7.18 Inspection and Repair Techniques Flashcards
What is the life span of an aircraft based on?
The life span of an aircraft is generally specified based on the stresses the structure receives over time.
What philosophy is used in aircraft structure design?
Aircraft structures are designed with a stressed skin philosophy where the fuselage skin along with bulkheads, frames, beams, and ribs are all load carriers.
What adds to the stresses and fatigue on the aircraft structure during flight?
Pressurisation cycles add to the stresses and fatigue on the aircraft structure during flight.
What should be carried out to achieve the overall design life limit of the aircraft?
Regular, scheduled inspections should be carried out as per the manufacturers guidelines.
What are aircraft inspections?
Inspections can be visual examinations or manual checks to determine the condition of an aircraft or the condition of a component.
What is the purpose of an inspection system?
The purpose of an inspection system is to ensure that the aircraft is maintained to the highest possible condition.
What can result from failure to follow an inspection programme?
Failure to follow an inspection programme can result in the gradual deterioration of an aircraft’s airworthiness.
What can reduce operating defects and malfunctions?
Operating defects and malfunctions of equipment/components can be reduced if detected and rectified early.
What types of inspections can be performed on airframes and engines?
Airframe and engine inspections can range from basic pre-flight inspections to detailed inspections.
What are the two systems for scheduling aircraft inspections?
An aircraft inspection programme can be developed using flying hours or by using a calendar inspection system.
What is the calendar inspection system?
The calendar inspection system is an efficient system for a maintenance organisation to adopt, where required inspections are performed after a specified number of calendar weeks.
What happens in the flying hour system for inspections?
Aircraft using the flying hour system are inspected when a specified number of flying hours are accumulated.
What does the term ‘damage’ refer to in the Structure Repair Manual (SRM)?
In the SRM, ‘damage’ refers to a cross-sectional area or a permanent distortion of a structural member.
What is a defect in the context of aircraft inspection?
A defect is any event or condition which reduces the serviceability of the aircraft.
What are some signs of abnormality an engineer should look for?
Signs include leaks, overheating, fluid ingress, obstruction of drainage, distortion, dents, cracks, and corrosion.
What is abrasion in terms of aircraft damage?
Abrasion is a damaged area that results from scuffing, rubbing, or scraping, usually rough and irregular in shape.
What is corrosion?
Corrosion is damage resulting from electro-chemical action that changes the cross-sectional area.
What is a crack?
A crack is a partial fracture or full break in the material causing a significant cross-sectional area change.
What is a crease?
A crease is a damaged area that is depressed or folded back with sharp boundaries.
What does delamination refer to?
Delamination is the separation of plies in a multi-laminate material, often caused by impact or resin failure.
What is a dent?
A dent is a damaged area pushed in from its contour with no change in the cross-sectional area.
What is a disbond?
A disbond is a separation of materials due to adhesive failure and does not have to occur across the full surface.
What is a gouge?
A gouge is a damaged area causing a cross-sectional change due to a sharp object, resulting in a groove.
What constitutes a hole?
A hole is a complete penetration of the surface usually caused by impact from a sharp object.
What is a nick?
A nick is a local gouge with sharp edges, and a series of nicks can be considered equal to a gouge.
What is a puncture?
A puncture is damage that goes fully through a part thickness and has no regular shape.
What is a scratch?
A scratch is a line of damage in the material causing a cross-sectional area change, usually from contact with a sharp object.
What must be determined after finding damage?
The full extent and category of the damage must be determined.
What are the damage classifications?
The damage must be classified as Allowable Damage, Non-Allowable Damage, or Non-Repairable Damage.
What is Allowable Damage?
Allowable Damage is slight or of little significance, unlikely to propagate further damage.
What is Non-Allowable Damage?
Non-Allowable Damage exceeds allowable limits and must be repaired by removing the damaged area.
What is Non-Repairable Damage?
Non-Repairable Damage is damage that cannot be repaired, requiring complete component replacement.
What should be done before starting an inspection?
Ensure all required panels, access doors, fairings, and cowlings have been opened or removed and the structure is thoroughly cleaned.
What is the importance of using a checklist during inspections?
Using a checklist ensures that items to be inspected are not overlooked or forgotten.
What areas should be considered when developing a checklist for an aircraft inspection?
Areas include fuselage, systems, cabin, engine, landing gear, wings, empennage, propeller, and miscellaneous items.
What must any inspection provide?
An accurate assessment of the damage and the type of repair to carry out.
What are Non-Destructive Inspection methods (NDI)?
NDI methods are used to inspect damaged areas without causing further damage.
What aids are used for visual inspections?
Visual aids range from standard torches and mirrors to complex optical instruments.
What is the purpose of inspection mirrors?
Inspection mirrors allow for viewing behind flanges and brackets at various angles.
What is the function of a magnifying glass in inspections?
A magnifying glass helps clarify suspected defects, such as cracks or corrosion.
What is a borescope?
A borescope is an optical instrument used for inspecting the internal structure or components.
What types of borescopes are available?
Types include rigid, cold light, and flexible fibre optical systems.
What has been researched to improve aircraft metals?
Research has focused on improving corrosion resistance through materials, surface treatments, and protective finishes.
