When a normally-aspirated engine is overhauled, is an FAA Form 337 required?

When a normally-aspirated engine is overhauled, there is no requirement to complete an FAA Form 337. This form is typically required for major repairs and alterations that must be documented and submitted to ensure compliance with safety regulations and standards. However, a standard overhaul of a normally-aspirated engine is categorized as maintenance rather than a major alteration or repair.

Since such overhauls are recognized as routine maintenance performed in accordance with manufacturer guidelines and do not significantly change the structure, performance, or operational limits of the engine, the FAA does not require the completion of a Form 337 for this type of work. Therefore, retaining the form or submitting it to the FAA is unnecessary, reinforcing that the overhaul process can proceed without this documentation. This keeps the maintenance process straightforward and compliant with aviation regulations, ensuring that maintenance standards are upheld without unnecessary bureaucratic steps.