Airframe and Construction Repair Review

7/28/2019 Airframe and Construction Repair Review

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Airframe and Construction

Repair Review


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AIRFRAME the main structure or body of the airplane.

is a rigid framework made up of members such as beams, struts, andbars to resist deformation by applied load.

consist of a framework of vertical and longitudinal members coveredwith a structural skin that carries the large percentage of the stresses.

it involves the construction of a metal tube or cone without structuralmember.

the vertical members of the fuselage frames. Structural partitions that runsperpendicular to the longerons.

- lateral fuselage or nacelle member giving cross-sectional shape which is often circular. Alsoknown as FORMERS or RINGS that maintains the uniform shape of the structure.

(for semi-monocoque) the longitudinal members serves for stiffening the metal skin and

prevent it from bulging or buckling under severe stresses. to reinforce the intersecting structural members and to transfer

stresses from one member to another.

the main longitudinal member of a fuselage or nacelle.

the smooth outer cover of the aircraft. The materials used for the skin covering is usuallysheets aluminum alloy.

FUSELAGETRUSS

SEMIMONOCOQUE

MONOCOQUEBULKHEAD

FRAMESTRINGERSGUSSET OR GUSSET PLATES

LONGERONSKIN


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FUSELAGE


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WING aerofoil structure that produces lift of an airplane. CANTILEVER no external bracing is needed.

SEMI-CANTILEVER uses external bracing (strut, wires, etc.)

Spars it is the principal structural members of the wing.

Ribs used to give the shape of the wing and to transmit the load from the skin to

the spars.

Wing Tip smooth out the wing tip airfoil to give wing a finish look.

Fairing/Fillets used to smooth the airflow over the angles formed by the wingsand other structural units with the fuselage, shaped rounded panels or metal skin

are attached.

EMPENNAGE the complete tail assembly of an aircraft.

HORIZONTAL TAIL

Horizontal stabilizers fixed surface

Elevators movable surface

VERTICAL TAIL

Vertical stabilizers fixed surface (FIN)

Rudder movable surface

WING

CANTILEVER

SEMI-CANTILEVER

SPARS

RIBS

WING TIPS

FAIRING/FILLETS

EMPENNAGEHORIZONTAL TAIL

HORIZONTAL STABILIZERSELEVATORS

VERTICAL TAIL

VERTICAL STABILIZERS

RUDDER


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WING

* The fuel tank in a wing is called an INTEGRAL FUEL TANK.


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VERTICAL STABILIZER


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HORIZONTAL STABILIZER


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FLIGHT CONTROL SURFACES

PRIMARY GROUP

AILERON attached to both wings of an aircraft that goes up and down, thus, causing

the aircraft to roll at longitudinal axis.

RUDDER hinged to TE of the vertical stabilizer to turn about its vertical axis.

ELEVATOR attached to the TE of the horizontal stabilizer use for control on pitch up and

pitch down at its lateral axis.

SECONDARY or AUXILIARY GROUP their purpose is to reduce the force required to

actuate the primary controls, to trim and balance the aircraft in flight, to reduce

speed or shorten the landing run and the change the speed of the aircraft flight.

Trim tabs used to make fine adjustments to the flight path of the aircraft.

Balance tabs movement of the main control surface will give an opposite movement to

the tab.

Servo tabs referred to as flight tabs.

Flaps use to increase area of wing for the purpose of increasing lift.

Spoilers a device designed to reduce the lift of the wing. Use for speed brakes.

Leading edge devices a high lift device (SLATS) normally used on large transport

category.

LANDING GEAR - is the assembly that supports the aircraft during

landing or while resting or moving about on the ground.

FLIGHT CONTROL SURFACESPRIMARY GROUP

AILERON

RUDDERELEVATOR

SECONDARY or AUXILIARY GROUP

TRIM TABS

BALANCE TABS

SERVO TABSFLAPS

SPOILERSLEADING EDGE DEVICES

LANDING GEAR


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FLIGHT CONTROL SURFACE


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5 Major Stresses to which all Aircraft Subjected

TENSION is the stress that resist a force tends to null apart.

