Appendix A medium or high). Credit for fire mitigation capability can be given to zones that contain a fire detection and suppression system, or a zone that is designated a “fire zone.” Potential effects of a fire in such zones could then possibly be rated at a lower level. Consideration can also be given to whether the fire could be easily detected by crewmembers or passengers and to whether, if there was a fire, it could be extinguished or controlled by available means. Fire can result in severe outcomes, such as wire-to-structure or wire-to-wire shorting and arcing, in areas such as the cockpit, electrical power centers, and those that contain power feeder cables, which are subject to chafing, if they have flammable materials close by. A fire in these areas could present a high risk to continued safe flight and landing.
Potential effects of fire must also be considered when wiring is in close proximity (within 2 inches/50 mm) to both primary and backup flight controls. A GVI alone may not be adequate if a fire caused by failure of the wiring poses a risk to aircraft controllability.
At minimum, all EWIS in the zone will require a GVI at a common interval. For operators with a ZIP, this may be defined as a zonal GVI. For operators without a ZIP, it is a GVI of all EWIS in the zone.
The logic in figure 2 begins by asking a question:
• For airplane models with a ZIP, the logic asks: “Is zonal GVI alone effective for all EWIS in the zone?”
• For airplane models without a ZIP, the logic asks: “Is a GVI of all EWIS in the zone at the same interval effective for all EWIS in the zone?”
This step calls for consideration of whether there are specific items or areas in the zone that are more vulnerable to damage or contamination than others and thus may warrant a closer or more frequent inspection.
Such a determination could result in selection of a more frequent GVI, a stand-alone GVI (for operators with a zonal inspection program), or even a detailed inspection (DET). The intent is to select a DET of EWIS only when it is determined that a GVI will not be adequate. The person performing the EZAP should avoid unnecessarily selecting DET where a stand-alone GVI is adequate. Over-use of DET dilutes the effectiveness of the inspection.
The level of inspection required may be influenced by tasks identified in step 5 and step 6.
For example, if you have selected a cleaning task in step 5 and step 6 that will minimize accumulation of combustible materials in the zone, this may justify selecting a stand-alone GVI instead of a DET for the wiring in the zone.
b. Selecting an Inspection Interval. The inspection interval is determined by using a rating system that rates the likelihood of accidental damage and the hostility of environmental factors.
A-8
Appendix A The rating tables are designed to define increasing inspection frequency based on increasing risk of accidental damage and increasing severity of the local environment within the zone.
Refer to EZAP Worksheet 4 in this appendix.
The example “Interval Determination” table on EZAP Worksheet 4 provides a range of intervals you can choose from. Please note that these intervals are only an example. The particular intervals chosen should be compatible with the interval framework used in the existing maintenance or inspection program as detailed in the current MRBR. Your choice of interval should be based on the reasons for assigning specific rating values for hostility of environment and likelihood of accidental damage. You should also use your knowledge of the types of EWIS components to be inspected.
As an example, for a hostility of environment rating of 3 and a likelihood of accidental damage rating of 3, the table gives a range of inspection intervals. It says that the inspection should occur as frequently as every A check but the interval could be as long as once every 1C check. You should base your choice on the reasons that a 3 rating was assigned.
• The importance of assessing likelihood of accidental damage is that the higher the likelihood of accidental damage from multiple sources, the more frequent the inspection task should be. If, on the other hand, all of the factors except one have been rated as a 1, then the inspection interval could be somewhat longer.
• The choice of the inspection interval should also be based on what type of environment the EWIS is located in. Just as with the ratings for likelihood of accidental damage, the more the EWIS is exposed to various harsh environmental conditions, the more frequent the inspection interval should be. You should consider the assigned ratings from both of these tables—“Hostility of Environment” and “Likelihood of Accidental Damage”—and use sound maintenance judgment to assign the inspection task interval.
The selection of inspection tasks possible in this step is specific to whether the maintenance program includes a zonal inspection program (ZIP) or not.
For ZIP programs, the possible inspection tasks are:
• Zonal GVI
• Stand-alone GVI
• DET For non-ZIP programs, the possible inspection tasks are:
• GVI
• DET At the conclusion of this step you will have determined the required inspection level and interval for wiring in the zone. Task consolidation in step 9 allows consideration of whether A-9
Appendix A an inspection selected as a result of this analysis can be considered accomplished as part of the existing maintenance program.
STEP 9: Consider consolidation with existing inspection tasks in systems and powerplant and/or zonal programs.
