Welding jigs and fixtures Purpose 1.To minimize distortion caused by heat of welding 2.To permit welding in more convenient position 3.To increase welding efficiency and productivity. 4.Minimise fitting up problem.

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AE 703-AIRFRAME MAINTENANCE AND REPAIR
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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
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• DAMAGE CLASSIFICATION
• NEGLIGIBLE DAMAGE
• PATCH REPAIRABLE DAMAGE
• DAMAGE REPAIR BY INSERTION
• DAMAGE REQUIRING REPLACEMENT

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NON DESTRUCTIVE INSPECTION(NDI) 1.VISUAL
INSPECTION 2.DYE PENETRANT INSPECTION 3.FLUORESCEN
T PENETRATION INSPECTION 4.MAGNETIC PARTICLE
INSPECTION 5.RADIOLOGICAL (X RAY)
INSPECTION 6.EDDY CURRENT INSPECTION
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GUIDELINES FOR RIVET REPAIR DESIGN 1.RIVET
REPLACEMENT 2.RIVET DIAMETER 3.RIVET
SPACING 4.REPAIR WIDTH RIVET REPAIR
DESIGN(GENERAL,APPLIED,CALCULATED) 1.DETERMINATI
ON OF THE RIVET DIAMETER 2.DETERMINATION OF
NUMBER OF RIVETS 3.DETERMINATION OF RIVET SPACING
AND LAYOUT
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• 
  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

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

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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.
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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.
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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.
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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 Supporti
ng, clamping grounding, imparting
movement Fixture classification Those that act
on the work being welded Those that act on the
welding equipment
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• 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

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• 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

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ELCETRIC ARC WELDING DC WEEKLY MONTHLY YEA
RLY GAS WELDING DAILY MONTHLY
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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.

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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.
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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
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Thermosetting plastics

• 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
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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,POLYS
TER,POLYETHYLENE,POLYVINYL CHLORIDE.
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Thermoplastics

• 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
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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 suns 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.

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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

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

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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.
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HELICOPTER FLIGHT CONTROLS IT CONTROLS 1.MOVEMEN
T ABOUT THE THREE AXES OF THE AIRCRAFT 2.THE
ENGINE POWER 3.THE ROTOR SYSTEM LIFT. THE
CONTROL CONSISTS OF CYCLIC CONTROL,ANTITORQUE CONT
ROLS,THROTTLE AND COLLECTIVE CONTROL
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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)
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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.
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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.
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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
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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 A
ND 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.
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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.ELECTR
ICAL CONTROL SYSTEM ARE INSPECTED IN ACCORDANCE
APPROVED PRACTICES. CONTINUITY OF ELECTRICAL
CIRCUITS MAY BE TESTED.
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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.
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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.
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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.
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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.
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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.
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CHEMICAL AGENTS FACTOR STANDS
FOR FLAMMABLE AND CORROSIVE TOXIC OR REACTIVE
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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,TOL
UENE .
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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.
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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
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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