AC 21.101-1B

Advisory circular · Establishing the Certification Basis of Changed Aeronautical Products

Approved
March 11, 2016
Last reviewed
July 5, 2017
Family
AC 21.101-1 · 4 versions
Revision
B
14 CFR parts
21
Cited by
1 AD

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed October 23, 2026.

Show pages 136–147
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Appendix H H-2 Table H-1. Tabular Form for Documenting a Proposed Certification Basis 14 CFR Section Amendment Levels Applicant Justification for Lower Amendment Level and Comments Affected Area Existing TCDS Amendment Amendment at Date of Application Proposed Amendment Level Subpart A – General

Subpart B – Flight

H.1.5 Best Practices.

H.1.5.1 Account for all regulations, even if they are not applicable.

H.1.5.2 Mark regulations that are not applicable as N/A.

H.1.5.3 If more than one amendment level is used depending on the area of the aircraft, list all areas and amendment levels at each area with proper justification.

H.1.5.4 If the justification is long, provide the justification below the table and only place the regulatory reference and note in the comment field.

H.1.5.5 Include airworthiness regulations required by other 14 CFR parts

(e.g., parts 91, 121, 125, 135) of affected areas.

H.2 Example 2.

Pages H-3 through H-9 of this appendix contain another example for documenting a proposed certification basis.

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Appendix H H-3 Title of Design Change Product Name or Change to Type Certificate [XXXX] Proposed Certification Basis Pursuant to 14 CFR 21.101

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Appendix H H-4

1. I NTRODUCTION.

1.1 R EFERENCE DOCUMENTS.

Reference Title [1] Section 21.101 Designation of applicable regulations [2] AC 21.101-1B Establishing the Certification Basis of Changed Aeronautical Products [3] XXXX Application letter [4] Type Certificate YYYY Product type certification basis [5] Document ZZZZ Certification plan [6] <The above referenced documents are examples. Each applicant should reference documents appropriate to their products and procedures.>

1.2 A CRONYMS.

Acronym Meaning AC Advisory Circular AFM Airplane Flight Manual ELOS Equivalent Level of Safety IP Issue Paper MOC Means of Compliance SC Special Condition TC Type Certificate <This section constitutes a representative list of acronyms. Each applicant should provide an acronym list appropriate for their product and document.>

1.3 P URPOSE OF THE DOCUMENT.

The purpose of this document is to propose the certification basis applicable to [Product Design Change] in accordance with 14 CFR 21.101.

<Note that this optional document is intended to be used for changes to type certificated products for which the change or a portion of the change is significant at the product level pursuant to § 21.101. Not significant changes being accomplished concurrently with significant changes(s) would also be identified in this document.>

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Appendix H H-5

1.4 P URPOSE OF THE CHANGE.

High-level description of the project (e.g., Airplane Model 123 is being modified from a passenger configuration to an all-cargo configuration).

2. D ESIGN DEFINITION.

2.1 BASELINE PRODUCT.

The type design to be changed, which is also known as the “baseline product,” is the Model Series___ (this should be a specific product configuration, such as a specific serial number or line number).

The reference product certification basis is TCDS No. [XXXX], issued on [DATE].

2.2 DESIGN CHANGE AND BASELINE PRODUCT COMPARISON SUMMARY.

<Example table where the product is an airplane. This is a representative set of data that may be provided by the applicant.> Specification Model Series X Model Series Y Max Taxi Weight – MTW (lbs) A1 A2 Max Takeoff Weight – MTOW (lbs) B1 B2 Max Landing Weight – MLW (lbs) C1 C2 Max Zero Fuel Weight – MZFW (lbs) D1 D2 Max Length (ft, in) E1 E2 Max Height (ft, in) F1 F2 Wing Span (ft, in) G1 G2 Horizontal Tail Span (ft, in) H1 H2 Fuel Capacity (gal) I1 I2 Total Cargo Volume (ft3) J1 J2 Max Passenger Limit – one class seating (occupants) K1 K2 Engine Types L1 & M1 L2 Maximum Engine Thrust T1 T2

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Appendix H H-6

2.3 DESCRIPTION OF DESIGN CHANGE, GROUPING AND CLASSIFICATION.

2.3.1 SIGNIFICANT CHANGE(S).

<Describe here the stand-alone change(s) and/or change grouping(s) that are part of the proposed changed product and are proposed as significant. Include with each stand-alone change or change grouping the relevant accumulated change(s) and the applicable physical and/or functional effects. Note, the description should be detailed enough to identify why the change or change grouping is proposed as significant.> The following group of changes is proposed as significant based on [AC 21.101-1, Appendix A, “[Description of Change in Appendix A]] or [the general configuration is not retained, principles of construction are not retained, or assumptions for certification of the product to be changed do not remain valid].

