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Maintaining air conditioning systems on aircraft

URN: SEMAE3305
Business Sectors (Suites): Aeronautical Engineering Suite 3
Developed by: Enginuity
Approved on: 2021

Overview

This standard identifies the competences you need to carry out maintenance activities on aircraft air conditioning systems, in accordance with the aircraft maintenance manual, approved change documentation (service bulletin) and airworthiness requirements. It covers both fixed wing and rotary winged aircraft, and covers the units and components which provide a means of pressurising, heating, cooling, moisture controlling, filtering and treating air used to ventilate the areas of the fuselage within the pressure zone, as applicable to the aircraft type. The maintenance activities will include the removal, fitting and testing of a range of air conditioning system components. You will be expected to use the approved procedure for correctly isolating the system before breaking into the system circuit. You will remove the required components and fit approved replacements, as appropriate. You will then need to test and adjust the completed system to meet the aircraft maintenance manual, change documentation (service bulletin) and airworthiness requirements.

Your responsibilities will require you to comply with the specific practices and procedures identified in the aircraft manual, change/service bulletin documentation and airworthiness requirements for the maintenance activities undertaken, and to report any problems with these requirements 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 thoroughly, 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 maintenance techniques and procedures to aircraft air conditioning systems. You will understand the removal, fitting and testing methods and procedures, and their application, along with the air conditioning system maintenance requirements. You will know how the equipment 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 maintenance activities, correcting faults and for ensuring that the equipment is maintained to the required standard.

You will understand the safety precautions required when working on aircraft air conditioning systems, especially those for isolating the system, ensuring system cleanliness and the avoidance of contamination. 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:

  1. This standard is designed to cover the practical experience requirements of the Airline Transport Association (ATA) Chapter 21 Air Conditioning.
  2. To display competence in this standard it is necessary to both remove and fit aircraft air conditioning system components. You must remove components; however, you may fit a replacement component where the original was previously removed by another person. You should also be aware of how to leave a system in a safe condition if maintenance tasks cannot be completed. This covers both the physical systems and the job documentation.

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 maintenance schedules to carry out the required work
  3. carry out the maintenance activities within the limits of your personal authority
  4. carry out the maintenance activities, and replace components in the specified sequence and in an agreed timescale
  5. report any instances where the maintenance activities cannot be fully met or where there are identified defects outside the planned schedule
  6. complete relevant documentation in accordance with organisational requirements
  7. dispose of waste materials in accordance with safe working practices and approved procedures
  8. leave the aircraft and system in a safe and appropriate condition, free from foreign object debris on completion of the activities

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 air conditioning systems (including any specific legislation, regulations/codes of practice for the activities, equipment or materials)
  2. the importance of maintenance on air conditioning systems, and impact upon (Extended Range Twin-Engine Operations Procedures) ETOPS systems, Electrical Wiring Interconnect Systems (EWIS), legislation and local procedures
  3. the hazards associated with carrying out maintenance activities on aircraft air conditioning systems, and with the tools and equipment used, and how to minimise them and reduce any risk
  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 manuals, log books, flight logs, charts, circuit and physical layouts, specifications, symbols used in aircraft air conditioning systems, and other documents in the maintenance activities

  9. how to carry out currency/issue checks on the specifications you are working with
  10. terminology used in aircraft air conditioning systems, and the use of system diagrams and associated symbols
  11. the principles of operation of the aircraft air conditioning system being worked on (such as system layout, compression, distribution, pressurisation control, heating, cooling, temperature control and air contaminant control; indication and warning), along with corresponding safety devices
  12. the various types of pipe and component that make up the aircraft air conditioning system (such as rigid and flexible pipes; ducting; supporting devices; valves used for pressure, flow and directional control; pumps; heaters; cooling units; air cycle units; cabin blowers; mechanical and electrical control devices)

  13. the techniques used to remove components from aircraft air conditioning systems without damage to the components or surrounding structure (such as removal of components, and the need to protect the circuit integrity by fitting blanking plugs and labelling exposed circuits)

  14. the various mechanical fasteners that will need to be removed and replaced, and their methods of removal and replacement (such as threaded fasteners, special securing devices)

  15. the various types of electrical connector that are used, methods of unlocking, orientation indicators and locating and locking-in of the connections
  16. methods of lifting, handling and supporting components/equipment during the maintenance activities
  17. the importance of aircraft husbandry and of ensuring that, throughout the maintenance activity, the aircraft and work area are maintained free from foreign objects, and that any exposed components or pipe ends are correctly covered/protected, and the implications of foreign object debris (FOD) to the safety of the aircraft
  18. recognition of contaminants, and the problems they can create: the effects and likely symptoms of contamination in the system
  19. the need to label and store correctly components that require repair or overhaul, and to check that replacement components have the correct part/identification markings and accompanying release documentation
  20. how to fit components into the circuit (such as the use of gaskets/seals and jointing/sealing compounds; ensuring the correct tightness of pipe fittings and connections; eliminating stress on pipework/connections; carrying out visual checks of all components; checking the security of joints and that the system is safe to re-charge)
  21. how to make adjustments to components/assemblies to ensure that they function correctly
  22. why securing devices need to be tightened to the correct torque, locked and labelled, and the different methods that are used
  23. how to carry out routine servicing of the aircraft air conditioning system (including checking for leaks, checking and changing filters, cleaning outflow valves)
  24. the types of test to be carried out on the aircraft air conditioning system (such as functional checks, pressure tests, pressure balancing, air temperature tests, safety interlock tests, leak checks)
  25. the methods and procedures to be used to carry out the various tests on the air conditioning system
  26. the need to apply test pressures in incremental stages, and to check all readings and pressures at each stage
  27. how to record the results of each individual test and the documentation that must be used
  28. how to analyse the test results and how to make valid decisions about the acceptability of the aircraft air conditioning system
  29. why tool/equipment control is critical and what to do if a tool or piece of equipment is unaccounted for on completion of the activities
  30. the procedures to be followed if the equipment or system fails to meet the test specification
  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 and scrap components
  33. the extent of your own authority and to whom you should report if you have problems that you cannot resolve

