Every time an aviation maintenance technician (AMT) picks up a wrench, the FAA expects that work to be based on approved data. This requirement is not a bureaucratic formality—it is the legal and technical backbone of the entire airworthiness system. Approved data tells the technician not just how to perform a task, but also confirms that the method meets the design standards the FAA used when it certificated the aircraft. Without properly cited and recorded approved data, a maintenance entry is incomplete, the work may be considered unapproved, and the aircraft could be grounded.
For the AMT General written exam and for daily shop life, you need to know two distinct things: what qualifies as FAA-approved data, and how you properly reference it in the maintenance record. This article covers both in depth.
What Approved Data Actually Means
The term "approved data" refers to technical information that has been reviewed and accepted by the FAA—either directly, or through a process the FAA has sanctioned. It is fundamentally different from acceptable data, which is information such as manufacturer service bulletins or industry standards that a technician may use to support approved data but that does not by itself authorize a repair or alteration.
The critical regulatory foundation is 14 CFR Part 43, which governs maintenance, preventive maintenance, rebuilding, and alteration. Section 43.13(a) requires that each person performing maintenance use methods, techniques, and practices acceptable to the Administrator (or, if specified, those prescribed by the manufacturer's maintenance manual or ICA), along with tools and equipment appropriate to the work. For major repairs and major alterations specifically, the requirement that the work be accomplished using data approved by the FAA flows from the definitions in 14 CFR Part 43, Appendix A together with 43.13, while Appendix B prescribes the form and content of the record—including the use of FAA Form 337—for documenting that work.
Categories of FAA-Approved Data
The FAA recognizes several primary categories of approved data. Understanding each one helps you both cite it correctly and choose the right source for the job.
Type Certificate Data Sheets (TCDS)
A Type Certificate Data Sheet is published by the FAA for every type-certificated product—aircraft, engine, or propeller. The TCDS lists the official design specifications, operating limitations, required equipment, and eligible configurations. Because it flows directly from the Type Certificate, it carries the highest inherent authority and is considered approved data. When a maintenance action must be verified against a specific configuration or limitation, the TCDS is often the first place to look. TCDS documents are publicly available through the FAA's online registry.
Airworthiness Directives (ADs)
An Airworthiness Directive is a regulation—specifically, it has the force of law under 14 CFR Part 39. When the FAA issues an AD, it typically mandates specific inspections, modifications, or operational limitations using prescribed methods. The AD itself, along with any referenced instructions for continued airworthiness (ICA) incorporated by the AD, constitutes approved data for the required action. When recording AD compliance, the maintenance entry must identify the AD number, revision, and the method of compliance used.
FAA-Approved Manufacturer's Maintenance Manuals and Instructions for Continued Airworthiness (ICA)
When a manufacturer creates an aircraft or component, they must provide Instructions for Continued Airworthiness as required by 14 CFR Part 21. These ICAs—which include the Aircraft Maintenance Manual (AMM), Component Maintenance Manuals (CMM), Structural Repair Manuals (SRM), and Illustrated Parts Catalogs (IPC)—are reviewed and accepted by the FAA as part of the type certification process. Once the FAA accepts them, they become approved data for maintenance. It is essential to note that only FAA-approved revisions of these manuals apply; using a superseded revision without proper authorization can invalidate the work.
Supplemental Type Certificate (STC) Data
When an alteration goes beyond what the original type design allows, an STC must be obtained. The STC package includes FAA-approved installation and maintenance instructions. Any work performed under an STC must follow those specific instructions—they are the approved data for that modification. The STC number and the revision level of the instructions used should be recorded in the maintenance entry.
FAA-Approved Repair Specifications (Repair Station Approvals)
Certificated Repair Stations operating under 14 CFR Part 145 may have FAA-approved Repair Specifications (RSPECs) that define specific repair methods and processes. These are approved data for work performed within the scope of the repair station's rating. Similarly, certain military standards, Technical Orders, or industry specifications may be approved by the FAA for specific applications—but only when the FAA has explicitly accepted them for that use.
Field Approvals (FAA Form 337)
For major repairs or major alterations that are not covered by existing approved data, a technician holding an Inspection Authorization (IA) may develop a repair scheme and submit it for field approval. The FAA may approve this data on a case-by-case basis, resulting in an FAA-approved FAA Form 337. Once approved, the 337 and any attached data sheets become approved data for that specific repair on that specific aircraft. Per AC 43.9-1 guidance, the original completed 337 is generally retained in the aircraft's permanent records, with a copy forwarded to the FAA; technicians should always verify current distribution procedures against the latest FAA Order 8900.1 guidance, as routing details have changed over time.
