Par 309 Page 38 insulation. This attack can result in system or equipment failure. The presence of nests, holes in packaging, and excrement indicate animal or insect attack. This problem is generally more severe in equipment that is in storage or has been out of service for a long period of time.
Figures 3-9, 3-10, and 3-11 show the effects of animals. Frequent inspection of the equipment or shipping containers is the best method of controlling this problem.
FIGURE 3-9. ANIMAL DROPPINGS ON ELECTRICAL COMPONENTS
Par 309 Page 39 FIGURE 3-10. RODENT DROPPINGS IN BILGE AREA
Par 309 Page 40 FIGURE 3-11. BIRD NEST IN ENGINE PYLON
Par 309 Page 41 FIGURE 3-12. LINT ACCUMULATION IN CROWN AREA
Par 309 Page 42 FIGURE 3-13. LINT ACCUMULATION ON ELECTRICAL CONNECTOR
Par 309 Page 43 FIGURE 3-14. LINT ACCUMULATION ON WIRING BUNDLE
Par 309 Page 44 FIGURE 3-15. LINT ACCUMULATION ON ELECTRICAL SWITCH
310.
EFFECTS OF DUST/LINT ACCUMULATION. Avionics equipment is subject to dust and lint accumulation. This condition is generally evident when the equipment has been installed for long periods of time and can become more severe with forced cooling air. In addition to the dust and lint accumulation from the movement of air, dust and lint can be attracted by magnetic fields from electric currents surrounding wiring and equipment. Dust can also accumulate on the surfaces of components and on the interior surfaces of components if that equipment has ventilating holes and louvers. The problem with accumulation of dust and lint is it will trap and hold moisture which can provide the electrolyte for corrosion and fungus growth (see Chapter 2, Paragraph 205, Corrosive Conditions). Additionally, dust and lint can degrade avionics equipment by being a conductor or an insulator. When dust and lint act as a conductor in the presence of moisture, they can provide a path for a current flow to either ground as a short or an unwanted circuit path between components. When dust and lint act as an insulator the avionics equipment can overheat causing premature failure. Severe accumulations of dust can appear as long stringy clumps, similar to Spanish moss hanging from trees, but on a smaller scale.
Figures 3-12 through 3-15 show examples of dust and lint accumulation. Frequent inspections and general cleaning of equipment will control the accumulation of dust and lint.
311 through 400. RESERVED.
Par 401 Page 45 CHAPTER 4. CLEANING AND PRESERVATION
401. GENERAL. The materials, equipment, and techniques described in this chapter are intended to assist the avionics technician at an avionics repair facility. This chapter discusses avionics cleaning and repair facility requirements, specialized support equipment to support cleaning, corrosion removal, drying of avionics equipment, and the different processes of cleaning, drying, preserving, packaging, handling, and shipping avionics equipment.
402. AVIONICS CORROSION CLEANING FACILITY. An avionics cleaning and repair facility should include as a minimum the following resources for the cleaning, drying, preserving, packaging, handling, and shipping of avionics equipment:
a. Adequate lighting and a temperature/humidity-controlled ventilation system.
b. Adequate space for safe operation of avionics cleaning and corrosion control equipment.
c. Operating instructions for each piece of equipment.
d. All hazardous materials (HAZMAT) and material safety data sheets (MSDS) for materials used.
e. Safety equipment and protective personal equipment as required by local, state, and Federal ordinances.
f. Personnel trained in the recognition of corrosion on avionics equipment as specified in this AC.
g. Personnel trained in the safe and proper operation of support equipment.
h. Quality assurance inspectors trained in the operational characteristics and restrictions of each piece of support equipment.
i. Avionics technicians who can recognize the various electrical and electronic equipment and components.
403. MATERIALS AND SUPPORT EQUIPMENT REQUIREMENTS.
a. General. Avionics technicians must understand the functions, capabilities, and restrictions associated with each piece of specialized support equipment, and the hazards of the cleaning and corrosion removal products and preservation materials. This knowledge will prevent injury to personnel and damage to avionics equipment and support equipment.
b. Materials. Consumable cleaning and corrosion removal products and preservation materials listed in Appendix 1 and Appendix 2 may be used as specified on avionics equipment if none were identified by the Original Equipment Manufacturer (OEM) or equipment operator.