This step in the procedure examines the potential for consolidation between the tasks derived from the EZAP and inspections that already exist in the maintenance program. Consolidation would require that the inspections in the existing maintenance program are performed in accordance with the inspection definitions provided in this AC. Consolidation with the fuel tank ICA is required by § 26.11(b) where possible. Compare new tasks identified by the EZAP logic against existing tasks in the maintenance program to ensure that:
a. Tasks are compatible with each other. Existing maintenance tasks and EZAP-generated inspection or maintenance tasks (such as restoration tasks) should not compromise or negate each other. For example, an EZAP-generated task should not compromise existing fuel tank system wire maintenance requirements (for example, those generated by SFAR 88) such as separation or configuration specifications.
b. Task intervals are aligned to the maximum extent possible so undue disturbance of EWIS and other systems located within the zone does not occur. However, the inspection interval you choose must ensure that the intent and reason for the EWIS inspection is not compromised. The EZAP-generated task interval is determined by completing EZAP Worksheet 4 in this appendix.
Example:
Results of the EZAP for a particular zone indicate that using an existing zonal GVI is an effective inspection task for all of the EWIS in the zone. The analysis should be continued to determine the appropriate inspection interval (EZAP Worksheet 4). If the results of the analysis contained on EZAP Worksheet 4 indicate that the EWIS inspection interval is greater than the interval for the existing zonal GVI, the existing zonal GVI interval should be used for the EZAP-identified inspection task. The existing zonal GVI interval cannot be escalated solely based on results of the EZAP analysis. The EZAP only analyzes the need for inspection type and frequency for EWIS within a zone. It does not analyze all of the systems in the zone. Therefore, its results cannot be used as the sole reason to escalate an existing zonal inspection task.
c. Redundant (or duplicate) tasks are consolidated into a single task.
For inspection programs that include a zonal inspection program (ZIP):
• You should not adjust the interval of the stand-alone inspection to match the interval of the existing zonal inspection solely for the purposes of aligning the separate task intervals. Task intervals should only be aligned if the interval will ensure that the safety objectives of identifying the stand-alone GVI in the first place can be met. One A-10
Appendix A of the criteria for considering task interval alignment is access requirements for the zone. Task intervals should be aligned to the maximum extent possible so undue disturbance of EWIS and other systems located within the zone does not occur. If a task is aligned with an existing zonal inspection, it must be identified as an EZAP-related task to prevent the possibility that it could be deleted or inappropriately escalated.
• Stand-alone GVIs and DETs identified by the EZAP should not be consolidated into the ZIP. They must be introduced and retained as dedicated tasks in the scheduled maintenance program under ATA 20 (the ATA category for electrical wiring), or ATA 28 in the case of combined SFAR 88 and EWIS inspection tasks. These tasks, along with tasks identified to reduce accumulation of combustible materials (known as cleaning or restoration tasks), should be uniquely identified to ensure they are not consolidated into the zonal program or deleted during future program development.
Within Maintenance-Steering-Group-3-based MRBRs, these may be introduced under ATA 20 with no failure effect category assigned. While a stand-alone GVI and a DET cannot be combined with existing zonal inspections, the intervals for performing them should be aligned with other maintenance tasks in the zone, such as zonal GVIs, to the extent possible.
Note:
In the past, there has been some confusion about using existing zonal GVIs in lieu of EZAP- identified stand-alone GVIs. However, a zonal GVI does not satisfy the intent of a stand alone GVI. Although on the surface it may appear that the zonal GVI would accomplish the same inspection of the EWIS within a zone that a stand-alone GVI would, it does not. This is because the stand-alone GVI forces the maintenance technician to pay particular attention to the EWIS that is identified as being necessary to inspect. It is this particular attention that will help ensure that EWIS degradation issues are identified and corrected before a potential safety issue arises. While a zonal GVI is a recognized and effective inspection technique, it does not focus particular attention on EWIS or any other system or structural component within the zone and, therefore, cannot be used in lieu of a stand-alone GVI when the EZAP identifies a stand-alone GVI as necessary.
For programs without a ZIP:
Although some non-zonal inspection programs may already include some dedicated inspections of EWIS that may be equivalent to new tasks identified by an EZAP, it is expected that a significant number of new EWIS inspections will be identified for introduction as dedicated tasks in the system and powerplant program. All new tasks identified by an EZAP should be uniquely identified to ensure they are not deleted during future program development.
A-11
Appendix A For programs with or without a ZIP:
The following guide can be used for programs with or without a ZIP to determine proper consolidation between EZAP-derived inspections and existing inspections of the same item or area. When an EZAP task is selected for consolidation, the documentation should include a record identifying it for traceability purposes.