What is the primary goal of improvements in aircraft metals?
The improvements aim to reduce aircraft maintenance and improve reliability.
Is corrosion still a problem for aircraft?
Yes, corrosion and its control remain real problems requiring continuous preventive maintenance.
What is essential for maintaining aircraft serviceability?
Early identification and removal of corrosion through regular and precise inspections.
What must be done with all corrosion found on aircraft?
All corrosion must be immediately and completely removed.
What should be checked after corrosion removal?
The extent of the damage should be examined against allowable limits in the Structural Repair Manual.
What is essential after corrosion removal?
The repair area must receive the correct surface protection to prevent further corrosion.
What are some corrosion preventive maintenance actions?
Actions include adequate cleaning, thorough lubrication, detailed inspections, prompt treatment of corrosion, and maintaining drainage.
What is required before starting any corrosion removal process?
A visual inspection using tools like magnifying glasses or borescopes.
What are signs of corrosion on painted surfaces?
Signs include a scaly or blistered surface, change of color, and blisters in the paint.
What should be done with areas affected by corrosion?
All affected areas must be treated immediately.
What is the initial assessment of corrosion important?
It can be less costly to repair than to proceed with further steps.
What must be done to adjacent areas before corrosion removal?
Protect them against chemical strippers and cleaning agents using masking paper and tape.
What should be done before using cleaning agents?
Read the Material Safety Data Sheet (MSDS) as they can be dangerous.
What are the two methods of paint removal?
Mechanical for light corrosion and chemical for heavy corrosion.
What must be removed to prevent cross contamination during corrosion removal?
Any fasteners affected by corrosion.
What are the steps involved in corrosion removal?
Cleaning, stripping, removing corrosion products, neutralizing residual materials, and restoring protective films.
What personal protective equipment is needed when using abrasive tools?
Safety goggles or a face shield.
What is abrasion by hand suitable for?
Areas of light corrosion.
What is wire brushing used for?
To remove heavy corrosion and embedded paint or dirt.
Why should wire brushing not be used on aluminum parts?
It can embed fine particles and cause further corrosion.
What is the procedure for wire brushing?
Remove loose corrosion with a hand scraper, then use a wire brush for remaining traces.
What is grinding used for?
To remove corrosion using motorized grinding wheels.
What should be avoided when grinding?
Generating hot temperatures that can change material properties.
What is the procedure for grinding?
Grind until a firm corrosion-free surface is achieved, then polish with fine abrasive paper.
What is abrasive blasting not recommended for?
Internal use.
What personal protective equipment is required for abrasive blasting?
Respirator, hearing protection, eye protection, gloves, and safety shoes.
What is the procedure for abrasive blasting?
Remove corrosion with the correct media like glass beads.
How can you check if corrosion has been completely removed?
Using a 10x magnifying glass.
What is the purpose of neutralization in corrosion removal?
To complete corrosion removal where deep corrosion is found on aluminum alloys.
What is the neutralizing procedure?
Prepare a solution of chromic acid and water, apply, allow to work, rinse, and dry.
What precautions must be taken when using chromic acid?
Ensure proper ventilation and wear appropriate PPE.
What is a common surface treatment for aluminum and magnesium alloys?
Chromic acid inhibitor.
What is sodium dichromate solution used for?
Surface treatment of aluminum.
What is the most common type of corrosion on steel?
Ferrous oxide (rust).
What is the best method for controlling corrosion on steel?
Complete removal of corrosion followed by restoring protective coatings.
What is a widely used chemical for rust removal?
Phosphoric acid.
What must be done when using chemical rust removal products?
Isolate the part from any non-ferrous metals.
What is the corrosion resistance consideration for stainless steel and nickel chromium alloys?
They are used where corrosion resistance is a major consideration.
What does the chemical rust removal solution do?
It creates a chemical reaction that converts rust into a water-soluble compound that can be scrubbed or washed away.
What must be done before treating steel parts in an airframe?
The steel part must be removed from the airframe for treatment.
What is necessary when using chemical rust removal products?
The part must be isolated from any non-ferrous metals.
What materials are stainless steel and nickel chromium alloys used for?
They are used where corrosion resistance is a major consideration in structural parts and components.
What is a common appearance of corrosion on stainless steels?
Corrosion usually appears as pitting, which is typically black in color.
How should corrosion be removed from stainless steel and nickel chromium alloys?
Use the same procedures as those given for carbon steel.
Where are titanium alloys commonly used in aircraft?
In high temperature areas and where high strength members are exposed to a corrosive environment.
What can cause deterioration on titanium surfaces?
The presence of salt deposits and metal impurities, identified as black or white colored oxide.
What cleaning methods are prohibited for titanium parts?
The use of steel wool, iron scrapers, or steel brushes.
How can titanium surfaces be cleaned?
By hand using permissible aluminium polish or a mild abrasive and polish with fibre brushes.
What should be done after cleaning titanium surfaces?
Treat the surfaces with a suitable solution of sodium dichromate and wipe with dry cloths.
What is the purpose of pre-treatments in corrosion protection?
To increase corrosion resistant properties and provide a good surface for paint adhesion.
What is sacrificial corrosion prevention?
