EASA Module 7 cheat sheet

FOD prevention: account for every tool and loose item before and after a task; stray objects can jam flight controls or be ingested by engines.

Compressed gas cylinders are stored upright, secured, with valve caps fitted; oxygen is kept at least 6 m from flammable gas or separated by a fire-resistant wall.

Before fuelling or defuelling, bond the aircraft to earth and the fuel source to the aircraft; no ignition sources or transmitting HF radios within the fuelling zone.

Hydraulic fluids such as Skydrol are skin and eye irritants; use nitrile gloves and eye protection, and flush spills with water as stated on the safety data sheet.

Fire classes: A = solids, B = flammable liquids, C = gases, D = metals; select an extinguisher rated for the class - water on a metal fire is dangerous.

Lock out and tag out electrical, hydraulic and pneumatic systems before maintenance; verify zero energy and fit pins or covers to actuators.

Jacking: confirm weight and CG are within jacking limits, use the specified jack points, fit safety locks, and keep personnel off the aircraft unless the procedure requires it.

Hearing protection is required where noise exceeds 85 dB(A) over an 8-hour exposure; use additional protection above 105 dB(A).

Ladder use: 4:1 slope, extend about 1 m above the landing, secure top and bottom, and maintain three points of contact.

Torque wrenches are calibrated at defined intervals (commonly 12 months) and after any overload or drop; the calibration record is retained.

Cap or plug all open lines, ports and fittings immediately after disconnection to prevent contamination and FOD ingress.

Lockwire is fitted so tension pulls the fastener in the tightening direction, with 6–8 twists per inch and a 3–6 mm pigtail.

Cotter pins: use the correct diameter, fit a plain washer where specified, and spread the legs 90°–120° with one leg bent down and one up.

Thread repair inserts (e.g. Helicoil) restore damaged threads; the hole is drilled and tapped oversize and the insert is locked by tang or key.

Corrosion protection: abrade to bare metal, apply conversion coating, prime within the specified time, then seal joints with approved sealant.

Use only approved cleaning agents; chlorinated solvents are prohibited on titanium and on stressed stainless steel because of stress-corrosion cracking.

Shadow boards and tool control reduce FOD; tools are marked and inventoried, especially for fuel tank and engine work.

Micrometer reading = barrel main scale + (thimble scale × 0.01 mm); check the zero setting before use.

Vernier caliper resolution is typically 0.02 mm; read the main scale, then the vernier graduation that aligns with a main-scale line.

Torque = force × perpendicular lever arm; a torque wrench measures applied torque, not bolt preload, which depends on friction and lubrication.

Calibrated measuring tools carry an ID and a calibration label traceable to a national standard; out-of-date tools are quarantined.

Borescopes allow internal inspection of engines and structures without disassembly; findings are recorded by location and orientation.

Use a torque wrench within its stated range (typically 20–100 % of full scale); a click-type wrench is not used to loosen fasteners.

Screwdrivers must match the slot or recess size; an ill-fitting blade damages the fastener and surrounding structure.

Multimeters: select function and range before connecting; voltage is measured in parallel and current in series.

Third-angle projection places each view on the side of the object from which it is seen; first-angle places it on the opposite side.

The title block carries drawing number, part number, scale, revision, sheet number and approvals; always work to the latest revision.

Hidden features are shown by dashed lines; section views use hatching to show cut material.

A tolerance is the permitted variation from the nominal dimension, stated as limits, plus/minus values or a fits symbol.

ATA 100 chapters group aircraft systems (e.g. 27 flight controls, 32 landing gear) and are used for manuals and maintenance tasks.

The aircraft zone system locates components by major zone, sub-zone and station for maintenance and weight records.

A bill of materials lists part numbers, descriptions and quantities needed to assemble the item shown.

Drawing scales express the ratio of drawing size to actual size; dimensions are never scaled from the drawing - use the stated values.

Standards such as ISO, AN, MS and NAS define fastener and fitting dimensions; substitutions require approval.

Clearance fit: the largest permissible shaft is smaller than the smallest permissible hole, so a gap always exists.

Interference fit: the smallest permissible shaft is larger than the largest permissible hole, so the parts must be pressed or shrunk together.

Tolerance is the difference between upper and lower limits; allowance is the intentional minimum clearance or maximum interference between mating parts.

Hole-basis system uses H for the hole (lower deviation zero), with a–h for clearance, j–n for transition and p–zc for interference shafts.

