GUIDANCE FOR APPROVED MODEL LIST (AML) 

SUPPLEMENTAL TYPE CERTIFICATE (STC) 

APPROVAL OF PART 23 AIRPLANE AVIONICS 

INSTALLATIONS 

AC 23-22 

JANUARY 27, 2005 

Initiated By: ACE-100

1/27/05 AC 23-22 

FOREWORD 

The advisory circular (AC) system became effective in 1962. It provides a single, uniform, 

agency-wide system that the Federal Aviation Administration (FAA) uses to deliver advisory 

material to FAA customers, industry, the aviation community, and the public. This AC sets 

guidelines for using the Approved Model List (AML) Supplemental Type Certificate (STC) 

process for the installation approval of avionics for 14 CFR, part 23 airplanes. 

S/ 

David R. Showers 

Acting Manager, Small Airplane Directorate 

Aircraft Certification Service 

i (and ii) 

1/27/05 AC 23-22 

CONTENTS 

SECTION PAGE

Foreword 

Chapter 1. General Information 

1. What is the purpose of this AC? ....................................................................................1 

2. Who does this Advisory Circular (AC) apply to?..........................................................1 

3. What is incorporated or cancelled by this AC? .............................................................1 

Chapter 2. Introduction 

1. Why write this AC? ......................................................................................................3 

2. What documents are related to this AC? ......................................................................4 

3. What are common definitions for the terms used in this AC?......................................6 

4. What is an AML STC? .................................................................................................6 

5. What does existing guidance say about AML STC approvals?....................................7 

6. What avionics can be approved under the AML STC process? ...................................8 

7. What are some limits of the AML STC process? .........................................................9 

Chapter 3. AML STC Process 

1. What are the key process steps to an AML STC? ......................................................11 

2. How is the AML created?...........................................................................................11 

3. What is the Model Qualification Process?..................................................................13 

4. How is an avionics AML STC amended? ..................................................................14 

Chapter 4. AML Documentation Requirements 

1. What is the required detail in the data package submittal for an AML? ....................15 

2. What is the required detail in the installation instructions?........................................ 16 

3. What must the installation instructions address?........................................................17 

4. What Continued Airworthiness Considerations must be addressed? .........................19 

Chapter 5. Model Qualification Process Requirements 

1. Evaluation of Physical Location of Installed Equipment .............................................21 

2. Evaluation of the Applicability of the Proposed STC ..................................................21 

3. Evaluation of Intended Function of the Proposed Equipment......................................21 

4. Evaluation of the Installation Complexity of the Proposed Equipment .......................22 

5. Evaluation of Operational Requirements of the Proposed Equipment.........................22 

6. Pilot Evaluation and Human Factors Issues for the Proposed Equipment ...................23

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AC 23-22 1/27/05 

Appendix 1 Generic Model Qualification Process Sample Document......................A1-1 

Appendix 2 Example AML STC...................................................................................A2-1 

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1/27/05 AC 23-22 

CHAPTER 1. GENERAL INFORMATION 

1. What is the purpose of this AC?

a. This advisory circular (AC) sets guidelines for using the Approved Model List 

(AML) Supplemental Type Certificate (STC) process for the installation approval of 

avionics for 14 CFR, part 23 airplanes. It also applies to airplanes certified under a prior 

certification basis, such as Civil Air Regulations (CAR) part 3 or Aeronautics Bulletin 7-A. 

Guidance provided in this AC applies only to avionics installations using the AML STC 

process. For other types of modifications to part 23 airplanes seeking to use the AML STC 

process, the Aircraft Certification Office (ACO) should coordinate with the Small Airplane 

Directorate. Avionics AML STC guidance provided in this AC addresses the following: 

(1) Avionics eligible for the AML STC process 

(2) Model Qualification Process used by the STC holder and the FAA to either 

create or edit the AML 

(3) Level of Detail required for the installation instructions for an AML STC, 

including a list of acceptable equipment that can be integrated under the STC. 

b. Material in this AC is neither mandatory nor regulatory in nature and does not 

constitute a regulation. In addition, this material is not to be construed as having any legal 

status and should be treated accordingly. However, it is designed to provide standardization 

guidelines for AML STC approvals. The AML STC process may be used whenever the 

ACO and the applicant agree that it is suitable. This AC is not applicable to any products 

certified under part 25, 27, or 29. 

c. This guidance does not replace the ability of an applicant to get a field approval for a 

major alteration, as outlined in FAA order 8300.10, Volume 2, Chapter 1. It is meant to 

provide an alternative path for installation approval of avionics equipment and to promote 

standardization through Certification Engineering involvement on multiple-model 

installations of the same equipment. 

2. Who does this Advisory Circular (AC) apply to? 

This AC provides guidance to Federal Aviation Administration (FAA) personnel, 

equipment manufacturers, and avionics equipment installers. 

3. What is incorporated or canceled by this AC? 

a. This guidance does not address design approval for part 23 avionics systems, which 

is already addressed in existing FAA documents, such as Order 8150.1B. It is meant to 

clarify installation approval under the AML process for part 23 avionics. 

b. The guidance in this AC augments and clarifies the information provided in 

cancelled Notice 8110.43, Supplemental Type Certificates Applicable to Several Type 

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AC 23-22 1/27/05 

Certificated Products, issued 3/6/1992. The information from Notice 8110.43 has been 

incorporated into this AC in Appendix 2. 

c. This AC also cancels Policy Statement PS-ACE100-2002-002 on the installation 

approval of Multifunction Displays (MFD) using the AML STC process. PS-ACE100-

2002-002 did not address Primary Flight Displays or other avionics systems and limited 

the use of the AML process to non-flight critical applications. This AC incorporates the 

information in PS-ACE100-2002-002 and provides guidance to expand the use of the 

AML to other types of avionics systems and standardize the AML approval process. 

2 
1/27/05 AC 23-22 

CHAPTER 2. INTRODUCTION 

1. Why write this AC? 

a. The Safer Skies initiative and the Advanced General Aviation Transportation 

Experiment (AGATE) program determined that modern avionics could provide pilots 

with better information and reduce general aviation accidents. Until recently, hardware 

costs and certification costs made it impractical to build new technology avionics systems 

for part 23 use. As new technology is introduced, hardware costs continue to come

down. In contrast, the avionics installation approval process has increasingly become

more rigorous for applicants seeking installation approval of new systems in part 23 and 

CAR 3 airplanes. Also, the existing approval processes often provide an inconsistent 

level of FAA oversight. 

b. Applicants sought the approval path of least resistance, which has increased the 

number of follow-on field approvals for installation of avionics systems in small 

airplanes. Field approvals are typically based on a single STC with little or no follow-on 

ACO involvement, which may only be suitable for certain types of installations. For 

more complex avionics installations, a follow-on field approval may not properly address 

interface considerations to existing equipment. This warrants a change in the avionics 

approval process for part 23 and CAR 3 airplanes. The resulting streamlined process 

needs to provide the proper measure of certification oversight, but it must provide similar 

advantages to the field approval process. 

c. The “Industry and FAA Avionics Approval Guide” describes the certification 

process for design and installation approval and suggests expanded use of the AML 

process to streamline part 23 avionics installation approvals. However, the lack of clear 

guidance on AML approvals has led ACOs to develop their own avionics approval 

procedures, resulting in a lack of standardization. There is a clear need for a standardized 

approach to the AML avionics approval process, including criteria for the suitable use of 

the process, which this AC is designed to provide. 

d. Existing AML approvals range in complexity from simple “single wire” 

installations of supplemental systems to complex Primary Flight Display (PFD) systems 

that provide flight critical information. Each avionics system presents a unique set of 

certification requirements. Complex systems require greater certification detail to deal 

properly with compliance issues for models with slightly different certification bases. 

For example, showings of compliance to part 23, § 23.1331 requirements for electrical 

power may be slightly different from model to model and must be clearly documented 

under the AML process. 

e. This AC serves to clarify the AML process for part 23 avionics approvals. It 

clearly outlines the requirements for creating a Model Qualification Process, determining 

a suitable certification basis, creating detailed installation instructions with equipment 

suitable integration procedures, determining data package details, creating procedures for 

amending the AML, and other items. The AML process is designed to allow a single set 

of compliance data to be applied to multiple models, where suitable. The intent is to 

3 
AC 23-22 1/27/05 

avoid duplication of testing and data gathering while honoring the agency's primary 

responsibility to determine the airworthiness of the altered product. 

f. It is important the applicant and the FAA ACO agree to the use of the AML 

process early in a certification project. The resulting STC, with its associated AML, 

should lessen the need for installers to request field approvals, but is not meant to lower 

the certification requirements for a particular installation approval. If done properly, an 

AML STC may save valuable resources for both industry and the FAA by reducing the 

number of individual STC approvals. 

