Advisory Circular (AC) No. 500-016 Issue 1

Establishing The Certification Basis Of Changed Aeronautical Products

File No. 5009-6-500 AC No. 500-016
RDIMS No. 528226-V3 Issue No. 01
Issuing Branch Aircraft Certification Effective Date 2004-12-01

1.0 Introduction

1.1 Purpose
1.2 Guidance Applicability
1.3 Description of Changes
1.4 Termination

2.0 References

2.1 Reference Documents
2.2 Cancelled Documents
2.3 Explanation of Terminology

3.0 Background

3.1 CAR to FAR and JAR Requirements Correspondence Matrix
3.2 Discussion

4.0 Establishing the Certification Basis of Changed Products (Steps 1 to 4)

4.1 Step 1 of Figure 1 - Identify the Proposed Change to an Aeronautical Product
4.2 Step 2 of Figure 1 - Is the Change Substantial?
4.3 Step 3 of Figure 1 - Will the Latest Standards Be Used?
4.4 Step 4 of Figure 1 - Is the Proposed Change Significant?

5.0 Using the Criteria to Determine Significance at the Product Level (STEP 4)

6.0 Showing Compliance with Earlier Standards (Steps 5 and 6)

6.1 Step 5 of Figure 1 - For every area, is the area affected by the proposed change?
6.2 Step 6 of Figure 1 - Are the latest standards practical and/or do they contribute materially to the level of safety?

7.0 Excepted Products

8.0 Special Conditions - Airworthiness

9.0 Effective Period For An Application To Change A Certificate

10.0 Restricted Category Aircraft

10.1 Special Purpose Operations
10.2 Ex-Military aircraft

11.0 Documentation

12.0 Headquarters Contact

Appendix A - Classification of Changes
Appendix B - Procedure for Evaluating the Practicality of Applying the Latest Standards to a Changed Product
Appendix C - The Use of Service Experience in the Certification Process



1.0 Introduction

1.1 Purpose

The purpose of this Advisory Circular (AC) is to provide guidance in establishing the certification basis of changed aeronautical products and identifying the conditions under which it will be necessary to apply for a new type certificate.

1.2 Guidance Applicability

This document is applicable to all Transport Canada (TC) personnel, delegates and industry.

1.3 Description of Changes

This document, formerly AMA No. 500/16, is reissued as an AC. With the exception of minor editorial changes the content is unaltered.

1.4 Termination

This document does not have a terminating action. It will however, be reviewed periodically for suitability of content.

2.0 References

2.1 Reference Documents

It is intended that the following reference materials be used in conjunction with the following documents:

  1. Part V Subpart 11 of the Canadian Aviation Regulations (CARs) - Approval of the Type Design of an Aeronautical Product;
     
  2. Part V Subpart 13 of the CARs - Approval of Modification and Repair Designs;
     
  3. Chapter 511 of the Airworthiness Manual (AWM) - Approval of the Type Design of an Aeronautical Product; and
     
  4. Chapter 513 of the AWM - Approval of Modification and Repair Designs.

2.2 Cancelled Documents

As of the effective date of this document, AMA No. 500/16 dated 10 June 2003 is cancelled.

2.3 Explanation of Terminology

The following is a summary of the terminology used throughout this advisory material.

  1. Certification Basis - The applicable airworthiness standards as established in section 511.07, 511.13, and 513.07 of the CARs, as appropriate, Special Conditions-Airworthiness, Equivalent Level of Safety Findings, and Exemptions applicable to the product to be certificated.

    Note:

    This AC is not intended for determining the applicable aircraft noise, fuel venting and engine emissions standards for changed products.
     

  2. Changes Where the General Configuration Is Not Retained (Significant Change to General Configuration) - A change to the general configuration at the product level that is likely to require a new model designation because of the need to distinguish the different product with other product models, e.g. performance, interchangeability of major components, etc.
     
  3. Changes Where the Principles of Construction Are Not Retained (Significant Change to Principles of Construction) - A change at the product level to the materials and/or construction methods that affects the overall product's operating characteristics or inherent strength and would require extensive re-investigation to show compliance.
     
