The 411 on Form 337
By Rebekah Waters, FAA Safety Briefing Magazine
There are plenty of reasons to pursue a career in aircraft maintenance. Maybe you have a knack for fixing things. Maybe you enjoy working with your hands. Maybe you want to play an important role in flight safety. Whatever it is, I bet it isn’t a love of paperwork! Regardless, paperwork, in the form of maintenance records, is important to safety and is a requirement of the job. Proper documentation also helps ensure each aircraft you work on stays airworthy. Undocumented repairs and alterations could lead to conflicts in the aircraft that create dangerous situations for pilots and passengers. This is especially true when you perform a major repair or alteration. That’s why the FAA created Form 337 to ensure standard and efficient documentation. Let’s look at what it is and when to use it.
When you perform or supervise any major repair or alteration, you must fill out Form 337. This form serves three main purposes. First, it provides aircraft owners and operators with a record of major repairs and major alterations, indicating the details and approvals. Secondly, it provides the FAA with a copy for inclusion in the aircraft records at the FAA’s Aircraft Registration Branch. Finally, it documents and records that you conducted a compatibility assessment in accordance with the Form 337 NOTICE, which states:
Weight and balance or operating limitation changes shall be entered in the appropriate aircraft record. An alteration must be compatible with all previous alterations to assure continued conformity with the applicable airworthiness requirements.
This notice is included for a good reason — if you sign off on the work, you are responsible.
An important part of using this form is knowing when to use it. Form 337 must be used when you perform or supervise any major repairs or alterations. But what is considered a major repair or alteration? 14 CFR part 1 defines a major alteration as an alteration not listed in the aircraft, engine, or propeller specifications that might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness, or is not done according to accepted practices or cannot be done by elementary operations. It defines a major repair as a repair that, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness, or that is not done according to accepted practices or cannot be done by elementary operations.
Whether you’re documenting a major repair or a major alteration, it is important to make sure you enter a clear, concise, and legible statement that describes the work you completed. Keep in mind, the description should be sufficiently detailed so that a person unfamiliar with the work can still understand what was done, and what methods and procedures you used to do it. If required to adequately explain the location and details of the repair or alteration, you can include diagrams and drawings. Before signing off on Form 337 and approving the aircraft for return to service, it is your responsibility to ensure that all the work described in item 8 on the form matches approved data and that all the information presented on the form is complete.
Remember, you must complete the form in duplicate. Give one copy to the owner or operator and send one to the FAA Aircraft Registration Branch, P.O. Box 25504, Oklahoma City, OK 73125. Not documenting major repairs and alterations is more than just a violation. It’s a breach of both safety and trust that can have serious consequences. Form 337 isn’t just paperwork — it’s a key part of aviation safety!
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Rebekah Waters is an FAA Safety Briefing associate editor. She is a technical writer-editor in the FAA’s Flight Standards Service.