2. What documents are related to this AC?

a. Orders, regulations, policy statements, and other FAA documents: 

HBAW 98-18 Checklist for Instructions for Continued 

Airworthiness for Major Alterations 

Order 8100.5A Aircraft Certification Service Mission, 

Responsibilities, Relationships, and Programs 

Order 8110.4B Type Certification 

Order 8150.1B Technical Standard Order Procedures 

Order 8300.10 Airworthiness Inspector’s Handbook 

Volume 2, Chapter 1, Perform Field Approval of 

Major Repairs and Major Alterations, Change 16 

Order 8110.37C Designated Engineering Representative (DER) 

Guidance Handbook 

Order 8110.48 How To Establish The Certification Basis For 

Changed Aeronautical Products 

Order 8110.49 Software Approval Guidelines 

Title 14 CFR, part 21 Certification Procedures for Products and Parts 

Title 14 CFR, part 23 Airworthiness Standards: Normal, Utility, 

Acrobatic, and Commuter Category 

Airplanes 

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1/27/05 AC 23-22 

b. Advisory Circulars 

You may get copies of the current publication of the ACs listed below from the U.S. 

Department of Transportation, Subsequent Distribution Office, Ardmore East Business 

Center, 3341 Q 75th Avenue, Landover, MD 20785. The ACs are also available on the 

Internet at http://www.faa.gov/certification/aircraft. 

AC 21-40 Application Guide for Obtaining a Supplemental 

Type Certificate 

AC 23.1309-1C Equipment, Systems, and Installation in Part 23 

Airplanes 

AC 23.1311-1A Installation of Electronic Displays in Part 23 

Airplanes 

AC 23-15A Small Airplane Certification Compliance Program 

AC 23-17A Systems and Equipment Guide for Certification of 

Part 23 Airplanes 

AC 23-8B Flight Test Guide for Certification of Part 23 

Airplanes 

AC 43.13-1B Acceptable Methods, Techniques, and Practices - 

Aircraft Inspection and Repair 

AC 43.13-2A Acceptable Methods, Techniques, and Practices - 

Aircraft Alterations 

AC 20-138A Airworthiness Approval of Global Navigation 

Satellite System (GNSS) Equipment 

c. Other Applicable FAA and Industry Documents or Job Aids 

The FAA and Industry Guide to Product Certification, January 1999, located on 

the web at: http://www.faa.gov/certification/aircraft/av-info/dst/CPIGUIDE.pdf 

The FAA and Industry Guide to Avionics Approvals, April 2001, available on the 

web at: http://www.faa.gov/certification/aircraft/AVCPIcov.pdf 

GAMA Publication Number 10, Recommended Practices and Guidelines for 

Part 23 Cockpit/Flight Deck Design, available on the web at: 

http://www.gama.aero/pubs/onlineCatalog.php

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AC 23-22 1/27/05 

GAMA Publication No. 12 - Recommended Practices and Guidelines for an 

Integrated Cockpit/Flightdeck in a Part 23 Airplane, available on the web at: 

http://www.gama.aero/pubs/onlineCatalog.php

3. What are common definitions for the terms used in this AC? 

AD Airworthiness Directive 

AML Approved Model List 

CFR Code of Federal Regulations 

CPI Certification Process Improvement 

DER Designated Engineering Representative 

FHA Functional Hazard Assessment 

GAMA General Aviation Manufacturers Association 

GPS Global Positioning System

ICA Instructions for Continued Airworthiness 

MFD Multi-Function Display 

PSCP Project Specific Certification Plan 

STC Supplemental Type Certificate 

TC Type Certificate 

TCDS Type Certificate Data Sheet 

4. What is an AML STC? 

a. An AML STC is similar to a multimodel STC, which applies to multiple airplanes 

listed on the same TCDS. However, an AML STC goes one step further by allowing the 

STC to apply to several different TCs. This allows a single STC to address several 

different TCs by documenting the data and limits suitable to each of the several different 

aircraft. This is a more efficient use of resources compared to multiple single-model 

approvals for an installation that is similar or identical for several different models. See 

Order 8110.4B for more information on the STC process. 

b. To keep track of the various models, an AML is created and attached to the STC 

(FAA form 8110-2). Whenever another model is added or a document is amended, the 

AML is changed and not the STC. This lessens the number of STC approvals and may 

be a more efficient use of resources compared to multiple single-model approvals. 

However, any change to the AML requires FAA approval. 

c. STC approvals with an AML have the same data requirements as an STC 

applicable to a single model of aircraft. However, when making avionics modifications it 

is possible to combine the current approval process with some of the advantages of the 

field approval process. Field approvals typically allow for data from a single STC to be 

reused for multiple approvals where similarity can be clearly shown. However, they are 

often carried out with little or no follow-on ACO involvement, which may only be 

suitable for simple installations where Part 43 “acceptable data” clearly addresses 

differences between the existing approval and the follow-on installation. The AML 

provides an advantage, since ACO engineering involvement is required for each 

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1/27/05 AC 23-22 

installation on each model on the AML and differences are evaluated and documented 

clearly in the installation instructions. 

d. For more complex avionics installations (See Chapter 1, Section 6.c), it may be 

more suitable for the applicant to address interface considerations to existing equipment 

upfront for each proposed model on an AML through a prototyping approach. 

e. This process allows portions of the compliance data to be reused, and new 

showings of compliance for each model to be provided as needed. The AML process is 

meant to provide the proper measure of certification oversight, but also provide a 

streamlined approval process for part 23 avionics. Further guidance on the STC process 

is available in AC 21-40. 

5. What does existing guidance say about AML STC approvals?

a. Order 8110.4B, section 4-2a(4), clearly provides for a single STC data package to 

be used for multiple airplane models, provided the following conditions are met: 

(1) The STC data package consists of a principal design and certification data 

package for the change and either a master installation package for all eligible type 

certificated products or a separate installation package for each eligible type certificated 

product. 

(2) Any design or installation differences between eligible products are identified 

in the design and installation data. 

(3) Installation complexity is similar on all eligible products. 

(4) The change does not require a large reevaluation of the type-certificated 

product's airworthiness. 

(5) Either the flight or operational characteristics, or both, of the type-certificated 

product remain unchanged. 

(6) The change does not create an acoustical change to the type-certificated 

product (See §21.93 and FAR Part 36 to define an acoustical change). 

(7) The eligible type certificated products, applicable FAA approved documents, 

and the certification basis for each model are listed on a special page known as the 

“Approved Model List (AML)” attached to the STC under the following conditions: 

(a) Whenever a type certificated product is added or one of the FAA approved 

documents is amended, deleted, or added, the AML itself is amended and approved by 

the FAA, not the STC. 

 (b) An AD is required to remove a product from an AML in the case where 

some unsafe condition exists unless the STC holder can prove no installation was made. 

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AC 23-22 1/27/05 

The applicant should always coordinate with the responsible ACO to determine the best 

course of action for removing a model from the AML using existing FAA process. 

Existing installations may be affected if the ACO determines that an unsafe condition 

exists for a particular model, which may require the removal of the equipment in 

question. 

(c) An STC with an AML can be transferred in total to another holder but 

cannot be split into more than one STC. 

b. The “Industry and FAA Avionics Approval Guide” states that, for avionics 

equipment with similar installation requirements on several aircraft models, a generic 

approach to the approval process should be considered. The goal of the generic STC 

approval process is to develop installation instructions that can be used to install avionics 

equipment in several different aircraft models. These installation instructions will not 

repeat complete STC programs and will allow the reuse of compliance data where 

suitable. Title 14 CFR, part 21, § 21.101, also supports this idea. 

c. This AML STC approach can reduce the effort for follow-on approvals the 

avionics installers must get and should reduce the number of field approvals that are 

performed. It will streamline the STC approval process and allow multiple models to be 

approved at once. However, there has been some confusion of defining “type design” in 

discussions about this generic approval process. This guidance seeks to clarify that a 

single compliance data package is suitable for AML approvals if applicability of the data 

package to different models and likeness between type designs can be clearly shown and 

documented. By identifying installation requirements up front, the AML STC process 

simplifies the approval of installation data for other models. 

