Skip to Content


Advisory Circular (AC) 23-21, Airworthiness Compliance Checklists Used to Substantiate Major Alterations for Small Airplanes

Document Details

Information about this document as published in the Federal Register.

Document Statistics
Document page views are updated periodically throughout the day and are cumulative counts for this document including its time on Public Inspection. Counts are subject to sampling, reprocessing and revision (up or down) throughout the day.
Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

Start Preamble


Federal Aviation Administration, DOT.


Notice of issuance of advisory circular.


This notice announces the issuance of Advisory Circular (AC) 23-21. This advisory circular provides guidance material for the creation and use of airworthiness compliance checklists that can be used when making major alteration to small airplanes. These checklists may be used by Airframe and Powerplant (A&P) mechanics with Inspection Authorization (IA) and by Federal Aviation Administration (FAA) Airworthiness Safety Inspectors (ASIs). The checklists identify the data requirements and their approval methods for several common major Start Printed Page 61900alterations and identify the supporting documentation that may be used to support approval for return to service after aircraft alteration. Use of these airworthiness compliance checklists should be limited to alterations that have been determined to be “major” alterations, as defined in 14 CFR, part 1. They should not be used for complex alterations that require a Supplemental Type Certificate (STC), per FAA Order 8300.10. This advisory circular is intended to work in conjunction with and complement AC 43-210, Standardized Procedures for Requesting Field Approval of Data, Major Alterations, and Repairs. This advisory circular does not change any previously released FAA guidance material such as FAA Orders and AC's listed in section 4 of this advisory circular. The intent of this advisory circular is to provide a tool to work within existing approval processes. Material in this advisory circular is neither mandatory nor regulatory in nature and does not constitute a regulation. The use of these checklists during the return to service of a major alteration is not mandatory nor does it alter any previously acceptable method. The draft advisory circular was issued for Public Comment on May 28, 2004 (69 FR 30738). There were no comments received for the draft advisory circular.


Advisory Circular (AC) 23-21 was issued by the Manager, Small Airplane Directorate on September 30, 2004.

How to Obtain Copies: A paper copy of AC 23-21 may be obtained by writing to the U.S. Department of Transportation, Subsequent Distribution Office, DOT Warehouse, SVC-121.23, Ardmore East Business Center, 3341Q 75th Avenue, Landover, MD 20785, telephone 301-322-5377, or by faxing your request to the warehouse at 301-386-5394. The policy will also be available on the Internet at​AC.

Start Signature

Issued in Kansas City, Missouri on September 30, 2004.

David R. Showers,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.

End Signature End Preamble

[FR Doc. 04-23547 Filed 10-20-04; 8:45 am]