Applying a thin layer of different metal with a lower electrolytical potential than the main metal.
What pre-treatment is used for aluminium alloys?
Chromic or Sulphuric Anodising.
What is the purpose of anodising?
To form oxide coatings that increase the performance of the surface.
What is the anodising process for aluminium?
It forms a layer of aluminium oxide (Al²O₃) which is hard, inert, and can absorb dyes.
What is the difference between tank method and selective method in anodising?
Tank method involves dipping components in a large tank, while selective method uses an electrical power pack for local plating.
What is the effect of alloy composition on anodised coatings?
The alloy composition and heat treatment condition significantly affect the resultant coating.
What should be avoided when cleaning anodised surfaces?
Harsh acidic or alkaline cleaners.
What is the warning associated with sulphuric acid?
It is corrosive and highly toxic, causing severe skin or eye irritation.
What is the purpose of phosphate coatings?
For corrosion resistance, lubricity, or as a foundation for subsequent coatings or painting.
What are the three main types of phosphate coatings?
Manganese, Iron, and Zinc.
What is the function of chemical conversion coatings?
To roughen the surface for better paint adhesion and provide corrosion protection.
What is a paint finish?
Coatings that are manually painted or sprayed on components.
What are the two main reasons for paint finishes on aircraft?
A decorative finish and protection against corrosion, erosion, and mechanical damage.
What does the Airbus three-layer surface protection system consist of?
Wash Primer, Paint Primer, and Coating Lacquer.
What does Boeing’s two-layer surface protection system consist of?
Paint Primer and Coating Lacquer.
What does partial or total renewal of paint finish involve?
Sanding and repainting an aged or damaged paint finish.
What is included in a basic renewal of paint finish?
Complete removal of paint, corrosion inhibition, and rebuilding the paint system.
What is the Wash-Primer FCR?
The Wash-Primer Filiform Corrosion Resistant (FCR) primer consists of phosphoric acid parts and zinc-chromate pigments.
How should the Wash-Primer FCR be used?
It must be covered with a paint or intermediate primer layer and is not to be used as a one-layer primer.
What is the role of the FCR primer in the interior structure?
It acts as corrosion protection for the sheet metal parts.
What is the role of the FCR primer on the outer surface?
It acts primarily as adhesion contact, improving the adhesion of the three-layer paint system.
What happens if the minimum cure time is not observed?
Corrosion protection and adhesion are impaired.
Under what conditions is the use of FCR primer not recommended?
In humidity higher than 75% or temperatures below 15 °C.
What must be applied after the FCR primer?
Aerodur S15/90 or CF Primer 37047 must be subsequently applied.
To what type of steel should Wash-Primer FCR not be applied?
It must not be applied to steels with a breaking strength of more than 180 KSI (1240 N/mm2).
What are the widely used intermediate primers?
Aerodur S 15/90 and Aerodur CF 37047.
What is the pot lifetime after preparation for intermediate primers?
6 hours at temperatures of 18-22 °C.
What is the dry time for intermediate primers?
Dry so that dust does not cling after 30 minutes.
What is the cure time for epoxy primers?
24 hours at 18 °C.
What is the resistance of epoxy primers to hydraulic oil?
Resistant to hydraulic oil (short contact) after 36 hours.
What is the purpose of coating lacquers?
They are applied as the last layer on previously applied wash primers and intermediate primers.
What type of products are currently used for coating lacquers?
Polyurethane products (PU or PUR coating lacquers).
What can protect coating lacquers against aging?
An additional clear varnish can protect against general aging and decay.
What are electrically conductive paints used for?
They are used as antistatic primers for plastic components.
What must be done before applying coating lacquer over antistatic primer?
A resistance test or a conductivity test must be performed by trained personnel.
What are water-displacing inhibitors used for?
To stop corrosion that has already started and to make surfaces water-repellent.
What are some examples of water-displacing inhibitors?
LPS 3, Boeshield T9 H5, Tectyl, Adrox, Dinitrol.
What precautions should be taken when using Dinitrol products?
Ensure proper ventilation, wear PPE, and keep away from heat or ignition sources.
What is Dinitrol AV 8 used for?
It is used as precautionary corrosion protection in landing gear areas.
What is Dinitrol AV 30 known for?
It builds up an elastic film that does not crack when deformed.
What is the cure time for Dinitrol AV 100?
The cure time is about six hours.
What is the purpose of the Structural Repair Manual (SRM)?
The SRM covers specific types of repairs to an aircraft structure or component, encompassing nearly every repair deemed appropriate by the manufacturer.
What should be consulted before starting any aircraft repair?
It is highly recommended to consult the manufacturer’s maintenance manual and the structural repair manual.
What is the objective of an aircraft repair?
The objective is to restore damaged parts as close to their original condition as possible.
What is usually the principal requirement in any aircraft repair?
Strength is usually the principal requirement in any repair.
What are primary structures in an aircraft?
Primary structures are critical load-bearing structures such as the fuselage, wings, stabilisers, flight control surfaces, and landing gear.
What are secondary structures in an aircraft?
Secondary structures provide enhanced aerodynamics and include elements like fairings.
What are the two classifications of repair in the SRM?
