Global Series Environmental Corrosion Guidelines - December 2016

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  Infoservice 2016 Environmental Corrosion Control and Prevention Guidelines Global Series  2 of 53 Infoservice 2016 Environmental Corrosion Control and Prevention Guidelines – Global Series Click here to go to table of content Corrosion, which can be defined as the deterioration of metal by its reaction to its environment, is in fact a process of nature by which a metal tries to return to its natural state. Steel rusts to iron oxide, and aluminum oxidizes and corrodes back to bauxite.Certain environmental factors are not readily controllable by the operator, such as: the salt-laden atmosphere in marine locations or the airborne pollutants of industrial areas. Inspection and corrosion prevention frequencies become a variable in such circumstances.The following factors should be considered by the operator when evaluating local environmental conditions: (1) MARINE ATMOSPHERE Areas adjacent to salt water normally result in an atmosphere containing salt particles or salt saturated spray. The degree of salinity of the body of water, temperature and the direction of the prevailing winds create wide variations in the corrosive properties of the atmosphere in coastal regions. It must be remembered that salt water is an excellent electrolyte and therefore, a promoter of corrosion. (2) CONTAMINATED ATMOSPHERE The atmosphere of urban and industrial areas usually contains a high concentration of pollutants. These pollutants combine with water to form highly corrosive liquids; for example, Sulphur compounds can form Sulphur based acids.The contaminated atmosphere can be an even greater hazard when the prevailing winds carry pollutants from a nearby industrial plant to the aircraft parking area. (3) RAINFALL Moderate rainfall in temperate or cold climates does not constitute an environmental problem. Heavy rainfall or hail can result in damage to the finish which will help to initiate corrosion.Tropical rains coupled with hot humid atmosphere have a tendency to accelerate corrosion. Refer to the following paragraphs on relative humidity and high temperature. (a) Relative Humidity High relative humidity coupled with high temperature results in a water-saturated atmosphere in the aircraft while on the ground. After takeoff, condensation occurs providing the medium for the onset of corrosion.High humidity at lower temperatures is less of a problem, while the least harmful conditions are those with low relative humidity. (b) Temperature High temperature and low humidity are the most desirable conditions because any moisture in the aircraft is dried out. Similarly, an extremely cold atmosphere is also usually dry. Combinations of high temperature and high humidity provide the worst environment from the corrosion standpoint.  3 of 53 Infoservice 2016 Environmental Corrosion Control and Prevention Guidelines – Global Series Click here to go to table of content (4) RUNWAY CONDITIONS Aircraft operating from gravel, dirt or grass runways or from runways treated with sodium chloride for ice removal are exposed to adverse conditions due to deterioration of the finish and the deposit of corrosive materials. (5) OPERATING ALTITUDE Aircraft operating at relatively low altitudes combined with marine atmosphere are exposed to a greater extent to airborne pollutants than aircraft operating at higher levels. (6) AIR TIME Frequent cycling of the aircraft, especially in hot, humid zones, will create a greater moisture build-up than can be expected on aircraft with longer air time. This is due to the aircraft being exposed to a fresh supply of water-saturated air at every landing, which will condense out in the subsequent flight. (7) VOLCANIC GASES Corrosive gases from volcanos are carried in the atmosphere in some regions. There is also a “fallout” zone downwind of active volcanos which could be an undesirable element. (8) AIRBORNE ABRASIVES Blowing sand, volcanic ash or coral dust have an erosive effect on the finish and may find its way into the interfacing surfaces of moving parts or into bearings. This abrasion not only creates a wear problem, it exposes unprotected metal to corrosion. The abrasive material itself may also be corrosive, as would be the case with sand from salt water beaches.Corrosion control and prevention will determine the aircraft’s integrity for its projected life. It is necessary to recognize corrosion in its early stages to avoid serious damage leading to costly repairs. A customized maintenance program based on aircraft environment and operation would provide enhanced protection against aircraft corrosion. This newsletter is a compilation of references and information to be used as a guide to assist maintenance crews in developing customized maintenance practices when operating/exposed to harsh environments. Information published in the Infoservice is considered accurate.However, the information contained in Technical Manuals takes precedence at all times.    4 of 53 Infoservice 2016 Environmental Corrosion Control and Prevention Guidelines – Global Series Table of content have hyperlinks.Click on the list to go directly to your page. TABLE OF CONTENTS GENERAL AIRCRAFT CORROSION INFORMATION ...................................................................................11ATA 05 – Time Limits / Maintenance Checks ..............................................................................................14 AMM Tasks .....................................................................................................................................................14   - 05-51-48-210-801 – General Visual Inspection After Volcanic Ash Contamination ...............................14  - 05-51-50-210-801 – Inspection of Aircraft after Contamination with Salt Based Runway De-Icing Products ...................................................................................................................................14 Reduced Scheduled Inspection Intervals Table .............................................................................................15 ATA 12 – Servicing ......................................................................................................................................19 AMM Tasks .....................................................................................................................................................19   - 12-21-00-110-808 – Cleaning of the External Surface of the Aircraft .....................................................19  - 12-21-00-110-809 – Cleaning of the Undercarriage Area for Salt Removal ............................................19  - 12-21-00-110-810 – Cleaning of the Landing Gear and Undercarriage area ..........................................19  - 12-21-00-170-801 – Removal of SAE Type II, III or IV Fluid Residue form the Wing Trailing Edge .........19 ATA 20 – Standard Practice ........................................................................................................................20 SPM Tasks .......................................................................................................................................................20 - 20-14-05-02 – Cleaning and Corrosion Protection of Metal Conduits on Electrical Harness – Maintenance Practices ......................................................................................20  - 20-20-00-02 – Electrical Connectors – Maintenance Practices .............................................................20 ATA 27 – Flight Control ...............................................................................................................................21 AMM Tasks .....................................................................................................................................................21   - 27-00-00-220-802 – Detailed Inspection of the Aileron, Elevator and Rudder Control Cables in the Forward Avionics Compartments (FS202.75 to FS280.00) ...........................................................21  - 27-00-00-220-803 – Detailed Inspection of the Aileron, Elevator and Rudder Control Cables in the Main Avionics Compartment, FS280.00 to FS557.00 ...................................................................21  - 27-00-00-220-804 – Detailed Inspection of the Aileron, Elevator and Rudder Control Cables in the Mid−Lower Fuselage Compartment − (FS557.00 to FS781.00) ....................................................21  - 27-00-00-220-807 – Detailed Inspection of the Elevator and Rudder Control Cables in the Aft Power Distribution/ECS Compartment − (FS781.00 to FS861.00) ..........................................21  - 27-00-00-220-808 – Detailed Inspection of the Elevator and Rudder Control Cables in the Aft Equipment Compartment − (FS861.00 to FS987.55) ..............................................................21  - 27-00-00-220-809 – Detailed Inspection of the Elevator and Rudder Control Cables in the Fuselage/Stabilizer Section − (FS987.55 to Rear Spar) .................................................................22  - 27-10-00-220-801 – Detailed Inspection of the Aileron Control Cables in the Main Landing Gear (MLG) Wheel Well and Mid Wing−to−Fuselage Fairing ...............................22
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