Document ID: chunk:federal_register_of_legislation:F2007L04654:body:0:p2
Version: federal_register_of_legislation:F2007L04654
Segment Type: other
Provision Reference: 
Character Range: 2810–5903

approved maintenance document, Appendix I to this Order specifies the means by which an approved system must be selected.

4 Selection of dye penetrant processes

       4.1When, for a given application, a dye penetrant process is specified in Civil Aviation Orders or an approved maintenance document, a process of equal or greater sensitivity may be used.

       4.2When no dye penetrant process is specified for a given application in Civil Aviation Orders or an approved maintenance document, Appendix II to this Order constitutes an approved dye penetrate process.

5 Control of penetrant materials and equipment

       5.1A dye penetrant inspection must not be made unless the dye penetrant materials and equipment have been checked within the time and according to the procedures specified in Appendix III to this Order.

Appendix I

This Appendix specifies the means of selecting suitable dyes penetrate systems for
given applications.

1 The classification of dye penetrant systems

       1.1Dye penetrant systems (as defined in Civil Aviation Order 108.10) may be classified in the following 7 groups:

              Group 1 Consisting of a solvent-removable colour contrast penetrant, a penetrant remover (solvent), and a liquid suspended or liquid soluble developer.

              Group 2 Consisting of a post-emulsifiable colour contrast penetrant, an emulsifier, and a liquid suspended or liquid developer.

              Group 3 Consisting of a water-washable colour contrast penetrant and a liquid suspended or liquid soluble developer.

              Group 4 Consisting of a water-washable fluorescent penetrant and a dry, liquid suspended or liquid soluble developer.

              Group 5 Consisting of a post-emulsifiable fluorescent penetrant, an emulsifier and a dry, liquid suspended or liquid soluble developer.

              Group 6 Consisting of a high-sensitivity, post-emulsifiable fluorescent penetrant, an emulsifier and a dry, liquid suspended or liquid soluble developer.

              Group 7 Consisting of a solvent-removable fluorescent penetrant, a remover (solvent) and a dry, liquid suspended or liquid soluble developer.

Note   The above groupings are similar to those given in the US Military Specification Mil-25135C. This specification defines a minimum sensitivity requirement for each group. A given system may, however, be of a sensitivity considerably higher than this minimum. Thus, it is possible, for instance, for a Group 4 system to be of Group 6 sensitivity.

       1.2Solvent removers and emulsifiers may be used in a liquid or foamed form.

2 Choice of system

       2.1The use of colour contrast penetrant systems (Groups 1, 2 or 3) is acceptable:

(a) where the flaws to be located are relatively, large and open at the surface such as would be normally the case in sheet metal parts; or

(b) when the roughness of the surface to be inspected is such as to negate the greater sensitivity of fluorescent penetrants.

       2.2When the flaws located are small fatigue or stress corrosion cracks, or cracks which are 'tight'