITCHOR ANGLE OF THE PLANE OR DISK THROUGH WHICH THE MAIN ROTORBLADES ROTATE. THE DIRECTION IN WHICH A HELICOPTER IS POINTED IS CONTROLLEDBY THE ANTITORQUE ROTOR(TAIL ROTOR)

TRACKING AND BALANCING THE MAIN ROTOR

TRACKING OF A HELICOPTER ROTOR MEANS DETERMINING IF ONEBLADE FOLLOWS THE PATH OR TRACK OF THE OTHER BLADE OR BLADESAS THEY ROTATE DURING OPERATION.TWO PRICIPAL METHODS OF ROTOR TRACKING ARE

1.STROBOSCOPIC LIGHT TRACKING2.FLAG TRACKING

THE ELECTRONIC EQUIPMENT USED IS VIBREX TRACK AND BALANCESYSTEM.IT IS USED TO CORRECT TRACK AND BALANCE BY DEVELOPINGDATA IN THE FLIGHT THROUGH THE USE OF ACCELEOMETERS ANDSTROBOSCOPIC LIGHTS.THE SIGNALS FROM THESE DEVICES AREREFERED ROTOR POSITION BY MEANS OF MAGNETIC PICK UPAND INTERRUPTER SYSTEM.

FLAG TRACKING METHOD:

IN THIS METHOD A TRACKING FLAG IS CONSTRUCTED FROM ALUMINIUM OR STEEL TUBING. THE FLAG PORTION SHOULD BE MADE OF STRONG,LIGHT WEIGHT FABRIC TAPE.THE REINFORCING TAPE USED IN AIRCRAFT FABRIC WORKIS A SUITABLE MATERIAL.THE MAIN ROTOR BLADE TIPS ARE COLOREDWITH GREASE PENCILS,USING A DIFFERENT COLOUR ONEACH TRIP.

INSPECTION AND MAINTENACE OF LANDING GEARA THROUGH INSPECTION OF LANDING GEAR INVOLVES THE CAREFUL EXAMINATION OF THE ENTIRE STRUCTURE OF THE GEAR ,INCLUDING THE ATTACHMENTS TO THE FUSELAGE OR WING,STRUT,WHEELS,BRAKES,ACTUATING ,MECHANISM,FOR RETRACTABLE GEAR,GEAR HYDRAULIC SYSTEM ANDVALVES,GEAR DOORS,AND ALL ASSOCIATED PARTS.

1.FIXED GEAR INSPECTION

2.INSPECTION OF RETRACTABLE LANDING GEAR

INSTALLATION AND MAINTENANCE OF INSTRUMENTS

THE INSTALLTION OF INSTRUMNET REQUIRES THAT THEY BE MOUNTEDTO A METAL INSTRUMENT PANEL OR SUBPANEL.REGARDLESS OF THE TYPE OF MOUNT ,THE INSTALLATION SHOULD ALLOW THE PILOT OR CREW MEMBER TO CLEARLY VIEW THE INSTRUMENT FROM A NORMAL FLIGHT POSITION.THE INSTALLATIONSHOULD CAUSE A MINIMUM OF OPERATIONAL INTERFERENCE WITH CONTROL SYSTEMS AND OTHER INSTRUMENTS.

INSTRUMENT SHOULD BE CHECKED FOR PROPER OPERATION,CONDITONAND PLACEMENT OF RANGE MARKINGS,CONDITION OF CASES,CLEANLINESS OF CASE VENT FILTERS,SECURITY OF MOUNTING,AND TIGHTNESS OF TUBE AND ELECTRICAL CONNECTIONS.GYRO INSTRUMNETS SHOULD BE CHECKED FOR GYRO ERECTION TIME AND UNUSUAL NOISE DURING OPERATION.

INSPECTION AND MAINTENACE OF FIRE PROTECTION SYSTEMS

MECHANICAL PARTS ARE EXAMINED FOR THE DAMAGE,WEAR,SECURITY OF MOUNTING AND COMPLIANCE WITH TECHNICAL AND REGULATORY REQUIREMENTS.ELECTRICAL CONTROL SYSTEM ARE INSPECTED IN ACCORDANCE APPROVED PRACTICES.CONTINUITY OF ELECTRICAL CIRCUITSMAY BE TESTED.

INSPECTION AND MAINTENANCE OF ICE PROTECTION SYSTEM

THE INSPECTION OF PNEUNATIC MECHANCIL DEICER SYSTEMS REQUIRE AN EXAMINATION OF THE DEICER BOOTS FOR CONDITION,ADHERENCE TO THE PROTECTED SURFACE AND CONDITION OF THE SURFACE OF THE BOOTS.DURING INSPECTION AND MAINTENACE THE TECHNICIAN SHOULD DETERMINE WHETHER THE CONDUCTIVE COATING IS INTACT AND EFFECTIVE.OPERATIONAL TESTS ARE PERFORMED AS SPECIFIED IN APPROPRIATE INSTRUCTIONS.THE INFLATION OF THE TUBES IN THE BOOTS CAN BE EASILY BE OBSERVED.