A transition fit may give either a small clearance or a small interference depending on the actual sizes produced.

Surface roughness Ra is the arithmetic mean deviation of the profile; a lower Ra value means a smoother surface.

Thermal expansion: ΔL = L × α × ΔT; allow clearance for dissimilar materials at operating temperature.

Wear limits in the maintenance manual give the maximum permissible clearance before repair or replacement is required.

Wire size is specified in AWG; a smaller AWG number means a larger cross-section and higher current capacity.

Current rating is derated for bundles, high ambient temperature and altitude; use the ratings in the aircraft maintenance manual.

Minimum bend radius for a wire bundle is typically 10 times the bundle outer diameter; support at the intervals stated in the manual.

Route power and signal wires separately to avoid EMI; where separation cannot be maintained, cross at 90°.

Bonding resistance between primary structure and equipment is typically 2.5 mΩ or less; recheck after paint or structural repair.

Connectors: check pin and socket condition, keyway, contact retention and torque; never force a connector into engagement.

Insulation resistance is measured with a megohmmeter at the specified test voltage; a low reading indicates moisture, contamination or damage.

Splices are limited by the maintenance manual; they must be accessible and are not permitted in fuel tanks or fire zones without approval.

Rivet pitch is typically 3–4 diameters and edge distance at least 2 diameters, increased near joint ends and edges.

Deburr rivet holes and apply primer before riveting; a countersink must be flush with the skin within the specified tolerance.

AN/JIC flare fittings use a 37° flare; SAE 45° fittings are not interchangeable with 37° fittings and must not be mixed.

Hose installation: respect minimum bend radius, avoid twist by clocking the hose, and torque fittings with a backup wrench.

Control cable tension is set with a tensiometer and corrected to a reference temperature; turnbuckles are lockwired or fitted with locking clips.

Swaged cable terminals require a go/no-go gauge check and proof load; thimbles protect the cable eye.

Bearings: preload removes internal clearance; excessive preload causes overheating and early failure, so lubricate with the specified grease.

Springs are rated by rate (N/mm), free length and solid height; replace if cracked, permanently set, or shorter than the minimum length.

Soldering melts filler below 450 °C; brazing melts filler above 450 °C; welding melts the parent metal.

Cleanliness is critical: oxides and grease prevent wetting, so use the specified flux and remove residues after soldering.

Heat sinks protect nearby components during soldering; use the minimum heat and time consistent with a sound joint.

Aluminium alloys 2024 and 7075 are heat-treatable; welding them needs special processes and usually reduces strength in the heat-affected zone.

Welding symbols show joint type, weld size, length, spacing and finish on a reference line with an arrow to the joint.

Hydrogen embrittlement can affect high-strength steel that has been plated, pickled or welded; baking after processing reduces the risk.

Store electrodes and filler rods dry and as specified by the manufacturer; damp electrodes cause porosity.

Material certificates give chemical composition and mechanical properties; maintain traceability from receipt to installation.

Moment = weight × arm; CG = total moment ÷ total weight.

The datum is the fixed reference from which all arms are measured; arms forward of the datum are negative.

Weight shift: ΔCG = (weight moved × distance moved) ÷ total aircraft weight.

Empty weight includes unusable fuel and full oil; adding crew, payload and usable fuel gives the take-off weight.

Maximum take-off, landing and zero-fuel weights are limits that must never be exceeded.

Ballast may be fixed or removable; its location and attachment must be approved and recorded in the weight report.

Towing: use the approved tow bar and tow points, do not exceed turning limits, and keep a qualified person at the controls.

Storage: fit covers and control locks, use desiccant and preservative oil, and run or rotate engines at the specified intervals.

Tag every disconnected part and line with its part number and location; record serial numbers before removal.

NDT methods: dye penetrant (surface), magnetic particle (ferromagnetic surface and near-surface), eddy current, ultrasonic and radiography (internal).

Torque sequences are usually crisscross or spiral from the centre outward, applied in stages where specified.

Use the approved lubricant on threads and seats; wet and dry torque values differ and are not interchangeable.

Rigging restores control surface travel and cable tension to manual values; check clearances through the full range of movement.

Corrosion removal must not exceed allowable blend-out limits; blend out smoothly and restore protective coatings.

After assembly, perform functional and leak tests and record the results in the maintenance record.

Return to service requires a certified release by appropriately approved personnel with the correct documentation.