Supplied B1 Module 07A textbook: PDF pages 423–492.
Preparation and visual inspection
Review the maintenance history and use the applicable task and inspection checklist. Make the area safe, establish access and observe leakage or deposits before cleaning removes evidence. Adequate lighting, magnification, mirrors and access are necessary; looking at an inaccessible region from a distance is not a detailed inspection. Check condition, security, wear, deformation and cracking against the specified limits. Record location, size and orientation of defects so a subsequent assessment can be reproduced. Restore inspection access correctly after the work.
Why note leakage before cleaning? Cleaning may remove evidence needed for diagnosis.
Defects and corrosion mechanisms
Cracks, dents, scratches, fretting, wear and corrosion have different significance according to location and load. Uniform corrosion removes surface material; pitting concentrates attack; galvanic corrosion involves dissimilar materials in an electrolyte. Crevice and intergranular attack can be difficult to see fully. Exfoliation is associated with corrosion product growth separating layers in susceptible material. Do not judge depth only by the amount of visible deposit. Identify material and corrosion type before selecting removal and inspection methods.
What conditions support galvanic corrosion? Dissimilar conductive materials connected in an electrolyte.
Removal, assessment and reprotection
Remove corrosion only by the approved method and assess remaining material thickness and damage dimensions. Cleaning products, abrasives and chemical treatments must be compatible with the material and nearby equipment. Removing corrosion may expose unacceptable loss of section; repainting does not restore that lost strength. Apply the required treatment, primer, sealant and protective finish after assessment. Control contamination and drainage so the initiating conditions do not remain. Document the repair and any follow-up inspection required.
What must be checked after corrosion removal? Remaining material and damage against approved limits.
Structural repair data
The structural repair manual defines applicable limits and standard repairs for identified structure and damage. Verify aircraft effectivity, location, material and dimensions. A repair outside the manual's scope needs approved design data through the proper process. Reinforcement changes local stiffness and load paths, so a larger patch is not automatically safer. Check fasteners, edge distances, sealing and finish specified by the repair. Maintain records that identify the repair data and final condition; photographs alone do not replace the required record.
What is required when damage is outside published repair limits? Approved repair or disposition data.
Fatigue and ageing-aircraft programmes
Fatigue is damage associated with repeated loading, often beginning at stress concentrations. A small crack may grow under many normal cycles before rapid failure. Inspections and life limits work together; inspection cannot automatically extend a safe-life limit. Ageing-aircraft programmes may address structural fatigue, corrosion and widespread fatigue damage. Follow the applicable intervals, thresholds and inspection methods. Record findings consistently because trends may reveal recurring damage or ineffective protection. Calendar age, cycles and hours represent different exposure measures.
Why can repeated normal loads matter structurally? They can initiate and grow fatigue damage.
Penetrant and magnetic-particle inspection
Penetrant inspection detects surface-breaking discontinuities in suitable non-porous materials. Cleaning, penetrant dwell, excess removal and developer application are controlled steps. Magnetic-particle inspection detects surface and some near-surface discontinuities in ferromagnetic materials. Magnetisation direction affects sensitivity to crack orientation. Neither method is a universal inspection for all materials or depths. Evaluate indications under the specified criteria and apply post-cleaning or demagnetisation when required. Personnel qualification, equipment checks and process control are part of a valid result.
What material condition is necessary for magnetic-particle inspection? A suitable ferromagnetic material.
Eddy-current inspection
An alternating magnetic field induces eddy currents in a conductive part. Defects and changes in material or geometry alter the probe response. The method can detect suitable surface and near-surface conditions and may work through certain coatings under an approved technique. Conductivity, permeability, frequency and lift-off affect the signal. Use reference standards and the correct probe/setup, then interpret the indication rather than assuming every signal is a crack. Eddy current does not require a liquid penetrant but still requires controlled surface and probe conditions.
Which material property is fundamental to conventional eddy-current testing? Electrical conductivity.
Ultrasonic and radiographic inspection
Ultrasonic inspection uses sound propagation and reflections to assess internal features and defects. Coupling, orientation and calibration matter; a defect poorly aligned with the sound beam may be difficult to detect. Radiography uses penetrating radiation and records differences in attenuation. It needs radiation-safety controls and can reveal suitable internal defects, but sensitivity depends on orientation, material and geometry. No method finds every defect equally well. The approved inspection technique defines coverage, reference standards and acceptance.
Why must NDT method selection consider defect orientation? Sensitivity depends on the relationship between the defect and inspection energy.
Borescope and remote visual inspection
A borescope permits inspection through limited access using an optical or video system. Plan the inspection path, identify the exact part and document findings with orientation and location. Image scale and perspective can mislead, so use the specified measurement function or comparison method. Protect the probe and aircraft from contact damage and account for removable tips. An obscured region has not been inspected merely because nearby structure was visible. Use the equipment and acceptance guidance for the particular engine or component.
What is a key limitation of borescope images? Perspective and access can limit measurement and coverage.
Controlled disassembly and assembly
Isolate energy, drain or depressurise as required and mark relationships using an approved method. Keep matched parts together, protect openings and record orientation. Replace single-use items and use correct seals, lubricants, torque values and locking. Check dimensions, clearances and safety-critical steps before access is lost. Do not force an assembly to hide misalignment. Complete required independent checks, functional tests and restoration. A clean bench and orderly trays reduce errors but do not replace the task instructions.
Why retain matched parts together during disassembly? Their established relationship may be necessary for correct reassembly.
Troubleshooting logic
Start with a clear symptom, conditions and evidence. Verify the report and distinguish causes from consequences. Use fault-isolation data, test equipment and measurements to narrow possibilities. Change one factor at a time where practical, record results and avoid random replacement. Consider intermittent faults, environmental conditions, power and interfaces. After rectification, reproduce relevant conditions through the specified verification test and restore the aircraft. A successful reset alone is weaker evidence than a fault cause followed by a controlled satisfactory test.
Why is random component replacement inefficient? It may not identify the cause and can introduce new faults.
Apply the knowledge
Work through these examples before starting the quiz. Explain why the other choices would not meet the requirement.
A crack is fully subsurface in non-ferromagnetic material. Is penetrant inspection alone sufficient?
No; penetrant needs a surface-breaking path — Select an approved method sensitive to the actual defect and material.
An eddy-current indication changes when probe lift-off changes. What is appropriate?
Interpret it using calibration and the approved technique — Lift-off and material factors can affect the signal.
A repair manual excludes the damaged area from a standard repair. What is required?
Approved data appropriate to that location — Effectivity and location restrictions matter.
A component reaches its life limit but passes visual inspection. What is correct?
Apply the life limit; inspection does not automatically extend it — Life limits and inspections are distinct controls.
During reassembly a single-use locking item has been removed. What is appropriate?
Replace it as the approved task requires — Single-use requirements are part of the controlled assembly process.
Two components are replaced together and the symptom disappears. What remains uncertain?
Which change addressed the cause — Controlled diagnostic changes improve understanding of cause and effect.
A proposed structural patch is larger than the published repair. Does size alone prove acceptability?
No; stiffness and load transfer need approved assessment — Repair geometry affects the structural load path.
A repair calls for a specific material temper. What must be used?
The specified material or an approved equivalent — Material condition is part of the approved repair design.