  4. Changes That Invalidate the Assumptions Used for Certification (Significant Change to the Assumptions Used for Certification) - A change to the product level assumptions associated with the compliance demonstration, performance, or operating envelope that by itself is so different that the original assumptions are invalidated.
     
  5. Earlier Standards - those amendments to the airworthiness standards that were in effect prior to the date of application for the change, but not prior to the existing certification basis.
     
  6. Existing Certification Basis - the airworthiness standards recorded in the Type Certificate Data Sheets (TCDS) of the product to be changed.
     
  7. Latest Standards - the amendment level of the airworthiness standards that is in effect on the date of application for the change.
     
  8. 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 standards were applied.
     
  9. 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). Product level change is defined at the aircraft, aircraft engine or propeller level of change.
     
  10. Significant Change - a product level change to the type certificate to the extent that it changes one or more of the following: general configuration; principles of construction; or the assumptions used for the certification criteria, but not to the extent to be considered a substantial change. Not all product level changes are significant.
     
  11. Substantial Change - a product level design change that is so extensive that a substantially complete investigation of compliance with the applicable standards is required, and consequently a new type certificate, in accordance with section 511.14 or 513.14 of the CARs.

3.0 Background

3.1 CAR to FAR and JAR Requirements Correspondence Matrix

The table below, identifies the correspondence between Title 14 of the Code of Federal Regulations (14 CFR) Part 21 "CERTIFICATION PROCEDURES FOR PRODUCTS AND PARTS", hereafter referred to as the Federal Aviation Regulations (FAR), the European Joint Aviation Authorities Joint Aviation Regulations (JAR) and the Canadian CARs regulatory numbering practices.

SUBJECT TRANSPORT CANADA FAA JAA
CAR 511 CAR 513 FAR 21 JAR 21
Effective Period of an Application 511.06 513.06 21.101(e) 21.101(e)
Applicable standards for design change 511.13 513.07 21.101 21.101
  • 1 Use of latest standards on design change
511.13(1) 513.07(1) 21.101(a) 21.101(a)
  • 2 Applicable standards for appliances and/or repairs
511.13(2) 513.07(2) Not applicable Not applicable
  • 3 Use of earlier standards on a not significant design change
511.13(3) 513.07(3) 21.101(b)(1) 21.101(b)(1)
  • 4 Criteria for significant change
511.13(3)(a) 513.07(3)(a) 21.101(b)(1)(i) 21.101(b)(1)(i)
  • 5 Criteria for significant change
511.13(3)(b) 513.07(3)(b) 21.101(b)(1)(ii) 21.101(b)(1)(ii)
  • 6 Use of earlier standards on not affected areas
511.13(4)(a) 513.07(4)(a) 21.101(b)(2) 21.101(b)(2)
  • 7 Use of earlier standards when latest standard will not contribute materially to safety or will not be practical
511.13(4)(b) 513.07(4)(b) 21.101(b)(3) 21.101(b)(3)
  • 8 Limit of earlier standards
511.13(5) 513.07(5) 21.101(b) 21.101(b)
  • 9 Excepted aircraft
511.13(6) 513.07(6) 21.101(c) 21.101(c)
  • 10 Application of Special Conditions
511.13(7) 513.07(7) 21.101(d) 21.101(d)
  • 11 Treatment of aircraft in the restricted category
511.13(8) 513.07(8) 21.101(f) Not applicable
  • 12 Elect to comply
511.13(9) 513.07(9) No equivalent No equivalent
  • 13 Extension of the effective period of an application for a design change
511.13(10) 513.07(10) 21.101(e)(2) 21.101(e)(2)
  • 14 Applicable standard for aircraft issued a Special Certificate of Airworthiness - Limited
Not applicable 513.07(11) No equivalent No equivalent
Reclassification of Aircraft to Restricted Category 511.12(5) 513.08 21.101(f) Not applicable.
Changes to a Type Design Requiring a New Type Certificate 511.14 513.14 21.19 21.19
Applicable requirements for STCs Not applicable 513.07(1) 21.115(a) Invokes 21.101 21.114 Invokes 21.97(2) and 21.101


3.2 Discussion

Section 511.14 and 513.14 of the CARs identify the conditions under which an applicant for a design change is required to make an application for a new type certificate. Subsection 511.13(1) and 513.07(1) of the CARs require an applicant for a change to a type design to meet the latest standards, except where the change is not significant, where areas of the product are not affected, where it would not be practical, or where it would not contribute materially to the level of safety of the changed product.

