What paperwork is necessary for the installation of a magneto that was not approved for an engine when certificated, but is approved for the engine when installed according to an STC?

• A. A form FAA 337 must be completed stating that the installation was done in accordance with the STC.
• B. No paperwork is required.
• C. A maintenance release is required.
• D. ADs must be amended.

Answer: (A)

When an installation is approved by an STC, you must have a formal record showing that the work was accomplished per that STC. The form used for this is FAA Form 337, Major Alteration or Other Work—it's the official way to document that the installation was completed in accordance with the approved design and data.

Completing 337 provides a verifiable, FAA-recognized record that the modification is authorized and properly carried out. It stays with the aircraft’s records and is important for future inspections, airworthiness determinations, and any subsequent changes. Without this form, there’s no formal, traceable proof to FAA or maintenance personnel that the STC requirements were followed, even though the STC itself authorizes the installation.

Other paperwork, like a simple maintenance release, isn't sufficient to document compliance with an STC for a major alteration, and ADs aren’t about certifying that a specific installation was performed per an STC. So the required step is to file the FAA 337 stating the installation was done in accordance with the STC.