6. What avionics can be approved under the AML STC process? 

a. Critical and noncritical avionics system installations can be addressed using the 

AML process, provided the ACO and applicant agree the process will adequately address 

the certification requirements for a given system, and its installation on other model 

aircraft. The term ”critical'' refers to those functions identified by a (§ 23.1309) hazard 

analysis whose failure would contribute to, or cause, a failure condition that would 

prevent the continued safe flight and landing of the airplane. AML STC approvals can be 

separated into two classifications, simple or complex, depending on the system

installation complexity. 

b. A simple system is defined as a stand-alone equipment installation that 1) has 

well understood requirements for power, antenna, and other interfaces, and 2) does not 

require substantial model specific configuration settings to be applied. A simple AML 

STC involves an installation that is repeated easily for all the airplanes listed on the AML 

using a generic set of installation instructions and a generic configuration setting. 

However, before using a generic set of installation instructions, the applicant must clearly 

document and show similarity between the aircraft on the AML. Further compliance 

findings and formal conformity inspections may not be required after an initial showing 

8
1/27/05 AC 23-22 

of compliance to §21.33 for simple systems if similarity is clearly documented for every 

model on the AML. The ACO and applicant must agree on this approach, and it must be 

documented in the Certification Plan and the Model Qualification Process. This 

approach is clearly recommended in existing guidance for stand-alone GPS receivers in 

AC 20-138A and should also be applicable to radios, horizontal situation indicators, 

course deviation indicators, and other typical avionics components. 

c. Complex systems are defined as systems that require model specific interface or 

installation configuration changes or as single or multiple component systems that 

require significant data communication and integration with existing equipment, or both. 

A complex AML STC may involve either an installation where similarity is not as easily 

shown between models or where the modification requires model specific changes for 

each airplane on the AML, or both. This may be handled by using model specific 

installation instructions added as an appendix to the generic set of instructions, or by 

separate model specific installation instructions clearly referenced on the AML. The 

applicant should “prototype” the system installation as each model is added to the AML 

to ensure that model specific requirements are addressed and integrated into the 

installation instructions. For complex installations, specific compliance and conformity 

inspections are necessary using model specific information in the installation instructions 

to comply with §21.33. 

d. Complex AML STC approvals should be handled more like multimodel STC 

approvals, and require model specific documentation for each model listed on the AML. 

For example, it may be necessary to produce a model specific System Safety Assessment 

for each model on the AML to satisfy §23.1309 for complex systems. It may be possible 

to use one set of §23.1309 compliance data for simple systems. 

e. Regardless of the equipment being approved, the AML STC installation 

instructions must be detailed to allow multiple model installations. This should reduce 

the number of deviations from the STC data package that are sought for follow-on 

installations. The idea is to reduce the number of cases where maintenance data, 

accepted under part 43 rules, is used to support an installation when the STC data 

package either 1) does not correspond to the airplane, 2) does not address a particular 

interface, or 3) is incomplete. This may require more work up front for the applicant, but 

should reduce the number of problems for future installations. 

7. What are some limits of the AML STC process? 

a. The AML STC process is subject to the same guidelines and limits discussed in 

Order 8110.4B and 14 CFR, part 21, Subpart E. Therefore, it may not be suitable for 

new and novel features. The applicant and the ACO should coordinate on each specific 

certification project to determine if the AML process is applicable. The Small Airplane 

9 
AC 23-22 1/27/05 

Directorate should be involved in determining when an AML is applicable in cases where 

new and novel features are present through the Certification Project Notification (CPN) 

process according to Order 8110.4B. 

b. Order 8110.4B states that if an applicant presents a foreign registered airplane as 

an article for inspection or test under any STC approval, the applicant must provide 

evidence the civil aviation authority of the State of Registration agrees to the 

modification to the airplane. This also applies to AML approvals. 

c. The AML STC process should not be applied to those systems whose installation 

configuration varies significantly among various serial number aircraft of the same

model, or those systems that can directly control the aircraft. For example, an AML STC 

would not be suitable for autopilot installations. For autopilot installations, there may be 

serial number specific airplane-rigging problems that have to be taken care of on a caseby-case basis. Another example would be a Reduced Vertical Separation Minimum

(RVSM) STC approval where model and serial number specific static pressure system

characteristics could preclude a generic approach to the certification project. There are 

cases where the static source error correction curve for RVSM approval is only 

applicable to a single serial number airplane. The part 91 RVSM guidance material 

contains details on group approval methods for RVSM approval. 

d. High Intensity Radiated Fields (HIRF) and lightning compliance, as well as 

assumptions made during the Functional Hazard Analysis (FHA) and System Safety 

Assessment (SSA) for a particular system, may limit the use of the AML process since 

these items can be model dependent. The applicant and the ACO must agree on a process 

to allow these items to be addressed in a generic manner for the models on the AML, and 

agree on Continued Airworthiness procedures to maintain compliance for these items. 

e. Deviations from the original approval to allow an installation on a particular 

model listed on the AML will require the installation instructions to be modified. The 

approval can also be completed under an individual STC, depending on the scope of the 

deviation. Existing processes in FAA Order 8300.10 must be used to determine when a 

deviation to the AML STC is necessary. A deviation is necessary when the installation 

does not match the equipment list and/or equipment integration approved in the original 

installation. Any deviations from the original STC must be documented and approved 

either by an ACO engineer, a DER, or the field inspector. The AML process is not meant 

to be a blanket approval that delegates the integration of additional equipment to the 

installer without FAA involvement. 

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1/27/05 AC 23-22 

CHAPTER 3. AML STC PROCESS

1. What are the key process steps to an AML STC? 

a. The AML STC process is similar to other STC processes, with added steps to 

allow the requirements for the approval to span across type data sheets. Avionics 

installation approvals should follow the requirements in 14 CFR, part 21, subpart E, the 

guidance in Order 8110.4B, and the “Industry Guide to Avionics Approvals,” with the 

guidance in this AC. Figure 1, on the next page, shows a generalized flowchart for the 

AML process. For AML STC projects, the applicant is expected to submit a Project 

Specific Certification Plan (PSCP), following the CPI Process. 

b. It is important for the applicant and the responsible ACO to coordinate at the start 

of the program to document properly the AML process in the PSCP or other FAA 

approved Certification Plan, which should include: 

(1) Development of a Model Qualification Process (see Chapter 3, Section 3) 

(2) Development of AML amendment procedures (see Chapter 3, Section 4) 

(3) Agreement on data package requirements (see Chapter 4). 

2. How is the AML created? 

a. Eligibility for each model on the AML must be clearly documented by the 

applicant. For simple systems, it may be easier to prove similarity or identicality. For 

complex systems, the applicant may need to “prototype” the system installation as each 

model is added to the AML. This will ensure that model specific requirements have been 

addressed and integrated into model specific sections in the installation instructions and 

other documentation. 

b. An applicant cannot simply apply engineering judgment to create the AML, but 

the applicant must document a repeatable decision process to include each model on the 

AML and the methods used to determine applicability. Also, the assumptions and limits 

for the approval must be clearly stated to avoid confusion for future installations or 

amendments to the AML. For example, RTCA/DO-160 environmental qualification 

performed during design approval for a particular operating environment on one model 

may not be suitable for other models being proposed for addition to the AML. Also, 

assumptions made during the FHA may limit which models can qualify for addition to 

the AML. 

11 
AC 23-22 1/27/05 

Standard

Avionics

Certification 

Process

Product

Proposed for

Certification

AML

STC?

Develop/Submit

PSCP

NO

YES

Installation

Complete & 

Cert Testing

Complete

FAA ACO 

Issues

Certificate

Coordinate

Model Qualification Process,

AML Amendment Process, &

AML Data Pkg Requirements

with ACO

Standard

Avionics

Certification 

Process

Generate/Amend

Model List & 

Issue 8110-3

Develop/Submit

AML PSCP

Develop/Amend 

Installation

Instructions

End of Project

New

Models or

Other

Changes?

