• Fleet demographics.
• Maintenance considerations.
• Operator input.
• Economics.
205. MAINTENANCE ACTIONS AND SERVICE INFORMATION. Based on the evaluation described above, the DAH will establish an LOV. The LOV may depend on maintenance actions and, if so, you must identify them. Maintenance actions could be inspections, modifications, or replacements.
a. For each required inspection, you should include—
• The structure to be inspected.
• The method of inspection.
• The ISP (the point in time at which to begin inspections).
• The repeat interval.
b. For required modifications or replacements, you should include—
• The structure to be modified or replaced.
• The method of modification or replacement.
• The SMP (the point in time to begin the modification).
The service information for these maintenance actions must include all the information above plus the procedures for accomplishing them. See Appendix 6 for further information on ISP and modification start point.
c. The maintenance actions required to support the LOV, if any, fall into one or more of the following categories—
(1) Mandatory Maintenance Actions Supporting the LOV. DAHs may decide to use only existing type design data and maintenance actions for which service information has been mandated by an AD. Modifications and replacements mandated by AD would be identified with the airplane structural configuration to be evaluated, and thus would be already included in the LOV. If an inspection previously mandated by AD to address WFD will be used to support the LOV, it should be identified and included with the LOV.
(2) Maintenance Actions Identified and Already Issued. DAHs may choose to use previously published service information to establish the LOV. A list of such maintenance actions must be submitted to the responsible Aircraft Certification Service office. The FAA will then issue ADs to ensure that operators perform these maintenance actions to support the LOV.
(3) Maintenance Actions Identified, but Not Issued. DAHs may propose to support an LOV farther out in time by using new maintenance actions—maintenance actions for which service information has not yet been published. In this case, the DAH must submit to the responsible Aircraft Certification Service office a list identifying each of those maintenance actions and a binding schedule for when they will be made available. This schedule should allow for the time required by the FAA AD rulemaking process, as well as for the time required for operators to incorporate those maintenance actions into their maintenance programs and carry out those maintenance tasks. This is to ensure that high-time airplanes do not pass the threshold for beginning inspections or modifications before those inspections or modifications have been made mandatory.
206. REQUIREMENT FOR ALS. The ALS of the Instructions for Continued Airworthiness (ICA) is required by part 25, Amendment 25-54 (September 11, 1980) and later. Airplanes certificated to Amendment 25-54 and later will have an ALS specifying those items with mandatory replacement or inspection times and related structural inspection procedures approved under § 25.571. Before 1980 those airworthiness limitations had been contained in chapter 5 of the airplane maintenance manual. Under § 26.21, a DAH with airplanes that do not have an ALS must create one and include the LOV. If an airplane does have an ALS, the DAH must revise it to include the LOV. Any new ALS and any ALS revision must be submitted to the responsible Aircraft Certification Service office for review and approval.
207. SUPPORTING DATA. Supporting data for the LOV must include:
a. Identification of the airplane structural configurations that were evaluated.
b. Summary of the operational statistics of the fleet, including accumulated flight cycles and flight hours.
c. Assumptions made about operational loading.
d. Identification and description of the structure susceptible to WFD.
e. Identification and description of the analytical methods used in the WFD evaluation.
f. Results of the WFD evaluations.
g. Guidance on reporting inspection findings (see paragraph 210 and Chapter 4 of this AC for further information).
208. RESPONSIBLE AIRCRAFT CERTIFICATION SERVICE OFFICE APPROVAL.
The items that require FAA approval are:
a. The compliance plan.
b. An ALS with the LOV incorporated (and supporting data).
c. The list of any required maintenance actions not mandated by ADs.
d. A binding schedule for publishing any required service information not yet published.
The time it takes for FAA approval of compliance data will be determined by the quality of the DAHs’ submissions and the responsiveness of DAHs to issues raised by the FAA.
209. MAKING LOV DATA AVAILABLE. Once the initial LOV is approved by the responsible Aircraft Certification Service office, you must make the LOV available to operators of affected airplanes. This could be by normal business procedures, such as through the existing revision distribution processes, by website access, by email, or by U.S. mail.
210. DAH REPORTING. Reporting requirements for DAHs remain the same. However, when reporting structural defects in compliance with existing rules, DAHs should include the following information:
a. Description (with a sketch) of the damage, including crack length, orientation, location, flight cycles/hours, and condition of structure.
b. Results of follow-up inspections by operators that identify similar problems on other airplanes in the fleet.
c. Findings from inspections performed during repair, modification, or replacement that identify additional similar damage sites.
d. Description of adjacent repairs within the same structure.