- Repairs evaluated for damage tolerance (Category A, B, or C). 2. Repairs not evaluated (Permanent, Interim, or Time-Limited).
What defines a Category A repair?
A permanent repair for which the inspections given in the Zonal Inspection are sufficient and no other actions are necessary.
What defines a Category B repair?
A permanent repair requiring supplemental inspections at specified thresholds and repeat intervals.
What defines a Category C repair?
A time-limited repair requiring supplemental inspections at specified thresholds and repeat intervals, followed by a replaced or reworked repair.
What is a Permanent Repair?
A repair where no action is necessary, except for the operator’s maintenance.
What is an Interim Repair?
A repair with necessary structural strength that can stay on the aircraft indefinitely, requiring inspections at specified intervals.
What is a Time-Limited Repair?
A repair with necessary structural strength but insufficient durability, requiring replacement after a specified time.
What is an external repair?
An external repair is a cover repair applied quickly to minimize aircraft downtime, typically field-oriented.
What is a flush repair?
A flush repair is an insertion repair used to replace an external repair, normally a workshop-type procedure.
What does the SRM include?
The SRM includes structural damage criteria, material identification, typical repairs, substitute materials, fastener information, and procedures related to structural repairs.
Who approves the information in the SRM that affects structural integrity?
The information is approved by the European Union Aviation Safety Agency (EASA) or the Federal Aviation Administration (FAA).
What should be done if a typical repair cannot be found in the SRM?
Consider general repair practices, prepare a specific repair design, or replace the damaged part.
What is the standard numbering system for the SRM?
It is a three-element system: chapter, section, and subject.
What does Chapter 51 of the SRM cover?
Chapter 51 covers Structures - General.
What does Chapter 52 of the SRM cover?
Chapter 52 covers Doors.
What does Chapter 55 of the SRM cover?
Chapter 55 covers Stabilisers.
What is the purpose of the page blocks in the SRM?
Page blocks are used to separate topics such as general information, allowable damage, and repair.
How should one use the SRM to find repair data?
Check allowable damage limits, identify material, and obtain repair data from the relevant chapter and section.
What is required as aircraft age?
Deeper and thorough inspections of the structure are required to ensure the aircraft remains airworthy.
What is the major factor affecting aging aircraft?
Corrosion is the major factor.
What should operators develop to address aircraft aging?
Operators need to develop a corrosion prevention programme.
What can prolonged stress on aircraft cause?
Weaknesses, cracks, and failures of the metal structures and components.
What role do manufacturers play in aircraft maintenance?
Manufacturers ensure inspection and maintenance of older aircraft is performed.
What are Airworthiness Directives (ADs)?
ADs alert operators of newly discovered areas of concern and the appropriate action required.
What has Boeing developed for the 737?
Mandatory procedures for inspection and airframe modification.
What was designed for Boeing 747s?
A different programme based on historical knowledge from operational incidents.
What did the Aloha Airlines incident illustrate?
Strong design was not enough; older airframes require more thorough inspection and maintenance.
What is the National Aging Aircraft Research Program (NAARP)?
A program developed by the FAA to study how age affects aircraft.
What are the two areas the FAA divided aircraft into?
Structures and electrical systems.
What are the three kinds of damage that lead to failure?
Corrosion damage, fatigue damage, and accidental damage.
What causes corrosion damage?
The process of corrosion or oxidation.
What is fatigue damage?
Damage caused by repeated flexing of structural components.
What is accidental damage?
Damage resulting from impacts or severe weather conditions.
What must operators of aging aircraft develop?
Practices to assure continued airworthiness through inspection, monitoring, and corrective maintenance.
What is fatigue in aircraft structures?
Fatigue primarily occurs in metal components through cyclic loading patterns.
What is a good example of fatigue?
Bending a metal paper clip backwards and forwards until it fails.
What can initiate fatigue?
A microscopic crack at a location of high stress.
What influences the rate of fatigue in aircraft operations?
The number of landings and take-offs, including pressurisation cycles.
What operations increase fatigue rates?
High ‘G’ manoeuvres, aerobatics, aerial mustering, and aerial agriculture.
What is safe-life in aircraft design?
Specifies a ‘safe’ lifespan within which there is no significant risk of structural failure.
What is fail-safe design?
A structure that can sustain limit load even when one of the elements has failed.
What is damage tolerance in aircraft design?
A design philosophy that allows cracks to be detected before they affect flight safety.
What is the purpose of a Corrosion Prevention and Control Programme (CPCP)?
To prevent corrosion through regular inspections and surface treatments.
What are common methods for corrosion removal?
Chemical and mechanical methods.
What are corrosion-prone areas in aircraft?
Aircraft galleys, lavatories, battery compartments, and landing gear areas.
What should be done if battery acid is encountered?
Ensure proper ventilation, wear PPE, and dispose of any spillage properly.
What is crucial for corrosion inspection?
Early detection and repair to minimize damage.
What can indicate corrosion on painted surfaces?
Changes in paint color or integrity, such as blistering or scaling.
What issues can arise with certain materials under specific conditions?
Certain types of materials become troublesome under certain operating/environmental conditions and require attention.
How do magnesium skins fare against corrosion?
