Aircraft Maintenance: Workmanship and Standards

Workmanship in Aircraft Maintenance

• Workmanship refers to the skill level used in making a product or completing a job.
• Factors include worker's skill, product quality, labor, AME attitudes, duty of care (self, others, equipment), and adherence to standards.

Standards

• Standards are agreed-upon ways of doing things, formally recorded or informal procedures.
• Standards offer accurate measurements, lower production costs, improve product performance, uniformity, interoperability and functionality.
• Benefits include improved health, safety, environment, communications, competition, international trade, and quality of life.
• Private standards are for internal use by the developing orgainsation
• National standards (e.g., Australian Standards [AS]) are from a country's National Standards Body (NSB).
  • Most standards are enforced by laws and some can be voluntary.
• International standards are produced by the International Organisation for Standardisation ISO.

Tools

• Tools ease tasks, improve efficiency, and require correct usage and care.
• Proper tools and knowledge provide speed, accuracy, and safety and prevent injuries.
• Regular, preventative maintenance extends the life of vital and expensive tools.
• Use each tool for its intended purpose to avoid damage and prevent injury or death.
• Avoid scattering tools, especially on machinery or electrical equipment and stow tools neatly when not in use.
• Avoid using damaged toolsto prevent injuries or inaccurate measurements.
• Clean tools post-use, as oily, dirty tools are dangerous.
• Inventory tools post-use to prevent losses.
• Engineers' tool care reflects efficiency and is subject to observation.

Tool Control and FOD Prevention

• Tool control impacts safety.
• Misplaced tools can cause permanent damage and/or safety risks.
• Foreign Object Damage (FOD) costs the aerospace industry $4 billion annually, mainly from aircraft engine damage due to foreign objects.
• Tool Control Programs are enforced by maintenance organizations, that are guided by the Maintenance Organisation Exposition (MOE).
• The MOE ensures tooling management, distribution, and post-use return, including:
  • User records
  • Location of use
  • Checks for tool presence after maintenance
• Aviation Australia uses shadow boards and tool tags, relying on workforce honesty.
• Tool control programs aim to protect personnel and prevent aircraft damage, addressing:
  • Lost tools
  • Damaged hardware
  • Miscellaneous rubbish
• Tool control relies on user responsibility, with management providing support.
• Key elements include:
  • Area control
  • Tool identification
  • Addressing FOD critical zones

Area Control

• Work control zones use signs, floor markings, access limits, personnel limits, and item tracking.

Tool Identification

• Tool control areas use permanently identified tools via color-coding or engraving.

FOD Critical Zones

• Maintain awareness of working near flight controls, engine controls, and engine inlets to prevent hazards.
• Document all items in FOD critical areas, transport employee tools in contained cases and bags.
• Implement a Tool Control Program to track tools from use until returned.
• Tool control varies by workplace, but basics remain.

Toolboxes

• Custom foam inserts allow technicians to see that each tool is in place.
  • Missing Tool = color (yellow or red) is revealed in the space

Shadow Boards

• Shadow Boards indicated:
  • Where the tool belongs
  • Whether the tool is missing

Tool Marking

• Color-coding differentiates tools by work area, like using blue-coded tools in one area, and red in another.
• Tool marking identifies owners, often using Vibra Peen or laser etching.
• Mark tools with employee initials, which are more versatile than company specific numbers.
• Tool logs list employees and their tool markings for easy identification.
• Tool marking aids in returning found tools and compliance with reporting.
• Accomplish Tool inventories regularly, after each work tas,.
• Aircraft maintenance organizations frequently condcut these at the beginning and end of shifts.

Tool Control Program & Workshop Materials

• Missing tool reporting is an important process, so the maintenance culture must encourage employees to report all missing tools.
• It should be clear how often tools need to be inventoried, reported etc.
• An important part is designating the person who has the authority to release the aircraft if a tool cannot be located.
• Common workshop materials:
  • Greases
  • Oils
  • Solvents
  • Sealants
  • Contact cements
  • Paints
  • Paint strippers
• The Material Safety Data Sheet (MSDS) and a specification sheet need to be available.
• Flammable materials (solvents, paints, strippers, cements, greases, oils) need to be stored in an appropriate flammable storage facility.
• Materials that are highly toxic require compliance with MSDS, PPE usage, and ventilation.
• Aircraft sealants may need refrigeration and need expiry checks.
• Properly seal containers for reuse, and dispose of two-pack sealants per regulations.

Aircraft Drawings and Dimensions

• Reference edges are used for aircraft drawing dimensions.
• Dimension placement options:
  • Perpendicular to dimension lines
  • Parallel to drawing bottom (conventional).
• Fabricated sheet metal parts have size ranges for acceptability.
• The (″) symbol denotes inches in drawings.

Tolerance and Allowance

• Tolerance is the difference between a dimension's nominal size and its upper and lower limits.
  • Example: ±0.010 in, calculated as the upper limit minus the lower limit (e.g., 5.310 in. – 5.290 in. = 0.020 in.).
• Standard tolerance in aircraft drawings with common fractions is ±1/64 in.
• Allowance is the difference between nominal dimension and an upper or lower limit.
• Precise cylindrical parts, need a smaller size range than sheet metal repairs.

Clearance and Interference

• Clearance = A 'positive allowance'
• Interference = A 'negative allowance'

Tooling Inspection and Calibration

• Aircraft maintenance organisations must regularly inspect/calibrate tools.
• Tool labels must show:
  • Date of last test
  • Next due date
  • Authorised signature
• Maintain a register with calibration records and standards used.

Procedures for Calibration, Use & Storage

• Follow manufacturer instructions for inspections/calibrations.
• Accurate measurement requires proper tool usage.
• Ensure tool calibration before use with a calibration tag.
• Calibrate tools via approved individuals, with prescribed life limits.
• Ensure tools ‘zero' correctly before use, with the use of a precision black.
• Use of personal measuring tools is prohibited unless maintained by an approved organization.
• Torque wrenches need checks, calibration with a torque analyzer at 90°.
• Calibrate hydraulic pumps with water, oil, or gas.
• Recalibrate micrometers, by rotating the sleeve.
• Beware temperature extremes during calibration.
• Affix calibration labels/tags post-checks and check before use.