10. Enhanced Zonal Analysis Procedure

The Enhanced Zonal Analysis Procedure (EZAP) identified in Appendix A of this AC is designed to permit appropriate attention to be given to electrical wiring installations. This is achieved by providing a means to identify applicable and effective tasks to minimize accumulation of combustible materials and address wiring installation discrepancies that may not otherwise be reliably detected by inspections contained in existing maintenance programs.

For aircraft models operating on maintenance programs that already include a dedicated Zonal Inspection Program (ZIP), the logic described in this TP will result in enhancements to those programs, and the zonal inspection requirements may not differ greatly from the existing ZIPs.

In analysis conducted under the EZAP, items such as plumbing, ducting, systems installations, etc., should be evaluated for possible contribution to wiring failures. In cases where a General Visual Inspection is required to assess degradation of these items, a Zonal GVI within a ZIP may be considered as appropriate.

For those operators that do not have a dedicated ZIP, application of the logic is likely to result in identification of a large number of wiring related tasks that will need to be consolidated within the existing Systems/Powerplant Program.

In either case, any new tasks identified by the logic may be compared with existing tasks and credit given for equivalent tasks already contained in the maintenance program. For operators with ZIPs that already contain Zonal GVIs, the number of new tasks that must be added to the program may be significantly fewer than for an operator without a dedicated ZIP. Therefore, operators without a ZIP may find it beneficial to develop a ZIP in accordance with an industry-accepted methodology in conjunction with application of the EZAP.

The logic and procedures identified in this TP apply to TCs, STCs, and Service Bulletins. It is expected that the TC and STC holders would use the logic and procedures to identify any need for additional instructions for continued airworthiness. Operators may be required to use the logic to identify additional instructions for STCs where the STC has been "orphaned" (i.e., no longer supported by the STC holder).

While TC Holders are required to conduct the EZAP for all zones in an aircraft, it may be determined that EZAP for a Service Bulletin or STC is not necessary where the modification does not appreciably affect the zones where it is installed. Appendix C, "Determination if Service Bulletin Modification or STC Requires EZAP", was developed to identify modifications that sufficiently affect zone attributes to warrant re-application of EZAP to the entire zone.