Compatibility of Changes to Type Design Installed on Aircraft

AC 20-188 · FAA

Public domain · FAAAdvisory Circulars

Overview

The Compatibility of Changes to Type Design Installed on Aircraft (AC 20-188) is a public-domain FAA advisory circular, republished here as a free chaptered HTML edition with a linked table of contents and the official PDF.

Publisher: FAA
Document: AC 20-188
Pages: 7
Chapters: 2

Key points

This advisory circular (AC) provides guidance on determining the compatibility of changes to type design installed on aircraft.
Installers must assess whether new design changes are compatible with previously approved modifications to ensure safety.
Compatibility issues can arise from various combinations of installations, including autopilots, navigation equipment, and structural modifications.
Owners and operators should ensure compatibility determinations are made before installation to avoid ineligibility for return to service.
Non-compatible installations may require additional alterations or FAA approval to establish compatibility.

Frequently asked questions

What is the purpose of AC 20-188?

The purpose of AC 20-188 is to provide engineering guidance to installers on determining the compatibility of changes to type design installed on aircraft.

Who is affected by this advisory circular?

This AC affects persons and organizations who own, operate, or maintain aircraft.

What should an owner or operator do before installing a change to type design?

An owner or operator should ensure that a compatibility determination is made and discuss the intended installation with the installer prior to starting the installation.

What are some examples of installations that may create compatibility issues?

Examples include installing autopilots on modified aircraft, multiple modifications to the same structure, and changes affecting ice protection system operation.

What happens if an installation is determined to be non-compatible?

If an installation is non-compatible, the aircraft may not be approved for return to service until the issue is resolved.

Appendix A

12/07/2016 AC 20 – 188 Appendix A Definitions Appendix A.

All definitions are provided solely for the context of this advisory circular.

Installer. An installer is anyone who replaces or adds articles, parts, or materials used in the alteration of any aircraft that has a United States airworthiness certificate or is responsible to ensure airworthiness prior to returning an altered aircraft to service.

Modification. A modification is a change to type design installed on the aircraft.

Type Club. A type club is an organized group of people with a common interest in a particular aircraft type or brand of aircraft. Information is a type club’s primary resource to members and a type club often provides technical expertise for aircraft models that no longer have an active design approval holder supporting continued operational safety. In some cases, a type club may even be the design approval holder of the aircraft itself.

A-1

Next: Appendix B →

Appendix B

12/07/2016 AC 20 – 188 Appendix B Advisory Circular Feedback Form Appendix B.

If you find an error in this AC, have recommendations for improving it, or have suggestions for new items/subjects to be added, you may let us know by (1) complete the form online at https://ksn2.faa.gov/avs/dfs/Pages/Home.aspx or (2) emailing this form to 9-AWA-AVS-AIR- DMO@faa.gov Subject: AC 20-188 Date: ___________ Please check all appropriate line items: An error (procedural or typographical) has been noted in paragraph _______ on page _______ .

Recommend paragraph _______ on page _______ be changed as follows: In a future change to this AC, please cover the following subject: (Briefly describe what you want added.)

Other comments: I would like to discuss the above. Please contact me.

Submitted by: _________________________________ Date: __________________ B-1