M7.2 Workshop Practices Rev 3 Jan 2025 PDF

AAE4109 Aircraft Maintenance Practices (HKAR-66 M6(B1) Part D and M7(B1) Part B) M7.2 Workshop Practices Jan 2025 2 M 7.2 Workshop Practices >Care of tools, control of tools, use of workshop materials; dimensions, allowances and tolerances, standards o...

AAE4109 Aircraft Maintenance Practices (HKAR-66 M6(B1) Part D and M7(B1) Part B) M7.2 Workshop Practices Jan 2025 2 M 7.2 Workshop Practices >Care of tools, control of tools, use of workshop materials; dimensions, allowances and tolerances, standards of workmanship; calibration of tools and equipment, calibration standards. Jan 2025 3  Introduction > Despite the enormous advances in the mechanisation and computerisation of the engineering industry in general, there remains the requirement for a high degree of hand skills on the part of technicians who are engaged in the day-to- day maintenance of aircraft and their associated components. > While the majority of aerospace components are manufactured under stringent standards, in factory (and laboratory) conditions, it is necessary to remove many items of equipment for cleaning, inspection, overhaul and, if needed, repair before they are, subsequently, re-installed in their appointed locations. > These actions may entail the use of many specialist tools and materials, which are used while following written procedures, while it is quite possible that some, comparatively simple, repairs may call upon such basic hand skills as the cutting, filing, drilling, riveting and painting of metals or other materials. > No matter whether there are specialist or basic skills required, all will demand a certain quality of the work practices (and of the work-force) involved. Jan 2025 4 Jan 2025 5  Machine Work and Bench Work > Major activities in workshop practices include machine and bench works. > Machine work is the process of shaping materials from workpiece with the use of machine tools. Machine tools include lathes, milling machines, drilling machines, grinders, etc > Bench work relates to works performed by hands with hand tools rather than machine tools. Operations that can be placed on a bench or in a bench vise to be worked on. Examples of bench work include chipping, sawing, drilling, reaming, and tapping etc. Jan 2025 6 Jan 2025 7  Lathe > A lathe is a machine tool used to shape wooden or metallic products. It furnishes a wooden or metal piece by rotating it about an axis while a stationary cutting tool keeps removing unwanted material from the workpiece to form the desired shape. > These machines are used for various product fabricating operations such as sanding, drilling, cutting, deformation, and turning. They are employed in the metalworking, thermal spraying, glass processing, and wood tuning of various artistic products. > Being one of the most ancient machinery tools able to perform a wide range of fabrication tasks, it is also known as the “Mother of All Machine Tools.” Jan 2025 8 Jan 2025 9 The Working Process of a Lathe Machine > Step 1: The piece to be worked upon is placed between the headstock and tailstock. It is buckled with the chuck that helps put the workpiece into a stable position by gripping it from the outside. > Step 2: The workpiece is rotated with the help of a spindle which is connected to a motor. It makes the workpiece rotate at its axis. > Step 3: A cutting tool is then placed in the tool holder that holds the cutter at an appropriate distance from the rotating workpiece so its blades can cut the workpiece as desired. Different types of cutting tools are used for different desired shapes and materials. Jan 2025 10 Jan 2025 11  Milling Machine > Milling machines, whether manual or computer numerical control (CNC) machines, remove metal from workpieces, getting the desired shape and dimensions using a spinning tool called a milling cutter. Unlike a lathe machine, on which a workpiece spins and the cutting tool moves into it to create cylindrical shapes, the milling machine employs end mills, face mills, dovetail cutters, and various other milling cutters to machine flat and irregular surfaces, including those that are concave or convex. > Milling machines are not all that complicated in theory: A machine operator fastens a workpiece to the machine tool’s work table using a work holding device, such as a clamp or vice. The workpiece is moved through the X and Y-axis as the milling cutter removes the material and a skilled worker or CNC program directs it on a manual or CNC milling machine. Jan 2025 12 Jan 2025 13  Care of Tools > Tools can be divided into general tools and special tools. > General tools are those tools that are purchased by individuals and kept in their tool boxes. They will include such item as, screwdrivers, spanners, socket sets etc. They may also include test instruments such as multi- meters. > Special tools that are bought and kept by the company in the stores and these may be dedicated to an aircraft or engine type. They may include specialist equipment too large to keep in tool boxes and expensive equipment and test sets. They will usually include special to type adapters, tools, test sets etc. Jan 2025 14  Care of Tools > Tools not being used should be placed in a safe place to avoid damage or loss. Tools may break or lose accuracy if they are dropped on the floor. > Tools should be put tidy inside a tool box. > Precision tools should be properly cleaned, adjusted, and lubricated after use so that they will be ready for the next use. Also check for calibration date is applicable. > Tools with sharp tips and points can be easily damaged. Don’t carry them in your pocket as this may cause personal injury. > The electric cord of power tools should be kept in good condition to avoid electric shock. Jan 2025 15  Care of Tools > Cleaning – All tools benefit from being kept clean. It also means less chance of contamination of the equipment being worked on (contamination of fluid systems, air conditioning systems etc). > Most metal tools are kept in good condition by the application of a thin oil or an oil based solution (such as WD40), which is then wiped clean using a clean