COMPRESSION is the stress that resist a crushing force.

TORSION is the stress that produce twisting.

SHEAR is the stress that resists the force tending to causeone material to slide over an adjacent layer.

BENDING is a combination of compression and tension.

STRESS is an internal force of a substance which opposes or resistdeformation can cause strain.

STRAIN is the deformation of a material or substance.

TENSION

COMPRESSION

TORSION

SHEAR

BENDING

STRESS

STRAIN


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PROPERTIES OF MATERIALS

HARDNESS - The property of a material that enables it to resist

penetration, wear, or cutting action or permanent distortion.

BRITTLENESS is the property of a metal which allows little bending or

deformation without shattering.

MALLEABILITY property of metals which allows them to be bent or

permanently distorted without rupture.

STRENGTH - The ability of a material to resist deformation.

PLASTICITY - The capability of an object or material to be stretched and to

recover its size and shape after its deformation.

DUCTILITY - The property which allows metal to be drawn, bent or twisted

into various shapes without breaking. ELASTICITY property which enables a metal to return to its original

shapes when the forces which causes the change of shape is removed.

HARDNESS

BRITTLENESS

MALLEABILITY

STRENGTH

PLASTICITY

DUCTILITY

ELASTICITY


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TOUGHNESS a material which possesses toughness will withstand tearing

or shearing and maybe stretched or otherwise deformed without breaking.

DENSITY the weight of a unit volume of the materials.

FUSIBILITY the ability of a metal to become liquid by the application of

heat.

CONDUCTIVITY the ability of a metal which enables to carry heat or

electricity THERMAL EXPANSION

Contraction ability of metals to shrink when subjected to cooling.

Expansion expand upon the application of heat.

TOUGHNESS

DENSITYFUSIBILITY

CONDUCTIVITY

THERMAL EXPANSIONCONTRACTIONEXPANSION


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Aircraft Metals

Two Main Group of Aircraft Metals:

NON-FERROUS METALS the term that describes metals

which are have elements other than Iron as their base.

Aluminum, Copper, Titanium, and Magnesium are some of

the common non-ferrous metals used in Aircraft

Construction and Repair.

FERROUS METALS any alloy containing iron as its chief

constituent, most common ferrous metal in aircraftstructure is steel, an alloy of iron with a controlled amount

of carbon added.


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NON-FERROUS METALS:1. ALUMINUM AND ITS ALLOYS

- Pure aluminum lacks sufficient strength to be used in aircraft Quenching

construction. However, its strength increases considerably when it isALLOYED, or mixed with compatible metals.

TYPES OF ALUMINUM ALLOYS:

1. Cast Alloys those suitable for casting in sand, permanent mold or diecasting.

2. Wrought Alloys those which may be shaped by rolling, drawing or forging.These are the most widely used in aircraft construction, being used forstringers, bulkheads, skin, rivets, and extruded sections.

GENERAL CLASSES OF WROUGHT ALUMINUM ALLOYS:

1. Non-Heat Treatable Alloy the mechanical properties obtained by cold

working are destroyed and any subsequent heating cannot restore it exceptby additional cold working.

2. Heat Treatable Alloy alloy which responds readily to heat treatmentwhich results in considerable improvement of the strength characteristics.Greater strength is obtained and used for structural purposes.


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HEAT TREATMENT is a series of operations involving the heatingand cooling of metals in their solid state. Its purpose is to make the metal

more useful, serviceable and safe for a definite purpose.

SOLUTION HEAT TREATMENT is the process of heating certainaluminum alloys to allow the alloying elements to mix with the

base metal.

QUENCHING rapid cooling by means of water, oil, brine, etc.

SOAKING or HOLDING held the temperature within about plus

or minus 10 degrees Fahrenheit of this temperature and the basemetal until the alloying elements is uniform throughout.

NATURAL AGING when an alloy is allowed to cool at room

temperature and can take several hours or weeks.

