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Removing and replacing components of aircraft power transmission systems

URN: SEMAE3149
Business Sectors (Suites): Aeronautical Engineering Suite 3
Developed by: Enginuity
Approved on: 2021

Overview

This standard identifies the competences you need to carry out the removal and replacement of components of aircraft power transmission systems, in accordance with approved procedures and it covers rotary winged aircraft. You will be required to select the appropriate tools and equipment to use, based on the operations to be performed and the components to be removed. The aircraft power transmission system components to be removed will include items such as drive shafts, drive shaft supports, gearbox assemblies, couplings, mechanical fasteners, accelerometers, vibration monitoring equipment, and main and tail rotor assemblies.

The removal and replacement activities will include taking all necessary safeguards to isolate the system, support and lift removed and replaced parts, replacing faulty equipment at component or unit level, setting and adjusting replaced components and leaving the power transmission system in a safe condition and ready for testing.

Your responsibilities will require you to comply with organisational policy and procedures for the removal and replacement activities undertaken, and to report any problems with these activities that you cannot personally resolve, or that are outside your permitted authority, to the relevant people. You must ensure that all tools, equipment and materials used are correctly accounted for on completion of the activities, and that all necessary job/task documentation is completed, accurately and legibly. You will be expected to work with a minimum of supervision, taking personal responsibility for your own actions and for the quality and accuracy of the work that you carry out.

Your underpinning knowledge will provide a good understanding of your work, and will provide an informed approach to applying the appropriate removal and replacement techniques and procedures to aircraft power transmission systems. You will understand the removal and replacement methods and procedures, and their application, along with the power transmission maintenance requirements. You will know how the power transmission system functions, the common problems that can occur, the purpose of the individual components and associated defects, in adequate depth to provide a sound basis for carrying out the removal and replacement activities, and for ensuring that the equipment is replaced to the required standard. In addition, you will have sufficient knowledge of these components to ensure that they are fit for purpose and meet the specifications, thus providing a sound basis for carrying out the replacement.

You will understand the safety precautions required when working on aircraft power transmission systems, especially those for isolating the equipment and for lifting and handling heavy and bulky components. You will be required to demonstrate safe working practices throughout and will understand your responsibility for taking the necessary safeguards to protect yourself and others in the workplace.

Notes To display competence in this standard, it is necessary to both remove and replace components from aircraft transmission systems. You must remove components; however, you may fit a replacement component where the original was previously removed by another person.

Performance criteria

You must be able to:

  1. work safely at all times, complying with health and safety and other relevant regulations, directives and guidelines
  2. follow the relevant aircraft manuals and publications to carry out the required work
  3. establish and where appropriate, mark component orientation for re-assembly
  4. ensure that any stored energy or substances are released safely and correctly
  5. carry out the removal and replacement activities, within the limits of your personal authority
  6. remove and replace the required components, using approved tools and techniques
  7. take suitable precautions to prevent damage to components and the surrounding structure
  8. complete the relevant documentation, in accordance with organisational requirements
  9. label and store (in an appropriate location) components that require repair or overhaul
  10. dispose of waste materials and scrap components, in accordance with safe working practices and approved procedures
  11. leave the aircraft and the system in a safe and appropriate condition, free from foreign object debris and in a condition ready for testing

Knowledge and Understanding

You need to know and understand:

  1. the specific safety practices and procedures that you need to observe when working on aircraft power transmission systems (including any specific legislation, regulations/codes of practice for the activities, equipment or materials)
  2. the importance of maintenance on, and impact upon (extended twin operations procedures) ETOpS systems, legislation and local procedures
  3. hazards associated with removing and replacing aircraft power transmission system components, and with the tools and equipment used (such as handling oils, greases, stored pressure/force, lifting and moving heavy and bulky components, misuse of tools, using damaged or badly maintained tools and equipment, not following laid- down maintenance procedures), and how to minimise them and reduce any risks
  4. the requirements and importance of understanding and applying human factors as defined by the regulatory requirements and the potential impact if these are not adhered to