Scope/range

Scope Performance

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  1. Carry out all of the following during the maintenance of the aircraft air conditioning system:

    1. ensure that appropriate authorisation to work on the aircraft is obtained, and observe all relevant isolation and safety procedures
    2. obtain and use the correct documentation (such as job instructions, technical instructions, aircraft manuals and maintenance documentation)
    3. obtain the correct tools and equipment for the activity, and check that they are in a safe, tested and usable condition and within current calibration dates
    4. 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
    5. ensure the safe isolation of the air conditioning equipment before breaking into the system
    6. ensure that relevant safety devices and mechanical/physical locks are in place (where appropriate)
    7. use approved removal, fitting and testing techniques and procedures at all times
    8. return tools and equipment to the correct storage location on completion of the activities
    9. ensure that the work carried out is correctly documented and recorded
    10. ensure that any outstanding tests are correctly documented

  2. Carry out maintenance activities on three of the following parts of an aircraft air conditioning system:

    1. compression                
    2. heating         
    3. temperature control
    4. distribution                   
    5. cooling           
    6. air contaminant control
    7. pressurisation control      
    8. filtration control    
    9. humidity control

  3. Remove and fit four different aircraft air conditioning system components, at least one must be from group A:

Group A:

1.  reservoirs/supply tanks       
2.  pressure intensifiers   
3.  valves (such as by-pass, shut-off, check, pressure relief, temperature control, outflow, anti-g)
4.  air receivers               
5.  diffusers               
6.  compressor                    
7.  cooling units            
8.  regulators                 
9.  heat exchanger 
10.  safety devices
11.  pumps                    
12.  cabin blowers  
13.  air-conditioning packs
14.  air cycle unit            
15.  vapour cycle unit   
16.  pressure/pressurisation controller

Group B:
17. filters                               
18. hoses             
19. gauges
20. strainers including water separator 
21. gaskets and seals        
22. sensors
23. earthing straps/jumper braids 
24. unions and couplings    
25. electrical controls (solenoids, motors, switches)
26. rigid pipework                    
27. ducting
28. actuating mechanisms     
29. scoops        
30. other specific components

  1. Carry out fifteen of the following maintenance activities:

    1. removing access panels and covers to expose components to be removed
    2. carrying out fault diagnosis and system checks
    3. preparing the system for maintenance (such as isolating, de-pressurising, draining fluids)
    4. disconnecting electrical connections  
    5. replacing single use items (such as seals, filters, gaskets)
    6. disconnecting/removing hoses and pipes                 
    7. removing securing devices and mechanical fasteners
    8. refitting components in the correct position, orientation and alignment
    9. dismantling equipment to an appropriate level 
    10. setting, and adjusting replaced components (such as travel, working clearance)
    11. ensuring that any part-dismantled components are secure/supported   
    12. making mechanical connections
    13. covering (protecting) exposed components,    
    14. making electrical connections wires, pipework or vents
    15. torque loading as required
    16. checking components for serviceability
    17. re-pressurising the system
    18. replacing damaged/defective components  
    19. carrying out a system functional check
    20. ensuring that replacement components have the correct part numbers
    21. labelling (and storing in the correct location) components that require repair or overhaul
    22. applying bolt locking methods (such as split pins, wire locking, lock nuts)
    23. carrying out area inspections prior to task close-up

  2. Service/check the aircraft air conditioning system, to include carrying out five of the following:

    1. checking filters
    2. cleaning outflow valves
    3. checking fluid content of reservoirs (such as deodorisers, insecticides)
    4. checking operation of air conditioning/heating system
    5. checking operation of pressurisation system
    6. checking indicating systems
    7. replenishing vapour system
    8. checking safety devices

  3. Carry out three of the following tests on the aircraft air conditioning system:

    1. cabin pressure test                          
    2. airline vapour tests
    3. pressure balancing                         
    4. reduced system test
    5. bulkhead and dome pressure tests     
    6. equipment functional test
    7. air flow tests                   
    8. visual inspection
    9. leak test                              
    10. built in test equipment (BITE) test
    11. air temperature tests            
    12. 'special-to-type' tests
    13. safety interlock test                         
    14. aircraft self-test printout

Using one of the following:
15. aircraft power source/system    
16. ground test rig

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

    1. job cards/work sheets              
    2. aircraft cabin log
    3. computer records                     
    4. aircraft log book
    5. aircraft technical log

  2. Carry out maintenance on aircraft air conditioning systems in compliance with one of the following:

    1. Civil Aviation Authority (CAA)/European Aviation Safety Agency (EASA)
    2. Extended Range Twin-Engine 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. aircraft maintenance manual/approved change documentation (service bulletin)
    8. manufacturers standards and procedures

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

SEMAE3305

Relevant Occupations

Engineer, Engineering, Engineering and Manufacturing Technologies, Engineering Technicians

SOC Code

5234

Keywords

engineering; aeronautical; airworthiness requirements; pressurising; heating; cooling; moisture controlling; filtering; treating; fuselage; pressure zone; removal; fitting; isolating; system circuit