Kind Reminder: Due Date is 26 February 2024 For Compliance of EASA Part-26

In aviation history, three aircraft accidents stand out regarding distinct structural failures: the Comet DH-106 1954 fuselage fatigue failure, B707 Luska tailplane failure, and B737 Aloha incident. These tragedies highlight the catastrophic consequences of structural degradation in aircraft, prompting regulatory authorities like the FAA and EASA to take essential actions for the continuous airworthiness of large transport category planes.

In the EU, the journey began with JAR 26, encompassing additional airworthiness requirements. Most of the requirements were simple, and there was enough approved design data to support them.

In the US, for more complex requirements such as?SFAR 88 (Fuel Tank Safety) was found that operators could fail to meet the requirements if not adequately supported by TCHs. Therefore, the regulations for ageing aircraft structures were amended to place requirements on design approval holders in addition to operators to ensure timely compliance.

Additional airworthiness requirements for Design Approval Holders in the U.S. were introduced in CFR14 Part 26 in 2008 for repairs and alterations, followed by 2011 for LOV and WFD evaluation similar to Part-26. FAA employed airworthiness directives for SSIDs and CPCPs. Ongoing developments have led to additional measures, which are now incorporated into EASA Part-26 following the EU Commission Implementing Regulation 2020/1159. This Regulation amends the additional airworthiness specifications in Commission Regulation (EU) 2015/640 (Part 26)

A significant part of this regulation addresses fatigue cracking, corrosion, and environmental degradation on FCSs. FCS describes structural parts susceptible to fatigue cracking, with fractures potentially leading to catastrophic aircraft failure. Let's take a closer look at the details of this regulation.

The Aircraft Aging Structures section of this regulation spans from point 26.300 to point 26.370 of Part 26, covering 16 different topics. Sections 26.300 to 26.309 apply to Type Certificate holders, while 26.330 to 26.334 relate to STCs. Operators are subject to Section 26.370, which is a comprehensive and complex regulation despite its shortness.

Design approval holders must create data to support continuing structural integrity programs for certain categories of large airplanes. At the same time, the operators of these airplanes need to update their aircraft maintenance programs to include this data and address any negative effects changes, or repairs may have on each airframe and its maintenance requirements.

According to point 26.370, operators must demonstrate compliance with this regulation in their Aircraft Maintenance Program under four key headings:

1. An approved damage-tolerance-based inspection program.
2. A means for addressing the adverse effects that repairs and modifications may have on fatigue-critical structures and inspections.
3. An approved LOV.
4. A CPCP program.

While LOV is likely already included in operators' AMPs since its due date was in August 2021, the other three elements have a due date of February 26, 2024. Until this time, operators must ensure their current AMP revisions include a CPCP program, all available DTIs related to repairs and modifications, and an implementation plan for repairs and modifications without available DTIs requiring Damage Tolerance Evaluation. Have a look at the EASA website for further information:?Ageing Aircraft Structure Rule | EASA (europa.eu) And ensure that your operator is in compliance with the regulation before it is due.

Orhan DUMAN