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S8C16 - AIRCRAFT CLEANING AND CORROSION CONTROL

Table of Contents

INTRODUCTION

EXTERNAL SURFACE OF AIRCRAFT

CLEANLINESS OF AIRCRAFT

Cleaning of Aircraft and Aeronautical Product

Cleaning Materials for Use on Aircraft

MOISTURE REPELLENT FLUIDS

EMPLOYMENT OF PERSONNEL IN SURFACE FINISHING PROCESSES

CORROSION

Removal of Corrosion

APPROVED PAINTS

RECORDING ACTION

INTRODUCTION

1. Aircraft cleaning and corrosion control is carried out to maintain aircraft in a satisfactory materiel condition. This is achieved through the maintenance and application of aircraft cleaning programs, corrosion prevention and removal processes and protective surface finishes.

2. ADF aircraft are very susceptible to corrosion due to the materials from which they are constructed and the environment in which they operate. All aircraft have scheduled maintenance operations designed to preserve their condition and to rectify minor defects resulting from the operating environment.

3. This chapter prescribes the AMO procedures to be followed when performing cleaning and corrosion control activities on aircraft and aeronautical product.

EXTERNAL SURFACE OF AIRCRAFT

4. In order to minimise damage to the external surface of an aircraft, rubber soled footwear is to be worn when carrying out servicing operations. Wing mats are to be used when it is necessary to stand on a wing, unless using existing non-slip walkways. Tools, other hard objects and servicing equipment are not to be rested directly on or dragged over the surface of an aircraft.

5. All cowlings and removable panels are to be handled with care to prevent damage and to ensure contour and accuracy of fit is not impaired. Cowlings and removable panels must not be placed directly onto a hard surface. They are to be placed on padded trestles or suitably padded to provide protection from damage.

6. All repairs to an aircraft or aeronautical product finish must be executed with care. Complete re-finishing of aircraft or aeronautical product is only to be done where approved paint shop facilities are available.

CLEANLINESS OF AIRCRAFT

NOTE

Areas of the aircraft structure in the wake of exhaust gas flow are liable to rapid corrosion if the exhaust gas deposits are not removed regularly and the aircraft finish is not maintained in good condition.

7. Cleanliness of aircraft is important, as dirt particles impair the efficiency of aerodynamic surfaces and aircraft working parts. When mixed with oil or grease, dirt is a dangerous abrasive. Dirt particles absorb fuel and oil, prolonging vaporisation, and thereby increasing the fire risk. Dirt particles also absorb moisture and other matter which may cause corrosion. Dirt particles and other matter may conceal defects and may compromise the technical airworthiness of an aircraft. Aircraft are to be cleaned regularly to remove dirt particles, oil, grease, and exhaust gas stains.

Cleaning of Aircraft and Aeronautical Product

8. The periodicity and/or procedures to be followed for the cleaning of aircraft and aeronautical product are detailed in the relevant aircraft publications or other approved instructions. Blanking plugs/covers are to be applied to all intakes, vents, pitot heads and any other points considered necessary to prevent the ingress of cleaning materials or water into the interior of the aircraft/aeronautical product. On completion of the cleaning process, all blanks/covers fitted at the start of the cleaning operation are to be removed and the interior of the aircraft checked for the ingress of cleaning materials or water.

Cleaning Materials for Use on Aircraft

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Before using any cleaning substance, refer to the applicable Safety Data Sheets (SDS) for the correct safety procedures and personal protective equipment.

9. Cleaning Solutions. Only cleaning solutions approved and authorised by the relevant Systems Program Office (SPO) are to be used on aircraft.

10. Cleaning Rags. Unless otherwise specified by the relevant SPO, only clean, white, cotton rags must be used during maintenance on aircraft and aeronautical product. These rags must be free of any object capable of causing damage to the aircraft surfaces, eg buttons, press studs, zips, etc. Rags are identified on MILIS as ‘Rags, Wiping’.

11. Oxygen Systems. Only cleaning products or materials approved and authorised by the relevant SPO must be used on dry breathing oxygen systems.

