AE 703-AIRFRAME MAINTENANCE AND REPAIR

1. AE 703-AIRFRAME MAINTENANCE AND REPAIR

2. 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 BE FULLY UNDERSTOOD . 1.TO RESTORE TO ORIGINAL STRENGTH 2.ORIGINAL CONTOUR 3.MINIMUM WEIGHT 4.ORIGINAL SHAPE

3. DAMAGE CLASSIFICATION: • NEGLIGIBLE DAMAGE • PATCH REPAIRABLE DAMAGE • DAMAGE REPAIR BY INSERTION • DAMAGE REQUIRING REPLACEMENT

4. NON DESTRUCTIVE INSPECTION(NDI): 1.VISUAL INSPECTION 2.DYE PENETRANT INSPECTION 3.FLUORESCENT PENETRATION INSPECTION 4.MAGNETIC PARTICLE INSPECTION 5.RADIOLOGICAL (X RAY) INSPECTION 6.EDDY CURRENT INSPECTION

5. GUIDELINES FOR RIVET REPAIR DESIGN: 1.RIVET REPLACEMENT 2.RIVET DIAMETER 3.RIVET SPACING 4.REPAIR WIDTH RIVET REPAIR DESIGN:(GENERAL,APPLIED,CALCULATED) 1.DETERMINATION OF THE RIVET DIAMETER 2.DETERMINATION OF NUMBER OF RIVETS 3.DETERMINATION OF RIVET SPACING AND LAYOUT

6. WELDING • WELDING IS A PROCESS USED FOR JOINING METAL PARTS BY • EITHER FUSION OR FORGING. • TYPES • FORGE WELDING • FUSION WEDING • TYPES OF FUSION WELDING: • OXYACETYLENE WELDING • ELECTRIC ARC WELDING • ELECTRIC RESISTANCE WELDING • INERT GAS ARC WELDING

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

8. TYPES OF WELD JOINTS: • BUTT JOINTS • TEE JOINTS • LAP JOINTS • EDGE JOINT • CORNER JOINTS • FLANGE BUTT JOINTS

9. Welding jigs and fixturesPurpose 1.To minimize distortion caused by heat of welding 2.To permit welding in more convenient position3.To increase welding efficiency and productivity.4.Minimise fitting up problem.

10. Welding jigs and fixturesPurpose 1.To minimize distortion caused by heat of welding 2.To permit welding in more convenient position3.To increase welding efficiency and productivity.4.Minimise fitting up problem.

11. 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.

12. Welding Fixtures A 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 Characteristics Supporting, clamping grounding, imparting movement Fixture classification Those that act on the work being welded Those that act on the welding equipment

13. Maintenance of Electric resistance welding eqpt • Weekly • 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

14. Three monthly/Quarterly • 1.Check cooling hoses for rust and damage • 2.Run a test on sequencer timer using oscilloscope • 3.Inspect entire air system • Annually • 1.Clean transformer with secondaries • 2.Replace the hoses of air if reqd • 3.Clean machining cabinet and paint if necessary • 4.Check excess wear in all moving parts. • 5.Clean controls • Consult manufacturer in case of doubts

15. ELCETRIC ARC WELDING –DC WEEKLY MONTHLY YEARLY GAS WELDING DAILY MONTHLY

16. Origins of Plastics - synthetic plastics. • 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.

17. ADVANTAGE OF PLASTICS 1.PLASTICS ARE USED IN PLACE OF GLASS FOR WINDOWS BECAUSE THEY 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.

18. 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 them to be formed in a controllable manner. Any further heating normally Results 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

19. Thermosetting plastics Cross-linked molecules • 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.

20. THERMOPLASTICS IT HAS THE PROPERTY OF SOFTENING WHEN HEATED AND HARDENING AND 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 REFORMING CAN BE REPEATED MANY TIMES. 3.THERMOPLASTICS ARE THEREFORE RECYCLABE. Eg TEFLON,POLYCARBONATE,POLYSTER,POLYETHYLENE,POLYVINYL CHLORIDE.

21. Thermoplastics Long chain molecules • 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.

22. Why use plastics • 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.

23. Clear Acrylic (Perspex) • It was first used to make aircraft canopies. It is ten times more impact resistant than glass. • Image: Perspex top of a container

24. 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 STABILITY 3.IT IMPROVES PLASTIC RESISTANCE TO CRAZING

25. COMPOSITE INSPECTION(NDI) • ACOUSTIC EMISSION • HOLOGRAPHY • ULTRASONICS • X AND N RAYS • THERMOGRAPHY • RING TESTS

26. 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 AFTER FINAL ASSEMBLY.THERE IS OVERLAP BETWEEN THE ASSEMBLY OPERATION AND RIGGING OPERATION.

