14.3 FAA Form 337 Execution, Maintenance Record Entries & Logbook Rules
Key Takeaways
- FAA Form 337 is used to record Major Repairs and Major Alterations; the executing party must provide the original copy to the aircraft owner/operator and submit a duplicate copy to the local FAA FSDO within 48 hours of return to service.
- Under 14 CFR Part 43 Appendix B, whenever an extended-range fuel tank is installed in the passenger or baggage compartment, a third copy of Form 337 must be placed permanently on board the aircraft.
- Major repairs and alterations require FAA-Approved Data (STCs, TCDS, ADs, FAA-approved SRMs, DER Form 8110-3, or FAA Field Approvals); Advisory Circular AC 43.13-1B is acceptable data and cannot serve as approved data for major work unless specifically authorized.
- 14 CFR §43.9 maintenance entries require 4 items (description, date, name of performer, signature/certificate of approver), while §43.11 inspection entries require exact mandatory certification statements.
- 14 CFR §91.417 separates temporary records (retained for 1 year or until superseded) from permanent records (total time, life-limited parts, overhaul times, AD status, and major alteration Form 337s retained permanently and transferred upon sale).
Last updated: August 2026
14.3 FAA Form 337 Execution, Maintenance Record Entries & Logbook Rules
FAA Airframe Subject Matter Focus: Airframe technicians and Inspection Authorization (IA) holders must maintain flawless compliance with FAA documentation mandates. This section explores the execution and multi-copy distribution of FAA Form 337 (Major Repair and Major Alteration), the critical legal hierarchy of Approved Data vs. Acceptable Data, the precise regulatory anatomy of 14 CFR §43.9 and §43.11 logbook endorsements, and the permanent vs. temporary record retention requirements of 14 CFR §91.417.
1. FAA Form 337: Purpose, Execution & Multi-Copy Distribution
FAA Form 337 (Major Repair and Major Alteration: Airframe, Powerplant, Propeller, or Appliance) provides the FAA and the aircraft owner with a formal, standardized record of major work accomplished on a certificated aeronautical product.
FAA FORM 337 DISTRIBUTION WORKFLOW
[ Major Repair or Major Alteration Completed ]
│
[ Form 337 Executed & Block 7 Signed by IA / 145 ]
│
┌─────────────────────────┼─────────────────────────┐
│ │ │
▼ ▼ ▼
┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐
│ ORIGINAL COPY │ │ DUPLICATE COPY │ │ THIRD COPY │
│ (Delivered to │ │ (Submitted to │ │ (Mandatory ONLY │
│ Aircraft Owner/ │ │ Local FAA FSDO │ │ for Fuel Tanks │
│ Operator) │ │ within 48 Hours)│ │ in Cabin/Cargo) │
└─────────────────┘ └─────────────────┘ └─────────────────┘
Form 337 Distribution Mandates (14 CFR Part 43 Appendix B)
- Standard Distribution (Two Copies):
- Original Copy: Delivered directly to the aircraft owner or registered operator, who must retain it in the aircraft permanent records (14 CFR §91.417(a)(2)(vi)).
- Duplicate Copy: Submitted by the approving person/facility to the local FAA Flight Standards District Office (FSDO) within 48 hours after the aircraft is approved for return to service. (The FSDO reviews and forwards the document to the FAA Aircraft Registration Branch in Oklahoma City for microfilming onto the aircraft's permanent civil registry file).
- Special Passenger/Baggage Compartment Fuel Tank Rule:
- Under 14 CFR Part 43 Appendix B, paragraph (c), whenever an extended-range auxiliary fuel tank is installed in the passenger compartment or a baggage compartment, the person making the installation must execute an additional (third) copy of Form 337.
- This third copy must be retained permanently on board the aircraft (typically stowed in the aircraft flight manual pouch alongside the airworthiness certificate and operating limitations).