NO

YES

Installation

Complete & 

Cert Testing

Complete

FAA ACO 

Issues

Certificate

or AML

Figure 1 – General Process AML STC Approvals 

12 
1/27/05 AC 23-22 

c. It may necessary for an applicant to split an AML into sections to separate models 

into groups where similarity can be clearly shown. They may be split according to 

operational capabilities, certification basis, airplane classification under AC 23.1309, or 

by other model characteristics that can be clearly grouped. This would allow installation 

considerations for each group to be addressed separately. 

d. The AML should contain a list of the most recent STC documentation to track 

revisions and changes as the AML is amended. It may be necessary for eligibility for 

each model on the AML to be revisited if a major change is made to an existing AML 

approval, such as a change to system design or intended function. 

3. What is the Model Qualification Process? 

a. The Model Qualification Process is a procedure, agreed on by the ACO and the 

applicant, that is used by the STC holder to capture specific engineering decisions, design 

attributes, limitations, and assumptions made during the system development or 

Technical Standard Order (TSO)/design approval. This helps standardize the AML STC 

approval process by formally documenting the engineering analysis used to determine 

applicability and eligibility of a given model for the AML STC. 

b. The Model Qualification Process should capture assumptions made during the 

design phase of a particular piece of equipment and may preclude a model from being 

included on the AML because of these assumptions. For example, a decision by the 

equipment manufacturer to develop system software to current revision of RTCA/DO178 Level C for critical functions may limit the installation eligibility. According to 

AC 23.1309-1C, Figure 2, by only certifying to software level C for critical functions, 

installations for part 23 aircraft over 6,000 pounds are not acceptable and require a higher 

software development level. See Appendix 1 for more information. 

c. The Model Qualification Process requires detailed foreknowledge of the system

and the models proposed for the AML. The data submitted with the AML should include 

information showing the Model Qualification Process has been specifically applied to 

each model on the AML to verify applicability. The submittal should also include a form

8110-3 that approves the Model Qualification data package and recommends approval of 

the AML. The 8110.3 should include a clarifying note stating, "This approval is for 

engineering design data only and is not an installation approval," according to Order 

8110.37C. The 8110-3 should reference applicable Part 23 requirements that could 

influence applicability for models on the proposed AML, given the design assumptions 

for the equipment being installed. Examples include §23.1301, §23.1309, and §23.1353. 

More detail on data package requirements is available in Chapter 4. 

d. The Model Qualification Process should evaluate each model on the AML to 

verify the assumptions used during HIRF and lightning compliance, and during the 

System Safety Assessment, are valid. These items can be installation dependent, so a 

formal process must be in place to make sure compliance data is applicable to each model 

proposed for the AML and that common installation and wiring practices are adhered to. 

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AC 23-22 1/27/05 

The applicant and the ACO must agree on a process to allow these items to be addressed 

in a generic manner for the models on the AML, and agree on Continued Airworthiness 

procedures to maintain compliance for these items. 

e. More information on this process may be found in Chapter 5, “Model 

Qualification Process Requirements.” 

4. How is an avionics AML STC amended? 

a. Changes that affect the original basic system approval must be addressed as an 

amendment to the STC itself and may require further showing of compliance. For 

example, changing the intended function of a box by installing modified software would 

require an amendment to the STC itself and may also influence what models can be on 

the AML. Another example would be a change to the way the equipment is installed that 

could influence system functionality or the certification assumptions made during the 

original approval. 

b. When an AML STC is amended to add a model, the documentation associated 

with the AML is amended and not the STC itself. The responsible ACO and the 

applicant must agree on the procedures to amend the AML; however, the following is a 

list of the basic steps involved. 

(1) The applicant proposes a model to be added to the AML. 

(2) The applicant subjects the proposed model to the Model Qualification 

Process. 

(3) The applicant modifies installation instructions, and other documents, as 

needed to accommodate the new model. 

(4) The applicant submits a data package and a form 8110-3 documenting the 

applicability of the STC to the model in question and recommending approval 

to add the model to the AML. According to Order 8110.37C, form 8110-3 

should contain a clarifying note stating, "This approval is for engineering 

design data only and is not an installation approval.” 

(5) The FAA reviews the submittal and amends the AML. 

(6) The FAA issues the new AML with the new model added. 

c. Changes to or approval of the AML is not delegated to a DER since this would 

allow new models to be added to the AML (new STC approvals) without FAA oversight. 

A Designated Alteration Station (DAS) with authorized privileges may amend an AML 

for which it holds an STC if the data package and other STC documentation discussed 

above is submitted for FAA review according to the existing DAS agreement for STC 

approvals. 

d. As mentioned in Order 8110.4B, an AD must be issued to remove a model from

an AML. See Chapter 2, Section 5.a.(7).b.

14
1/27/05 AC 23-22 

CHAPTER 4. AML DOCUMENTATION REQUIREMENTS 

1. What is the required detail in the data package submittal for an AML? 

a. The detail contained in a data package submittal for an AML approval is agreed 

on between the applicant and the responsible ACO at the beginning of the AML approval 

process. The detail required will be directly related to the complexity and intended 

function of the installation and the complexity of the models listed on the AML. The 

data package can be split into a principal design and certification data package for the 

STC modification and into either a “master” installation package for all eligible typecertificated products, or into separate installation packages for each eligible typecertificated product. 

b. According to Order 8110.4B, and 14 CFR, part 21, § 21.101, there are STC 

procedures in place to reduce unnecessary administrative burdens on the applicant and 

the FAA. Once an applicant has shown that a design change meets the airworthiness 

requirements necessary for FAA approval, later similar alterations may not require the 

same data package detail and may not require the same tests as the first approval. This 

philosophy is used to allow an applicant to benefit from previous work. 

c. A key element of the AML process is a single set of compliance data to be 

applied potentially to multiple models. The intent is to avoid duplication of testing and 

data gathering while honoring the agency's primary responsibility to determine the 

airworthiness of the altered product. The compliance data package must be detailed 

enough to allow a compliance finding by the responsible ACO. However, it may be used 

to show compliance for multiple models on the AML if the Model Qualification Process 

clearly documents similarity between the models. For example, it may be possible to 

address electrical load analysis issues, hazard analysis issues, and other certification 

requirements in a generic fashion for the entire AML. The responsible ACO and the 

applicant must agree on this approach. 

d. The FAA may minimize or waive the need for the applicant to provide supporting 

data for specific AML approval requirements. This is based on prior FAA knowledge 

gained from the first installation done by an applicant for the first model on the AML. 

This depends on the criticality and intended function of a particular component and the 

similarity or identicality of the installations. This agreement should be documented in 

the AML STC Certification Plan. However, the intent is not to allow an applicant to use 

compliance data from another applicant's approval unless written permission is obtained 

to do so from the original STC holder. As with other STC approvals, the FAA will not 

supply an applicant with information submitted by a previous applicant. 

e. The generic approach to the conformity plan should be well defined in the 

Certification Plan or Model Qualification Process document and must have FAA 

concurrence. FAA Order 8110.4B and AC 21-40, application guide for obtaining a STC, 

provide more details on conformity inspections. 

15 
AC 23-22 1/27/05 

f. The ACO and applicant must agree whether an Aircraft Flight Manual (AFM) 

supplement is necessary. This will depend on the need for an aircraft limitation 

(23.1583) based on the equipment, operational complexity and the compelling nature of 

the equipment to draw the pilot’s attention. If it is determined that an AFM supplement 

is necessary, it should include a description of the system, aircraft limitations, emergency 

procedures, abnormal procedures, and normal procedures, and any changes to the 

performance of the airplane. The AFM supplement may also refer to the equipment user 

manuals for more detailed instructions on operating the equipment. For simple systems, 

a general supplement would be suitable for all approved models. The general supplement 

is then inserted into the existing flight manual with the cover page completed for make 

and model, registration number, and serial number. AC 23-8B, Flight Test Guide for 

Certification of Part 23 Airplanes, chapter 6, section 3, provides added guidance on AFM 

and approved manual material. If the airplane does not require an AFM, a “Supplemental 

Flight Manual” or pilot handbook should be developed to provide the same information. 

Order 8110.4B paragraphs 4-2.a. (4) (c) and (e) also set limits on expanding AFM model 

eligibility for an AML STC. 