• If the EZAP inspection interval and existing inspection interval are equal, but the
inspection levels are different, the more detailed inspection takes precedence (for
example, a 1C DET takes precedence over a 1C GVI).
• If the EZAP inspection interval and existing inspection interval are different, but the inspection levels are equal, the more frequent inspection interval takes precedence (for example, a 1C GVI takes precedent over a 2C GVI).
• If the EZAP inspection interval and level are different than the existing inspection interval and level, these tasks may be consolidated using the more frequent inspection and at the more detailed level (for example, a 1C DET takes precedent over a 2C GVI). When the more frequent inspection is less detailed, the tasks should not be consolidated.
For EZAP-developed STC tasks, it may not be possible for the STC holder to determine whether a ZIP exists on specific airplane that will use the STC. If a ZIP exists, consolidation of EZAP-derived STC tasks into an operator’s ZIP will be the responsibility of the operator and should be approved by the operator’s FAA principal inspector or cognizant Flight Standards District Office (FSDO). AC 120-99, Incorporation of Electrical Wiring Interconnection System (EWIS) Instructions for Continued Airworthiness into an Operator’s Maintenance Program, will contain guidance related to this.
Note:
The more frequent inspection at the more detailed level should be used, unless it is judged that performing the more detailed inspection too frequently can result in stressing/disturbance of EWIS components.
In cases where the STC holder determines a requirement for a GVI that should not be consolidated into a ZIP, this stand-alone GVI should be specifically identified as such in the EZAP-derived ICA for the STC.
A-12
Appendix A
3. Examples of Typical EZAP Worksheets.
a. For Anyone Required to Conduct an EZAP Evaluation. The following pages contain worksheets you can use to conduct an EZAP. The first six worksheets contain notes to assist you in proper use of the worksheet. There are blank worksheets in appendix H of this AC that you can copy and use to conduct the analysis.
• EZAP Worksheet 1: Enhanced Zonal Analysis – Details of Zone
• EZAP Worksheet 2: Enhanced Zonal Analysis – Assessment of Zone Attributes
• EZAP Worksheet 3A – For Airplane Models with a Dedicated Zonal Inspection Program (ZIP): Enhanced Zonal Analysis – Inspection Level Determination Based on Zone Size, Density, and Potential Impact of Fire
• EZAP Worksheet 3B – For Programs without a Dedicated Zonal Inspection Program (ZIP): Enhanced Zonal Analysis – Inspection Level Determination Based on Zone Size, Density, and Potential Impact of Fire
• EZAP Worksheet 4 – Intervals Based on “A” and “C” Checks: Enhanced Zonal Analysis – Interval Determination Based on Hostility of Environment and Likelihood of Accidental Damage
• EZAP Worksheet 5: Enhanced Zonal Analysis – Task Summary A-13
EZAP WORKSHEET 1 05/04/10 Enhanced Zonal Analysis - Details of Zone (steps 1 and 2 of figure 1) Zone Number: Zone Description:
Hydraulic plumbing Comments Hydraulic component (valves, actuators, pumps) Pneumatic plumbing Pneumatic components (valves, actuators) EWIS - power feeder (high voltage, high amperage) EWIS - motor driven devices A-14 EWIS - instrumentation and monitoring Use this area to describe the zone location, access, and boundaries. List the content of the zone such as installed equipment, wiring, other EWIS EWIS - data bus components, plumbing, components. Also note significant EWIS related items. Examples: "Wire bundle routed within 2 inches of high-temperature Electrical components anti-ice ducting." or "Zone contains IDG, RAT, APU and forward galley Primary flight control mechanisms power feeder cables."
Secondary flight control mechanisms The intent of the description is to provide the analyst with a clear understanding of what is in the zone and how it could potentially affect Engine control mechanisms wiring and other EWIS components within the zone.
Fuel system components Insulation Oxygen system components Potable water system components Appendix A AC 25-27A Waste water system components
EZAP WORKSHEET 2 05/04/10 Enhanced Zonal Analysis - Assessment of Zone Attributes (steps 3 through 7 of figure 1) Zone Number: Zone Description:
Answers and Explanations NO (Notes: Steps 1 & 2 Completed on worksheet 1)
3. Does the zone No further action is contain EWIS? YES necessary
3.
If the answer to the questions contained in step 3 and step 7 is "NO," then no further analysis is necessary.
