2. Objective

The objective of this TP is to enhance the maintenance of aircraft EWIS through adoption by the aviation industry of the following:

  1. Enhanced Zonal Analysis Procedure (EZAP). This TP presents an "enhanced zonal analysis procedure" and logic that will benefit all aircraft regardless of whether they currently have a structured zonal inspection program (see Appendix A. Enhanced Zonal Analysis Logic Diagram and Steps and Appendix B. EZAP Worksheets). Application of this procedure will ensure that appropriate attention is given to wiring installations. Using EZAP it will be possible to select stand-alone inspections (either General or Detailed) and tasks to minimize the presence of combustible material. The procedure and logic in this TP complement existing zonal analysis procedures and will also allow the identification of new wiring tasks for those aircraft that do not have a structured zonal inspection program.
  2. Guidance for General Visual Inspection (GVI). This TP clarifies the definition for a General Visual Inspection and describes what is expected from a stand-alone GVI or zonal inspection task.
  3. Protections and Cautions. This TP identifies information for the protection of aircraft EWIS and cautions to be added to maintenance instructions, that will lead to minimization of contamination and accidental damage while working on the aircraft.

The information concerning enhanced aircraft wiring maintenance that has been described in this TP applies to maintenance and inspection programs for all aircraft systems. When these new practices are used appropriately, it will improve the likelihood that EWIS degradation, including age related problems, will be identified and corrected. Therefore, the goal of enhanced wiring maintenance information is to ensure that maintenance actions, such as inspection, repair, overhaul, replacement of parts, and preservation, do not cause a loss of EWIS function, do not cause an increase in the potential for smoke and fire in the aircraft, and do not inhibit the safe operation of the aircraft.

To fully realize the objectives of this TP, air carriers, air operators, type certificate holders, STC holders, maintenance providers, repair stations and persons performing modifications or repairs, will need to rethink their current approach to maintaining and modifying aircraft wiring and systems. This may require more than simply updating maintenance manuals and work cards and enhancing training. Maintenance personnel need to be aware that aircraft EWIS should be maintained with the same level of intensity as any other system in the aircraft. They also need to recognize that visual inspection of wiring has inherent limitations. Small defects such as breached or cracked insulations, especially in small gage wire may not always be apparent. Therefore effective wiring maintenance combines visual inspection techniques with improved wiring maintenance practices and training.

Good wiring maintenance practices should contain a "protect, clean as you go" housekeeping philosophy. In other words, care should be taken to protect wire bundles and connectors during work, and to ensure that all shavings, debris and contamination are cleaned up after work is completed. This philosophy is a proactive approach to EWIS health. Wiring needs to be given special attention when maintenance is being performed on it, or around it. This is especially true when performing structural repairs, work under STCs or modifications.

To fully achieve the objectives of this TP it is imperative that all personnel performing maintenance on or around EWIS receive appropriate training. In addition to technical content regarding maintenance and inspection of EWISs, the training should also include sections on good maintenance practices, including the "protect, clean as you go" housekeeping philosophy. Advisory Circular AC-120-YY Aircraft Wiring Systems Training Program contains guidance on recommended content and lesson plans for this training.