TM 1-1520-265-231-18 Change 2This manual summarizes the steps necessary to perform satisfactory inspections. It includes thepreparation of the helicopter, the inspection area for NDI, safety rules to be observed, highlights ofeach inspection method, and specific safety precautions for each of these methods. For a detaileddescription of each method and its application, refer to the Technical Manual, NondestructiveInspection Methods, TM 1-1500-335-23. Specific instructions peculiar to each part being inspectedwill be included in the discussion of that inspection item as it is covered in this manual.1.4.2 SelectingtheNDIMethod. Factors governing the selection of an inspection method are:accessibility, portability of equipment, type of suspected damage, material composition of part to beinspected, surface condition, and degree of sensitivity required for the inspection. In many casesthe method selected will depend primarily on accessibility and practicality. For example, a threadeditem that may qualify for eddy current inspection may instead require the substitution of an ultrasonicinspection due to accessibility constraints. However, the ultrasonic inspection must be capable ofproviding equivalent sensitivity. Also, the type of inspection desired may adversely affect adjacentparts. Inspection methods in this manual were selected in order to provide maximum detectionsensitivity while requiring a minimum of removal or disassembly; and at the same time, protectadjacent areas from damage. Radiographic inspection is used only to examine areas partly or totallyhidden, or where the suspected damage is internal to the part. Where one method of inspection(primary) reveals an indication of a crack, another method (backup) should be used to verify if acrack is actually present. Quite often backup procedures are limited to disassembly and a goodvisual inspection. Certain cases may arise when another NDI method could be used to preventneedless or complicated disassembly. For example, a crack in a spar cap may not appear clearlyon radiographic film due to cloudiness caused by sealant or substructure clutter. A backup eddycurrent or ultrasonic method could be used for verification and if no indications were observed,disassembly would not be necessary. Whenever a backup method is used, it shall be specified inevery case where the initial damage indication may not be positive proof that a reject conditionexists.1.4.3 PreparationofHelicopterforNDI. Prior to NDI, the helicopter shall be prepared for safeground maintenance in accordance with applicable technical manuals listed in Table 1-1.1.4.4 PreparationofPartorAreaforNDI.WARNINGProlonged breathing of vapor from organic solvents, degreasers, or paint thinners isdangerous. Use respirators in confined areas per Occupational and EnvironmentalHealth Respiratory Protection Program (TB MED 502 (DLAM 1000.2)). Haveadequate ventilation. Avoid prolonged skin contact. Wear rubber gloves and goggles.All NDI methods require proper cleanliness of the part or area being inspected. Refer to Table 1-1 forthe applicable cleaning and corrosion control manual. The cleaning technique to be used will bedetermined by the type of foreign matter present, NDI method to be performed, and if the part isplated, painted, or has a protective coating. Scale and corrosion shall be removed completely beforeinspection. If removal of protective coatings, such as paint, phosphate coatings, black oxide, etc., isrequired, do not use removal methods that mechanically abrade the surface of the part to beinspected since this may cause damage or mask over potential surface cracks on the part. Someinspection methods, by their particular nature, will require that small openings and/or oil holesleading to obscure passages or cavities be plugged, such as the case of engine parts. A suitablenonabrasive material (i.e., Vaseline, grease, paraffin) should be used that is soluble in oil and can be
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