12. Disposal. Contaminated cleaning rags are to be disposed of in accordance with the applicable contaminate SDS.

MOISTURE REPELLENT FLUIDS

13. The periodicity and procedures to be followed for moisture repellent fluids are detailed in the relevant aircraft publications or other approved instructions. Moisture repellent fluids are composed mainly of corrosion inhibiting compounds in a low surface tension solvent. The repellent fluid displaces moisture and when it evaporates, leaves behind a thin film of corrosion inhibitor to provide temporary protection against further ingress of moisture. Repellent fluid is only to be applied in accordance with SPO approved procedures and all safety precautions detailed in the appropriate SDS are to be adhered to.

14. The repellent products which are approved and authorised for use are:

  1. PX24—General purpose de-watering and preservation of airframe, turbine engine compressors and support equipment.
  2. PX29—De-watering and preservation of electrical and electronic equipment.

15. The minimum amount of fluid is to be applied to de-water the surface and deposit a thin continuous film of corrosion preventive compound. Allow at least 10 minutes for fluid to evaporate before re-assembling equipment or re-making electrical connections.

16. Limitations and precautions to be observed are as follows:

  1. The moisture displaced by these fluids must be removed either by natural evaporation or forced evaporation utilising fans.
  2. The use of spray cans in conditions of high humidity may cause precipitation of moisture from surrounding air.
  3. Do not apply in areas where ignition may occur, eg on hot parts or on electrical equipment whilst in operation.
  4. The fluids used may attack some plastics and rubbers. Do not allow these fluids to contact perspex or stressed plastics.
  5. Do not use these fluids on continuous wire type fire detection elements.
  6. Do not use these fluids where they may come into contact with oxygen or oxygen systems.
  7. Do not use these fluids on carbon brushes, commutator faces or slip rings.

17. The protection given is ‘short term’ and the typical life span is:

  1. salt spray resistance – 50 hours
  2. outdoor exposure (protected from rain) – two weeks
  3. enclosed indoors – three months.

EMPLOYMENT OF PERSONNEL IN SURFACE FINISHING PROCESSES

18. In conducting corrosion control and surface finishing processes, priority is to be given to the use of mechanical methods and non-hazardous substances where these are effective. Hazardous substances for corrosion control and surface finishing processes may only be used when it has been established that no other process could achieve the required outcome.

19. When hazardous substances are used for corrosion control and surface finishing processes, supervisors and personnel conducting the actual process must have access to, and be familiar with, the current SDS for each hazardous substance being used, as well as all authorised documentation covering the process.

NOTE

Guidance on the use and method of using such hazardous substances contained within the relevant SDS and other documentation is to be strictly adhered to.

CORROSION

20. There are three classifications of corrosion:

  1. Heavy Corrosion. Heavy corrosion is corrosion which has penetrated the cladding or produced a deeply pitted or heavily roughened surface.
  2. Medium Corrosion. Medium corrosion is corrosion which has not penetrated the cladding but has produced roughening of the surface which can be detected easily with a blunt probe.
  3. Light Corrosion. Light corrosion is corrosion which has produced visible evidence but no perceptible roughness.

Removal of Corrosion

21. The corrosion removal and prevention procedures specified in the relevant aircraft publications or other authorised documentation is to be adhered to. If no instructions exist, direction is to be sought from the responsible Systems Program Office (SPO).

22. The products of corrosion take part in, and assist the process of corrosion. These contaminants are to be completely removed, paying particular attention to fasteners and around joints, before the rectification process continues.

APPROVED PAINTS

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Before using any chemicals or paints refer to the SDS for the relevant safety precautions, clean up and disposal procedures.

23. The prime means of specifying paint for use in ADF aviation is the Military Specification and the colour standard. Further information is contained in the relevant aircraft publications or other approved documentation.

NOTE

Before using any paint or catalyst, a check is to be made to ensure it is within shelf life. Before combining the base and the catalyst, they are to be inspected to ensure they have not suffered any deterioration.

RECORDING ACTION

24. All aircraft maintenance, including washing, cleaning and any corrosion rectification is to be completed in accordance with the relevant publication. Details must be entered in the recording and certification system and certified in accordance with Section 4 Chapter 2—Recording and Certification of Aircraft and Aeronautical Product Maintenance.

25. If applicable, all corrosion rectification is to be annotated on the aircraft Corrosion Record part of the Aircraft Log Pack.

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