27. HELICOPTER FLIGHT CONTROLS IT 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,ANTITORQUE CONTROLS,THROTTLE AND COLLECTIVE CONTROL

28. RIGGING OF HELICOPTERS MAIN ROTOR IS CONTROLLED BY TWO PRINCIPAL SYSTEMS, THE COLLECTIVE PITCH CONTROL AND CYCLIC PITCH CONTROL THE COLLECTIVE PITCH CONTROL CHANGES PITCH ON ALL BLADES OF THE MAIN ROTOR SIMUTANEOUSLY.COLLECTIVE PITCH IS ADJUSTED BY RAISING OR LOWERING THE COLLECTIVE PITCH LEVER. THE CYCLIC PITCH CONTROL IS EMPLOYED TO CHANGE THE PITCH OR ANGLE OF THE PLANE OR DISK THROUGH WHICH THE MAIN ROTOR BLADES ROTATE. THE DIRECTION IN WHICH A HELICOPTER IS POINTED IS CONTROLLED BY THE ANTITORQUE ROTOR(TAIL ROTOR)

29. TRACKING AND BALANCING THE MAIN ROTOR TRACKING OF A HELICOPTER ROTOR MEANS DETERMINING IF ONE BLADE FOLLOWS THE PATH OR TRACK OF THE OTHER BLADE OR BLADES AS THEY ROTATE DURING OPERATION.TWO PRICIPAL METHODS OF ROTOR TRACKING ARE 1.STROBOSCOPIC LIGHT TRACKING 2.FLAG TRACKING THE ELECTRONIC EQUIPMENT USED IS VIBREX TRACK AND BALANCE SYSTEM.IT IS USED TO CORRECT TRACK AND BALANCE BY DEVELOPING DATA IN THE FLIGHT THROUGH THE USE OF ACCELEOMETERS AND STROBOSCOPIC LIGHTS.THE SIGNALS FROM THESE DEVICES ARE REFERED ROTOR POSITION BY MEANS OF MAGNETIC PICK UP AND INTERRUPTER SYSTEM.

30. 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 WORK IS A SUITABLE MATERIAL.THE MAIN ROTOR BLADE TIPS ARE COLORED WITH GREASE PENCILS,USING A DIFFERENT COLOUR ON EACH TRIP.

31. INSPECTION AND MAINTENACE OF LANDING GEAR A 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 AND VALVES,GEAR DOORS,AND ALL ASSOCIATED PARTS. 1.FIXED GEAR INSPECTION 2.INSPECTION OF RETRACTABLE LANDING GEAR

32. INSTALLATION AND MAINTENANCE OF INSTRUMENTS THE INSTALLTION OF INSTRUMNET REQUIRES THAT THEY BE MOUNTED TO 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 INSTALLATION SHOULD CAUSE A MINIMUM OF OPERATIONAL INTERFERENCE WITH CONTROL SYSTEMS AND OTHER INSTRUMENTS. INSTRUMENT SHOULD BE CHECKED FOR PROPER OPERATION,CONDITON AND 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.

33. 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 CIRCUITS MAY BE TESTED.

34. 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.

35. TROUBLESHOOTING TROUBLE SHOOTING IS THE PROCESS OF IDENTIFYING THE CAUSE OF A MALFUNTION DETERMINING ITS SEVERITYH,ELIMINATING THE 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 AIRWORTHY CONDITION 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 TRUE CAUSE OF THE DISCREPANCY.

36. 2.THE SECOND STEP IN THE TROUBLESHOOTING PROCESS IS TO EVALUATE THE REPORTED DICREPANCY TO DETERMINE IF IT HAS AN ADVERSE EFFECT UPON THE AIRCRAFT AIRWORTHINESS. 3.THE THIRD STEP CORRECTIVE ACTION MUST BE TAKEN BEFORE ITS NEXT FLIGHT. TROUBLE SHOOTING CHARTS DESIGNED TO HELP THE TECHNICIAN IDENTIFY FAILED COMPONENTS.

37. 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.

38. 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 AGENTS 2.PHYSICAL AGENTS 3.BIOLOGICAL HAZARDS.

39. CHEMICAL AGENTS FACTOR STANDS FOR FLAMMABLE AND CORROSIVE TOXIC OR REACTIVE

40. 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 .

41. PERSONAL SAFETY EQUIPMENT 1.FIRE RETARDANT CLOTHING 2.FIRE EXTINGUISHER HANDLING AND STORAGE 1.LIMIT ACCESS TO OPEN FLAMES,SPARKS,HOT SURFACES ETC 2.LIMIT QUANTITY REQUIRED TO THE MINIMUM 3.STORE IN THE APPROVED CONTRAINERS AND DESIGNATED AREAS ONLY. 4.STORE FLAMMABLE TOXINS AND CORROSIVE TOXIC MATERIALS SEPARATELY.

42. 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 OILS 4.POLYMERS,EPOXIES AND PLASTICS 5.GASES SUCH AS CARBON DIOXIDE OR NITROGEN. 6.SENSITIZERS SUCH AS EPOXY SYSTEMS. 7.CARCINOGENS 8.REPRODUCTIVE HAZARDS

43. PHYSICAL HAZARDS THESE HAZARDS INCLUDE X RAY,MICROWAVES,BETA OR GAMMA RAYS,INVISIBLE LASER BEAMS AND HF SOUND WAVES BIOLOGICAL HAZARDS BIOLOGICAL HAZARDS ARE LIVING ORGANISMS THAT CAUSE ILLNESS OR DISEASE.SPREAD THROUGH AIR DROPLETS OR SPORES AND ENTER THE BODY THROUGH CONACT.eg cargo aircraft/baggage