FAA Form 337
FAA Form 337 (Major Repair and Alteration (Airframe, Powerplant, Propeller, or Appliance) is a form filed with the FAA to document major changes to an aircraft, including changes made per STC's. Instructions for it's use are contained in Title 14 CFR §43.9, Part 43 Appendix B, and AC 43.9-1.
Major Alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications-
- 1. That might appreciably affect weight, balance, structural strength, performance, Powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
- 2. That is not done according to accepted practices or cannot be done by elementary operations.
The form serves to:
- provide aircraft owners and operators with a record of major repairs or alterations indicating details and approval.
- provide permanent record for FAA in Oklahoma City (A copy may be retrieved at a later date for a small fee)
The aviation mechanic that performs the work must:
- Make an entry in the aircraft records making reference to the FAA Form 337.
- Give the signed original Form 337 to the owner and forward a copy of the form to the FAA FSDO in the area where the installer is operating within 48 hours.
- Per FAR §91.417, an additional copy of the Form must remain aboard the aircraft for certain work, such as the installation of extended range fuel tanks.
A log book entry is required with Form 337.
The FAA Aviation Safety Inspector guidance to perform Field Approval of Major Repairs and Major Alterations comes from FAA Order 8300.10 (Flight Standards Handbook Bulletin For Airworthiness (HBAW)) Change 10, Chapter 1.