2. What is the required detail in the installation instructions? 

a. The installation instructions and the Model Qualification Process are vital parts of

the AML process. The installation instructions should be suitable for the intended 

function of the system. These instructions must describe the installation in adequate 

detail such that the installation shop can determine if a particular serial number airplane 

is eligible. Follow-on installations are repeatable, so the installation will meet 

airworthiness requirements, and a conformity inspection can be performed to equipment 

lists and drawings, if required. If the system being certified is simple, it may be possible 

to use one set of generic installation instructions and apply them to all the models on the 

AML. The generalized installation guidelines could reference standard practices used in 

the installation, for example aircraft electrical wire selection as specified in Advisory 

Circular 43-13. 

b. For more complex systems, a more detailed set of installation instructions may be 

necessary. This may include a general section, with model specific appendices to address 

model specific installation considerations. New model specific sections may also be 

added to the instructions and approved by the FAA as necessary when each system is 

“prototyped” or when the system is installed on a new model as an amendment to the 

AML. The procedures for revising the installation instructions should be part of the 

AML amendment procedures between the responsible ACO and the applicant and should 

be clearly documented. 

c. In developing the installation instructions, the applicant may consult local 

avionics repair stations, the ACO, and Aviation Safety Inspectors from the FAA local 

Flight Standards District Office. Their support may provide insight into what is required 

for the installation instructions. The resulting AML STC should reduce the potential 

16
1/27/05 AC 23-22 

need of Flight Standards to issue follow-on field approvals for similar equipment 

installations. 

3. What must the installation instructions address? 

a. Definition of Intended Function for the System - The intended function of the 

system must be clearly stated so compatibility can be determined with existing equipment 

for each model on the AML. Also, the intended function should be the same for all the 

models on the AML, or it may be necessary to split the AML into different sections. 

There has been a trend to install equipment, mainly navigation related equipment such as 

moving maps, as nonrequired, “Not approved for primary navigation” or “SA-Only.” 

The basis for their installation approval has been that they must perform their intended 

function and not present a hazard to other equipment or the airplane. However, it is not 

acceptable to label an instrument as “SA-Only” and assume its failure in normal 

operation is acceptable. A safety assessment conducted by guidelines in AC 23.1309-1C 

is required to help define the potential safety concerns for a particular installation for the 

models on the AML. 

b. Human Factors Considerations - The FAA recognizes the need to address human 

factors issues. Human factors considerations must be addressed in the AML Certification 

Plan. Guidance to aid in this effort and other human factors considerations is contained 

in the FAA policy statement, PS-ACE100-2001-004. Also, AC 23.1523 addresses pilot 

workload, which should be considered for all the models on the AML. 

c. Wiring Considerations - This includes system schematics and wiring diagrams to 

describe adequately the connectivity of the equipment, including antennas. For simple 

installations, it may be acceptable for the applicant to reference specific sections and 

figures in AC 43-13 to document accepted installation practices, including wire routing 

and wire separation. For more complex installations, more detailed wiring information 

may be necessary. For example, specific wiring instructions are required to maintain 

HIRF and lightning compliance for follow-on installations of critical equipment. If these 

practices are not followed for a particular installation, the potential for safety hazards 

may exist. Wire routing and separation considerations must also be addressed according 

to accepted practices for the certification basis of the model being altered. However, 

depending on the installation, exact three-dimensional wire routing diagrams may not be 

value added, even for critical systems. The applicant and ACO must agree early in the 

approval process on the acceptable means to document wiring installation. Also, only 

wire specifically designed for airborne use should be installed in the aircraft, such as wire 

presented in AC 43.13-1B. 

d. Structural Considerations - If required, structural substantiation data must be 

submitted for antenna installations, and box mounting. AC 43-13 is not a satisfactory 

reference for antenna installations on pressurized airplanes. Also, depending on the 

certification basis of the airplane (Amendment 23-45 or later), damage tolerance issues 

must be addressed. 

17 
AC 23-22 1/27/05 

e. STC Assumptions and Limitations - Assumptions and limitations in the 

supporting data for the original approval of the STC must be clearly stated in the 

installation instructions. This is because an installation shop can address serial number 

specific considerations and seek further approval, if needed. For example, a particular 

serial number may have existing equipment or modifications that would preclude 

installation of the proposed modification or would require further FAA approval, despite 

being listed on the AML. 

f. Interface to Other Equipment - Data must be provided to document what 

equipment is approved to interface with the proposed system under the AML STC. 

Enough detail must be provided to document interface compatibility and interoperability 

assurance with other equipment. This should include any approved variations in protocol 

or data word formats that might influence proper functionality, operational 

characteristics, or changes to intended function. This may also include a list of 

equipment that is specifically not approved to interface with the equipment being 

installed. 

g. Electrical Load Analysis and Functional Hazard Assessment. Installation 

procedures should clearly state that electrical load analysis, functional hazard assessment, 

and other certification requirements remain in compliance. It is possible to apply a 

generic approach to the functional hazard assessment if worst-case assumptions are made 

for a typical installation. For example, the functional hazard assessment is performed 

during design approval with certain assumptions on system redundancy and back-up 

systems. The STC must contain details of these assumptions as limits to assure all 

models on the AML meet the terms of the original design approval assumptions. 

h. Pre- and Post-Installation Check Procedures 

(1) Provide either pre or post installation ground test or flight check procedures, 

or both, with clear and concise pass/fail criteria to verify the intended function of the 

system. Include a post-installation approval for return to service by the responsible party 

so a maintenance record entry can be made documenting the installation has been 

performed. 

(2) The ground test or flight check procedures, or both, should 1) evaluate 

operation of the system, 2) determine if the system is interfaced properly with other 

systems, 3) determine if the system performs its intended function, and 4) determine if 

there is unacceptable interference with other systems. For example, day/night lighting 

considerations must be addressed for a particular installation. 

(3) AC 23-8B, Flight Test Guide for Certification of Part 23 Airplanes, provides 

further guidance. Also consider part 91, § 91.407, to determine flight check requirements 

for post-installation test to verify intended function. In accordance with § 91.407(a) and 

(b)An operational flight check should be conducted by the applicant or designee to verify 

proper system function. Installations intended for Instrument Flight Rules (IFR) may be 

initially limited to Visual Flight Rules (VFR) until the proper functionality is shown to 

18
1/27/05 AC 23-22 

avoid the requirement for a special airworthiness certificate in experimental category 

before conducting an operational flight check. 

(4) Electromagnetic Interference (EMI) testing may reveal incompatibilities 

between the installed system and existing systems. For example, there may be potential 

interference from electric motors or ballasted lighting systems on sensitive navigation 

and attitude reference system sensors. The applicant should provide model specific 

checkout procedures for each model on the AML to address possible interference 

conditions. Laboratory EMI tests performed according to RTCA/DO-160 Section 21 for 

RF emissions provide confidence that installed equipment will perform without 

interference to existing aircraft systems. This represents the most efficient way to 

address the potential for EMI on multiple models. This approach would also account for 

variations in existing equipment and minimize EMI tests needed on each airplane model. 

Procedures for functional ground tests and flight checks should be provided as a final 

EMI check. Suggested remedies for interference include transfer of equipment, shielding 

techniques, or external filters. Recurrent EMI issues may warrant changes to the 

installation instructions that may need to be rolled back into the original AML STC 

approval. 

i. Any other items the responsible ACO considers necessary for a given AML 

approval

4. What Continued Airworthiness Considerations must be addressed? 

The following items should be addressed for each model on the AML to address 

continued airworthiness considerations: 

a. Instructions for Continued Airworthiness (ICA). 

(1) An ICA is required as part of the AML STC data package. Part 21, 

§ 21.50(b), states that a holder of an STC must provide at least one set of complete ICA 

prepared following § 23.1529, including any Airworthiness Limitations. 

(2) The ICA provides instructions necessary for authorized personnel to inspect 

and maintain the added equipment installed by the AML STC under the requirements of 

14 CFR, part 43, including procedures to address approved equipment interfaces. 

(3) The FAA is responsible under § 21.50 to accept the ICA. The Aircraft 

Evaluation Group (AEG) will aid the ACO engineer in showing the adequacy of the ICA 

and determining the acceptability of the ICA. 

(4) The ICA must be in a printed form when the first airworthiness certificate is 

issued, or before delivery of the first product, whichever is later. 