ARTIFICIAL AGING accelerating the aging process by cooling at anelevated temperature.

ANNEALING is the process that softens a metal and decrease

internal stresses.


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STRAIN HARDENING also referred to as COLD WORKING or WORK HARDENING.This requires mechanically working of metal (stretches, compresses, bends, drawn, etc.) below

its critical range.

2. MAGNESIUM AND ITS ALLOYS Magnesium alloy are used for cast and wrought form available in sheets, bars, tubing, and

extrusions. Magnesium is one of the lightest metals having sufficient strength and suitable

working characteristics for use in aircraft hardware. However, it is susceptible to corrosion and

tends to crack.

3. TITANIUM AND ITS ALLOYS Titanium and its alloys are light metals with very high strength. It has an excellent corrosion

resistance characteristics, particularly to the effects of salt water.

4. NICKEL AND ITS ALLOYS Nickel is the base element for most of the higher temperature heat-resistant alloys. While it is

much more expensive than iron, nickel provides an austenitic structure that has greater

toughness and workability than ferrous alloys of the same strength.

MONEL contains about 68 % nickel and 29% copper, along with iron and manganese.

It works well in gears and parts that require high strength and corrosion resistance

at elevated temperature.

INCONEL high strength, high temperature alloys containing approximately about 80%

nickel, 14 % chromium, and small amounts of iron and other elements.


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5. COPPER AND ITS ALLOYS It is easily identified by its reddish color and by the green and blue colors of its oxides and salt.

Copper has excellent electrical and thermal conductivity and it is primary metal used for

electrical wiring.

BRASS an alloy of copper and zinc.BRONZE an alloy of copper and tin.

FERROUS METALS:1. IRON Is like a chemical which is fairy soft, malleable and ductile in its pure form. It is silvery white in

color and is quite heavy, having a density of 7.9 grams per cubic centimeter.

2. STEEL To make steel, pig iron is re-melted in a special furnace. Pure oxygen is the forced through the

molten where it combines with carbon and burns. A control amount of carbon is then put back

into the molten. The molten steel is then poured into molds where it solidifies into ingots. The

ingots are then placed in a soaking pit where they are heated to a uniform temperature of

about 2200 degrees F. They are then taken from the soaking pit and passed through steel

rollers to form late or sheet metal.


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a. CARBON Carbon is the most common alloying element found in steel. When mixed with iron core

compounds of iron carbides called CEMETITE form. It is the carbon in steel that allows

the steel to be heat treated to obtain varying degrees of hardness, strength andtoughness. The greater the carbon content, the more receptive steel is to heat

treatment and therefore, the higher its tensile strength, and hardness. However, higher

carbon content decreases the malleability and weldability of steel.

LOW CARBON STEELS contains between 0.10 and 0.30 percent carbon. Primarily used in

safety wire, cable bushing, and threaded rod ends.

MEDIUM CARBON STEELS contains between 0.30 and 0.50 percent carbon.HIGH CARBON STEELS contains between 0.50 to 1.05 percent carbon and are very hard.

Primarily used in springs, files, and some cutting tools.

b. SILICON When it is alloyed with steel it acts as a hardener. When used in small quantities, it also

improves ductility.

c. PHOSPHOROUS Raises the yield strength of steel and improves low carbon steels resistance of

atmospheric condition. However, no more than 0.05 percent is normally used in steel,

since higher amounts cause the alloy to become brittle when cold.


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d. NICKEL Adds strength and hardness to steel and increase yield strength. It also slows the rate of

hardening when steel is heat treated, which increases the steels contains 3% nickel and

0.30% carbon, and used in producing aircraft hardwired such as bolts, nuts, rod end andpins.

e. CHROMIUM Alloyed with steel to increase strength and hardness as well as improve its wear and

corrosion resistance. It is used in balls and rollers of anti-friction bearings.

f. STAINLESS STEEL Is a classification ofCORROSION-RESISTANT STEEL (CRES) that contain large amount of

chromium and nickel. Their strength and resistant to corrosion make than well suited for

high-temperature applications such as firewalls and exhaust system components. It

contains 18% chromium and 8% nickel. It is referred as 18-8.

