Final answer:
An FAA Form 337, known as the Major Repair and Alteration form, must be completed when a normally aspirated engine with spur type reduction gearing is overhauled. The certified mechanic or repair station documents the major repair or alteration and submits it to the FAA for approval.
Step-by-step explanation:
When a normally aspirated engine with spur type reduction gearing is overhauled, an FAA Form 337 is required. The FAA Form 337 is also known as the Major Repair and Alteration form. It needs to be filled out by a certified mechanic or repair station to document any major repairs or alterations to airframes, engines, propellers, or appliances. The form is then submitted to the Federal Aviation Administration (FAA) for approval and inclusion in the aircraft's permanent records. This action ensures that all modifications meet the safety criteria set forth by the FAA and helps maintain an updated history of the aircraft's modifications for safety and regulatory purposes.