14 CHAPTER 3—§ 26.23 EXTENDED LOVs
300. GENERAL INFORMATION ABOUT CHAPTER 3. This chapter gives guidance for extending an LOV approved under § 25.571, § 26.21, or § 26.23. The requirements for extending an LOV are the same as those for establishing the initial LOV except for the differences noted in Table 2 below. This chapter explains the process involved, the documentation required, and the deliverables.
Table 2 Differences Between LOV And Extended LOV § 26.21 (Initial LOV—required) § 25.571 (Initial LOV—required) § 26.23 (Extended LOV—optional) Who Establishes the LOV? DAH Applicant Any Person (STC required if not DAH) What Airplanes Are Affected?
Airplanes > 75,000 lbs MTGW All Transport Category Airplanes Airplanes with an LOV per §§ 25.571,
26.21, 26.23 What Configuration is Considered?
Configuration at Effective Rule Date Configuration of production airplane Configuration at Approval Date of Extended LOV How are Maintenance Actions Mandated?
AD Placement in ALS Placement in ALS When is Unpublished Service Information Due?
By Date Indicated in the Binding Schedule By Date of TC Approval or Delivery of the First Airplane or Issuance of a Standard Certificate of Airworthiness or Date of LOV Approval, Whichever Occurs Latest By Date of Approval of the Extension Is Compliance Plan Required? Yes per § 26.21(d) Not Required by § 25.571 but Recommended as Part of the Normal Certification Process per Part 21 Not Required by § 26.23 but Recommended as Part of the Normal Certification Process per Part 21
301. APPLICATION FOR EXTENDED LOV. Any person may apply to extend an existing LOV established under § 25.571, § 26.21, or § 26.23. The applicant must demonstrate that WFD will not occur in the airplane up to the proposed extended LOV. The applicant should consider the age (flight cycles or flight hours or both) of high-time airplanes relative to the existing LOV to determine when to begin developing data to extend it. Because the data is likely to include
15 additional full-scale fatigue testing, the applicant should allow sufficient time (e.g., four years) to complete such testing and to submit the compliance data for approval. An extended LOV is a major change to the type design of an airplane. Thus any person applying for an extended LOV must use the processes for an ATC (subpart D of 14 CFR part 21) or STC (subpart E of part 21).
An extended LOV may also include specified maintenance actions, which would be part of the new LOV approval. Extended LOVs, along with any required maintenance actions for the extended LOV, would be incorporated into the ALS.
302. AIRPLANE STRUCTURAL CONFIGURATION FOR AN EXTENDED LOV.
Persons seeking approval of an extended LOV must identify the airplane structural configuration for each airplane model they are evaluating for WFD and perform that evaluation. The applicant need not extend the LOV for the entire group of airplanes for which the existing LOV was established and instead may extend the LOV for only a subset of those airplanes. The structural configuration considered must be the configuration evaluated for the existing LOV plus any additional modifications and replacements mandated by AD up to the approval date of the extended LOV.
303. ESTABLISHING AN EXTENDED LOV AND SUPPORTING DATA. The process for establishing an extended LOV, and the documentation required, is the same as that for an initial LOV. Depending on where in the life of the airplane the initial LOV was established, this may mean that full scale fatigue tests are necessary to substantiate the extended LOV. See AC 25.571-1 (as revised) for guidance on performing full-scale fatigue tests.
304. AIRWORTHINESS LIMITATIONS SECTION (ALS). Only DAHs may revise the ALS of the ICA for their airplanes. Anyone else adding limitations must do so in the form of a supplement. The extended LOV, along with any service information that supports it, must be incorporated into the ALS. TC holders would do this in the form of a revision, and other persons would add a supplement. Service information documented in the ALS or any supplement to it become airworthiness limitation items (ALI).
305. FAA APPROVALS FOR EXTENDED LOVs. For approval of an extended LOV the applicant and the FAA would follow the same procedures they use during approval of ATCs or STCs. For an extended LOV, the ALS, with the LOV and any required service information incorporated (and supporting data), requires FAA approval.
