Approval of Aircraft Structure Repair

Once the need for an aircraft repair has been established, Title 14 of the Code of Federal Regulations (14 CFR) defines the approval process. 14 CFR part 43, section 43.13(a) states that each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance shall use the methods, techniques, and practices prescribed in the current manufacturer’s maintenance manual or instructions for continued airworthiness prepared by its manufacturer, or other methods, techniques, or practices acceptable to the Administrator. AC 43.13-1 contains methods, techniques, and practices acceptable to the Administrator for the inspection and repair of nonpressurized areas of civil aircraft, only when there are no manufacturer repair or maintenance instructions. This data generally pertains to minor repairs. The repairs identified in this AC may only be used as a basis for FAA approval for major repairs. The repair data may also be used as approved data, and the AC chapter, page, and paragraph listed in block 8 of FAA Form 337 when:

a. The user has determined that it is appropriate to the product being repaired;
b. It is directly applicable to the repair being made; and
c. It is not contrary to manufacturer’s data.

Engineering support from the aircraft manufacturer is required for repair techniques and methods that are not described in the aircraft maintenance manual or SRM.

FAA Form 337, Major Repair and Alteration, must be completed for repairs to the following parts of an airframe and repairs of the following types involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication, such as riveting or welding. [Figure]
  • Box beams
  • Monocoque or semimonocoque wings orcontrol surfaces
  • Wing stringers or chord members
  • Spars
  • Spar flanges
  • Members of truss-type beams
  • Thin sheet webs of beams
  • Keel and chine members of boat hulls or floats
  • Corrugated sheet compression members that act as flange material of wings or tail surfaces
  • Wing main ribs and compression members
  • Wing or tail surface brace struts, fuselage longerons
  • Members of the side truss, horizontal truss,or bulkheads
  • Main seat support braces and brackets
  • Landing gear brace struts
  • Repairs involving the substitution of material
  • Repair of damaged areas in metal or plywood stressed covering exceeding six inches in any direction
  • Repair of portions of skin sheets by makingadditional seams
  • Splicing of thin sheets
  • Repair of three or more adjacent wing or control surface ribs or the leading edge of wings and control surfaces between such adjacent ribs

For major repairs made in accordance with a manual or specifications acceptable to the Administrator, a certificated repair station may use the customer’s work order upon which the repair is recorded in place of the FAA Form 337.

Approval of Aircraft Structure Repair
FAA Form 337, Major Repair and Alteration (Airframe, Powerplant, Propeller, or Appliance)

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