AUSTENITIC STEELS refers to 200 and 300 series stainless steel. Hardened only by cold-

working.FERRITIC STEELS contains no carbon. They do not respond to heat treatment.

MARTENSITIC STEELS - the 400 series of stainless steel. These are magnetic and it becomes

extremely hard if allowed to cool rapidly by cooling from an elevated temperature.


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g. CHROME MOLYBDENUM (chrome-moly) STEELS Commonly used alloy in aircraft. Making it an ideal choice for landing gear structures

and engine mounts.

h. VANADIUM When combined with chromium, vanadium produces a strong, tough, ductile steel

alloys. Most wrenches and ball bearings are made of chrome-vanadium steel.

i. TUNGSTEN Has an extremely high melting point and adds this characteristics to steel when it is

alloyed. Typically used for breaker contacts in magnetos and for high speed cutting tools.


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HEAT TREATMENT FOR STEELS:

ANNEALING is a form of heat treatment that softens steel and relievesinternal stress. It is heated about 50 degrees F above its critical

temperature, soaked for specified time then cooled.

NORMALIZING the process of forging, welding, or machining usually

leave stresses to the steel that could lead to failure. To normalize, it is

heated about 100 degrees F above its critical temperature and held thereuntil the metal is uniformly heat soaked, then removed from the furnace

and allowed to cool in still air.

HARDENING is heated above its critical temperature so carbon can

disperse uniformly in the iron matrix.

TEMPERING reduces the undesirable qualities of martensitic steel. It isheated to a level considerable below its critical temperature and held

there until it becomes heat soaked, then allowed to cool to room

temperature in still air.


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CASE HARDENING TREATMENTS:

1. CARBURIZING forms a thin layer of high carbon steel on the exterior of low

carbon steel.

PACK CARBURIZING is done by enclosing the metal in a fire-clay container and packing it

with a carbon-rich material such as charcoal. The container is then sealed, placed in

furnace, and heated.

GAS CARBURIZING is similar to pack carburizing except the carbon monoxide gas

combines with gamma iron and forms a high-carbon surface.

LIQUID CARBURIZING produces a high-carbon surface when a part is heated in a molten

salt bath of sodium cyanide or barium cyanide.

2. NITRIDING differs from carburizing in that a part is first hardened,

tempered and then ground to its finished dimensions before it is case

hardened.

3. CYANIDING is a fast method of producing surface hardness on an iron-

based alloy of low carbon content.


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WOOD STRUCTURES:

WOOD wood structures requires a great deal of handwork and therefore, are

extremely expensive.

SOLID WOOD used for some aircraft wing spars and is made of solid pie cut from a log. Most

solid cut by quarter sawing to prevent war page.

LAMINATED WOOD made up of two or three pieces of thin wood glued together with the

same direction.

PLY WOOD consist of three or more layers of thin veneer glued together so the grain of each

successive layer crosses the others at an angle of 45 degrees of 90 degrees.

2 BASIC SPECIES OF WOOD USED IN AIRCRAFT CONSTRUCTION:

1. HARDWOOD come from deciduous trees having broad leaves.

a. MAHOGANY this hardwood is heavier and stronger than spruce. Primary use in aircraft

construction is for face sheets of plywood used in aircraft skin.

b. BIRCH a heavy hardwood with very good shock resistant characteristics. It isrecommended for the face plies of plywood used as reinforcement plates on wing spars and in the

construction of wooden propellers.


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2. SOFTWOOD come from coniferous trees with needle like or scale like

leaves.

a. SITKA SPRUCE most common wood used in aircraft structures. It is relatively free

from defects, has a high strength to weight ration and available in large size. FAA chosen Sitka

Spruce as the reference wood for aircraft construction.

b. DOUGLAS FIR the strength properties exceed those of spruce; however, it is much

heavier. Further more, it is more difficult to work than spruce, and has a tendency to split.

c. NOBLE FIR slightly lighter than spruce and is equal or superior to spruce in all

properties except hardness and shock resistance. It is often used for structural parts that are

subject to heavy bending and compression loads such as spars, spar flange, and has tendency

to split.

d. BALSA an extremely light wood. Balsa lacks of structural strength, it is often sliced

across its grain for use as a core material for sandwich-type panels that requires lightweight

and rigidity.