16 CHAPTER 4—COMPLIANCE INFORMATION FOR OPERATORS
400. GENERAL INFORMATION FOR OPERATORS. This chapter tells operators how to incorporate an LOV approved by the responsible Aircraft Certification Service office into their maintenance programs. It applies to 14 CFR part 121 operators of transport category airplanes and to foreign air carriers or foreign persons operating U.S.-registered transport category airplanes under 14 CFR part 129. Under § 121.1115 and § 129.115, no one may operate an affected airplane unless it has an ALS with an LOV approved under Appendix H to part 25 or § 26.21. Under § 91.403(c), an operator must comply with any ALS referenced in operations specifications issued to it under part 121 or 129. This chapter describes the process for incorporating the ALS with the LOV into the maintenance program and the procedure for approval of the maintenance program revisions by the principal maintenance inspector (PMI). If a DAH develops maintenance actions to support the LOV under § 26.21, those maintenance actions would be mandated by AD. This chapter also provides guidance to operators who choose to incorporate an extended LOV. If there are any maintenance actions developed to support the extended LOV, they will be included in the ALS.
401. AIRWORTHINESS LIMITATIONS SECTION (ALS). Depending on the airplane’s certification basis, a DAH would have either revised an ALS or established a new one to include the LOV for affected airplanes. The DAH must make the ALS available to operators (see paragraph 209) for incorporation into their maintenance programs.
a. Airplanes Subject to § 26.21. For any existing airplane that does not have an ALS, the DAH must create one under § 26.21 to include an LOV. If an existing airplane does have an ALS, the DAH would revise it under § 26.21 to include an LOV.
b. Airplanes with TCs Applied for After January 14, 2011, Subject to § 25.571. Unlike § 26.21, § 25.571 applies to all transport category airplanes, regardless of the rule under which they are operated. Under § 25.571, the FAA may issue a design approval for an airplane model before full-scale fatigue testing has been completed. The DAH would establish the LOV after completion of this testing, in accordance with an FAA-approved schedule. Operators may operate such airplanes while the DAH is performing the fatigue testing. To do this, they must incorporate into their maintenance program the ALS with a number of cycles equal to ½ the number of cycles accumulated on the fatigue test article. Under § 91.403(c), operators may not fly these airplanes beyond that limitation. The number of cycles in the ALS may be revised by the DAH as additional cycles are accumulated on the test article. Although it is not required, operators may then revise their maintenance program to reflect the new number. Once fatigue testing is complete and the LOV is established and approved, operators may revise their maintenance program to include the LOV. If they do not, the previously described number of cycles entered into the ALS will serve as the LOV. The LOV is an
17 airworthiness limitation, and no airplane may be operated beyond the LOV stated in the ALS.
402. AIRPLANES WITHOUT LOVs. Operators may be faced with a situation where an LOV for a certain model airplane is not available for compliance with the operating rule. This may happen because the DAH has not provided an LOV, or it can happen because the operator wants to operate an airplane on the excluded list for § 26.21 and the DAH wasn’t required to develop one.
• If the DAH has not provided an LOV on an airplane for which it was required, the operator may use the default LOV published in Table 1 of § 121.1115 or § 129.115.
• If an operator intends to operate an airplane on the exclusion list of § 26.21, that operator may develop its own LOV or use the default LOV published in Table 2 of § 121.1115 or § 129.115.
Because these default LOVs are part of §§ 121.1115 and 129.115, there is no further need for approval from the responsible Aircraft Certification Service office. However, the operator must still receive PMI approval to incorporate the default LOV into its maintenance program.
403. ADDING AN AIRPLANE TO AN OPERATOR’S FLEET AFTER THE COMPLIANCE DATE HAS PASSED. Before an air carrier adds an airplane to its operations specifications, the following applies:
a. If the airplane was previously operated under an FAA-approved maintenance program, the new operator must ensure that the applicable LOV is incorporated into its maintenance program.
b. If the airplane was not previously operated under an FAA-approved maintenance program, the operator must incorporate the applicable LOV.
c. If the airplane is U.S.-registered, and will be in use in operations under 14 CFR part 129, the foreign owner or operator must incorporate the ALS containing the LOV into the maintenance program.
