Maintenance Practices
What you must know
Candidates must understand safety practices, aircraft handling and storage, ramp and hangar procedures, torque and tensioning, inspection techniques (visual, NDT methods such as dye penetrant, magnetic particle, eddy current, ultrasonic, radiography), and documentation. You should know the purpose and content of maintenance manuals, service bulletins, airworthiness directives, and the meaning of scheduled versus unscheduled maintenance. Tool control, foreign object debris (FOD) prevention, and lock-out/tag-out are core safety topics.
Traps to watch
- NDT method selection: magnetic particle only works on ferromagnetic materials; dye penetrant detects surface-breaking defects only; ultrasonic and radiography find internal defects.
- Torque: apply to the specified value with a calibrated wrench, account for lubrication (wet versus dry torque differ), and use the correct sequence for multi-bolt joints.
- FOD: a dropped tool or fastener can cause catastrophic damage; tool control and inspection after work are mandatory.
- Documentation: never sign for work not performed; certification and release-to-service are legal acts.
- Safety: depressurise, isolate electrical supplies, and fit locks/pins before working on moving surfaces.
Worked example
A crack is suspected just below the surface of an aluminium wing spar. Dye penetrant is unsuitable because it only reveals surface-breaking defects, and magnetic particle is unsuitable because aluminium is non-ferromagnetic. Ultrasonic inspection is the appropriate method for internal defects in this material.
Rule of thumb
Match the NDT method to both the material (ferromagnetic or not) and the defect location (surface versus internal).