NO . Is wiring or other NO
4. Are there, or are there EWIS components If the answer to question 5 is "YES" and a task is J likely to be, close to both primary identified that can significantly reduce the ur combustibles in the YES AND back-up hydraulic, YES likelihood of accumulation of combustible zone? mechanical, or electrical materials, the task and interval must be defined in flight controls? step 6. If the task identified is a cleaning (restoration) task to remove dust/lint accumulation from wiring, other EWIS components, and/or other
5. items within the zone, the interval for the task must be frequent enough to keep the zone, including the
5. Is there an effective task to significantly NO 8. EWIS inspection tasks determination. of accumulation of dust/lint on the EWIS and other EWIS, relatively clean based on the expected rate reduce the likelihood of accumulation of YES See worksheets 3A and 3B components components within the zone.
combustible materials? In all cases, after step 5 and/or step 6, the analysis
6. is continued to step 8.
6. Define task and interval. List on Continue the analysis Appendix A AC 25-27A worksheet 5, Task Summary area
EZAP WORKSHEET 3A - For Airplane Models with a Dedicated Zonal Inspection Program (ZIP) 05/04/10 Enhanced Zonal Analysis - Inspection Level Determination Based on Zone Size, Density, and Potential Impact of Fire (step 8 of figure 1, refer to figure 2) Zone Number: Zone Description:
Density / Zone Size —→ Zone Size Inspection Level Determination Based on Potential Effect of Fire in the Zone
• Assessment Small Medium Large Size / Density Factor 1 2 3 Low 1 2 3 Low Zonal GVI Zonal GVI Zonal GVI Density Medium 2 2 3 Potential Zonal GVI + Zonal GVI + Effects of Fire Medium Zonal GVI stand-alone GVI of stand-alone GVI of in the Zone some EWIS some EWIS High 2 3 Zonal GVI + Zonal GVI + Zonal GVI + High stand-alone GVI of stand-alone GVI and/or stand-alone GVI and/or some EWIS DET of some EWIS DET of some EWIS Circle appropriate result & insert below Circle appropriate result and answer questions in the boxes below RESULT YES Answers and Explanations
1. Is a Zonal GVI alone 2. List zone effective for the entire description and zone?* boundaries for Zonal - The tables on this worksheet are used to select the appropriate level of inspection for the EWIS in the zone GVI based on an assessment of zone size, density, and potential effects of fire in the zone.
This worksheet assumes the existing maintenance program already includes a dedicated zonal inspection program. It is assumed that an existing ZIP already includes a zonal GVT of all zones that contain wiring Define specific and other EWIS components, and that the inspection of the EWIS is included in the zonal GVI.
items/areas in the 2 Zonal GVI must be zone for which a If existing zonal GVI is an effective inspection task for all of the EWIS in the zone, the analysis must be augmented with a Stand-alone GVI is continued to determine the appropriate inspection interval (worksheet 4). During task consolidation afler stand-alone GVI justified completion of the analysis, the most frequent zonal GVI interval for the zone will take precedent.
and/or a DET inspection If the results of the analysis contained on worksheet 4 indicate that the EWIS inspection interval is greater than the interval for the existing zonal GVI, the existing zonal GVI interval cannot be escalated based
• If answer to box 1 is "YES," answer box 2 only and 4. Define specific solely on the results of the EZAP analysis.
then continue the analysis on worksheet 4 in order → zone for which a DET items/areas in the If a zonal GVI is not adequate for the EWIS in the zone, in addition to identifying the zonal GVI, the Appendix A AC 25-27A to determine the task interval. s justified 4 analyst must also identify the specific items/areas in the zone where a stand-alone GVI and'or DET inspection is necessary.
If answer to box 1 is "NO." answer boxes 2, 3, and 4 and then continue the analysis on worksheet 4 in order to determine the task interval.
EZAP WORKSHEET 3B - For Programs without a Dedicated Zonal Inspection Program (ZIP) 05/04/10 Enhanced Zonal Analysis - Inspection Level Determination Based on Zone Size, Density, and Potential Impact of Fire (step 8 of figure 1, refer to figure 2) Zone Number: Zone Description:
Density / Zone Size -• Zone Size Inspection Level Determination Based on Potential Effect of Fire in the Zone
• Assessment Small Medium Large • Size / Density Factor 2 Low 1 2 GVI of all EWIS in zone at GVI of all EWIS in zone at GVI of all EWIS in zone at Low same interval same interval same interval Density Medium 2 2 Effects of Potential Medium GVI of all EWIS in zone at same interval same interval + GVI of some GVI of all EWIS in zone at EWIS at more frequent GVI of all EWIS in zone at same interval + GVI of some EWIS at more Fire in the Zone interval frequent interval High 3 GVI of all EWIS in zone at GVI of all EWIS in zone at GVI of all EWIS in zone at same interval + GVI of some same interval + GVI of some High same interval + GV of some EWIS at more EWIS at more frequent EWIS at more frequent Circle appropriate result & insert below frequent interval interval and/or DET of some EWIS interval and/or DET of some EWIS RESULT Circle appropriate result and answer questions in the boxes below YES Answers and Explanations
1. Is a GVI alone 2. List zone effective for all EWIS in description and interval?* the zone at the same NO boundaries for GVI of all EWIS in the zone The tables on this sheet are used to select an inspection level based on zone size, density, and potential effect of fire in the zone. These factors are used to determine if a GVI of all EWIS in the zone at the same interval is adequate, or if some EWIS requires a more frequent GVI, or even a DET.