2. FAA Form 337 Anatomy & Field Approval Mechanics
FAA Form 337 is divided into eight discrete sections, each serving a specific legal function:
┌─────────────────────────────────────────────────────────────────────────────┐
│ FAA FORM 337 BLOCKS │
├─────────────────────────────────────────────────────────────────────────────┤
│ Block 1: Aircraft Identification (Make, Model, Serial No., N-Number) │
│ Block 2: Owner Information (Name and Physical Address) │
│ Block 3: For FAA Use Only (FAA Field Approval Stamp, Signature, Date) │
│ Block 4: Type (Checkboxes: Major Repair [ ] / Major Alteration [ ]) │
│ Block 5: Unit Identified (Airframe, Powerplant, Propeller, Appliance) │
│ Block 6: Conformity Statement (Mechanic / Repair Station certification) │
│ Block 7: Approval for Return to Service (IA, DAR, Repair Station Sign-off) │
│ Block 8: Description of Work Accomplished (Detailed engineering data, │
│ approved data citations, schematics, weight & balance, and ICA) │
└─────────────────────────────────────────────────────────────────────────────┘
Approved Data vs. Acceptable Data Hierarchy
One of the most heavily tested concepts in FAA regulations is the distinction between Acceptable Data and Approved Data:
| Classification | Definition & Legal Authority | Authorized Scope & Documents |
|---|---|---|
| Acceptable Data | Maintenance methods, techniques, and practices acceptable to the Administrator under 14 CFR §43.13(a). | • Authorized strictly for Minor Repairs, Minor Alterations, and Routine Servicing.<br>• Examples: FAA Advisory Circular AC 43.13-1B (Acceptability of Methods, Techniques, and Practices), manufacturer general service manuals, standard hardware manuals.<br>• Rule: AC 43.13-1B is NOT automatically approved data for major repairs/alterations unless specifically authorized. |
| Approved Data | Technical data that has received formal, documented approval from the FAA Administrator. Required for all Major Repairs and Major Alterations. | • Mandatory for Major Repairs & Major Alterations.<br>• Examples of Approved Data:<br> 1. Type Certificate Data Sheets (TCDS) and Aircraft Specifications.<br> 2. Supplemental Type Certificates (STCs).<br> 3. FAA Airworthiness Directives (ADs).<br> 4. Manufacturer Structural Repair Manuals (SRMs) explicitly stamped "FAA Approved".<br> 5. FAA Form 8110-3 (Statement of Compliance with Airworthiness Standards) signed by an authorized Designated Engineering Representative (DER).<br> 6. FAA Field Approval endorsed in Block 3 of FAA Form 337 by an FAA Aviation Safety Inspector (ASI). |
3. Maintenance Record Entries: 14 CFR §43.9 vs. 14 CFR §43.11
The Code of Federal Regulations strictly distinguishes between record entries for routine maintenance/repairs (§43.9) and record entries for formal inspections (§43.11).
LOGBOOK ENTRY REGULATORY ANATOMY
1. MAINTENANCE / REPAIR ENTRY (14 CFR §43.9)
┌─────────────────────────────────────────────────────────────────┐
│ 1. Description of work performed (or reference to data) │
│ 2. Date of completion of the work │
│ 3. Name of person performing work (if other than approver) │
│ 4. Signature, Certificate Number, and Kind of Certificate held │
│ by the person approving the aircraft for return to service │
└─────────────────────────────────────────────────────────────────┘
2. INSPECTION ENTRY (14 CFR §43.11 - 100-Hour / Annual / Progressive)
┌─────────────────────────────────────────────────────────────────┐
│ 1. Type of inspection and brief description of extent │
│ 2. Date of inspection and Aircraft Total Time in Service (TTIS) │
│ 3. Signature, Certificate Number, and Kind of Certificate held │
│ 4. Mandatory Exact Certification Statement: │
│ - If Airworthy: "I certify that this aircraft has been │
│ inspected in accordance with an (Annual/100-Hr) inspection │
│ and was determined to be in airworthy condition." │
│ - If Unairworthy: "I certify that this aircraft has been │
│ inspected in accordance with an (Annual/100-Hr) inspection │
│ and a list of discrepancies and unairworthy items dated │
│ [date] has been provided to the aircraft owner/operator." │
└─────────────────────────────────────────────────────────────────┘
Critical Contrasts Between §43.9 and §43.11
- Total Time in Service: 14 CFR §43.11 explicitly mandates recording the aircraft total time in service for all inspections. In contrast, 14 CFR §43.9 does not strictly mandate recording total time in service for a simple repair or component replacement (though it is standard industry best practice).