(5) FAA Order 8110.4B offers guidance on developing the ICA documents. 

19 
AC 23-22 1/27/05 

(6) The ICA should address maintaining HIRF and lightning protection 

compliance, including a list of specific wiring, bonding, or strapping requirements that 

must be maintained for the system. 

20 
1/27/05 AC 23-22 

CHAPTER 5. MODEL QUALIFICATION PROCESS REQUIREMENTS 

This chapter is designed to help the user of this AC design a Model Qualification 

Process. This process is used by the STC holder and the ACO to determine and 

document the applicability of an AML STC to a given airplane model. In contrast, the 

installation instructions are intended to be used by the installer to determine applicability 

of the STC to a particular serial number airplane. The Model Qualification Process is 

designed to be used to: 1) include a given aircraft model on the existing AML (to 

determine if the installation is appropriate under the AML), 2) determine if a particular 

model would require further compliance showing to be added to the AML, or 3) 

determine if an installation is complex enough to warrant an individual STC. The 

following list of items is meant only as a guideline and does not represent an exhaustive 

list of potential issues that must be addressed to qualify a model for an AML approval. 

1. Evaluation of Physical Location of Installed Equipment 

a. Will the equipment for the proposed modification fit in the model being 

considered? This should include considerations for available space for new equipment 

and for systems that will need to be moved or displaced to complete the modification. 

b. Is the proposed installation location, or proposed alternate mounting locations, 

compatible with the criticality and visibility of displayed information, including required 

announcements and warnings?

c. Is the environment suitable for the limitations of the equipment? This should 

include cooling considerations. 

2. Evaluation of the Applicability of the Proposed STC 

a. Is a particular model airplane configured in such a way that would preclude it 

from being eligible for the STC, although it is listed on the AML? This might be caused 

by existing equipment, where the interface is not covered in the installation instructions 

for the system, inadequate electrical capacity because of existing equipment, or other 

factors. 

b. Are the operational characteristics of a particular model airplane compatible with 

the assumptions made during the initial certification? For example, an airplane may be 

approved for CAT II approach from the factory, where adding new equipment and 

replacing it with the new system might cancel this ability. 

3. Evaluation of Intended Function of the Proposed Equipment 

a. Will the proposed equipment be able to perform its intended function in the model 

being considered? 

b. Is the intended function compatible with the equipment approval for the system, 

including software and hardware design assurance levels?

21 
AC 23-22 1/27/05 

c. Is the software development level of the proposed equipment compatible with the 

intended function for the category/classification of the model in question?

d. Does the intended function change for the model being considered compared to 

other models already on the AML? If so, the applicant may need to split the AML into 

sections or seek separate approvals. 

4. Evaluation of the Installation Complexity of the Proposed Equipment 

a. Will the proposed modification present unique model specific installation 

challenges for the models being considered? This should include an analysis of the 

complexity of the proposed modification with consideration to existing equipment that 

would typically appear on a given model. 

b. Will the proposed installation affect the electrical load analysis, the functional 

hazard assessment, or the calibration/operation of existing systems? 

c. How will calibration issues for the new equipment, EMI related issues, and the 

possible effects to the HIRF and lightning certification of the proposed model be 

addressed? 

d. How will the proposed modification interface with other existing systems on the 

model being proposed? What existing equipment is acceptable to interface with the new 

equipment?

e. Is specific training needed to install the system? Consider the existing installation 

instructions to see if more model specific details are needed to include the model in 

question. 

f. Are there continued airworthiness issues that should also be evaluated to see if 

any model specific issues exist? For example, consider the installation location of the 

equipment and whether this might influence inspection, calibration, or maintenance 

schedules of the equipment. 

5. Evaluation of Operational Requirements of the Proposed Equipment 

a. Will the proposed equipment change the operational capabilities of the model 

being considered? This should include an evaluation of possible changes to the 

following: 1) existing precision approach capabilities, 2) navigational accuracy and 

procedures, 3) current pilot workload, 4) special certification conditions, and 5) 

operational approvals for the model being proposed, such as RVSM or CAT II approval. 

b. Are there model specific limits and possible additions or changes to the AFM or 

AFM Supplements?

22 
1/27/05 AC 23-22 

6. Pilot Evaluation and Human Factors Issues for the Proposed Equipment 

Will the proposed modification create any issues that would warrant a pilot evaluation or 

any human factors concerns for the model being considered? This should include an 

evaluation of existing equipment, how the modification will affect the pilot's primary 

field of view, and how the system will be ground and flight tested after installation. 

Ground and flight test procedures should contain exact test procedures and expected 

response data, with clear pass/fail criteria for each test. 

23 (and 24) 

1/27/05 AC 23-22 

Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS SAMPLE DOCUMENT 

Disclaimer: 

The following sample document provides an example of a generic framework for the 

process used to show applicability of a given STC to a particular airplane model. The 

document proposes a structure for the formal engineering process that must be followed 

before a model can be added to the AML for a given STC. 

The sample Model Qualification Process document is provided only as an example for 

the agreement between the STC holder and the ACO. It is not meant to capture all the 

possible information that would be required to determine applicability or use of a 

particular airplane for a given STC. Depending on the complexity of the system being 

approved, the detailed steps of this process may need to be reduced or expanded in scope 

to allow suitable installation and certification requirements for a particular approval. 

A1-1 
AC 23-22 1/27/05 

Appendix 1 

CONTENTS

1 INTRODUCTION .............................................................................................. A1-3

1.1 Summary....................................................................................................... A1-3 

1.2 Definitions and Acronyms.............................................................................. A1-3 

1.3 Applicable Documents and References ........................................................ A1-3 

2 CERTIFICATION CONSIDERATIONS ............................................................ A1-3

2.1 AML STC Definition....................................................................................... A1-3 

2.2 AML STC Limitations and Assumptions ........................................................ A1-3 

2.3 Installation Overview ..................................................................................... A1-4 

2.4 AML Revision Process .................................................................................. A1-4 

3 DETERMINATION OF APPLICABILITY.......................................................... A1-4

3.1 Certification Basis ......................................................................................... A1-5 

3.2 Prior Considerations...................................................................................... A1-5 

3.3 Operational Considerations........................................................................... A1-5 

3.4 Installation Considerations ............................................................................ A1-6 

3.5 Final Approval ............................................................................................... A1-6 

4 SPECIFIC AIRCRAFT EVALUATIONS........................................................... A1-6

4.1 Intended Function ......................................................................................... A1-7 

4.2 Applicability Across Serial Numbers.............................................................. A1-7 

4.3 Physical Location of Installed Equipment...................................................... A1-7 

4.4 Interface to Existing Equipment..................................................................... A1-8 

4.5 Electromagnetic Interference ........................................................................ A1-8 

4.6 Human Factors.............................................................................................. A1-8 

5 ACCEPTANCE PROCESS .............................................................................. A1-9

5.1 Model Qualification Diagram ......................................................................... A1-9 

List of Tables and Figures 

Figure A1-1 AML Model Qualification Process Diagram ..................................... A1-10 

A1-2 
1/27/05 AC 23-22 

Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS 

SAMPLE DOCUMENT (CONTINUED) 

1 Introduction 

1.1 Summary 

This section should contain a brief summary of the scope and purpose of the document, 

including a brief description of the certification approval project itself. 

1.2 Definitions and Acronyms 

This section should contain any project specific definitions and acronyms applicable for 

the approval. 

1.3 Applicable Documents and References 

This section should contain a listing of applicable certification documentation for the 

STC being considered, any applicable regulatory references, and other guidance suitable 

for a particular approval.

2 Certification Considerations 

This section should contain an outline of the certification philosophy used by the ACO to 

approve the proposed modification. This information is provided so the reader is familiar 

with the basic certification assumptions surrounding the approval of the proposed 

modification. 

2.1 AML STC Definition 

This section should contain a clear definition of the AML STC as defined for the project 

approval in question. This includes a clear definition of the intended function of the 

equipment as provided in other certification documentation for the approval. 

2.2 AML STC Limitations and Assumptions 

This section should contain a summary list of assumptions made about the airplane, or 

equipment, for the initial certification that would influence the decision to include a given 

model on a proposed AML. One example would be the assumption that 

electromechanical back-up instruments are maintained and considered in the System

Safety Assessment for a Primary Flight Display installation. Another example would be 

the software development assurance level that relates to the failure condition 

classification and airplane classification under AC 23.1309-1C. 