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QUALITY OF WOOD:

Some of the categories a woods quality is based on include how straight thegrain is, the number of knots, pitch pockets, splits and presence of decay.

1. GRAIN DEVIATION regardless of the species of wood used aircraft construction, it must have

a straight grain. This means all of the woods fiber must be oriented parallel to the materialslongitudinal axis. A maximum of deviation of 1:15 is allowed. In other words, the grain mustnot slope more than 1 inch in 15 inches.

2. KNOTS it identifies where a branch grew from the tree trunk.

3. PITCH POCKETS small opening within the annual rings of a tree can fill resin and form pitchpocket. It slightly weaken the piece of wood.

4. CHECKS, SHAKE AND SPLITS

CHECKS a crack that runs across the annual rings of a board and occurs during theseasoning process.

SHAKE a crack or separation that occurs when two annual rings separates along theirboundary.

SPLITS a lengthwise separation of the wood caused by the wood fibers tearing apart.

5. STRAINS AND DECAY

STRAINS It is caused by decay usually appears streaks in the grain. Strains that uniformlydiscolor the annual rings are evidence of decay.

DECAY is caused by fungi that grow in damp wood, and is prevented by proper seasoningand dry storage. A simple way of identfying decayed wood is to pick at a suspected area withthe point of a knife. Sound wood will splinter, while a knife point will bring up a chunk ofdecayed wood.


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PLASTICS OR RESINS1. THERMOSETTING RESINS it hardens or set when heat of the correct

value is applied. It cannot softened and reshaped after having beensolidified.

2. THERMOPLASTIC RESINS can be soften by heat and reshaped or

reformed many times without changing composition, provided that the

heat applied is held with proper limits.

Types of Thermoplastic Material used for Aircraft Windshield and Side

Windows:

1. CELLULOSE ACETATE transparent and lightweight. It has a tendency to shrink and

turn yellow. When applied with acetone it softens.

2. ACRYLIC identified by trade names as Lucite or Plexiglas or in Britain Perspex. It is

stiffer than cellulose acetate. More transparent and for all purpose is colorless. It burns

with a clear flame and produces a fairly pleasant odor. If acetone is applied to acrylic it

leaves a white residue but remains hard.


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THERMOPLASTIC RESINS:

1. CELLULOSE ACETATE

2. POLYETHYLENE is made in low and high-density qualities. Low-density polyethyleneis made in thin, flexible sheet or film and is used for plastic bags, protective sheeting and

electrical insulation. High-density polyethylene is used for containers such as fuel tanks,

large drums and bottles.

3. VINYLS manufactured in a variety of types and has a wide range of application. Their

used in aircraft includes seat covering, electrical insulation, moldings, and tubing. They

are flexible and resistant to most chemical and moisture.

4. ACRYLIC RESIN a water clear plastic that has a light transmission of 92%. This

property, together with its weather and moisture resistance, makes it an excellent

product for aircraft windows and windshields.

5. POLYTETRAFLOUROETHYLENE (Teflon) is encountered in non-lubricated bearings,

tubing, electrical devices and other applications.


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TYPES OF MAINTENANCE, REPAIR, AND ALTERATIONS

PREVENTIVE MAINTENANCE is defined as simple or minor preservation operations and

the replacement of small standard parts not involving complex assembly operations.

Operations classed as preventive maintenance are as follows: Removal, installation, and repair of landing gear tires.

Replacing elastic shock-absorber cords on landing gear.

Servicing landing-gear shock struts by adding oil, air, or both.

Servicing landing gear wheel bearings, such as cleaning and greasing.

Replacing defective safety wiring or cotter keys.

