Maintenance Practices
Core concepts
Safety first: fire types and extinguishing agents, safe use of fluids and gases, and the precautions around flight controls and systems before work. Workshop practice covers tools, measuring instruments, calibration, tolerances, fits and clearances, and the reading of drawings and diagrams. You must know the sequence for disassembly, inspection, repair and reassembly, and the control of parts, tagging and traceability. NDT methods - visual, dye penetrant, magnetic particle, eddy current, ultrasonic and radiography - with their typical applications and limitations. Then: riveting and sheet-metal repair, soldering, brazing and welding, bonding and grounding, corrosion removal and treatment, control cable rigging and tension, control surface balancing, jacking, and aircraft storage and preservation.
Traps in questions
- Lockwire twist direction must pull the fastener towards tightness; the pigtail should not be able to loosen it.
- Torque values differ for dry and lubricated threads; always use the stated figure.
- Elastic versus plastic deformation - items stressed beyond yield must not be returned to service.
- Balancing after painting or repair - control surfaces must be rechecked.
- Magnetic particle inspection only works on ferromagnetic materials - a very common distractor.
Worked example
A fastener requires 20 N·m and you use a wrench 0.4 m long. Force = torque ÷ length = 20 ÷ 0.4 = 50 N applied at right angles. If the wrench is used at 30° to the perpendicular, the effective lever arm is reduced, so the applied force must increase to about 58 N to reach the same torque.
Rule of thumb
Torque = force × perpendicular lever arm. Keep the wrench perpendicular and recheck calibration status before use.