Changes Related to [Title of Significant Change X]:

[Title of High-Level Change C1] The areas of physical change are:

• [design change xx]

• [design change yy]

• [design change zz] The areas unchanged but affected by the change are:

• [affected area aaa]

• [affected area bbb]

• [affected area ccc] [Title of High-Level Change C2]…..

2.3.2 UNRELATED NOT-SIGNIFICANT CHANGES.

<Describe here the stand-alone changes or change groupings that are part of the modification but are unrelated to any of the significant changes described in paragraph 2.3.1.> [Title of High-Level Change D1]. [Description].

<The description must be just detailed enough to serve its purpose, which is to identify why each of those changes is not-significant and unrelated.> [Title of High-Level Change D2]. [Description]…..

3. IDENTIFICATION OF APPLICABLE REQUIREMENTS.

3.1 PROPOSED CERTIFICATION BASIS.

Based on the effective application date, [date], under the provisions of § 21.101, the applicable type certification standards for the [Title of Design Change] are proposed as

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Appendix H H-7 follows. The proposed certification basis includes exceptions to earlier amendments, exemptions, special conditions, and equivalent level of safety findings.

3.1.1 Requirements Effective at the Date of Application.

Applicable requirements in effect on the date of the application are:

<List the applicable parts and amendment levels here.> Example for FAA transport airplane:

• 14 CFR 25 through Amendment 25-138.

• 14 CFR 26 through Amendment 26-6.

• 14 CFR 34 through Amendment 34-5A.

• 14 CFR 36 through Amendment 36-29.

3.1.2 Section 21.101 Exception Rationale.

The completed rationale for each does not contribute materially to the level of safety (DCMLS) or impractical exception is provided in this section.

Exception 1:

Exception 2: ….

3.1.3 Optional Requirements Applicable requirements in effect on the date of the application are:

<List the applicable parts and amendment levels here.> Example for FAA transport airplane:

• 14 CFR 25.1419, Ice protection, Amendment 25-129.

• 14 CFR 25.1535, ETOPS approval, Amendment 25-120.

3.1.4 Requirements in Other 14 CFR Parts Applicable requirements in effect on the date of the application are:

<List the applicable parts and amendment levels here.> Example for FAA transport airplane:

• 14 CFR 121.215, Cabin interiors, Amendment 121-84.

• 14 CFR 121.316, Fuel tanks, Amendment 121-293.

3.1.5 Proposed Special Conditions.

Special Condition (or TBD) Title Effective Date (or TBD)

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Appendix H H-8

3.1.6 Equivalent Level of Safety.

ELOS Memo No.

(or TBD) Title Applicable Regulation

3.1.7 Exemptions.

Exemption No.

(or TBD) Title Applicable Regulation Date Issued (or TBD)

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Appendix H H-9 Proposed Certification Basis The certification basis is a complete extract from the applicable 14 CFR part [A] and reference the type design certification basis [B].

Column [C] identifies the specific requirement amendment level on the date of application. The changed product’s certification basis is proposed in last column [D].

Example for a part 25 airplane:

[A]

Requirement (or Title subparagraph) [B] Existing Type Design Amendment Level [C] Amendment Level on Application Date [D] Proposed Amendment for Changed Product Applicable Area Notes

25.25 Weight Limits 25-23 25-63 25-63 Product

25.33 Propeller speed and pitch limits

N/A 25-72 N/A — Not applicable to Change Product (Jet Aircraft)

25.1309(a) Equipment, systems, and installations

25-41 25-123 25-123 Changed and Affected Areas 25-41 25-123 25-41 Exception—Not Affected See example 1 section 3.1.2 in

25.1703 Function and installation: EWIS N/A 25-123 N/A Exception—Product See example 2 section 3.2.1 in

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Appendix I I-1 APPENDIX I. RELATED DOCUMENTS I.1 Related 14 CFR Regulations.

