Which document is typically used to authorize a major modification to the original type design?

Which document is typically used to authorize a major modification to the original type design?

• A. FAA Form 337
• B. Supplemental Type Certificate
• C. Airworthiness Certificate
• D. Technical Standard Order

Answer: (B)

Authorization of major modifications to the original design is handled by the Supplemental Type Certificate. An STC is the FAA-approved document that validates and documents a significant change to the aircraft’s type design, amending the existing certification basis and updating the Type Certificate Data Sheet. This clearance ensures the modification has been evaluated for safety, performance, and airworthiness before it can be installed on the aircraft. FAA Form 337, by contrast, is a record used to document alterations or repairs after they’ve been performed, notifying the FAA and recording what was changed. It does not grant approval for a design modification. The Airworthiness Certificate simply states that the aircraft is considered airworthy in its current configuration; it does not authorize changes. A Technical Standard Order defines standards for specific parts or appliances, not the authorization of modifying the aircraft’s design.

Authorization of major modifications to the original design is handled by the Supplemental Type Certificate. An STC is the FAA-approved document that validates and documents a significant change to the aircraft’s type design, amending the existing certification basis and updating the Type Certificate Data Sheet. This clearance ensures the modification has been evaluated for safety, performance, and airworthiness before it can be installed on the aircraft.

FAA Form 337, by contrast, is a record used to document alterations or repairs after they’ve been performed, notifying the FAA and recording what was changed. It does not grant approval for a design modification. The Airworthiness Certificate simply states that the aircraft is considered airworthy in its current configuration; it does not authorize changes. A Technical Standard Order defines standards for specific parts or appliances, not the authorization of modifying the aircraft’s design.