- Mandatory Statement: An inspection entry under §43.11 is legally invalid unless it includes the exact standardized airworthy or unairworthy certification phrase. A routine repair entry under §43.9 requires a description of work, but does not use the §43.11 inspection statement.
4. Maintenance Record Retention: 14 CFR §91.417
Under 14 CFR §91.417, the registered owner or operator is required to keep maintenance records organized into two legal tiers: Temporary Records and Permanent Records.
14 CFR §91.417 RECORD RETENTION TIERS
┌─────────────────────────────────────────────────────────────┐
│ Aircraft Maintenance Records │
└──────────────────────────────┬──────────────────────────────┘
│
┌──────────────────────────────┴──────────────────────────────┐
│ │
┌────────┴────────────────────────┐ ┌────────────────────┴────────────────────┐
│ TEMPORARY RECORDS (§91.417a1) │ │ PERMANENT RECORDS (§91.417a2) │
├─────────────────────────────────┤ ├─────────────────────────────────────────┤
│ • Records of maintenance, │ │ • Total Time in Service (Airframe, │
│ preventive maintenance, │ │ Engines, Propellers, Rotors) │
│ routine repairs, and minor │ │ • Current status of Life-Limited Parts │
│ alterations │ │ • Time Since Last Overhaul (TSOH) │
│ • 100-Hour, Annual, Progressive │ │ • Current Inspection Status & Dates │
│ inspection records │ │ • Current AD Compliance Status Log │
│ • RETENTION PERIOD: │ │ • FAA Form 337s for Major Alterations │
│ - Until work is repeated / │ │ • RETENTION PERIOD: │
│ superseded, OR for │ │ - Retained PERMANENTLY and │
│ - Exactly 1 YEAR after work │ │ TRANSFERRED WITH AIRCRAFT │
│ is completed │ │ upon sale/transfer of title │
└─────────────────────────────────┘ └─────────────────────────────────────────┘
Airworthiness Directive (AD) Permanent Record Requirements
Under 14 CFR §91.417(a)(2)(v), the permanent AD compliance record must contain specific statutory elements:
- The specific AD Number and Revision Date.
- The method of compliance utilized (e.g., "Inspected lower spar cap via high-frequency eddy current per AD 2026-08-04 Para (f)(1) and Boeing SB 737-53A1000").
- If recurring: the current aircraft total time/cycles/date, and the exact next due date, time in service, or cycle limit for subsequent recurring compliance.
- The signature, certificate number, and rating of the technician completing the action.
Test Your Knowledge
Following the completion of an Airframe Major Alteration and approval for return to service, how must the executing facility distribute the copies of FAA Form 337 under 14 CFR Part 43, Appendix B?
A
B
C
D
Test Your Knowledge
When an auxiliary fuel tank is installed in the passenger compartment of an aircraft, what additional regulatory requirement applies to FAA Form 337 under 14 CFR Part 43 Appendix B?
A
B
C
D
Test Your Knowledge
Under 14 CFR §91.417, which of the following maintenance records is classified as a Temporary Record that may be disposed of after 1 year (or after the work is repeated/superseded)?
A
B
C
D
Test Your Knowledge
Which of the following documents is classified as FAA-Approved Data that can be used directly to authorize an Airframe Major Repair or Major Alteration?
A
B
C
D