3. Define specific items/areas in the This worksheet is designed for operators whose existing maintenance zone for which GVI at program does not include a dedicated zonal inspection program. The Some EWIS requires more frequent minimum outcome of this analysis will always be a GVI of all EWIS in any GVI at more frequent interval is justified zone where the presence of combustible materials is possible and/or interval and/or DET wiring is located in close proximity to both primary and backup hydraulic or mechanical flight controls.
inspection
4. Define specific If a GVI of all EWIS in the zone at the same interval is adequate, the * If answer to box 1 is "YES," answer box 2 only and then continue the analysis on worksheet 4 in order to items/areas in the zone for which a DET analyst must identify the inspection requirement as "GVI of all EWIS in the zone" (box 2) and proceed to worksheet 4 to determine the GVI interval. Appendix A AC 25-27A determine the task interval. is justified If a GV of all EWIS in the zone at the same interval is not adequate, then If answer to box 1 is "NO." answer boxes 2, 3, and 4, the analyst must identify the specific items/areas in the zone where a and then continue the analysis on worksheet 4 in order to more frequent GVI (box 3) and/or a DET (box 4) is justified.
determine the task interval.
EZAP WORKSHEET 4 - Intervals Based on "A" and "C" Checks 05/04/10 Enhanced Zonal Analysis - Interval Determination Based on Hostility of Environment and Likelihood of Accidental Damage (step 8 of figure 1, refer to figure 2) Zone Number: Zone Description:
Likelihood of Accidental Damage Hostility of Environment Enter Number Here L 1 - Passive / 2 - Moderate / 3 - Severe Enter Number Here 1 - Passive / 2 - Moderate / 3 - Severe Ground handling equipment Temperature Foreign object debris (FOD) Vibration Weather effects (hail, rain, etc.)
Chemicals (toilet fluids, de-icing fluid, etc.)
Frequency of maintenance activities Humidity Fluid spillage Contamination Passenger Traffic Other Other Enter the Highest Number Here Enter the Highest Number Here Likelihood of Accidental Damage Interval Determination Interval selection is specific to each task identified on 2 3 worksheet 3A or 3B. For GV of entire zone, consider overall 1 14, 400 - 21,600 60 - 90 M 4C - 6C FH 7,200 - 14,400 FH 30 - 60 M 2C - 4C 3,600 - 7,200 FH 15 - 30 M 1C - 2C zone environment and likelihood of damage. For stand-alone GVI or DET, consider environment and likelihood of damage inspection. only in respect to the specific item/area defined for Examples of task interval ranges NOTE: Interval ranges are quoted in the rating table to 2C - 6C 1C - 4C A - 1C Hostility of 2 7,200 - 21,600 FH 3.600 - 14,400 FH 450 - 3,600 FH explain a typical arrangement of values. For a particular Environment 30 - 90 M 15 - 60 M 1 - 15 M application, these must be compatible with the interval framework used in the existing maintenance or inspection program (as detailed in the current MRBR). They may be 1C - 6C 1C - 4C A - 1C expressed in terms of usage parameter (for example, flight 3 3.600 - 21.600 FH 3,600 - 14,400 FH 450 - 3.600 FH hours or calendar time) or in terms of letter check.
15 - 90 M 15 - 60 M 1 - 15 M The inspection frequency should be based on increasing risk Appendix A AC 25-27A RESULT of accidental damage and increasing severity of the local Upon completion, enter all task and interval selections onto environment within the zone. In other words, the more worksheet 5, Task Summary ratings identified as moderate and severe should drive the inspection towards the lower end of the interval.
Enhanced Zonal Analysis - Task Summary EZAP WORKSHEET 5 05/04/10 Zone Number: Zone Description:
TASK SUMMARY Task Number Access Task Interval Task Description and Applicable Comments/Rationale/Assumptions Appendix A AC 25-27A