What is CPR in Aviation? (Changed Product Rule)

The Changed Product Rule (CPR) is a term widely used in the aviation industry to refer to the process of implementing modifications or changes to an aircraft’s design, systems, or components. It is a crucial aspect of aviation safety and regulatory compliance, ensuring that any alterations made to an aircraft meet the required standards and do not compromise its airworthiness.

CPR is governed by various regulatory bodies and organizations, including the Federal Aviation Administration (FAA) in the United States, the European Union Aviation Safety Agency (EASA), and other national civil aviation authorities. These entities define the guidelines and procedures that must be followed when introducing changes to an aircraft, emphasizing the importance of adherence to ensure the continued safety of flight operations.

Compliance with CPR is essential for both manufacturers and operators of aircraft. Manufacturers must carefully evaluate the impact of any proposed modification on the overall design, performance, and safety of the aircraft. Operators, on the other hand, need to ensure that any changes made, whether through modifications or repairs, comply with the applicable regulations to maintain the airworthiness of their fleet.

In this article, we will explore the Changed Product Rule in aviation and delve into its significance, requirements, and implementation processes, with a particular focus on the guidelines set forth by the FAA and EASA.

The Significance of the Changed Product Rule

The Changed Product Rule plays a vital role in ensuring the continued safety and reliability of aircraft. By requiring careful evaluation and adherence to specific standards, it minimizes the potential risks associated with modifications or changes made to an aircraft throughout its operational life. Here are some key reasons why the CPR is of utmost significance in aviation:

1. Safety Assurance

The primary objective of the Changed Product Rule is to maintain and enhance aviation safety. When modifications or changes are introduced into an aircraft, there is always a potential for unintended consequences or adverse effects on the overall system. CPR ensures that these risks are thoroughly evaluated, and appropriate measures are taken to mitigate them.

By complying with CPR, manufacturers and operators can mitigate safety hazards and prevent potential accidents or incidents caused by design flaws or inadequate modifications. This is especially critical in the dynamic and technologically advanced aviation industry, where aircraft systems and components continually evolve.

2. Regulatory Compliance

The aviation industry is highly regulated to ensure the highest standards of safety and operational integrity. The Changed Product Rule is an essential tool for maintaining regulatory compliance when it comes to introducing modifications or changes to an aircraft.

Both manufacturers and operators must follow the guidelines set forth by regulatory bodies such as the FAA and EASA. These regulations outline specific requirements, including certification processes, documentation, and testing procedures, that must be met to ensure the airworthiness of the aircraft and compliance with applicable regulations.

3. Improved Performance and Efficiency

CPR also plays a crucial role in maintaining and improving the performance and efficiency of aircraft systems. As technology advances and new innovations emerge, modifications and upgrades become necessary to enhance key aspects such as fuel efficiency, reliability, and system integration.

By implementing changes in compliance with the Changed Product Rule, manufacturers and operators can take advantage of technological advancements and optimize aircraft performance. This can result in reduced fuel consumption, increased range, improved system reliability, and enhanced overall operational efficiency.

CPR Implementation Processes and Guidelines

The Changed Product Rule encompasses various implementation processes and guidelines that manufacturers and operators must follow when introducing modifications or changes to an aircraft. These processes involve extensive evaluation, testing, documentation, and certification procedures to ensure regulatory compliance and airworthiness. The FAA and EASA provide regulations and guidelines specific to their respective jurisdictions. Let’s explore the implementation processes prescribed by these two prominent authorities:

The FAA’s Implementation Process

The FAA’s implementation process for the Changed Product Rule primarily focuses on the certification of major design changes and alterations to existing aircraft. The following steps outline the key requirements and procedures:

1. Design Assessment

Prior to initiating any design changes, the manufacturer must conduct a comprehensive assessment of the modification’s impact on the aircraft’s safety, performance, and structural integrity. This assessment involves conducting engineering analyses, tests, and evaluations to ensure that the proposed modification meets the FAA’s airworthiness standards.

During the design assessment, manufacturers must also consider any potential effects on other systems or components that may be impacted by the modification. This holistic evaluation ensures that the overall aircraft system remains coherent and fully functional.

2. Documentation and Submittal

After completing the design assessment, the manufacturer must prepare detailed documentation outlining the proposed design changes, supporting engineering analyses, and test results. This documentation typically includes:

  • Detailed drawings and technical specifications of the modification
  • Structural, aerodynamic, and systems analyses reports
  • Compliance checklists for applicable regulations and standards
  • Test plans and results
  • Installation and maintenance instructions

Once the documentation is complete, it is submitted to the FAA for review and approval. The FAA reviews the proposed changes to ensure compliance with airworthiness standards and regulatory requirements.

3. Testing and Evaluation

The FAA may require manufacturers to conduct various tests and evaluations to assess the impact of the proposed modification on the aircraft’s safety and performance. These tests may include:

  • Structural load testing
  • Stress testing
  • Durability and fatigue testing
  • Functional testing of modified systems or components

Testing and evaluation procedures may differ depending on the nature and complexity of the modification. The FAA provides specific guidelines and requirements for each type of test, ensuring a standardized evaluation process.

EASA’s Implementation Process

EASA’s implementation process for the Changed Product Rule follows a similar approach to the FAA’s, focusing on the approval and certification of major design changes. However, there are some differences in the specific guidelines and procedures. The key steps in EASA’s implementation process include:

1. Design Organization Approval

Before initiating any design changes, the manufacturer must hold a Design Organization Approval (DOA) issued by EASA. The DOA demonstrates the manufacturer’s compliance with the applicable regulatory requirements and their competence to design and approve design changes.

Having the DOA enables the manufacturer to independently approve minor design changes without involving EASA directly. However, major changes still require oversight and approval from EASA.

2. Design Change Evaluation

Prior to implementing any changes, manufacturers must evaluate the design change’s impact on aircraft safety, including its systems, structures, and performance. This evaluation must consider the applicable certification standards and regulations, ensuring compliance with EASA requirements.

The evaluation includes various analyses, such as stress analysis, fatigue and damage tolerance analysis, systems safety assessments, and electromagnetic compatibility assessments. These assessments provide evidence of the change’s safety and airworthiness.

3. Compliance Demonstration

Manufacturers must demonstrate compliance with EASA requirements for the proposed design changes. This typically involves preparing a compliance demonstration reporting package, which includes:

  • Detailed design change documentation
  • Analysis and test results
  • Compliance checklists
  • Installation and maintenance instructions

After completing the compliance demonstration, the manufacturer submits the package to EASA for review and approval. EASA assesses the proposed changes to ensure compliance with the applicable regulations and certification standards.


The Changed Product Rule plays a crucial role in the aviation industry, ensuring the continued safety, compliance, and performance of aircraft. By carefully evaluating the impact of modifications or changes and following specific implementation processes, manufacturers and operators can uphold the highest standards of safety and regulatory compliance.

Whether it’s the FAA’s detailed review and testing procedures or EASA’s compliance demonstration requirements, the implementation processes outlined by these regulatory bodies emphasize the importance of thorough evaluation, documentation, and certification to maintain airworthiness and operational integrity.

The Changed Product Rule, with its strict guidelines and procedures, represents a key aspect of aviation safety and paves the way for continuous improvement and innovation in the industry. By adhering to CPR, the aviation industry can embrace technological advancements and optimize aircraft performance while ensuring the utmost safety and security of flight operations.

For More: What is MCBF in Aviation? (Mean Cycles Between Failures)