Magnesium skins have limited issues with corrosion if the original surface finish is adequately maintained.
What happens during drilling or riveting tasks?
Drilling or riveting tasks tend to damage some of the original surface treatment, which is difficult to completely restore by touch-up procedures.
What causes corrosion in spot-welded metal skins?
Corrosion of a metal skin joined by spot welding is the result of trapped corrosive agents between the layers of metal.
How can corrosion be evidenced in spot-welded metal?
This type of corrosion is evidenced by corrosion appearing at the crevices through which the corrosive agents enter.
What is the best prevention for corrosion in seams and holes?
The best prevention is to keep potential moisture entry points filled with a sealant or a suitable preservative compound.
What challenges exist in inspecting aircraft fuel tanks?
With the aircraft fuel tanks located inside the wing and fuselage structures, it is difficult to gain access to inspect fittings and other components on the inside of the tank for corrosion.
Why are fuel tanks ideal for bacterial growth?
Fuel tanks are ideal areas for bacterial growth.
How can bacterial growth in fuel tanks be controlled?
Bacterial growth can be controlled with the use of growth-inhibiting additives added to the fuel when refuelling the aircraft.
What is a prime area for corrosion in aircraft panels?
The majority of aircraft panels incorporate a piano hinge, which is a prime area for corrosion to form due to dissimilar metal contact between the steel pin and aluminium hinge.
What must be included in the inspection of hinges?
Inspection of hinges must include a thorough clean followed by lubrication and actuation to ensure complete lubricant penetration.
What accumulates in wing flaps and spoilers recesses?
Wing flaps and spoilers recesses accumulate grease, dirt, and water.
Why do wing flaps and spoilers recesses go unnoticed?
These areas generally go unnoticed because the flaps and spoilers are retracted with the aircraft on the ground.
What is required for the inspection of wing flaps and spoilers recesses?
An inspection programme is required to perform a scheduled inspection of these areas.
What stresses do engine mount structures endure?
Engine mount structures are subjected to heat, vibration, and torque from the engine and its accessories.
What material are most reciprocating engine mounts made from?
The majority of reciprocating engine mounts are manufactured from welded tubular steel.
What is necessary for corroded tubing?
Corroded tubing must be cleaned and the structural integrity of the material must be tested.
What inspections are recommended for corroded tubing?
The use of eddy current and ultrasonic inspections are recommended.
How should wire control cables be inspected?
Wire control cables must be inspected to determine their condition at each inspection period.
What should be done if external corrosion is evident on wire control cables?
Relieve the tension on the cable and inspect the cable for internal corrosion.
What should be done with cables that have internal corrosion?
Cables with internal corrosion must be replaced.
How can light external corrosion be removed?
Light external corrosion can be removed with the use of a stainless steel wire brush.
What is needed after removing light external corrosion?
They can then be re-coated with a recommended preservative.
What must be regularly inspected in electronic and electrical compartments?
Electronic and electrical compartments, where circuit breakers, contact points, and switches are located, are sensitive to moisture and corrosive attack.
What may be required if design features prevent inspection of electronic components?
Component removal can be required to gain full access for a thorough inspection for corrosion.
What are NDI and NDT?
NDI (Non-destructive Inspection) and NDT (Non-destructive Testing) are methods used to determine the airworthiness of aircraft components without causing damage.
What is required before conducting NDI/NDT?
Specific procedures must be followed, including cleaning parts, removing them from the aircraft, and ensuring equipment calibration is valid.
What is a discontinuity?
An interruption in the normal physical structure of a part, such as cracks or inclusions, which may or may not affect its usefulness.
What is a defect?
A discontinuity that interferes with the usefulness of a part, affecting its serviceability.
What is an imperfection?
A departure of a quality characteristic from its intended condition.
What is a flaw?
An imperfection in an item or material that may or may not be harmful.
What are the advantages of visual inspection?
Inexpensive, highly portable, immediate results, minimum training, and minimum part preparation.
What are the disadvantages of visual inspection?
Only detects surface imperfections and generally only large discontinuities; misinterpretation of scratches is possible.
What is the penetrant dye method used for?
It detects surface defects in non-porous materials, such as aluminum and stainless steel.
What are the steps for performing a penetrant inspection?
- Clean the surface 2. Apply penetrant 3. Remove penetrant 4. Dry the part 5. Apply developer 6. Inspect results.
What is the purpose of a borescope?
A borescope is used for visual inspections in areas that cannot be accessed without disassembly.
What is the eddy current inspection method?
A method that uses electromagnetic fields to detect surface and subsurface imperfections in conductive materials.
What is the principle behind eddy current testing?
Alternating current induces a magnetic field that creates eddy currents in the material, which are affected by any flaws present.
What are typical defects found using eddy current testing?
Surface cracks, pits, subsurface cracks, and corrosion.
What safety precautions should be taken when using dye penetrants?
Use adequate ventilation, wear protective gear, and handle solvents carefully due to flammability and toxicity.
What is required for the calibration of eddy current test equipment?
A reference standard made from the same material as the item to be tested, containing known flaws or cracks.
What are typical defects found using eddy current testing?