• Section 21.16, Special conditions.

• Section 21.17, Designation of applicable regulations.

• Section 21.19, Changes requiring a new type certificate.

• Section 21.21, Issue of type certificate: normal, utility, acrobatic, commuter, and transport category aircraft; manned free balloons; special classes of aircraft;

aircraft engines; propellers.

• Section 21.93, Classification of changes in type design.

• Section 21.101, Designation of applicable regulations.

• Section 21.115, Applicable requirements.

I.2 FAA Orders.

• Order 8110.4C, Type Certification.

• Order 8110.48A, How to Establish the Certification Basis for Changed Aeronautical Products.

• Order 8110.56A, Restricted Category Type Certification.

• Order 8110.115, Certification Project Initiation and Certification Project Notification.

I.3 How to Get Publications.

I.3.1 Order copies of 14 CFR parts from the Superintendent of Documents, Government Printing Office, P.O. 979050, St. Louis, MO 63197. For general information telephone

(202) 512-1800 or fax (202) 512-2250. You can order copies online at www.access.gpo.gov. Select “Access” then “Online Bookstore.” Select “Aviation,” then “Code of Federal Regulations.”

I.3.2 Order copies of FAA orders and ACs from the U.S. Department of Transportation, Subsequent Distribution Office, M-30, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, MD, 20785. You can also get copies from the FAA website.

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Appendix J J-1 APPENDIX J. DEFINITIONS AND TERMINOLOGY J.1 Aeronautical Product.

The terms “aeronautical product” or “product” used in this guidance material includes type certificated aircraft, engines, and propellers J.2 Assumptions Used for Certification.

The assumptions used for certification are the evaluations and decisions that led to the approval of the baseline product’s characteristics. Examples of the product’s baseline characteristics include, but are not limited to—

• Design methodologies, methods of compliance, and standards used to achieve compliance to the regulations making up the certification basis;

• Structural, mechanical, electrical, propulsion, aerodynamic, performance, operational, and maintenance characteristics;

• Operational and flight envelopes defining the product performance and capabilities at specified weights, speeds, altitudes, load factors, and centers of gravity;

• Crashworthiness;

• Role or mission;

• Airworthiness and operational limitations; or

• Pilot training, if necessary.

J.3 Baseline Product.

It is an aeronautical product with a specific, defined approved configuration and certification basis that the applicant proposes to change.

J.4 Certification Basis.

The applicable airworthiness requirements as established in §§ 21.17 and 21.101, as appropriate, special conditions, equivalent level of safety findings, requirements under § 21.21(b)(2), and exemptions applicable to the product to be certificated.

J.5 Design Change.

A change in the type design of an aeronautical product. In the context of this document, the terms “change,” “modification,” “design change,” and “type design change” are synonymous.

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Appendix J J-2 J.6 Earlier Requirements.

The requirements in effect prior to the date of application for the change, but not prior to the existing certification basis.

J.7 Existing Certification Basis.

The requirements incorporated by reference in the type certificate of the baseline product to be changed.

J.8 Latest Requirements.

The requirements in effect on the date of application for the change.

J.9 Previous Relevant Design Changes.

Previous design changes, the cumulative effect of which could result in a product significantly or substantially different from the original product or model, when considered from the last time the latest regulations were applied.

J.10 Product Level Change.

A change or combination of changes that makes the product distinct from other models of the product (e.g., range, payload, speed, design philosophy). Product level change is defined at the aircraft, aircraft engine, or propeller level of change.

J.11 Secondary Change.

A change that is part of a significant physical change that does not contribute materially to the level of safety. Guidance is contained in paragraph 3.10.1.4 of this AC.

J.12 Significant Change.

A change to the type certificate to the extent that it changes one or more of the following, but not to the extent to be considered a substantial change: general configuration, principles of construction, or the assumptions used for certification. The significance of the change is considered in the context of all previous relevant design changes and all related revisions to the applicable regulations. Not all product level changes are significant.

J.13 Significant Change in Area.

For aircraft excepted under § 21.101(c) only: A change in an area is significant if the general configuration or the principles of construction in that area are not retained, or the assumptions used for certification of that area do not remain valid.

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Appendix J J-3 J.14 Substantial Change.

A change that is so extensive that a substantially complete investigation of compliance with the applicable regulations is required, and consequently a new type certificate is required pursuant to § 21.19.