A1-3 
AC 23-22 1/27/05 

Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS 

SAMPLE DOCUMENT (CONTINUED) 

This summary list should allow an initial review by the reader to help define whether a 

given model should be considered for inclusion on the AML. 

2.3 Installation Overview

This section should provide an outline of the installation, including a brief description of 

the basic steps of the installation and the equipment being installed. 

If a rearrangement of existing equipment or instruments is necessary, this section should 

provide an outline about what is being replaced, where the new instrumentation is to be 

placed, and the reinstallation of existing equipment. This section should reference 

sections that appear later in this document and other installation documentation that 

provides a greater level of detail for these items. 

This section should also provide an outline of whether there are model specific 

installation issues to be evaluated, including references to specific sections later in the 

document. If model specific installation instructions are needed, this section should 

provide a summary list of applicable installation documents. Model specific installation 

instructions should be used for complex installations where model-to-model variations in 

the installation, or system configuration, are significant. Also, a “prototyping” approach 

can be used, where each new model is added to the AML as installations are performed 

and the model specific installation issues are addressed. 

2.4 AML Revision Process 

This section should contain the agreed on process between the FAA and the applicant on 

how the AML is to be revised to add or remove a given model. This part of the 

document should provide a clear step-by-step process so the same method will be used 

each time the AML is revised. The process should state that the determining of eligibility 

should only be made by an individual with specific knowledge of the proposed model 

and the proposed modifications required by the STC. Also, AML revisions must be FAA 

approved. The step-by-step process should relate to later sections in this document and 

outline the steps for a determination of applicability. 

3 Determination Of Applicability 

This section should contain a summary of general steps that are used to determine if a 

proposed model should be included on the AML. This section should include a review of 

the certification basis of the proposed model, prior certification considerations applicable 

to the particular model, model specific installation limitations, and relevant operational 

considerations for the proposed model. The section should provide an outline of the 

A1-4 
1/27/05 AC 23-22 

Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS 

SAMPLE DOCUMENT (CONTINUED) 

engineering process that the installer would use to assure the installation is applicable for 

a particular model airplane. 

3.1 Certification Basis 

This section provides a detailed review of the certification basis that was briefly 

introduced earlier in the document for the AML approval. This should include 

information about the certification basis of the equipment and the airplane models on the 

AML. Order 8110.48 contains more detail on how to determine the certification basis for 

a changed product. 

It is possible for an airplane on the AML to have a different certification basis than the 

equipment in the proposed installation. For example, applicability of an STC could be 

limited to older part 23 airplanes, but the proposed system could be certified to the latest 

amendment. The rest of the airplane is left at the older certification basis, while the latest 

certification requirements are applied to the proposed equipment, according to existing 

§ 21.101 related guidance. 

This section should also contain reference to any certification item that was documented 

in issue papers for the approval in question. This will allow the terms of that issue paper 

to be captured as part of the Model Qualification Process so a consistent approach can be 

used. 

3.2 Prior Considerations 

This section should list any known items, related to prior STC approvals for the airplane 

model being proposed for the AML that would influence the proposed modification. 

This could include prior STC approvals or other considerations that are applicable to the 

project. For example, if a single model STC is being expanded to include other models 

where similarity can be clearly determined and documented, this section should contain 

that information. 

Also, this section should outline the proposed modification that could be affected by the 

combined effects of other STC installations, such as critical hazard analysis details, or 

electrical system load analysis limitations. 

3.3 Operational Considerations 

This section should contain an outline of the operational considerations for the proposed 

modification. For example, if the system is only certified for day VFR, this section 

should clearly state the limitations of the system so it is not misused. As another 

A1-5 
AC 23-22 1/27/05 

Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS 

SAMPLE DOCUMENT (CONTINUED) 

example, if the proposed installation can influence previously installed equipment and 

change an operational approval, such as CAT II approach capability or RVSM 

certification, these items should be addressed in this section. 

3.4 Installation Considerations 

This section should contain details of the installation that may vary from model to model. 

This section should state clearly whether a generic set of installation instructions are 

being used or if model specific installation instructions are to be used. This section 

should also contain a summary of the assumptions that qualify a particular airplane for 

the proposed installation. In the case of an antenna installation only structurally 

approved for installation on a nonpressurized airplane, this section should draw attention 

to the further certification involvement that will be needed for installation on a 

pressurized airplane. 

The section can refer to general guidelines and reference standard practices and 

procedures considered acceptable by FAA regulations. For example, for a generic 

installation where similarity between models on the AML can be clearly documented, 

specific references to AC 43.13-1B, “Acceptable Methods, Techniques, and Practices - 

Aircraft Inspection and Repair,” and AC 43.13-2A, “Acceptable Methods, Techniques, 

and Practices - Aircraft Alterations,” may be acceptable. 

3.5 Final Approval 

The final step to include the aircraft on the STC AML is FAA approval. A form 8110-3 

for Recommend Approval with a statement the proposed aircraft model(s) has been 

qualified through the FAA-approved Model Qualification Process and signed by an 

authorized DER should go with the AML data submittal. According to Order 8110.37C, 

the submittal should also include a clarifying note stating, "This approval is for 

engineering design data only and is not an installation approval." The FAA will review 

the form 8110-3 to approve the suggested revision to the AML as well as any applicable 

changes to the applicable documentation for the STC. 

4 SPECIFIC AIRCRAFT EVALUATIONS 

A specific aircraft evaluation is required to determine relevance of a given serial number 

airplane as a potential candidate for the proposed modification. An individual with 

specific knowledge of the aircraft make and model should perform the engineering 

analysis. The person’s knowledge must be extensive enough to answer each question in 

the AML decision tree and document those decisions to satisfy the ACO. This decision 

process can refer to specific written documentation from the original equipment 

manufacturer. This may be in the form of TCDS, specific aircraft drawings, photographs, 

or detailed reports. 

A1-6 
1/27/05 AC 23-22 

Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS 

SAMPLE DOCUMENT (CONTINUED) 

4.1 Intended Function 

This section should refer to any differences in intended function that may be present in 

the proposed installation, depending on the installed equipment for a given airplane. For 

example, it may be possible for one piece of equipment to be installed and used 

differently on two airplanes of the same model if one is approved for precision approach 

and the other is not. For another example, a multifunction display can be installed with 

varying capabilities, depending on the other equipment installed in the airplane. This 

section should document those variations so they can be evaluated when a particular 

airplane is being considered for the proposed modification. 

4.2 Applicability Across Serial Numbers 

This section should include details on specific airplanes within a series that may not 

qualify for the installation or would require further certification involvement. For 

example, it is possible for an aircraft to have changed during its production so some serial 

numbers may not be applicable for a given STC while others are applicable. 

4.3 Physical Location of Installed Equipment 

This section should provide details of the specific installation location proposed for the 

modification to determine if a given model will be able to accommodate the installation. 

Each aircraft identified as a potential candidate for the AML must provide a suitable 

mounting location for the proposed modification. The installation location may vary 

from model to model and from serial number to serial number, but the STC installation 

documentation should clearly state the installation requirements and limits for the 

proposed modification. This should include detailed instructions on how much an 

installation can vary before further certification involvement is needed. 

This section should address requirements for acceptable location, structural mounting, 

cooling, and wiring related issues. Also, installation requirements for equipment that is 

sensitive to installation location because of EMI issues, such as an Attitude Heading 

Reference System (AHRS), should be clearly described. 

For example, to install a GPS navigation system, this section should clearly state 

acceptable installation location, suitable remote annunciation requirements, and other 

items. Suitable guidance materials should be referenced where applicable, such as 

AC 20-138A and AC 23.1311-1A. For these installations, the GPS navigation receiver is 

typically found in the center radio stack. However, the location of the center radio stack 

varies from airplane to airplane model. This section should provide added information to 

clarify field of view requirements and acceptable installation locations for the AML 

installation. 

A1-7 
AC 23-22 1/27/05 

Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS 

SAMPLE DOCUMENT (CONTINUED) 

The proposed installation requirements should be consistent with existing FAA guidance 

materials suitable for the equipment. Also, references to specific sections in AC 43.13-

1B should be used, rather than general references, to document installation procedures 

and to satisfy the requirements of § 21.31 to describe the type design, when suitable. 