Lubrication not requiring disassembly other than removal of non-structural items such as cover

plates, cowlings, and fairings.

Making simple fabric patches not requiring rib stitching or the removal of structural parts or

control surfaces.

Replenishing hydraulic fluid in the hydraulic reservoir.

Refinishing decorative coating of fuselage, wings, tail group surfaces (excluding balanced

control surfaces), fairings, cowling, landing gear, cabin, or cockpit interior when removal or

disassembly of any primary structure or operating system is not required.

Applying preservative or protective material to components where no disassembly of any

primary structure or operating system is involved and where such coating is not prohibited or is

not contrary to good practices.

Repairing upholstery and decorative furnishings or the cabin or cockpit interior when the

repairing does not require disassembly of any primary structure or operating system or affect

the primary structure of the aircraft.


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Making small simple repairs to fairings, non-structural cover plates, cowlings, and small patches

and reinforcements not changing the contour so as to interfere with the proper airflow.

Replacing side windows where that work does not interfere with the structure of any operating

system such as controls, electrical equipment, etc.

Replacing safety belts.

Replacing seats or seat parts with replacement parts approved for the aircraft, not involvingdisassembly of any primary structure or operating system.

Troubleshooting and repairing broken circuits in landing light wiring circuits.

Replacing bulbs, reflectors, and lenses of position and landing lights.

Replacing wheels and skis where no weight and balance computation is involved.

Replacing any cowling not requiring removal of the propeller or disconnecting of flight controls.

Replacing or cleaning spark plugs and setting of spark plug gap clearance.

Replacing any nose connections except hydraulic connections.

Replacing pre-fabricated fuel lines.

Cleaning fuel and oil strainers.

Replacing batteries and checking fluid level and specific gravity.

Removing and installing glider wings and tail surfaces that are specifically designed for quick

removal and installation and when such removal and installation can be accomplished by the

pilot. The holder of a pilot certificate issued under FAR Part 61, may perform preventive maintenance on any

aircraft owned or operated by him that is not used in air carrier service. Preventive maintenance may also

be performed by certificated mechanics, repair stations, repairmen, air carriers, and others authorized by

the FAA. A person who plans to perform preventive maintenance must ascertain that the operation falls

within this category and that he is authorized to perform the work.


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CLASSIFICATION OF ALTERATIONS:

MAJOR ALTERATIONS is an alteration not listed in the aircraft, aircraft engine, or propeller

specifications (1) that might appreciably affect weight, balance, structural strength, performance, power

plant operation, flight characteristics and other factors of airworthiness or (2) that is not done according

to accepted practices or cannot be done by elementary operations.

Alterations of the following parts and alterations of the following types, when not listed in the aircraft

specifications issued by the FAA, are airframe major alterations:

- Wings

- Tail Surfaces

- Fuselage

- Engine mounts- Control system

- Landing gear

- Hull or floats

- Elements of an airframe, including spars, ribs, fittings, shock absorbers, bracing cowlings, fairings, and

balance weights

- Hydraulic and electrical actuating systems or components

- Rotor blades

- Changes to the empty weight or empty balance which result in an increase in the maximum

certificated weight or center-of-gravity limits of the aircraft.

- Changes in the basic design of the fuel, oil, cooling, cabin pressurization, electrical, hydraulic, deicing,

or exhaust systems.

- Changes to the wing or to fixed or movable control surfaces which affect flutter and vibration

characteristics.


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The following alterations of a power plant, when not listed in the engine

specifications issued by the FAA, arepower plant major alterations.

- Conversion of an aircraft engine from one approved model to another, involving any changes in

compression ratio, propeller reduction gear, impeller gear ratios, or the substitution of major engine parts

which requires extensive rework and testing of the engine.

- Changes to the engine by replacing aircraft engine structural parts with parts not supplied by the

original manufacturer or parts not specifically approved by the FAA administrator.

- Installation of an accessory which is not approved for the engine.

- Removal of accessories that are listed as required equipment on the aircraft or engine specification.

- Installation of structural parts other than the type of parts approved for the installation.