Acceptable Data vs. Approved Data: A Critical Distinction
Many exam questions exploit confusion between these two terms. Acceptable data includes manufacturer service bulletins, service instructions, service letters, Aviation Maintenance Publisher (AMP) guides, and FAA Advisory Circulars. These documents can inform the method of a repair but do not independently authorize a major repair or alteration. For example, a manufacturer's service bulletin might describe the procedure to replace a control cable. If following that procedure results in a minor repair, the service bulletin may serve as acceptable data to document method. If the repair is classified as major, the technician must either use an already-approved source (such as the SRM) or obtain a field approval to make the data "approved."
Recording Approved Data References in Maintenance Entries
Once the work is complete, the maintenance record entry must be descriptive enough that any authorized person reading it can determine exactly what was done and under what authority. Per 14 CFR 43.9, a maintenance record entry for work other than an annual or 100-hour inspection must include: a description of the work performed; the date of completion; the name of the person performing the work; and if the work was performed under a certificate, the certificate number and kind of certificate held.
Beyond the minimum regulatory requirements, proper professional practice demands that the entry also explicitly cite the approved data used. A well-written entry might read: "Repaired corrosion damage to lower left wing skin per Aircraft Structural Repair Manual, Document No. ABC-SRM-57, Revision 12, Section 57-10-03. Repair classified as minor per 14 CFR Part 43, Appendix A. Date: [date]. Signed: [Name], A&P Certificate No. [number]."
For AD compliance, the entry should state the AD number (e.g., AD 2023-04-07), the amendment number if applicable, and the specific paragraph or method of compliance used. For STC work, include the STC number and the revision of the installation data followed. For a field-approved 337, reference the 337 form number and the date of FAA approval.
Why Proper Citation Matters
Incomplete or missing data references create serious problems. If a technician cannot demonstrate that approved data was used, the FAA can determine the work was unapproved—making the aircraft unairworthy even if the physical repair is structurally sound. During accident investigations, maintenance records are scrutinized carefully; entries with no data references shift liability significantly toward the technician and the certificate holder. For repair stations and air carriers, missing data references can trigger certificate action.
From a practical standpoint, future technicians and inspectors rely on maintenance records to understand the aircraft's history. A vague entry that says only "repaired wing skin" gives the next IA performing the annual inspection very little to work with. An entry that cites the SRM section, classifies the repair, and notes the approval basis allows the next inspector to make an informed airworthiness determination quickly and confidently.
Key Numbers and Rules
- 14 CFR 43.9 — establishes the minimum content requirements for maintenance record entries for work other than inspections.
- 14 CFR 43.11 — governs entries for inspection work (annual, 100-hour, progressive).
- 14 CFR Part 43, Appendix A — defines what constitutes major vs. minor repairs and major vs. minor alterations; this classification determines whether approved data is mandatory.
- 14 CFR Part 43, Appendix B — prescribes the form and content requirements for recording major repairs and major alterations, including use of FAA Form 337.
- 14 CFR Part 39 — gives ADs the force of law; AD compliance is mandatory and must be documented.
- FAA Form 337 — required for major repairs and major alterations; per AC 43.9-1, the original is generally kept in the aircraft's permanent records with a copy forwarded to the FAA—always confirm current distribution procedures in FAA Order 8900.1.
- Manufacturer ICAs (AMM, SRM, CMM) are approved data only for the current FAA-accepted revision—always verify revision status before performing work.
Common Test Traps
- Service bulletins are NOT approved data by themselves. A service bulletin is acceptable data that can be used to support a method, but it does not independently authorize a major repair or alteration. The FAA exam frequently presents scenarios where a service bulletin is the only cited source for a major repair—that situation is non-compliant.
- Confusing the 337 distribution. For field-approved major repairs and alterations, general AC 43.9-1 guidance is that the original FAA Form 337 is retained in the aircraft's permanent records while a copy is forwarded to the FAA; verify current routing against FAA Order 8900.1, since procedures have evolved over time. Many students assume the reverse or forget that a copy must reach the FAA.
- Mixing up 43.9 and 43.11. Section 43.9 covers entries for maintenance work; Section 43.11 covers entries for inspections (annual, 100-hour). Each has specific required content—exam questions often test whether you know which section applies to which type of entry.
- Assuming any manufacturer document is automatically approved data. Only ICAs that have been reviewed and accepted by the FAA as part of the type certification process carry approved-data status. Informal service letters or preliminary documents do not.
- Outdated revision usage. Using a superseded revision of a maintenance manual without specific authorization can invalidate the work. Always confirm the current revision before citing a document as the basis for a repair.