404. EXTENDED LOVs. Any person may apply for an extended LOV. Section 26.23 defines an extended LOV as a major change to the type design of an airplane. An applicant must use the ATC or STC process when applying for an extended LOV. See Chapter 3 of this AC for further guidance. To operate an airplane to its extended LOV, operators may need to perform maintenance actions to prevent WFD from occurring. Those maintenance actions must be specified as ALIs in the ALS of the ICA. If an extended LOV is approved for an airplane, operators are not required to incorporate it unless they want to operate the airplane beyond the current LOV (initial or previously approved extended LOV) in effect. The person with the
18 approved extended LOV is not required to make it available to all operators of airplanes for which it is applicable.
405. PMI APPROVAL. Operators must submit maintenance program revisions, containing the ALS with the LOV, to the PMI or Flight Standards International Field Office for review and approval. After the PMI or Flight Standards International Field Office has found these changes acceptable, they would approve the revision through the existing approval processes for time limitations. Any subsequent revision to this limit will follow the same approval process. The ALS must be clearly distinguishable within the maintenance program.
406. OPERATOR REPORTING. Reporting requirements for operators remain the same.
However, when reporting fatigue-related structural defects in compliance with existing rules, operators should include the following information:
• Description (with a sketch) of the damage, including crack length, orientation, location, flight cycles/hours, and condition of structure.
• Results of follow-up inspections by operators that identify similar problems on other airplanes in the fleet.
• Findings from inspections performed during repair, modification, or replacement that identify additional similar damage sites.
• Description of adjacent repairs within the same structure.
Operators should also report the items above, and all suspected cases of MSD/MED, to DAHs and, if possible, provide them with the damaged structure for examination and further assessment.
Appendix 1 A1-1 APPENDIX 1
RELATED REGULATIONS AND DOCUMENTS The regulatory basis of this AC is comprised of the following parts of 14 CFR:
• Part 21, Certification Procedures for Products and Articles.
• Part 25, Airworthiness Standards: Transport Category Airplanes.
• Part 26, Continued Airworthiness and Safety Improvements for Transport Category Airplanes.
• Part 43, Maintenance, Preventive Maintenance, Rebuilding, and Alteration.
• Part 119, Certification: Air Carriers and Commercial Operators.
• Part 121, Operating Requirements: Domestic, Flag, and Supplemental Operations.
• Part 121, Subpart AA, Continued Airworthiness and Safety Improvements.
• Part 129, Operations: Foreign Air Carriers and Foreign Operators of U.S.-Registered Aircraft Engaged in Common Carriage, Subpart B, Continued Airworthiness and Safety Improvements.
You can download a copy of 14 CFR from the U.S. Government Publishing Office website at https://www.govinfo.gov/GovInfo. Below are the specific regulations pertinent to this AC:
a. § 21.3, Reporting of failures, malfunctions, and defects.
b. § 21.50, Instructions for continued airworthiness and manufacturer’s maintenance manuals having airworthiness limitations sections.
c. § 21.101, Designation of applicable regulations.
d. § 25.571, Damage-tolerance and fatigue evaluation of structure.
e. § 25.1529, Instructions for Continued Airworthiness.
f. Appendix H to part 25, Instructions for Continued Airworthiness.
g. § 26.21, Limit of validity.
h. § 26.23, Extended limit of validity.
Appendix 1 A1-2
i. § 43.13, Performance rules (general).
j. § 43.16, Airworthiness limitations.
k. § 91.403, General (under Maintenance, Preventive Maintenance, and Alterations).
l. § 121.703, Service difficulty reports.
m. § 121.1115, Limit of validity.
n. § 129.115, Limit of validity.
REFERENCES. The following list of related documents (as revised) is provided for information purposes and are not necessarily directly referenced in this AC.
a. Advisory Circulars. You can find the following ACs on the FAA’s website at https://www.faa.gov/regulations_policies/advisory_circulars and the Dynamic Regulatory System (DRS) at https://drs.faa.gov/browse.
(1) AC 20-107, “Composite Aircraft Structure.”
(2) AC 21.101-1, “Establishing the Certification Basis of Changed Aeronautical Products.”
(3) AC 26-1, “Part 26, Continued Airworthiness and Safety Improvements.”
(4) AC 25.571-1, “Damage Tolerance and Fatigue Evaluation of Structure.”
(5) AC 25.1529-1, “Instructions for Continued Airworthiness of Structural Repairs on Transport Airplanes.”
(6) AC 91-56, “Continuing Structural Integrity Program for Airplanes.”
(7) AC 91-82, “Fatigue Management Programs for In-Service Issues.”
(8) AC 120-16, “Air Carrier Maintenance Programs.”