Eddy current testing can detect various defects, including surface and subsurface flaws.
What is the ultrasonic inspection method?
An NDI technique that uses sound energy moving through the test specimen to detect flaws.
How is sound energy displayed in ultrasonic testing?
It is displayed on a CRT, LCD, computer data program, or video/camera medium.
What types of display patterns are used in ultrasonic testing?
A-scan, B-scan, and C-scan.
What are the two basic methods used in ultrasonic inspection?
Immersion test and contact testing.
What are the three basic ultrasonic inspection methods?
Pulse echo, through transmission, and resonance.
What does radiographic inspection use to identify defects?
X-ray and gamma-ray radiation.
What is produced when radiation passes through the part in radiographic inspection?
An invisible, or latent image in the film, which becomes a radiograph when processed.
What are the three major steps in the X-ray process?
Exposure to radiation, processing of the film, and interpretation of the radiograph.
What factors must be considered for radiographic exposure?
Material thickness and density, shape and size of the object, type of defect, characteristics of the X-ray machine, exposure distances, angles, film characteristics, and type of intensifying screen.
What are the radiation dangers associated with X-ray units?
Radiation is destructive to living tissue and can cause blood disorders, leukaemia, cancers, skin damage, and hair loss.
What is the Magnetic Particle Inspection (MPI) method used for?
Detection of surface and near-surface flaws in magnetic materials, primarily for crack detection.
How does the MPI method indicate a crack?
By displaying leakage flux around a flaw with fine iron particles that accumulate at the regions of flux leakage.
What materials can the MPI method be applied to?
All metals that can be strongly magnetised, such as ferritic steels and irons.
What methods can produce magnetisation for MPI?
Applying a permanent magnet, passing a large current, using a current-carrying coil, or induced current methods.
What types of particles are used in MPI?
Iron particles, either dry or suspended in a liquid, and fluorescent particles requiring UV-A illumination.
How can indications of cracks in MPI be preserved?
By photography or using peel-off transparent adhesive film.
What do aircraft designers design besides components and systems?
They also design the assembly and reassembly processes.
What do manuals for aircraft maintenance contain?
They contain the approved methods of disassembly and reassembly.
Why is it important to follow the instructions in maintenance manuals?
Failure to follow instructions can cause damage to the aircraft.
What should be done if a procedure is not in the manual?
It is necessary to contact the manufacturer for guidance.
Where is the preferred location for disassembly of aircraft?
The controlled environment of the hangar.
What must be posted around an aircraft under maintenance?
Safety placards to warn others.
What must be placed on controls and switches during repairs?
“Do Not Operate” safety tags.
What should be ensured before starting any maintenance task?
All correct tooling, parts, servicing fluids, and support equipment must be available.
What is standard practice during major or minor maintenance checks?
To remove and replace malfunctioning components.
What should be done with parts removed during major maintenance checks?
They must be labelled and stored safely.
What must be done with unserviceable components removed?
They must also be labelled for identification.
What type of labels do maintenance organisations use?
Pre-printed labels that identify the aircraft registration, part number, serial number, location, and reason for removal.
What is recommended for small items like bolts and screws during disassembly?
The use of small “tie on bags” with identification labels.
Where are major replacements typically completed?
At a large approved maintenance base (hangar).
What is required for the maintenance of engines, propellers, landing gears, and wheels?
Some form of maintenance, either a simple condition check or a full overhaul.
What does the Aircraft Maintenance Manual (AMM) provide?
Detailed instructions on dismantling and reassembly of components.
What types of components are included in minor maintenance?
Hundreds of small components, including hydraulic and pneumatic components.
What is necessary for operators with a small fleet needing repairs?
They can send components to an approved third-party maintenance organisation.
What skills are required for disassembly and reassembly procedures?
A wide range of skills to ensure correct removal, dismantling, re-assembly, and re-installation.
What do maintenance manual chapters 20 and 70 include?
Standard practices that must be used during overhaul.
What must be followed regarding torque values on aircraft fasteners?
The manufacturer’s torque value must always be followed.
What is a jig used for in assembly?
To ensure high dimensional accuracy during the manufacture, repair, or rigging of a component.
What items are usually discarded after removal?
Filters, sealing rings, fuels, and oils must be disposed of in appropriate biohazard waste bins.
What should be done if a seized fastener is encountered?
Use penetrating oil or apply heat or cold to assist in removal.
What must be followed during assembly of aircraft parts?
The manufacturer’s instructions and any specified testing procedures.
What materials are primarily used for solid rivets?
Aluminium solid rivets are mainly used with high strength aluminium alloy components.
What are the two groups of special fasteners?
Shear and tension applications.
What are the components of a blind fastener?
A hollow body with a manufactured head and a pin or stem.
What is the first step in selecting a rivet?
Accurately measure the diameter of the hole.
What should be done if the rivet dimensions are not known?
Increase the diameter of the hole to the next standard size if necessary.
What is the purpose of a fastener dipping gauge?
To ensure the rivet is shortened or cut to the required length if necessary.
What should be inspected after rivets are installed?
Ensure the joint is tight and that the rivets are fully seated and correctly formed.
What can indicate that rivets have not been correctly heat treated?
A large number of cracks found in installed rivets.