4.4 Interface to Existing Equipment 

The proposed modification may require interfaces into the aircraft’s existing equipment. 

This section should provide enough detail for a specific model to be evaluated to make 

sure suitable interfacing can be performed for a given model. This could include, but is 

not limited to, the following: 

• Navigation System Interface [(Horizontal Situation Indicator (HIS) and or Course 

Deviation Indicator (CDI)] 

• Antenna Installations (GPS, Communication, and Navigation systems) 

• Electrical System Interface (Including an electrical load analysis impact study) 

• Interface to other systems, such as the Pitot Static system, autopilot, and Angle of 

Attack sensors. 

When interfaced with external equipment, extensive instructions should be provided to 

ensure the interface with the equipment is properly wired, properly configured, and 

properly tested. The installation manual should contain detailed test procedures, with 

expected system response, for each interface. This can include both ground test and 

flight check procedures, when necessary. 

4.5 Electromagnetic Interference 

This section should contain specific tests to ensure the proposed installation does not 

electronically or magnetically interfere with existing equipment, or conversely. This 

section should also list any equipment in the proposed installation that may be 

susceptible to EMI, such as an AHRS or a GPS system. The installation instructions 

should include ground tests and operational flight checks. 

4.6 Human Factors 

This section should contain details related to human factors considerations for the 

proposed installation including the basic design of the system, the certification basis, the 

intended function of the equipment, and the installation location of the equipment. 

A1-8 
1/27/05 AC 23-22 

 Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS 

SAMPLE DOCUMENT (CONTINUED) 

5 ACCEPTANCE PROCESS 

5.1 Model Qualification Diagram 

The following decision process in Figure A1 is presented as an example to determine 

applicability of a given model to the AML. It is a graphic representation of the decision 

points outlined previously in the document. Once an airplane has been identified as a 

potential candidate to be included on the AML, a qualified person with specific 

knowledge of the model in question may use this decision process to qualify the aircraft. 

Specific installation questions must be answered and clearly documented to prove the 

applicability of a particular model. 

A1-9 
AC 23-22 1/27/05 

Appendix 1 

APPENDIX 1 - GENERIC MODEL QUALIFICATION PROCESS SAMPLE 

DOCUMENT (CONTINUED) 

Start:

Proposed Model for

addition to the AML

Update the installation

instructions to include

modification information

to install the new

equipment.

1

Does the model

have the required systems

& equipment to satisfy the

assumptions made during the

first certification

approval?

Is there an existing

approval to add the

required equipment?

Are the installation

instructions adequate

to cover installation of

the new

equipment?

Does the

proposed model have

a suitable mounting

location for the

proposed

modification?

Does the installation

meet the requirements of

the applicable rules and

guidance?

(E.g. AC 23.1311-1B

for displays)

Does the

installation manual

provide adequate detail to

complete the installation in

accordance with the

original approval?

Is the intended function

for this model the same as

what was approved for

the original system

certification effort ?

Are there any

model specific issues

that would preclude

the installation of

the proposed

equipment?

Does the installation

provide an equivalent

level of safety to

the original system

certification effort ?

Are the current

continued airworthiness

instructions adequate

for the proposed

model?

Can additional data be

added to the installation

instructions to substantiate

this installation?

2

No

Yes

Yes

Yes

No

No

3 4

5 6

Yes

Continue

with step 5

No

Return to Start

Yes

Yes

No

Yes

No

Yes

Yes No

No X

No

Update the installation

instructions with

model specific

requirements to enable

 the inclusion of this

 aircraft onto the AML.

Yes

Update the continued

airworthiness instructions

to accommodate the

proposed model.

(Require FAA review)

No

Yes The model can be

added to the AML

Return to Start

The model cannot

be added to the AML

7 8

9 10

11

16

14

15

13

12 17

No Go

To X

Go

To X

Go

To X

Figure A1-1 – AML Model Qualification Process Diagram

A1-10 
1/27/05 AC 23-22 

Appendix 2 

APPENDIX 2 – EXAMPLE AML STC

Disclaimer: 

The following sample STC documents are provided as an example and are not meant to 

capture all the possible information that would be required to document the applicability 

and limits of every STC. Depending on the complexity of the system being approved, the 

details contained on the STC and the AML may need to be reduced or expanded in scope 

to allow suitable installation and certification requirements for a particular approval. 

A2-1 
AC 23-22 1/27/05 

Appendix 2 

APPENDIX 2 – EXAMPLE AML STC AND APPROVED MODEL LIST 

(CONTINUED)

A2-2 
1/27/05 AC 23-22 

Appendix 2 

APPENDIX 2 – EXAMPLE AML STC AND APPROVED MODEL LIST 

(CONTINUED)

Approved Model List For: 

Equipment Description and Part # 

Manufacturer Name 

STC Number 

FAA Approved: ______________________ 

Manager 

Aircraft Certification Office 

Federal Aviation Administration 

Office Location 

A2-3 
AC 23-22 1/27/05 

Appendix 2 

APPENDIX 2 – EXAMPLE AML STC AND APPROVED MODEL LIST 

(CONTINUED)

1. AML Revision Log

Revision No. Pages Description FAA Approval Date 

(-) ALL Initial Release Signature Date

A2-4 
1/27/05 AC 23-22 

Appendix 2 

APPENDIX 2 – EXAMPLE AML STC AND APPROVED MODEL LIST 

(CONTINUED)

2. Introduction 

This document is the FAA Approved Model List for STC No. XX for installing the 

Model Number and Description of System into eligible aircraft. 

Revisions to the AML must be coordinated between the STC holder and the responsible 

ACO, and require FAA approval. 

IMPORTANT NOTES: (Example only, edit for specific STC approval)

This STC is only applicable to the 14 CFR, part 23, Class I aircraft, as defined in 

Advisory Circular AC 23.1309-1C, which are listed in this AML. Installations in 14 

CFR, part 23 Class II, III and IV, part 25, part 27 and part 29 aircraft are not authorized 

under this STC. 

This STC assumes the following equipment is already installed on each airplane eligible 

for this proposed modification. The following equipment must be properly linked to 

meet the intended function for the system, as certified under this AML approval. 

List of required equipment that is not part of this approval. 

List added limits of the STC that might influence applicability of the STC to any serial 

number being considered for the modification. 

A2-5 
AC 23-22 1/27/05 

Appendix 2 

APPENDIX 2 – EXAMPLE AML STC AND APPROVED MODEL LIST 

(CONTINUED)

3. Certification Basis 

The certification basis for each model qualified for this modification is detailed below. 

Note: Variation in cert basis from model to model is allowed if properly documented in 

this section and approved by the FAA. For such cases, it may be necessary to reflect 

these variations in model specific compliance checklists. 

Note: List any regulations that have been applied to the system itself under the 

assumption the rest of the airplane stays at the original certification basis according to 

§ 21.101 and associated guidance. Examples include §§ 23.1301 and 23.1309 for 

electronic systems, which may not have been considered in the original certification 

basis of each model. 

Aircraft 

Make 

Aircraft 

Model 

Type Data Sheet Certification Basis 

Manufacturer Model TCDS# CAR3, Part 23 Amendment Level. 

A2-6 
1/27/05 AC 23-22 

Appendix 2 

APPENDIX 2 – EXAMPLE AML STC AND APPROVED MODEL LIST 

(CONTINUED)

4. Approved Model List 

Aircraft 

Make 

Aircraft 

Model 

Type 

Certificate 

Number 

Required Approved Data and Added 

Model Specific Limitations 

AML 

Amendment 

Date 

Make Model TCDS # Master Document List: 

List Manufacturer Master Document Number(s)

and STC No. 

Airplane Flight Manual Supplement: 

List Generic or Model Specific Airplane

Flight Manual Supplement 

Installation Instructions: 

List Generic or Model Specific Installation

Instructions 

Instructions for Continued 

Airworthiness: 

List Generic or Model Specific System 

Instructions for Continued Airworthiness 

Equipment Configuration: 

List Generic or Model Specific Equipment 

Configuration Details

Additional Limitations: 

List Limitations or reference to list of

limitations in some other document

associated with the STC 

Additional Documents

As needed, such as Electrical Load 

Analyses, System Safety Assessments, 

Functional Hazard Assessments to meet

§23.1309.

A2-7 (and A2-8)