Validation and Verification: Perspectives as per ARP4754 and ISO 26262
- Harshal Vaid
- May 16
- 5 min read
While often used interchangeably in a colloquial manner, Validation and Verification (V&V) hold distinct meanings within system and safety engineering. How these terms are interpreted depend on the specific industry context. Precise understanding of V&V is vital for technical accuracy and effective communication amongst development teams.
V&V are important processes in safety engineering for new product development—whether in aerospace, automotive or other domains. They ensure that a new product not only complies with defined specifications, standards, and regulatory requirements but also fulfills its intended purpose. Product development involves a myriad of requirements, including design, regulatory, safety among others; these requirements form the stepping stones for a successful development of a product.
Despite the critical role of V&V, they are often misunderstood due to their nuanced definitions across different industries and safety standards.
Leveraging our decades of experience in both Aerospace and Automotive domains, this post outlines the approach for Validation and Verification (V&V) from aircraft development and automotive functional safety point of view.
ARP 4754B, Guidelines for Development of Civil Aircraft and Systems
Validation
As per ARP4754B, validation is defined as the process of determining whether the requirements for an aircraft are correct and complete. It is ensuring that the specified requirements are sufficiently accurate so that the aircraft will meet the needs of customers, users, suppliers, maintainers, certification authorities and the stakeholders within the organization.
In essence it tries to answer the question, Are we building the right aircraft?
The validation process at each level of the requirement hierarchy should involve all relevant technical disciplines including System Safety. Validation must consider both intended functions and unintended behaviours. The importance of validation cannot be understated as subtle errors or omissions in the requirements identified early in the development cycle, therefore reducing the exposure to subsequent redesign, retrofits or inadequate system performance.
Several methods have been established to support validation. As per ARP4754B, these include: traceability, analysis, modelling, test, similarity, and engineering review.
The aircraft, system, item level and safety requirements guiding aircraft development will be subject to validation. To validate a requirement means to make sure its content translates accurately to a higher level or a regulatory requirement. Overall, validation is the process by which engineers ensure that the system will meet the need and the requirements of the aircraft (or rotorcraft).
Verification
Verification, as per ARP4754B, is the evaluation of implementation of requirements to determine that they have been met. The purpose of verification is to ascertain that each level of the implementation meets its specified requirements.
It tries to answer, Have we built the aircraft right?
The verification process objectives are as follows: confirm that the intended functions have been correctly implemented, ensure that the requirements have been satisfied, and substantiate that the conclusions drawn are correct for the system as it has been implemented.
The inputs to the verification process are a set of baselined, documented and validated requirements for the aircraft, system or item and a complete description of the system or the item that needs to be verified. Recognizing the complexities of modern system development, ARP4754B outlines that due to the iterative nature of the development process, verification may appear repeatedly during the lifecycle of the aircraft.
Four basic methods may be employed in the verification of the aircraft and any system or item. Appropriate verification methods should be selected to ensure the implementation of each requirement is fully verified.
I. Inspection/Review
II. Analysis
III. Testing or demonstration
IV. Similarity/Service Experience
ISO 26262:2018, Road Vehicles - Functional Safety
Verification
Verification, as defined by ISO 26262, is the determination whether or not an examined object meets its specified requirements. It is an iterative process implemented in all phases of the safety lifecycle of safety-related systems comprised of electrical, electronic and software components.
Verification can be understood as an umbrella term that reviews the correctness, completeness and the implementation of the safety goals, functional and technical safety concepts as well as item level requirements in road vehicles. Verification ensures that every step taken in the development process correctly implements the outputs of the previous steps and is suitable and adequate to achieve the required Automotive Safety Integrity Level (ASIL). ISO 26262-8:2018, Clauses 6 and 9 provides guidelines for conducting the verification activities in the different stages of development of road vehicles.
Table 1 illustrates the verification methods as per ISO 26262. Appropriate verification methods are selected for relevant phases of development and their respective clauses. Additionally, ISO 26262-8:2018, Clause 9 also describes the following activities in relation to verification:
Verification Planning,
Verification Specification, and
Verification execution and evaluation.
Verification ensures that safety requirements are not only properly defined and allocated but are also suitable and adequate to achieve functional safety throughout the lifecycle. Verification activities serve as evidence that each object is built right and supports safe interaction within and across system boundaries, forming the backbone of traceable and justifiable safety assurance.
Table 1: Verification Methods as per ISO 26262:2018,
(appropriate methods maybe selected at applicable level of development)
SNO. | METHODS | NOTES |
|---|---|---|
1 | Inspection | Correctness and Completeness check for implementation of requirements |
2 | Walkthrough | Correctness and Completeness check for implementation of requirements |
3 | Simulation | Can be used as a fault injection test to support argumentation of completeness and correctness of system architecture with respect to faults |
4 | Prototyping and Testing | Can be used as a fault injection test to support argumentation of completeness and correctness of system architecture with respect to faults |
5 | Design Analyses | Deductive Safety Analyses & Inductive Safety Analyses |
Safety Validation
It is defined as the assurance, based on examination and tests, that the safety goals are adequate and have been developed with a sufficient level of integrity. The safety validation is conducted as per ISO 26262-4:2018, Clause 8.
In ISO 26262:2018, safety validation is the structured process of confirming—at the vehicle level—that the implemented system actually achieves its intended safety goals in real-world operating conditions. Unlike verification, which checks whether the product is built correctly, safety validation focuses on demonstrating, typically at the vehicle level or in a representative environment, that the implemented safety measures are truly effective in mitigating failures and avoiding harm.
It involves confirming that the functional and technical safety concepts are appropriate, complete, and effective, including the assumptions made during hazard analysis, human controllability, environmental conditions, and external mitigation measures. Ultimately, safety validation provides the final evidence that the system as integrated into the vehicle can prevent or mitigate hazards and thus avoid harm to occupants and other road users.
Conclusion
While both aerospace and automotive industries emphasize rigorous Validation & Verification (V&V) processes, ARP4754B and ISO 26262:2018 apply these principles differently based on their respective safety-critical environments.
In aerospace, ARP4754B emphasizes rigorous validation to confirm that requirements meet regulatory and stakeholder needs before the design begins, followed by verification to ensure that implementation and compliance with specifications is achieved.
In contrast, ISO 26262:2018 treats verification as an ongoing process throughout development, ensuring correctness, completeness, and consistency of safety goals, architectures, and implementations. Safety validation ensures these goals and concepts are not only appropriate but also effectively achieved at the vehicle level.
Finally, in the aerospace industry, Validation is an iterative activity on the left side of the V-model, while Verification appears on the right-side that substantiates requirement implementation all the way to aircraft level. However, in the automotive industry, Verification occurs throughout the safety lifecycle, with Safety Validation appearing on the right side of the V-model at the vehicle level.
Comments