What should be done when removing a rivet?
Work on the manufactured head to avoid damaging the rivet hole.
What should be done when removing a rivet?
Remove it carefully to retain the rivet hole’s original size and shape.
What happens if a rivet is not removed properly?
The strength of the joint can be weakened, and the replacement of rivets is made more difficult.
Where should you work when removing a rivet?
Work on the manufactured head, as it is more symmetrical about the shank.
What tools can be used to remove rivets?
Use hand tools, a power drill, or a combination of both.
What should be done to support thin metal or unsupported structures during rivet removal?
Support the sheet with a back-up block while driving out the shank.
What should you do if the rivet shank is unusually tight?
Drill the rivet about two-thirds through the thickness of the material and then drive the rest of it out with a drift punch.
What safety precautions should be taken when removing rivets?
Wear eye protection and any other Personal Protection Equipment (PPE).
What should you check for before drilling a rivet?
Check whether there is anything behind the rivet (wire loom, pipes etc).
What should you do before drilling a rivet head that is covered in sealant or paint?
File it slightly to produce a flat.
How should you drill a rivet head?
Drill into the exact centre of the rivet head to the approximate depth of the head.
What should be used to support the structure when removing a rivet?
Use a back-up block, preferably wood or a dedicated backup block.
What should you do after removing rivets?
Inspect the hole for any signs of damage.
What is the procedure for removing countersunk rivets?
Drill into the exact centre of the rivet head to the approximate depth of the head and remove the head by breaking it off.
What should you do if the rivet hole becomes enlarged or damaged?
Drill or ream the hole for the next larger size rivet.
What is the maximum size for replacing certain rivets with 2117 rivets?
It is acceptable to replace 2017 rivets of 3⁄16 in (4.7 mm) diameter or less and 2024 rivets of 5⁄32 in (4 mm) diameter or less with 2117 rivets for general repairs.
What are the two standard forms of blind rivets?
Friction Lock and Mechanical Lock.
What is a characteristic of friction lock rivets?
They lose considerable strength if their centre stem falls out due to damage or vibration.
What is a mechanical lock rivet designed to do?
Prevent the centre stem of a rivet from falling out due to vibration.
What is a disadvantage of a mechanical lock rivet?
If a rivet is too short for an application, the lock ring can set prematurely, resulting in a malformed shank header.
What is the installation process for Hi-Lok fasteners?
The fastener hole must be drilled and reamed to an interference fit, then the fastener is tapped into the hole.
What should be avoided when removing Hi-Lok fasteners?
Do not use a chisel and hammer as this can cause damage to the hole.
What is sealing in aircraft manufacturing?
Sealing is a vital process used to contain fuel, maintain cabin pressure, reduce fire hazards, exclude moisture, prevent corrosion, and fill gaps on the aircraft exterior.
Why is fuel tank sealing critical?
Fuel tank sealing is critical because fuel leakage is a safety item and can result in grounding the aircraft until the problem is corrected.
What are the four levels of sealing?
The four levels of sealing are Absolute, Extensive, Intermediate, and Limited.
What is the definition of sealing?
Sealing is a process that confines liquids and gases within a given area or prevents them from entering areas from which they must be excluded.
How is sealing accomplished?
Sealing is accomplished by closing all structural passages that fluids can penetrate.
What are sealants used for in fuel areas?
In integral fuel tanks, seals must contain fuel for the life of the aircraft under various conditions of temperature, pressure, and structural loading.
What is the purpose of seals in pressurized areas?
Seals maintain pressure at a predetermined minimum level under all flight conditions.
What do seals protect against in corrosion areas?
Seals protect the structure by preventing entry of corrosive fluids.
What are the categories of sealing compounds?
Sealing compounds are divided into two categories: silicone and non-silicone.
What is the application time for sealants?
Application time is the time in hours after thawing during which the sealant can be readily extruded from the sealant gun and applied to the structure.
What is squeeze-out life?
Squeeze-out life is the time in hours after thawing during which a faying surface sealant can be squeezed out of a joint when fasteners are installed.
What is tack-free time?
Tack-free time is the time in hours after thawing that is required for the sealant to cure sufficiently so that it will not transfer to the finger or to a plastic film.
What is cure time?
Cure time is the time in hours after thawing that is required for the sealant to cure firmly enough to be handled without damage or deformation.
What are the environmental considerations for sealants?
Sealants must maintain adhesion and flexibility under various environmental and stress conditions, including differential pressure and operating temperature ranges.
What precautions should be taken with silicones?
Uncured silicones must be protected from contact with CO2 sources to prevent bubbling or foaming.
What is the importance of cleaning before sealing?
Cleaning is crucial as sealant will not adhere to contaminated surfaces.
What is the cleaning process before sealing?
Preliminary cleaning involves removing loose materials, followed by final cleaning with solvent-dampened wiping materials.
What is machine mixing of sealants?
Machine mixing is done using specialized equipment to ensure reliable and consistent mixing of two-part sealants.
What is the procedure for hand mixing sealants?
To hand-mix sealant kits, verify the correct material and mix thoroughly to ensure uniform color.
How should sealant be thawed?
