EASA CS-25 Easy Access Rules for Large Aircraft

The organization known simply as EASA is the European Aviation Safety Agency. The “EASA CS-25 Easy Access Rules for Large Aircraft” standard, developed by this organization, contains the applicable rules for large aircraft. This standard includes current certification specifications and acceptable compliance tools displayed in an easy-to-read format, consolidated with enhanced navigation features via links and bookmarks. The standard is regularly updated to incorporate changes and evolution in current certification specifications and acceptable compliance tools. The latest revision is published dynamically online with filters to obtain regulatory material tailored to needs, search functions for quick access to relevant sections, and easy navigation for computers, tablets, and mobile phones.

The EASA CS-25 Certification Specifications for Large Aeroplanes is a comprehensive set of airworthiness standards. These specifications apply to large, turbine-powered aircraft with a maximum takeoff weight exceeding 5.700 kg. EASA CS-25 outlines the minimum safety and performance requirements that such aircraft must meet to receive type certification for operation within the European Union.

The CS-25 is divided into several subsections, each addressing specific aspects of aircraft design and performance. The CS-25's key components are:

• Subsection B - Flight: Covers flight performance, controllability, stability and manoeuvrability.
• Subpart C - Structure: Addresses structural integrity, including load factors and fatigue requirements.
• Subsection D – Design and construction: Focuses on general design principles and construction standards.
• Subsection E - Powerplant: Concerns the engine installation and associated systems.
• Subpart F - Equipment: Specifies requirements for onboard equipment, including avionics and safety systems.
• Subsection G - Operating limitations and information: Defines operating limits and information required for safe operation.
• Subsection J - Auxiliary power unit installation: Covers the standards for auxiliary power unit installation.

Additionally, CS-25 includes the following appendices that provide detailed guidance on specific topics:

• Annex I: Automatic take-off thrust control system
• Appendix K: Interaction of systems and structure
• Annex H: Continuing airworthiness instructions

While EASA CS-25 serves as a critical framework for aircraft certification, it is considered soft law, meaning it is not legally binding. Manufacturers can propose alternative compliance paths, provided they demonstrate an equivalent level of safety. This flexibility allows for innovation while maintaining rigorous safety standards.

Recent updates to this document bring improvements related to survivability after landing (emergency water landings) and improved specifications for installed systems and equipment used by flight crews.

The importance of the EASA CS-25 lies in its central role in ensuring the safety, airworthiness and regulatory compliance of large commercial and transport aircraft operating within or certified by the European Union. The EASA CS-25 is considered critical in terms of:

• Ensures safety and airworthiness: EASA CS-25 defines minimum safety standards for the design, construction, performance and operation of large aircraft (generally over 5.700 kg MTOW). It covers all aspects affecting safety, including structural integrity, flight performance, systems, emergency procedures and crashworthiness.
• Regulatory framework for certification: The primary reference used by EASA when assessing whether a new aircraft type or a modification to an existing aircraft meets type certification requirements. Without compliance with CS-25 or equivalent safety standards, an aircraft cannot legally operate within the European Union.
• Ensures international compliance: The CS-25 is highly compliant with Federal Aviation Administration (FAA) regulations (Part 25), supporting global aircraft certification and international cooperation. Aircraft certified to the CS-25 are more readily accepted in other major aviation markets, simplifying export and international operations.
• Provides guidance to manufacturers and designers: Aircraft manufacturers (Airbus, Boeing, etc.) use CS-25 as a design baseline to ensure new aircraft are certifiable. It reduces certification risks by enabling design teams to make decisions aligned with regulatory expectations early in the process.
• Supports continued airworthiness and upgrades: The CS-25 isn't just for new designs; it's also for modifications, repairs, and upgrades to existing aircraft. This ensures that even older aircraft continue to meet evolving safety standards.

In short, EASA CS-25 is the backbone of safe large aircraft design and operation in Europe, ensuring the highest levels of public and environmental safety while supporting both regulatory oversight and industry innovation.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services to businesses in accordance with the "EASA CS-25 Easy Access Rules for Large Aircraft" standard.