lint free cloth. > Files are cleaned using a steel or brass brush. > Test-sets are kept clean and free from liquids. Should they become contaminated then they are to be returned to the manufacturer for dismantling, cleaning, assembly and testing. Jan 2025 16  Care of Tools > Storage – Most tools are simply stored in a secure box. Socket sets, spanner sets etc are usually stored in the special box. This not only keeps them all in one location for easy to find, but also aids the process of checking all tools are present at end of shift. > Delicate tools and instruments will be supplied and kept in boxes (micrometers, verniers, watchmaker’s screwdrivers, slip gauges etc). > Some large/special tools will be stored in a secure room. These may be placed on shelving or hung on ‘shadow boards’. These boards have clips or other supports screwed to them onto which the tool is hung. > When the correct tool is clipped into the correct place on the board then it’s shadow cannot be seen. Jan 2025 17  Care of Tools Examples of tool storage boxes with shadow boards Jan 2025 18  Control of Tools > Tool Checks – It is most important that tools and any loose articles are not left on aircraft after completion of work. They are a serious hazard as they can jam controls, block system pipes etc. The term ‘loose articles’ applies to anything left on an aircraft after maintenance – this includes rags, split pins, locking wire, and tools. > It is most important that a loose article check is carried out after every task on the aircraft, engine, component, and as a double check a tool-check is also carried out. > Each person working on the aircraft should check his/her tool kit after each task and at the end of the working day, or before the next flight to ensure that all tools are accounted for. Jan 2025 19  Control of Tools > Any special tools used from the tool-store should be returned and the person in-charge of the store should do a tool check to see that there are no tools missing. > If, during these checks, a tool is found missing then the aircraft should not be allowed to fly until it has been found. The search will include the work areas of the aircraft, all tools boxes, the tool store, hangar/workshop area, rubbish bins, scrap bins etc. A check will also be made of the signing in and out book of the tool store to see if this record shows who has had what tool, and when. > It is always a good practice to carry out a loose article check of the work area on the aircraft after completion of the task – in some organisations it is a mandatory requirement which must be signed. Jan 2025 20  Use of Workshop Materials > There are wide variety of materials used in workshops, many of them require some form of control in their handling. This control can involve: i. Safety: relating to such topics as the toxicity, corrosiveness or other health risks associated with the use of certain materials. ii. Management: referring to the storage, use and correct handling of all materials whether they are solid, liquid, or, in some instances, gaseous. iii. Economy: involving such matters as to the using of the correct dosage or proportions when mixing compounds, using only as much material as required for a specific task and to the keeping in stock of only sufficient materials and thus avoiding ‘lifed’ items reaching their expiry dates before being used. Jan 2025 21  Use of Workshop Materials > For safety, management and economy issues, many workshop materials are issued in a controlled fashion. > Toxic materials may cause health risks which can be controlled by controlling the handling and storage of this type of substance. > Highly corrosive materials pose a similar issue where close control is required to prevent material damage. > Control of other materials may just be due to a desire to manage accurate inventory control so that quantities are known and available when needed. Jan 2025 22  Use of Workshop Materials > Abrasive papers, solder and brazing materials, wire wool, oil spill powder and so on, all require control of issue and use, though they may not, normally, require stringent safety precautions. > A huge range of liquids can be used in the workshop situation, some of which are harmless and some of which are extremely toxic. It is vital that the work- force is aware of the risks involved when dealing with any materials, and especially when working within enclosed areas. > Some materials are flammable and must, therefore, be stored outdoors or in specially designed (such as explosive proof) cabinets. > These include oils, greases, some adhesives, sealing and glazing compounds in addition to many paints, enamels and epoxy surface finishes. When stored, the materials and storage cabinets are kept out of direct sunlight in a workshop or hangar. Jan 2025 23  Use of Workshop Materials > When handling materials that give off fumes, it is necessary to have the area well ventilated and/or have the operator wearing a mask or some form of remote breathing apparatus. The finished work may also give off fumes for some time afterwards, so care must be taken to keep it ventilated if necessary. > All liquids must only be used for the purpose for which they are designed and never mixed together, unless the two materials are designed to be mixed, such as with two part epoxy adhesives and sealants. Jan 2025 24  Use of Workshop Materials > Many liquids used in workshops and in the hangar have a fixed 'life'. The expiration date is printed on the container and must be checked before use. Many materials are unsafe if used beyond their expiry date. > The disposal of liquids is a critical operation, it must only be carried out in accordance with company, local, national, and international regulations. > Chemical wastes must never be disposed of by pouring them into spare or unidentified containers and they must not be allowed to enter the ‘domestic’ drains systems. > Disposal of chemical waste is under the control of Waste Disposal Ordinance in Hong Kong. Jan 2025 25  Use of Workshop Materials > Another area of hazardous workshop materials is that of gases stored in high pressure containers such as nitrogen and