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I would appreciate someone explaining or identifying the regulation that explains when 337's are required in the maintenance of an airplane.
I realize you posted this awhile ago, but here are the references,
For the aircraft owner;
FAR 91.417 Maintenance Records - paragraph (a) describes the types of records that must be kept and paragraph (b) describes the length that they need to be kept.
Your specific question is relevant to paragraph (a)(2)(vi) "copies of the forms prescribed by FAR43.9(a) of this chapter for each major alteration to the airframe and currently installed engines, rotors, propeller, and appliances."
here is how long you have to keep them
FAR 91.417 (b)(2) "The records specified in paragraph(a)(2) of this section shall be retained and transferred with the aircraft at the time the aircraft is sold."
For the Mechanic; (Where your question is really relevant)
FAR 43.9 Content, form, and disposition of maintenance, preventive maintenance, rebuilding and alteration records (except inspections..........)
FAR 43.9(d) "in addition to the entry required by paragraph (a) of this section, major repairs and major alterations shall be entered on a form, and the form disposed of, in the manner prescribed in appendix B, by the person performing the work."
Paragraph (a) of FAR 43.9 simply states (in my own words) that each person that maintains, or performs maintenance (including preventive maintenance), alterations on an aircraft or aircraft component, appliance, propeller or rotor, shall make an entry in the maintenance record with a description of work performed, date of completion , name of who did the work, and the signature and certificate number of the person responsible for the work.
Hope this is all clear now, other references that pertain to this subject are;
FAR 1.1 Major Alteration
FAR 1.1 Minor Alteration
FAR 43 Appendix A "Major Alterations, Major Repairs, And Preventive Maintenance"
FAR 43 Appendix B "Recording Of Major Repairs, Major Alterations"
A form 337 is required when there has been a major alteration done to the original approved design. All certified aircraft have a type certificated (TC) design that is approved by the FAA. When someone makes a major change to the original design it must be documented by a form 337 filled out and signed by a technician holding an Inspection and Authorization (IA) certificate. There can be major or minor alterations and that is determined by the technician installing the part(s). If it's a major alteration it will require the form. The person installing the part can deem the alteration "minor" but the FAA can disagree with the assertion and require the form if they substantiate their reasoning. Example: replacing a deice boot on a propeller blade with a PMA replacement could be deemed "minor". The design is considered "altered" merely by having a different part number than the original part but since the replacement is identical in size, shape, weight, and function, the alteration is minor and does not require a form. However if the replacement deviates substantially from the original design to as to change weight, size, function, or flight dynamics, it would be considered a major alteration and would require the form to document those changes and impacts. Many times if the replacement part is approved by the FAA under an STC (supplemental type certificate) it will often require determination of that addition to be a major or minor alteration and possibly the need for a form 337. Totally confused now?
Hey guys, this is really a great help for me too in maintenance of an airplane. I have also want to know about 337 in details. Thanks!
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