- Removal of accessories that are listed as required equipment on the aircraft or engine specification.

- Installation of structural parts other than the type of parts approved for the installation.

- Conversions of any sort for the purpose of using fuel of a rating or grade other than that listed in the

engine specifications.

Minor Alterations of either an airframe or a power plant are alterations other than

major alterations.


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CLASSIFICATION OF REPAIRS

Repairs of airframes and power plants are classified as either major or minor depending upon the typeand effect of the repair. A major repair is one which, if improperly done, might appreciably affect theweight, balance, structural strength, performance, power plant operation, flight characteristics, or otherqualities affecting airworthiness; or one which is not done according to accepted practices or cannot bedone by elementary operations.

Repairs to the following parts of an airframe and repairs of the following types, involving thestrengthening, reinforcing, splicing, and manufacturing of primary structural members, or theirreplacement (when replacement is by fabrication such as riveting or welding), are airframe majorrepairs:

- Box beams

- Monocoque or semi-monocoque wings or control surfaces

- Wing stringers or chord members

- Spars- Spar flanges

- Members of truss-type beams

- Thin sheet webs of beams

- Keel and chine members or boat hulls or floats

- Corrugated sheet compression members which act as flange material of wings or tail surfaces

- Wing main ribs and compression members

- Wing or tail surface brace struts- Engine mounts

- Fuselage longerons

- Members of the side truss, horizontal truss, or bulkheads

- Main seat support braces and brackets

- Landing gear brace struts


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- Axles

- Wheels

- Skis and ski pedestals

- Parts of the control system such as control columns, pedals, shafts, brackets, or horns

- Repairs involving the substitution of material

- The repair of damaged areas in metal or plywood stressed covering exceeding 6 in. in any direction

- The repair of portions of skin sheets by making additional seams

- The splicing of skin sheets

- The repair of three or more adjacent wing or control surface ribs or the leading edge of wings and

control surfaces between such adjacent ribs

- Repair of fabric covering involving an area greater than that required to repair two adjacent ribs

- Replacement of fabric on fabric covered parts such as wings, fuselages, stabilizers, and controlsurfaces

- Repairing of removable or integral fuel tanks and oil tank, including re-bottoming the tanks

Repairs of the following parts of an engine and repairs of the following types are

powerplant major repairs:

- Separation or disassembly of a crankcase or crankshaft of a reciprocating engine equipped with anintegral superchargers

- Separation or disassembly of a crankcase or crankshaft of a reciprocating engine equipped with

other than spur-type propeller reduction gearing

- Special repairs to structural engine parts by welding, plating, metalizing, or other methods.


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Annual and 100-hr inspections

According to the provisions of FAR, Part 91, no person may operate an aircraft unless, within the

preceding 12 calendar months, it has had an annual inspection and has been approved for return to

service by an authorized person. An inspection for the issuance of an Airworthiness Certificate will serve

as a substitute for the annual inspection.

A 100-hr inspection is similar to the annual inspection; however, it may not be substituted for theannual inspection unless it is performed by a person certificated or otherwise authorized to make annual

inspections and is entered as an annual inspection in the aircraft maintenance records (log book).

A 100-hr inspection is required on every aircraft used for carrying persons for hire other than the crew or

for giving flight instruction. This means the aircraft must undergo a complete inspection, as set forth in

FAR, Part 43, within every 100 hrs of operating time. After the 100-hr limitation may be exceeded by not

more than 10 hr if necessary to reach a place at which the inspection can be made. The excess time,

however, is included in computing the next 100 hr of time in service.

Progressive inspection

A progressive inspection requires the setting up of a schedule, specifying the intervals in hours or days

when routine and detailed inspections will be performed, including instructions for exceeding an

inspection interval by not more than 10 hr while enroute, and for changing an inspection interval

because of service experience.

Progressive inspection are usually established by air carriers in order to provide for better utilization ofaircraft. Approval for such an inspection system requires that a properly authorized person or agency

supervise the inspection procedures and that an inspection procedures manual be available and readily

understandable to pilot and maintenance personnel. Aircraft subject to an approved progressive

inspection system need not undergo the 100-hr inspection otherwise required.