Par 403 Page 46
c. Materials Used For Cleaning. Table 4-1 contains a list of the various cleaning compounds and solutions, their characteristics, application, mixing instructions, and restrictions.
The cleaning of avionics equipment can be accomplished using the following processes:
CAUTION: Some of the materials identified in Table 4-1 can create hazardous conditions or damage equipment unless used strictly in the applications and manner described.
CAUTION: Some of the materials identified in Table 4-1 are chlorofluorocarbons (CFCs), an ozone depleting substance (ODS). These materials may be banned from use by environmental restrictions.
(1) Solvents are effective in dissolving greases and oils. Solvents can be applied by wiping, brushing, soaking, or spraying.
(2) Detergent and water in varying concentrations are used to remove dust, dirt, salt deposits, greases, and oils. Detergent and water cleaning mixtures can be applied by wiping, brushing, soaking, and spraying.
(3) Distilled or fresh water is used to dilute Isopropyl Alcohol or detergents for use in cleaning and as a final rinse. Water may also be used to remove dust, dirt, salt deposits, and cleaning solutions. Application is by wiping, brushing, soaking, and spraying.
Par 403 Page 47 TABLE 4-1. AVIONICS CLEANING MATERIALS Description Characteristics Application Restrictions Cleaning Compound, Aircraft Surface, MIL-PRF-85570, Type II General cleaning agent for light soil and dirt in equipment bays, on external cases, covers, and antenna assemblies.
Mix per manufacturer’s instructions or 1 part cleaner in 10 parts distilled water. Apply with cleaning cloth. Rinse with fresh water and wipe dry.
Do not use around oxygen fittings or oxygen regulators as fire or explosion may result.
Heavy concentrations of surface grime, oil, exhaust smudges, and fire extinguishing chemicals in equipment bays and on external cases and covers.
Mix per manufacturer’s instructions or 1 part cleaner in 6 parts distilled water. Apply with cleaning cloth. Rinse with fresh water and wipe dry.
Never use full strength.
Do not allow to dry on surface.
Detergent, Liquid, Nonionic MIL-D-16791, Type 1 Cleans transparencies, acrylic plastics, and glass.
Also used in the water-based Solvent Spray Cleaning Booth and Aqueous Ultrasonic Cleaner for removing contaminants.
For hand cleaning, apply with flannel cloth. Let dry; then remove with dry flannel cloth.
Mix per manufacturer’s instructions or 1 fluid oz.
per gallon of water.
Cleaning and Lubricating Compound, Electrical Contact, MIL-PRF-29608, Type 1 A cleaner-lubricant compatible with potting compounds, rubbers, and insulation. Contains 3 to 5% silicon. May be used for cleaning and lubricating electrical contacts.
Apply by spraying an even film to the surface.
Wipe clean with disposable applicator or pipe cleaner.
Do not use as a substitute for MIL-C-81302, Type I or Type II. Avoid application to areas requiring soldering or coating.
Cleaning Compound, Solvent, Trichlorotrifluoroethane, MIL-C-81302, Type II General cleaner for light to medium to heavy dirt, dust, contaminants, and fire extinguishing chemicals.
Used in the Solvent Ultrasonic Cleaner.
Do not use on acrylic plastics and acrylic conformal coatings. Do not use on unsealed aluminum electrolytic capacitors. Damage may result to end caps and cause leakage.
Dry Cleaning, Solvent, MIL-PRF-680, Type II General purpose cleaner for heavy dirt, dust, contaminants, and fire extinguishing chemicals in equipment bays and on external cases, covers, structural hardware, mounts, racks, etc.
Apply by wiping or scrubbing affected area with cleaning cloth, cheesecloth, or brush.
Wipe clean with cleaning cloth.
Do not use around oxygen, oxygen fittings, or oxygen regulator as fire or explosion may result.
