The STG meeting provides a forum to coordinate airframe structural safety and industry issues between operators, manufacturers and regulators. All three share key roles in assuring continued airworthiness. STGs were chartered by the Airworthiness Assurance Working Group (AAWG) in 1988 to address aging airplane issues. The AAWG charter was retired in 2017 but the STGs have remained engaged.
In this topic we would like to discuss New rules released to address aging aircraft structural issues for Boeing.
Released on August 5, 2020
Certification Specifications (CS) and Guidance Material (AMCs and GM) released on December 17, 2020
Entry into Force (EIF) date is February 26, 2021
Applies to aircraft registered in an EASA Member State or registered in a third country and used by an operator established or residing in the European Union
The rule addresses the aspects of the FAA aging airplane initiatives (similar to 14 CFR Part 26):
Widespread Fatigue Damage (WFD)
Limit of Validity (LOV)
Required Service Actions
Damage Tolerance Evaluation and Inspections for Airplane Structure, Changes and Repairs
AWL/SSID/SSIP
Repair Evaluation Guidelines (REG)
Identification of Fatigue Critical Structure
Corrosion Prevention and Control Program (CPCP)
Additionally, it includes a requirement to monitor the validity of the continuing structural integrity program which was not included in the FAA Part 26 regulation.
Here you can find EU Regulation Number and the Title:
26.300 - Continuing structural integrity programme for ageing aeroplanes structures –general requirements
6.301 - Compliance Plan for (R)TC holders
26.302 - Fatigue and damage tolerance evaluation
26.303 - Limit of Validity
26.304 - Corrosion prevention and control programme
26.305 - Validity of the continuing structural integrity programme (not a part of FAA rule)
26.306 - Fatigue critical baseline structure
26.307 - Damage tolerance data for existing changes to fatigue critical structure
26.308 - Damage tolerance data for existing repairs to fatigue critical structure
26.309 - Repair evaluation guidelines
26.330 - Damage tolerance data for existing supplemental type-certificates (STCs), other existing major changes and existing repairs affecting those changes or STCs
26.331 - Compliance Plan for STC holders
26.332 - Identification of changes affecting fatigue critical structure
26.333 - Damage tolerance data for STCs and repairs to those STCs approved on or after 1 September,2003
26.334 - Damage tolerance data for STCs and other changes and repairs to those changes approved before 1 September 2003
26.370 - Continuing airworthiness tasks and aircraft maintenance
Overview of EASA Rule:
Operator Requirements (26.370)
26.370 Continuing airworthiness tasks and aircraft maintenance programme
(utilizes the TCH data from 26.302 –26.304 and 26.306 –26.309)
(a) Operators shall ensure the continuing airworthiness by preparing the maintenance programme that shall include:
(i) an approved damage-tolerance-based inspection programme;
(ii) a means for addressing the adverse effects that repairs and modifications may have on fatigue-critical structure and on inspections provided for in point (a)(i);
(iii) an approved LOV;
(iv) a CPCP
(b) The following deadlines shall apply to the obligation referred to in paragraph (a):
(i) the aircraft maintenance programme shall be revised to address the requirements of points (a)(i), (a)(ii) and (a)(iv) before 26 February 2024 or before operating the aeroplane, whichever occurs later;
(ii) the aircraft maintenance programme shall be revised to address the requirements of point (a)(iii) before 26 August 2021, or 6 months after the publication of the LOV, or before operating the aircraft, whichever occurs later.
Current Status
Boeing has submitted the following documents to EASA to meet rule requirements:
Boeing Compliance Plan for Points 26.302 to 26.309 –submitted on May 25, 2021
Boeing Compliance Plan for Points 26.331 to 26.334 -submitted on August 24, 2021
Fatigue Critical Baseline Structure (FCBS) Lists for 717, 727, 737, 747, 757, 767, 777, 787, D-11 and MD-80 models –submitted on June 24, 2021
Boeing has not received comments or concurrence from EASA yet on the compliance plans. EASA and Boeing had discussions before submittal and there was general agreement on acceptable compliance approaches.