  5. the protective equipment that you need to use for both personal protection (PPE)  and protection of the aircraft

  6. what constitutes a hazardous voltage and how to recognise victims of electric shock

  7. how to reduce the risks of a phase to earth shock (such as insulated tools, rubber matting and isolating transformers)

  8. how to extract and use information from aircraft maintenance manuals, history/maintenance reports, flight logs, and other documents needed in the removal and replacement process

  9. how to carry out currency/issue checks on the specifications you are working with
  10. terminology used in aircraft power transmission systems
  11. the principles of how the transmission system and equipment functions, its operating sequence, the working purpose of individual units/components and how they interact
  12. the techniques used to remove components from aircraft power transmission systems, without damage to the components or surrounding structure (such as release of pressures/force, proof marking, extraction of components) and the need to protect the system integrity by fitting blanking plugs and ensuring exposed components are correctly covered/protected

  13. the various mechanical fasteners to be removed and replaced, and their method of removal and replacement (such as threaded fasteners, special securing devices)

  14. the various types of electrical connector that are used, methods of unlocking, orientation indicators and locating and locking in of the connections

  15. the importance of applying electrostatic discharge (ESD) procedures when working on sensitive equipment
  16. methods of lifting, handling and supporting the components/equipment during removal and replacement activities
  17. the identification and application, fitting and removal of different types of bearings (such as roller, ball, thrust)
  18. methods of checking that components are fit for purpose, and how to identify defects and wear characteristics
  19. the use of measuring equipment (such as micrometers, Verniers, expansion indicators and other devices)
  20. the need to replace `lifed' items (such as seals and gaskets)
  21. the need to correctly label and store components that require repair or overhaul, and to check that replacement components have the correct part/identification markings
  22. how to replace and reconnect components into the system (such as the use of gaskets/seals and jointing/sealing compounds; ensuring correct orientation, position and alignment; tightening securing devices to the required torque; replacing locking and securing devices; eliminating stress on pipework/connections; ensuring that pipework and cables are correctly supported at suitable intervals; carrying out visual checks of all components)
  23. how to make adjustments to components/assemblies to ensure that they function correctly (such as setting working clearance, setting travel, preloading bearings)
  24. why securing devices need to be tightened to the correct torque, locked and labelled, and different methods used
  25. recognition of contaminants and the problems they can create; the effects and likely symptoms of contamination in the power transmission system
  26. why electrical bonding is critical, and why it must be both mechanically and electrically secure
  27. the importance of making `off-load' checks before running the equipment under power
  28. how to check that tools and equipment are free from damage or defect, are in a safe and usable condition, and are configured correctly for the intended purpose
  29. the need to control and account for all tools and equipment used during the removal and replacement activity and what to do if a tool or piece of equipment is unaccounted for on completion of the activities
  30. how to use lifting and handling equipment in the maintenance activity
  31. the recording documentation to be completed for the activities undertaken and, where appropriate, the importance of marking and identifying specific pieces of work in relation to the documentation 
  32. the procedure for the safe disposal of waste materials, scrap components, oils and fluids
  33. the problems associated with removing and replacing power plant components, and how they can be overcome
  34. the extent of your own authority and to whom you should report if you have a problem that you cannot resolve

Scope/range

Scope Performance

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  1. Carry out all of the following during the removal and replacement activity:

    1. obtain clearance to work on the aircraft, and observe all relevant safety procedures
    2. obtain and use the appropriate documentation (such as job instructions, aircraft manuals, technical instructions, and other relevant maintenance documentation)
    3. adhere to procedures or systems in place for risk assessment, COSHH, personal protective equipment and other relevant safety regulations and procedures to realise a safe system of work
    4. obtain the correct tools and equipment for the activity, and check that they are in a safe, tested and usable condition and within current certification/calibration date
    5. ensure the safe isolation of the power transmission system before commencing work on the equipment ensure that all relevant safety devices and mechanical/physical locks are in place (where appropriate)
    6. where appropriate, apply electrostatic discharge (ESD) protection procedures
    7. use approved removal and replacement techniques and procedures at all times
    8. ensure that components and surrounding structures are maintained free from spillages, damage and foreign objects
    9. return all tools and equipment to the correct location on completion of the activities