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CONTINUOUS AIRWORTHINESS INSPECTION PROGRAMS OF LARGE & TURBINE-POWERED MULTI-ENGINE AIRPLANES:

AIRCRAFT INSPECTIONS this element deals with the routine inspections, servicing, and tests performedon the aircraft at prescribed intervals. It includes detailed instructions and standards (or relatedreferences) by work forms, job cards, and other records which also serve to control the activity and torecord and account for the tasks that comprise this element. Each airline is free to develop its own

terminology, which is assigned to the different parts the inspection program. The use of terms such as A-check and D-Check as is illustrated in Figure 16-5 is common in a continuous inspection program. Figure16-5 provides an example of the continuous inspection program.

SCHEDULED MAINTENANCE this element concerns maintenance tasks performed at prescribedintervals. Some are accomplished concurrently with the inspection tasks that are part of the inspectionelements and may be included on the same form. Other tasks are accomplished independently. Thescheduled tasks include the replacement of life-limited items and components requiring replacement forperiodic overhaul; special inspections such as X-rays, checks, or tests for on-condition items; lubrications;

and so on. Special work forms can be provided for accomplishing these tasks or they can be specified by awork order or some other document. In any case, instructions and standards for accomplishing each taskshould be provided to ensure that it is properly accomplished and that it is recorded and signed for.

UNSCHEDULED MAINTENANCE this element provides instructions and standards for theaccomplishment of maintenance tasks generated by the inspection and scheduled maintenanceelements, pilot reports, failure analyses, or other indications of a need for maintenance. Procedures forreporting, recording, and processing inspection findings, operational malfunctions, or abnormaloperations, such as hard landings, are an essential part of this element. A continuous aircraft logbook can

serve this purpose for occurrences and resultant corrective action between scheduled inspections.Inspection discrepancy forms are usually used for processing unscheduled maintenance tasks inconjunction with scheduled inspections. Instructions and standards for unscheduled maintenance arenormally provided by the operators technical manuals. The procedures to be followed in using thesemanuals and for recording and certifying unscheduled maintenance are included in the operatorsprocedural manual.

Type When Who What


46/46

No. 1 service

"walk-around"

Before each flight Mechanic and pilot

Exterior check of aircraft and engines for

damage and leakage; includes specific

checks such as brake and tire wear

No. 2 serviceDuring overnight layovers at maintenance

locations; at least every 45 hours of domestic

flying or 65 hours of international flying Mechanics

Same as No. 1 service plus specific

checks including oils, hydraulics, oxygen,

and unique needs by aircraft type

A-checkApproximately every 200 flying hours, or about

every 15 to 20 days - depending on type of

aircraft 3-5 Mechanics

More detailed check of aircraft and

engine interior including specific checks,

services, and lubrications of systems

such as ingnition, generators, cabins, air

conditioning, hydraulics, structure,

landing gear

B-/M-/L-checks Heaviest level of routine line maintenance;approximately every 550 flying hours or every

40-50 days; work performed overnight 12-80 Mechanics

Similar to A-check but in greater detail,

which specific aircraft and engine needssuch as torque tests, internal checks, and

flight controls

C-check

Every 12-15 months, depending on aircraft

type; airplane out of service for 3-5 days

From 150-200 mechanics and

inspectors - depending on

aircraft type

Detailed inspection and repair of aircraft,

engines, components, systems and

cabin, including operating mechanisms,

flight controls, and structural tolerances

D-check

Most intensive inspection; every 4-5 years,

depending on aircraft type; airplane out of

service up to 30 days

From 150-300 mechanics and

inspectors - depending on

aircraft type

Major structural inspections for detailed

needs which include attention to fatigue

corrosion; aircraft is dismantled,

repaired and rebuilt as required; systems

and parts are tested, repaired or

replaced

Figure 16-5

Documents

Airframe and Construction Repair Review