Definition
An approved change to the original type design of an aircraft, engine, propeller, or appliance that alters its configuration, performance, or operating characteristics from the manufacturer's certificated baseline. Product modifications are accomplished under FAA-approved data, such as a Supplemental Type Certificate (STC), an approved alteration, or manufacturer service documentation.
Plain English
A formally approved change made to an aircraft or one of its parts that makes it different from how it was originally built and certified.
Context Anchor
Seen in aircraft maintenance records, service instructions, inspection discussions, and approval paperwork for changes made to an aircraft, engine, or propeller.
Derivation
From Latin 'modificare' — to limit or set bounds. In aviation maintenance, the word kept the sense of 'making a controlled change,' which is why a modification is always tied to approved data rather than free-form alteration.
Why Pilots Care
Determines whether the change requires FAA approval and ensures the aircraft remains safe and legal to fly.
Intuition Check
Do not read “product” here as a store item or consumer good. In FAA maintenance language, it usually means an aircraft, aircraft engine, or propeller. Do not read “modification” as just any casual change. In aviation, the change may need approval, inspection, and a maintenance record entry.
Example Sentence 1
Before signing off the aircraft, the mechanic confirmed that the product modification installing the new avionics suite was supported by an approved STC.
Example Sentence 2
A product modification must be evaluated to confirm it does not affect the aircraft's original certification basis.