Par 403 Page 48 Description Characteristics Application Restrictions Cleaner for smoke damage removal on internal chassis components.
Apply by scrubbing affected area with cleaning cloth, toothbrush, or typewriter brush. Wipe clean with cleaning cloth.
When used for smoke damage removal, always follow up with a solution of 1 part deionized water and 1 part Isopropyl Alcohol, TT-I-735.
Cleaner for smoke damage removal on circuit components and laminated circuit boards.
Apply by wiping or scrubbing affected area with cleaning cloth or toothbrush. Wipe clean with cleaning cloth.
May cause swelling of silicone rubber seals in equipment exposed for long periods.
Cleaner for removal of Water-Displacing Compound, MIL-PRF-81309, Type II or Type III, MIL-DTL-85054; and Corrosion Preventive Compound, MIL-PRF-16173, Grade 2, 3, and 4.
Apply by brush or toothbrush. Wipe clean with cleaning cloth.
May soften some plastics, wire harness tubing, and plastics coating on wiring. Test affected area for adverse reaction prior to general application.
Isopropyl Alcohol, TT-I-735 General purpose cleaner and solvent for removal of salt residue and contaminants common to internal avionics equipment. General cleaner for internal chassis components.
Apply a solution of 1 part deionized or distilled water and 1 part Isopropyl Alcohol, TT-I-735, to affected area with cleaning cloth or toothbrush.
Isopropyl Alcohol, TT-I-735, is highly flammable. All applications of Isopropyl Alcohol, TT-I-735, and water may be air dried or dried by portable air blower or oven.
Solvent cleaner for solder flux residue in all electronics, electrical equipment, and microminiature circuit applications.
Apply a solution of 1 part deionized or distilled water and 3 parts Isopropyl Alcohol, TT-I-735, and scrub the solder joint and adjacent area with an acid brush or toothbrush. Wipe clean with cleaning cloth.
Par 403 Page 49 Cleaner for bacteria and fungi attack on all metals and nonmetals.
Apply a solution of 1 part solvent Trichlorotrifluoroethane, MIL-C-81302, Type II, and 1 part Isopropyl Alcohol, TT-I-735, to affected area with cleaning cloth. Wipe clean and air dry.
Cleaner for saltwater immersion and fire extinguishing agents on all internal circuit components and laminated circuit boards.
Apply a solution of 1 part Isopropyl Alcohol, TT-I-735, and 9 parts solvent Trichlorotrifluoroethane, MIL-C-81302, Type II, to affected area with cleaning cloth, acid brush, or toothbrush.
Cleaner for electrical contact surfaces.
Apply a solution of 1 part deionized or distilled water and 1 part Isopropyl Alcohol, TT-I-735, to affected area with acid brush or pipe cleaner. Wipe clean and air dry.
Water, distilled Cleaner for solder flux residue in all electronics, electrical equipment, and microminiature circuit applications.
Apply a solution of 1 part deionized or distilled water to 3 parts Isopropyl Alcohol, TT-I-735, and scrub joint and adjacent area with acid brush or toothbrush. Wipe clean with cleaning cloth.
Deionized water is an acceptable substitute.
d. Hazardous Chemicals and Waste Generation. Many of the materials identified in this AC are hazardous and toxic to personnel not using appropriate personal protective equipment. These materials can also be potentially damaging to avionics equipment and aircraft if used in improper concentrations or misapplied. Prior to using any chemicals such as paint strippers, detergents, solvents, conversion coatings, primers, or paints, personnel should review the appropriate MSDS for warnings and cautions or the HAZMAT identification labels on the containers. Figure 4-1 provides a simple system of readily recognizable and easily understood markings which will give, at a glance, the general idea of the inherent hazards of any HAZMAT.
Additionally, the use of materials identified in this AC can, if improperly used or disposed of, create a hazard and contaminate the environment. Avionics technicians should use only the proper amount when mixing materials, close containers when not in use, use only the required amount to complete the intended procedure, and properly dispose of all materials in accordance with all Federal, state, and local regulations.