What is defined as an alteration that may significantly affect airworthiness when not in the aircraft specifications?

A major modification is defined as an alteration that may significantly affect airworthiness when it falls outside the established specifications of the aircraft. Such modifications can involve structural changes, alterations to the aircraft's systems, or modifications that could impact the safety or performance of the aircraft. It's vital that these modifications are carefully evaluated and approved to ensure compliance with regulatory standards, as they can introduce new risks or performance issues that were not present in the original design.

This distinction is essential in aviation safety and maintenance management. Major modifications must undergo a rigorous approval process, typically involving the aircraft manufacturer, regulatory bodies, and often require new flight tests or reassessments of the aircraft's performance.

In contrast, major repairs typically refer to fixes related to existing components that restore them to their original condition without significantly altering the aircraft's specifications. Major replacements involve the substitution of a significant part or component but do not alter the overall design or operation of the aircraft. Each of these categories is governed by different regulatory requirements, emphasizing the importance of understanding how modifications can affect an aircraft’s airworthiness status.