  2. Remove components from three of the following aircraft power transmission systems and replace components from three of the following aircraft power transmission systems:

    1. intermediate gear box         
    2. main gear box
    3. tail gear box                     
    4. nose/forward gear box
    5. main rotor head assembly  
    6. tail rotor assembly

  3. During the activities identified in scope 2 above, you must cover the removal and replacement of the following:

Major power transmission components: Remove and replace three of the following:

1.  drive shaft                       
2.  main rotor head    
3.  flexi couplings
4.  drive shaft support         
5.  tail rotor head   
6.  rotor brakes
7.  bearings                   
8.  dynamic seals     
9.  swash plate
10.  couplings                 
11.  control valves      
12.  gearboxes

Other power transmission components: Remove and replace four of the following:
13. static seals/gaskets                     
14. sensors
15. mechanical controls (plungers, springs, rollers)
16. locks and stops
17. electrical controls (solenoids, motors, switches)
18. control units
19. accelerometers                                
20. levers and linkages
21. other specific components

  1. Carry out all of the following removal and replacement activities:

    1. draining and removing fluids                        
    2. use of ground support equipment
    3. positioning and aligning replaced components
    4. supporting equipment to be removed
    5. dismantling equipment to an appropriate level
    6. disconnecting electrical connections                
    7. disconnecting/removing hoses and pipes         
    8. removing mechanical fasteners and securing devices
    9. using lifting operations (manual or automated)
    10. proof marking components to aid reassembly
    11. checking components for serviceability
    12. replacing all damaged/defective components
    13. replacing all 'lifed' items (such as seals, bearings, gaskets)
    14. applying gaskets and sealant/adhesives
    15. setting and adjusting replaced components
    16. making mechanical connections
    17. making electrical connections
    18. tightening fastenings to the required torque
    19. securing components using mechanical fasteners and threaded devices
    20. applying bolt locking methods (such as split pins, wire locking, lock nuts)
    21. making `off-load' checks before starting up
    22. applying and removing covering/protection to exposed components, wires, pipework or vents
    23. labelling (and storing in the correct location) components that require repair or overhaul
    24. protecting and preparing removed components for transportation for overhaul

  2. Remove and replace aircraft power transmission system components in compliance with one of the following:

    1. Civil Aviation Authority (CAA)/European Aviation Safety Agency (EASA)
    2. extended twin operations procedures (ETOpS) (where appropriate)
    3. Ministry of Defence (MoD)
    4. Military Aviation Authority (MAA)
    5. Aerospace Quality Management Standards (AS)
    6. Federal Aviation Authority (FAA)
    7. BS, ISO or BSEN standards and procedures
    8. customer standards and requirements
    9. company standards and procedures
    10. aircraft manufacturer's requirements

  3. Complete the relevant paperwork, to include one from the following and pass it to the appropriate people:

    1. job cards
    2. computer records
    3. aircraft service/flight log
    4. aircraft log book
    5. permit to work/formal risk assessment

Scope Knowledge

Values

Behaviours

​

You will be able to apply the appropriate behaviours required in the workplace to meet the job profile and overall company objectives, such as:

  • strong work ethic
  • positive attitude
  • team player
  • dependability
  • responsibility
  • honesty
  • integrity
  • motivation
  • commitment

Skills

Glossary

Links To Other NOS

External Links

Version Number

3

Indicative Review Date

2024

Validity

Current

Status

Original

Originating Organisation

Enginuity

Original URN

SEMAE3149

Relevant Occupations

Engineer, Engineering, Engineering and Manufacturing Technologies, Engineering Technicians

SOC Code

5234

Keywords

Aeronautical; engineering; aircraft power transmission systems; drive shafts; gearbox assemblies; couplings