How can a major alteration be signed off as a minor alteration?

To understand why the determination that a major alteration will not appreciably change flight characteristics allows it to be categorized as a minor alteration, it's essential to consider the definitions and regulations surrounding alterations in aircraft maintenance.

A major alteration is defined as a change to the aircraft that can significantly impact its performance, safety, or operating characteristics. However, if an alteration is evaluated and judged not to appreciably change the aircraft's flight characteristics or performance, it may be considered minor, allowing it to be signed off without the extensive official documentation required for major alterations. This assessment typically relies on the experience, judgment, and the specific technical knowledge of the person making the determination regarding the alteration.

The other options suggest conditions for signing off an alteration, but they do not align with the regulatory framework. For example, while a Supplemental Type Certificate (STC) provides a way to validate major alterations, it does not downgrade them to minor alterations. Documentation in aircraft specifications or cosmetic changes do not inherently change the classification of the alteration in terms of its impact on safety and performance, which is central to defining a major alteration.