Regulation: 26.302 Fatigue and damage tolerance evaluation
Boeing Compliance Approach:
Existing damage tolerance programs (SSID, AWL) are acceptable for compliance with the EASA regulations
Effect on Operators:
No effect
Regulation: 26.303 Limit of Validity
Boeing Compliance Approach:
Existing LOVs documented in the Airworthiness Limitations (AWL) are acceptable for compliance to the EASA rule
Boeing and EASA agreed –AWL documents will be updated with information on the EASA rule at the next revision of each document per Boeing standard procedures
Effect on Operators - Minimal effect -Existing LOVs and maintenance actions are unchanged
Boeing will release a Service Letter to operators required to comply with EASA Part 26 Point 370, including general information to support the operators showing of compliance to 26.370, including the Boeing AWL documents applicable for compliance to 26.303 LOV.
Regulation: 26.304 Corrosion prevention and control program
Boeing Compliance Approach:
Existing CPCPs are acceptable for compliance to the EASA regulations
Effect on Operators:
No effect
Regulation: 26.305 Validity of the continuing structural integrity program
Boeing Compliance Approach:
The key parts of the Boeing Plan:
The process will utilize data from the following sources to assess the continuing effectiveness of the structural integrity program and the assumptions it is based on.
Boeing Safety Process
Structures Task Group
Boeing will submit a description of the process which ensures the continuing structural program remains valid throughout the operational life of the airplane, taking into account service experience and current operations (due February 26, 2023).
Regulation: 26.305 Validity of the continuing structural integrity program
Boeing Compliance Approach :
The process includes criteria for summarizing structural findings, assessing and recording the contributing factors for the findings and a criteria for establishing when structure should be modified or the inspection program revised.
Note: The EASA rule proposes the addition of fleet sampling programs. Boeing’s response is that additional sampling programs are not required based on existing Boeing programs (Boeing Safety Process, 100% inspection for DT programs, CPCP, WFD inspection/modification programs).
Effect on Operators:
The STGs will continue to monitor aging fleet structural issues (i.e. Service Actions, CPCP, SSIP / AWL and emergent fleet issues)
Boeing will work with the operators in 2022 to formalize a plan that supports compliance to Point 26.305
AMC 20-20A, paragraph 5 provides additional guidance.
No additional effects are anticipated
Regulation: 26.306 Fatigue critical baseline structure
Boeing Compliance Approach:
Existing FCBS lists are acceptable for compliance with the EASA regulations
Effect on Operators:
No effect
Regulation: 26.307 Damage tolerance data for existing changes to fatigue-critical structure
Boeing Compliance Approach:
The identification of changes affecting FCS and the associated development of FCAS/FCMS lists and DTE/DTI per the FAA regulations meet EASA requirements
Effect on Operators:
No effect
Regulation: 26.308 Damage tolerance data for existing repairs to fatigue-critical structure
Boeing Compliance Approach:
The identification of repairs affecting FCS and the associated development of DTE/DTI per the FAA regulations meet EASA requirements
Effect on Operators:
No effect
Regulation: 26.309 Repair evaluation guidelines
Boeing Compliance Approach:
The existing REG documents meeting the FAA regulations are acceptable.
A new supplement to those documents which will define for operators subject to 26.370 that the implementation of the surveys must be achieved without exceeding the design service goal or within 7 years of EASA approval of the REG, whichever occurs later.
The supplement will also clarify compliance time for obtaining and implementing DTIs.
Effect on Operators:
The operators may be minimally affected by the EASA timeline for survey implementation referred to above.
Please note that all Regulations can be found on EASA website by regulation number.
In the next article we will provide more information on the Rotable Parts.
Picture by: Copyright © Dennis Muller - www.dennismuller.net