Which document would you consult to authorize installation of a major modification that deviates from the original design?

Which document would you consult to authorize installation of a major modification that deviates from the original design?

• A. Airworthiness Certificate
• B. FAA Form 337
• C. Supplemental Type Certificate
• D. Aircraft Listing

Answer: (C)

To authorize a major modification that departs from the original design, you need a Supplemental Type Certificate. The STC is the FAA-approved document that certifies the modification’s design meets applicable airworthiness standards and provides the installation data, limitations, and conditions. It updates the aircraft’s approved design basis and allows the modification to be installed legally on the specific aircraft model or serial number. The other options don’t serve as the design approval: an Airworthiness Certificate only states the aircraft is currently airworthy; FAA Form 337 records the alteration and seeks FAA acceptance, but the actual design approval comes from the STC; and an Aircraft Listing is not a regulatory authorization for modifications.

To authorize a major modification that departs from the original design, you need a Supplemental Type Certificate. The STC is the FAA-approved document that certifies the modification’s design meets applicable airworthiness standards and provides the installation data, limitations, and conditions. It updates the aircraft’s approved design basis and allows the modification to be installed legally on the specific aircraft model or serial number. The other options don’t serve as the design approval: an Airworthiness Certificate only states the aircraft is currently airworthy; FAA Form 337 records the alteration and seeks FAA acceptance, but the actual design approval comes from the STC; and an Aircraft Listing is not a regulatory authorization for modifications.