FAA Aviation Mechanic General (AMG)Regulations, Records and Human FactorsHard
A technician installs an autopilot system on a certificated airplane under an FAA-issued Supplemental Type Certificate (STC) that specifically covers that installation on that aircraft model. What must be documented on the FAA Form 337 to properly reflect FAA approval of the installation?
- AThe mechanic's personal opinion that the installation meets airworthiness standards
- BThe STC number and reference to the STC holder's approved data as the basis for approval
- CA statement that the installation is a minor alteration not requiring approved data
- DA note that the installation is field-approved with no supporting reference required
Show answer & explanationAnswer & explanation
Correct answer: B. The STC number and reference to the STC holder's approved data as the basis for approval
When a major alteration is performed under an STC, the FAA Form 337 must cite the STC number and reference the STC holder's FAA-approved data as the basis for the alteration's approval, providing traceability to already-approved engineering data.
Why the other options are wrong
- A. Incorrect; personal opinion is not valid approved data for a major alteration.
- C. Incorrect; installing an autopilot per an STC is a major alteration, not minor.
- D. Incorrect; field approval is a separate process used when no STC/approved data exists.
STC Documentation on Form 337
When a major alteration is accomplished under a Supplemental Type Certificate, the FAA Form 337 must reference the specific STC number and its approved data as the basis of approval.
- STC provides pre-approved engineering data for a specific modification
- Form 337 documents the major alteration and cites the STC number
- Aircraft records/equipment list must be updated after installation
- Using an STC avoids the need for a separate field approval
Memory trick: The STC number on Form 337 is the alteration's birth certificate—it proves FAA approval already exists.