Sealant should be thawed in warm water or at room temperature for approximately 30 minutes.
Ensure that sealant is completely thawed, as cold sealant will not adhere to the structure.
What should you do if sealant is thawed?
Properly thawed sealant will flow easily from the gun and will readily wet the surface.
Can thawed sealant be refrozen?
Never refreeze thawed sealant.
When is hand mixing of sealant necessary?
Hand mixing may occasionally be necessary for special jobs.
What should you check before hand mixing sealant kits?
Check the label to verify that you have the correct material and that the expiration date has not been exceeded.
How do you mix the accelerator for sealant?
Stir the accelerator thoroughly until all solids are dispersed and a smooth, uniform material is obtained.
What is the process for mixing sealant in a SemKit® cartridge?
Pull back the dasher rod, insert the ramrod, break the piston loose, and inject about 1/3 of the contents into the cartridge. Repeat until all contents are emptied. Hand mix for 50 strokes.
A stroke is one complete in-and-out cycle.
What materials should sealant removal tools be made of?
Sealant removal or cutting tools should be made of hardwood or metal no harder than 2024-T3 aluminium.
What is the purpose of a sealant gun?
A sealant gun is used for the initial application of sealants by extruding sealant from a cartridge when the trigger is depressed.
What types of nozzles are available for sealant application?
Nozzles are available in assorted sizes and shapes for various sealing requirements and can be cut for convenience.
What are the recommended rollers for spreading sealants?
Rubber rollers of approximately 50 Shore ‘A’ durometer hardness are recommended for spreading sealants.
What is a fillet seal?
Fillet seals are applied at the edges of structural joints and consist of beads of sealant that must adhere firmly to both sides of the seam.
What is the purpose of injection seals?
Injection seals are applied to fill channels and holes that occur as a result of structural design.
What are faying surface seals used for?
Faying surface seals prevent corrosion of aircraft structure and facilitate leak tracing in fuel tanks.
What is the purpose of an aerodynamic smoother?
An aerodynamic smoother fills skin gaps and faired surface discontinuities to provide a smooth surface and exclude water.
What is the seal plane?
The seal plane is the structural boundary on which the continuity of seal is established.
What is the basic method for sealing in integral fuel tanks?
Fillet sealing is the basic method used for fuel retention within the integral tank.
What are the requirements for sealing in integral fuel tanks?
Requirements are specified by manufacturers and/or by instructions given in the AMM chapter 28.
What is the process sequence for sealing the integral fuel tank?
- Apply a brush coat/precoat. 2. Apply a small first fillet. 3. Apply a full-size final fillet.
What is the function of metal seal caps in fuel tank fastener sealing?
Metal seal caps are used to prevent leakage by fitting over the protruding end of the fastener.
What are maintenance documents/manuals used for?
They assist the engineer with all maintenance during scheduled and unscheduled maintenance.
Examples of scheduled maintenance work?
Aircraft turn around, Daily checks, Planned checks.
Documents that help with scheduled maintenance?
Maintenance Planning Data (MPD) Document, Aircraft Maintenance Manual (AMM).
Examples of unscheduled maintenance work?
Flight faults, Ground faults, Service problems, Structural damage.
Documents that help with unscheduled maintenance?
Fault Reporting Manual (FRM), Maintenance Tips, Fault Isolation Manual (FIM), Structural Repair Manual (SRM), Dispatch Deviations Guide (DDG), Aircraft Maintenance Manual (AMM).
What do the maintenance documents/manuals guide the engineer through?
They guide the aircraft engineer through a logical fault-finding diagnosis to ascertain the defect and the rectification action to follow.
How are the manuals arranged?
They are arranged by the ATA chapter with specification codes relating to troubleshooting procedures and diagrams.
What are the recommended troubleshooting steps?
Identify the defect, Conduct a visual inspection, Conduct an operational check, Classify the defect, Locate and isolate the defect, Rectify the defect, Perform a final operational check.
What is essential when identifying a defect?
All defects must be transferred to a written record; relying on word of mouth is not acceptable.
How is a report of a defect generated?
By an aircraft technical logbook entry from an in-service defect, a routine maintenance procedure, or an airworthiness directive/service bulletin.
What should be done before starting the troubleshooting process?
Gain additional information by discussing the defect with the person who identified it and check previous technical entries in the logbook.
What should be included in a visual inspection?
Evidence of improper installation, material condition, leaks, looseness, and security.
What is required during an operational check?
Position the aircraft suitably and apply relevant power sources to replicate the defect.
What are the four basic categories of system operational malfunctions?
Mechanical, Hydraulic, Pneumatic, Electrical.
What can affect the operation of hydraulic systems?
External and internal leakages, total or partial restrictions, improper lubrication.
What are common electrical malfunctions?
Power failure, wiring fault, component failure.
What should be done if defects cannot be resolved by visual examination?
Use onboard maintenance systems or rely on practical experience and theoretical knowledge.
How are malfunctions usually rectified?
By component replacement, rigging adjustments, or bleeding the associated system.
What is required after completing system maintenance?
Perform an independent inspection and functional testing certified by another qualified engineer.
What must be checked after functional testing?
All associated paperwork must be checked for completion, including recording new parts installed.
