Module 7.1-7.2 Safety precautions and workshop practices
1,047 words · checked 2026-10-03 · Free
Module 7 (Maintenance practices) is the biggest basic paper: under EASA 76 questions for A, 80 for B1 and B3, 60 for B2/B2L, plus 2 essays (20 minutes each). Safety, workshop practices and tools are level 3 for every category - expect detailed, practical questions and essay topics.
Knowledge levels
| Sub-module | A | B1 / B3 | B2 / B2L |
|---|---|---|---|
| 7.1 Safety precautions - aircraft and workshop | 3 | 3 | 3 |
| 7.2 Workshop practices | 3 | 3 | 3 |
7.1 Safety precautions
Electricity
- Isolate circuits before work: open and collar/tag circuit breakers, remove fuses, disconnect the battery and ground power as required; follow lock-out/tag-out.
- Remember capacitors can hold charge; discharge them through a suitable resistor.
- Use insulated tools; remove rings and watches; never work alone on live high-voltage equipment.
- Electric shock: switch off the supply before touching the casualty (or move them with a dry non-conductive object), then first aid/CPR and call for help.
- Severity of shock depends on current through the body, its path and duration; as little as tens of milliamps across the chest can be fatal.
Gases - especially oxygen
- Oxygen is not flammable itself but makes other materials burn violently. Oil or grease in contact with high-pressure oxygen can ignite spontaneously. Keep oxygen equipment, tools and hands free of oil/grease; use only approved oxygen-compatible lubricants and tapes.
- No smoking or open flames within the specified distance during oxygen servicing; ground the aircraft; open valves slowly (rapid opening causes adiabatic heating).
- Oxygen cylinders: secure them, protect valves, keep away from heat. Aviator's breathing oxygen is dry (low moisture) to prevent freezing in valves.
- Other gases: nitrogen (asphyxiation risk in enclosed spaces), CO₂ (heavier than air, accumulates in low areas), inert gas cylinders handled with regulators and secured.
Oils and chemicals
- Hydraulic fluids (especially phosphate-ester, e.g. Skydrol) irritate eyes and skin and damage paint; wear goggles and gloves.
- Fuels, solvents, paint strippers, sealants and composite resins: read the safety data sheet (SDS), use personal protective equipment (PPE), ventilation and approved containers. Dispose of waste as hazardous waste.
- Battery electrolyte: acid (lead-acid) or alkali (NiCd) - wear face shield and gloves; keep neutralising agents ready.
Fuel tank safety and entry
- Fuel tanks are confined spaces with flammable and toxic vapours and low oxygen.
- Procedure (summary): defuel and drain; vent and purge the tank with fresh air; check the atmosphere with gas detectors (oxygen level and flammability, e.g. % LEL); obtain a permit/entry authorisation; remove sources of ignition (use approved intrinsically safe lights and tools, anti-static clothing, no electronic devices); ground the aircraft; a standby person (attendant) stays outside in constant contact; keep breathing apparatus and rescue equipment ready; continue ventilation and monitoring during the work.
- Fuel tank safety (FTS) and critical design configuration control limitations (CDCCL) - do not alter wiring, bonding or components inside fuel tanks without approved data.
Ballistic recovery systems
- Some light aircraft carry a ballistic parachute fired by a rocket. The rocket can be activated accidentally and kill or injure people in its path.
- Before working on the aircraft: identify warning placards, insert the safety pin in the activation handle, keep clear of the rocket exit area, follow the manufacturer's procedures for disarming and for handling expired rocket motors.
Fire and fire extinguishing agents
| Fire class (EU) | Fuel | Extinguishant |
|---|---|---|
| A | solid combustibles (wood, paper, fabric) | water, foam, dry powder |
| B | flammable liquids (fuel, oil, hydraulic fluid) | foam, CO₂, dry powder, halon/clean agent |
| C | flammable gases | dry powder (and shut off the gas supply) |
| D | flammable metals (magnesium, titanium) | special dry powder (class D), dry sand |
| Electrical | live equipment (not a separate EU class) | CO₂, dry powder, halon/clean agent - never water |
| F | cooking oils | wet chemical |
US classification uses C for electrical fires and has no class F.
- CO₂: no residue, good for electrical fires; cold discharge - do not hold the horn; asphyxiation risk in confined spaces.
- Dry powder: effective, but leaves corrosive residue - avoid on engines and avionics if possible.
- Halon (1211, 1301) and replacements: very effective, minimal residue; ozone-depleting (being phased out).
- Water: class A only; never on fuel, electrical or metal fires.
- Remedial actions: raise the alarm, stop the fuel or power source, use the correct extinguisher (aim at the base of the fire), evacuate, give first aid. Engine fire on start: continue cranking (turbine) to blow out the fire, shut off fuel.
Key fact: Never use water on electrical, fuel or magnesium fires. Keep oil and grease away from oxygen.
7.2 Workshop practices
Care and control of tools
- Every tool must be accounted for before and after a task: shadow boards, tool tags/tokens, tool checks at shift end - prevents FOD and tools left in aircraft (which can jam controls).
- Keep tools clean, serviceable and stored correctly; damaged tools are withdrawn.
- Personal tools must meet the organisation's standards and be listed.
Workshop materials
- Use only approved consumables (sealants, adhesives, lubricants, solvents); check shelf life and batch traceability, storage conditions (temperature, humidity), and segregate unserviceable or quarantine items.
- Rags and wipes contaminated with flammable liquids go in closed metal bins.
Dimensions, allowances and tolerances
- Nominal size: the basic dimension. Tolerance: the permitted variation (e.g. 25.00 mm ± 0.05 mm → limits 24.95-25.05 mm).
- Allowance: intentional difference between mating parts (clearance or interference).
- Limits: maximum and minimum permitted sizes.
Workmanship standards
Work must meet the manufacturer's data, approved standard practices (e.g. EASA-accepted standard practices, AC 43.13 equivalents where acceptable), cleanliness and correct torque/locking. Independent inspection is required for critical tasks (e.g. flight controls).
Calibration
- Measuring and test equipment (torque wrenches, micrometers, gauges, multimeters, pressure gauges, crimp tools) must be calibrated at defined intervals against standards traceable to national/international standards.
- Each item carries a calibration label (date, next due); out-of-date or damaged equipment must not be used and is quarantined.
- If equipment is found out of tolerance, work done with it since the last good calibration must be assessed.
Exam tips
- For essays on safety topics, list hazards, precautions and emergency actions in a logical order.
- Fuel tank entry: purge, test atmosphere, permit, attendant, ignition control, rescue plan.
- Calibration must be traceable to national standards.