oxygen. In general, follow operator shop and hangar safety practices when working with these gases. > All materials (and parts) are identified with the part number and the good receive number for traceability. Temporary protectives such as grease, paper, plastics coating or vacuum package should be left in position until the material is required for use. > General purpose hardware such as bolts and nuts are normally controlled as free-issue items. Such free-issue items shall be kept in a locked cabinet in each shop as applicable. Jan 2025 26  Use of Workshop Materials > Materials of an inflammable nature, such as thinners, paint etc. should be kept in a designated DG store which is approved for such storage of DG materials by Fire Services Department (FSD). > Material Safety Data Sheet (MSDS) is an important source of health and safety information. It is a document that contains information on the potential hazards (health, fire, reactivity and environmental) and how to work safely with the chemical product. Jan 2025 27  Use of Workshop Materials > A typical MSDS contain sections on the fire and explosive data, reactivity data, health hazard information, spill, leak and disposal procedure, special protection, and special precautions, etc. > All hazardous materials should have identifying labels adhered to them. As a general rule, these labels should never be removed. Jan 2025 28  Standards of Measurement and Calibration > In order to maintain a high accuracy of tools and equipment (e.g. measuring tools), they should be periodically calibrated against more accurate standards, and the deviations should be recorded for traceability and acceptance. > According to HKAR 145.40, the approved maintenance organisation shall ensure that all tools, equipment and particularly test equipment, are controlled and calibrated according to standards acceptable to the CAD at a frequency to ensure serviceability and accuracy. > The standards must have a higher accuracy then the test equipment, instrument being calibrated. Jan 2025 29  Standards of Measurement and Calibration > There are three-level hierarchy of measurement standards: > Primary Standards are at the top of the tree and are the master standards. Those units or instruments of highest quality and stability which are periodically calibrated by the National Institute of Standards and Technology (NIST) or by other contract calibration services which have direct traceability to NIST. > Secondary Standards are the next quality standard in the hierarchy. Those units or instruments with proven stability are calibrated from primary standards in a controlled environment. > Working Standards are in the third level of standard. They are periodically calibrated against a secondary standard. Working standards are used for the calibration of commercial and industrial measurement equipment. Jan 2025 30 Take Mass as example Jan 2025 31  Standards of Measurement and Calibration > Standards or Calibration Rooms – These have the specialist equipment and manuals to carry out the calibration and tests specified by the equipment manufacturer. > For some calibration works the environment is not of great importance – testing torque wrench equipment, testing multimeters for example. But for some other items the environment is critical. > Many ‘standards rooms’ have a controlled environment in that the temperature is kept strictly at 21°C and airborne particles (such as dust) are kept to a minimum. > Instruments that are temperature sensitive should be brought into the standards room 24 hours before the test to allow them to temperature stabilise. Jan 2025 32  Standards of Measurement and Calibration > Prior to calibration, the item is inspected for damage, contamination etc and any parts found unserviceable are changed. > Electrical Measuring Equipment – Multimeters, bonding testers etc. Measurement against standard known resisters, standard known voltages etc or against master instruments. > Torque Wrenches – These are tested on a standard test rig such as the Acratork test rig. (The test rigs are tested using a moment arm fitted horizontally to the square boss and accurate masses attached to the free end of the arm. The moment and hence the torque is calculated as mass times the distance from the mass attachment and the centre line of the boss (m x d = torque). Jan 2025 33  Standards of Measurement and Calibration > Pressure Gauges are calibrated against a master gauge or on rigs such as the Dead Weight Tester using known masses on a piston producing calculated pressures (pressure = force per unit area = F/A). > Dial Test Indicators can be checked using slip gauges and feeler gauges. The DTI is fixed to a rigid fixture on a surface table and slip gauges/feeler gauges are used to check the amount of pointer movement. Torque wrench calibration Jan 2025 34 Jan 2025 35  Calibration Certificates and Records > A calibration laboratory need to issues a certificate with the calibration of an instrument. The calibration certificate provides important information to give the instrument’s owner confidence that the device was calibrated correctly and to help show proof of the calibration. > A calibration certificate might include a statement of traceability or a list of the calibration standards used for the calibration, any data resulting from the calibration, the calibration date, and possibly pass or fail statements for each measurement result. > Calibration certificates vary because not all calibration laboratories follow the same industry standards, and they also can vary depending on where the calibration fits within the calibration pyramid or hierarchy. Jan 2025 36  Calibration Certificates and Records > Calibration records or certificates should, as a minimum, contain the following information for each appliance calibrated: Identification of equipment Limits of permissible error Standard used Authority under which the document was issued Results obtained Any limitation of use of equipment Uncertainty of measurement Date when each calibration was conducted Assigned calibration interval Jan 2025 37 Jan 2025 38 Jan 2025 39  Questions ? Jan 2025 40