(9) AC 120-73, “Damage Tolerance Assessment of Repairs to Pressurized Fuselages.”
(10) AC 120-93, “Damage Tolerance Inspections for Repairs and Alterations.”
b. FAA Policy. A copy of the following policy statement can be downloaded from DRS at https://drs.faa.gov/browse: PS-ANM110-7-12-2005, Policy Statement,
Appendix 1 A1-3 “Safety—A Shared Responsibility—New Direction for Addressing Airworthiness Issues for Transport Airplanes,” issued July 6, 2005, effective July 12, 2005.
c. FAA Orders. Copies of the following Orders can be downloaded from DRS at https://drs.faa.gov/browse.
(1) Order 8110.54, “Instructions for Continued Airworthiness Responsibilities, Requirements, and Contents.”
(2) Order 8900.1, “Flight Standards Information Management System.”
(3) Order 8110.104, “Responsibilities and Requirements for Implementing Part 26 Safety Initiatives.”
d. Related Documents. Copies of the following reports can be downloaded from the FAA website at https://www.faa.gov and the Airlines for America (A4A) website at https://publications.airlines.org, as applicable.
(1) A Report of the AAWG – Recommendations for Regulatory Action to Prevent Widespread Fatigue Damage in the Commercial Airplane Fleet, Revision A, dated June 29, 1999 (a report of the Airworthiness Assurance Working Group for the Aviation Rulemaking Advisory Committee Transport Aircraft and Engine Issues Group), at https://www.faa.gov/aircraft/air_cert/design_approvals/transport/aging_air craft.
(2) A Report of the AAWG – Widespread Fatigue Damage Bridging Tasks – Multiple Element Damage, dated July 23, 2003 (a report of the Airworthiness Assurance Working Group for the Aviation Rulemaking Advisory Committee’s Transport Aircraft and Engine Issues Group), at https://www.faa.gov/regulations_poli cies/rulemaking/committees/documents/media/TAEaaT6-aa-12151999.pdf.
(3) A Report of the AAWG – Recommendations for Regulatory Action to Enhance Continued Airworthiness of Supplemental Type Certificates, Final Report, dated January 21, 2003, at https://www.faa.gov/regulations_policies/rulemaking/com mittees/documents/media/TAEaaT1-03222001.pdf.
(4) A4A Spec 120: Removable Structural Components Industry Guidelines, Revision 2015.1, at https://publications.airlines.org/products/spec-120-removablestructural-components-industry-guidelines-revision-2015-1.
(5) A Report of the AAWG – Recommendations Concerning ARAC Tasking FR Doc. 04-10816, Re: Aging Airplane Safety Final Rule, 14 CFR 121.370a and 129.16, Task 3 Final Report, dated April 11, 2007, at https://www.faa.gov/sites/faa.gov/files/a ircraft/air_cert/design_approvals/transport/AAWGtask3Rpt.pdf.
Appendix 2 A2-1 APPENDIX 2
DEFINITIONS For purposes of this AC, the following definitions apply:
Airplane structural configuration—The approved type certificate (TC) design, which includes the original design, any model variations or derivatives, and alterations or replacements mandated by AD.
Airworthiness limitation item (ALI)—A maintenance action item identified in the Airworthiness Limitations section (ALS) of a design approval holder’s (DAH) Instructions for Continued Airworthiness (ICA). These items may contain mandatory modification or replacement times, mandatory inspection times, or inspection procedures.
Airworthiness Limitations section (ALS)—A collection of mandatory maintenance actions required for an airplane’s structure and fuel tank systems. The ALS is part of an airplane’s ICA.
For structural maintenance actions, the ALS includes structural modification times, replacement times, structural inspection thresholds and intervals, and related structural inspection procedures.
Alteration or modification—A design change made to an airplane. Within the context of this AC, the two terms are synonymous.
Amended type certificate (ATC)—An approved change to an airplane’s original TC made by the TC holder. Only the holder of the TC may apply for an ATC.
Baseline structure—The structure that is designed under the original TC or ATC for that airplane model.
Damage tolerance—The attribute of a structure that permits it to retain its required residual strength without detrimental structural deformation for a period of use after the structure has sustained a given level of fatigue, corrosion, or accidental or discrete source damage.
Design approval holder (DAH)—The term applied to the holder of any design approval, including TC, ATC, supplemental type certificate (STC), amended STC, parts manufacturer