Major Repair And Alteration

For certified aircraft, the FAA permits major modifications via many regulatory pathways, but the two most common in the GA fleet are via a Form 337 or a supplemental type certificate (STC). A Form 337, Major Repair and Alteration (Airframe, Powerplant, Propeller, or Appliance) is the documentation required for one-off repairs or modifications to an individual airframe, engine or prop. Supplemental Type Certificate (STC) modifications are more of a blanket approval designed to cover an entire family of aircraft types.

Key Takeaways:

• Form 337 and Supplemental Type Certificates (STCs) are the two main FAA-approved pathways for major modifications to certified aircraft.
• A Form 337 is for one-off modifications to an individual aircraft or component, whereas an STC provides a broader approval for a family of aircraft and involves more robust engineering and documentation, often including POH supplements.
• Both STCs and Form 337s ensure modifications meet FAA airworthiness standards, and any aircraft with major modifications lacking either of these documents warrants further investigation.

Key takeaways sponsored by Aviator Pro | Start Your Training ->

See a mistake? Contact us.