TROUBLESHOOTING

TROUBLE SHOOTING IS THE PROCESS OF IDENTIFYING THE CAUSE OF A MALFUNTION DETERMINING ITS SEVERITYH,ELIMINATINGTHE CAUSE,REPLACING OR REPAIRING DISCREPANT COMPONENTS,SYSTEMS ,OR STRUCTURES AND FINALLY RETURNING THE AIRCRAFT TO SEVICE.THE ULTIMATE OBJECT OF TROUBLESHOOTING IN AVIATION IS TO RETURN AIRCRAFT TO AN AIRWORTHYCONDITION OFFERING A HIGH PROBABILITY THAT THE MALFUNCTION OR DISCREPANCY WILL NOT RECUR. TROUBLE SHOOTGING IS MORE THAN JUST REPLACING MALFUNCTIONING COMPONENT OR MAKING A REPAIR.

1.THE FIRST STEP IN TROUBLESHOOTING IS TO IDENTIFY THE TRUECAUSE OF THE DISCREPANCY.

2.THE SECOND STEP IN THE TROUBLESHOOTING PROCESS IS TO EVALUATE THE REPORTED DICREPANCY TO DETERMINE IF IT HASAN ADVERSE EFFECT UPON THE AIRCRAFT AIRWORTHINESS.

3.THE THIRD STEP CORRECTIVE ACTION MUST BE TAKEN BEFOREITS NEXT FLIGHT.

TROUBLE SHOOTING CHARTS DESIGNED TO HELP THE TECHNICIAN IDENTIFY FAILED COMPONENTS.

VALIDATION OF TROUBLESHOOTING RESULTS.

THE FINAL STEP IN THE TROUBLESHOOTING PROCESS IS THE VALIDATION THAT THE ANALYTICAL STEPS OF THE TROUBLSHOOTING PROCESS WERE PROPERLY INTERPRETED.THIS OFTEN RESULTS IN THE NECESSITY FOR SOME TYPE OF OPERATIONAOL CHECK.THE PROCEDURES FOR SUCH A CHECK SHOUOLD BE SPECIFIED IN THE AIRCRAFT MAINTENANCE MANAUL.WHEN OPERATIONALLY CHECKING INTERMITTENT DISCRPANCIES,THE CHECK NEEDS TO INCLUDE THE SUPECTED CAUSES.

HAZARDOUS MATERIALS

THE AVIATION MAINTENANCE TECHNICIAN FREQUENTLY MUST WORK IN POTENTIALLY DANGEROUS ENVIRONMENTS.THE TECHNICIAN MAY NOT AWARE HE IS WORKING WITH HAZARDOUS MATERIALS.

THREE CATEGORIES.

1.CHEMICAL AGENTS2.PHYSICAL AGENTS3.BIOLOGICAL HAZARDS.

CHEMICAL AGENTS

FACTOR STANDS FOR

FLAMMABLEAND CORROSIVETOXICORREACTIVE

FLAMMABLES AND COMBUSTIBLES

FLAMMABLES ARE MATERIAL THAT MAY EASILY IGNITE IN THE PRESENCE OF CATALYST SUCH AS HEAT ,SPARKS,OR FLAME.THEY MAY IN THE FORM SOLID,LIQUID,OR GAS.COMBUSTIBLE LIQUIDS ARE VERY SIMILAR TO FLAMMABLE LIQUIDS,BUT THEY ARE NOT AS EASY TO IGNITE.THESE MATERIAL IN AVIATION INDUSTRY INCLUDE FUELS,PAINT RELATED PRODUCTS,ALCOHOLS,ACETONE,TOLUENE .

PERSONAL SAFETY EQUIPMENT

1.FIRE RETARDANT CLOTHING

2.FIRE EXTINGUISHER

HANDLING AND STORAGE

1.LIMIT ACCESS TO OPEN FLAMES,SPARKS,HOT SURFACES ETC2.LIMIT QUANTITY REQUIRED TO THE MINIMUM3.STORE IN THE APPROVED CONTRAINERS AND DESIGNATED AREAS ONLY.4.STORE FLAMMABLE TOXINS AND CORROSIVE TOXIC MATERIALSSEPARATELY.

TOXINS

TOXINS ARE GENERALLY DEFINED AS ANY SUBSTANCE THAT CAN CASUSE AN ILLNESS OR INJURY.

EIGHT CATEGORIES OF TOXINS.1.SOVENTS AND THINNERS FOR PAINTS,KETONES AND ADHESIVES.2.SOLIDS SUCH AS METAL DUST OR ASBESTOS.3.MACHINE LUBRICANTS,CUTTING FLUIDS AND OILS4.POLYMERS,EPOXIES AND PLASTICS5.GASES SUCH AS CARBON DIOXIDE OR NITROGEN.6.SENSITIZERS SUCH AS EPOXY SYSTEMS.7.CARCINOGENS8.REPRODUCTIVE HAZARDS

PHYSICAL HAZARDS

THESE HAZARDS INCLUDE X RAY,MICROWAVES,BETA OR GAMMARAYS,INVISIBLE LASER BEAMS AND HF SOUND WAVES

BIOLOGICAL HAZARDS BIOLOGICAL HAZARDS ARE LIVING ORGANISMS THAT CAUSEILLNESS OR DISEASE.SPREAD THROUGH AIR DROPLETS OR SPORESAND ENTER THE BODY THROUGH CONACT.eg cargo aircraft/baggage