This AC explains the criteria for the classification of design changes (significant versus not significant) under section 511.13 and 513.07 of the CARs and provides guidance for the determination of substantial changes under section 511.14 and 513.14 of the CARs. The intent of section 511.13 and 513.07 of the CARs is to enhance safety through the incorporation of the latest standards in the certification basis of changed products, to the greatest extent practicable.

This AC describes the application of the latest standards for the certification of significant design changes to aircraft, aircraft engines and propellers. Significant changes are generally distinct from the vast majority of major changes. In the assessment of whether a change is significant, all previous relevant design changes need to be taken into consideration along with any previous updates to the certification basis. The Minister must approve all changes, however, an applicant may comply with earlier amendments of the standards based upon a determination by the Minister, or a ministerial delegate, that the change is not significant, an area is not affected by a change, and compliance with the latest standards is not practical or does not contribute materially to the level of safety. Each change must be judged on its own merit when making the final determination of the certification basis.

Note:

Appliances and repairs are excluded from the application of these regulations.

This AC is applicable to all major changes to the type design of aircraft, aircraft engines and propellers. For purposes of this AC, an application for a change to a type design as described in subsections 511.12(1), 511.13(1), and 513.07(1) of the CARs is considered an application for a major change.

Other changes as described in subsection 511.12(2) of the CARs are considered to have no appreciable effect on airworthiness and are by definition not significant. Therefore, this AC applies equally to applications made for type certificate amendments and for the issuance of, or amendment of, supplemental type certificates and limited supplemental type certificates.

This AC and the methods illustrated in its Appendices are advisory material and are one way, but not the only way of showing compliance with the regulations.

The following aeronautical products, defined as an aircraft, engine, propeller and appliances, are eligible for a type certificate under Subpart 511 of the CARs:

Aeronautical Product Category Standards of Airworthiness
Gliders and Powered Gliders Chapter 522
Very Light Aeroplane (VLA) Chapter 523-VLA
Normal, Utility, Aerobatic and Commuter Aeroplanes Chapter 523
Transport Category Aeroplanes Chapter 525
Normal Category Rotorcraft Chapter 527
Transport Category Rotorcraft Chapter 529
Manned Free Balloons Chapter 531
Aircraft Engines Chapter 533
Propellers Chapter 535
Appliances and Other Aeronautical Products Chapter 537
Airships Chapter 541


An applicant may apply for a type certificate in any other category that does not fall within the categories listed above (e.g. tilt wing aeroplanes, hybrid aircraft). In addition, an applicant may also request certification of an aircraft in the Restricted Category for special purpose operations. AWM 511.05 defines special purpose operations as aerial work conducted for agriculture, fire prevention and suppression, aerial surveying, patrolling, weather control, aerial advertising, wildlife conservation, and any other specialized role. Once an aeronautical product is issued a type certificate, subsequent changes to the approved type design must be approved in accordance with either Subpart 511 or 513 of the CARs.

The intent of the referenced sections and subsections of the CARs is:

  1. Section 511.14 and 513.14 specify changes that require a new type certificate. When a new type certificate is required, section 511.07 specifies the applicable certification basis for the new product.
     
  2. When an application for a new type certificate is not required by section 511.14 or 513.14, then section 511.13 or 513.07, respectively, define the applicable standards for determining the certification basis for the changed product.
     
  3. Subsection 511.13(1) and 513.07(1) require a change to a type certificated product to comply with the latest standards, unless the change meets the criteria for the exceptions identified in subsection 511.13(3) through (6), or 513.07(3) through (6), respectively. The certification basis should not be dependent on whether the type certificate holder or an applicant for a supplemental type certificate or limited supplemental type certificate is originating the change. Where compliance with the latest standards for a significant change would not contribute materially to the level of safety, would not be practical, or is in an area not affected by the change, the applicant may comply with earlier standards. However, the applicant may not use airworthiness standards prior to those specified by the existing certification basis.
     
  4. Subsection 511.13(2) and 513.07(2) specify that the applicable standards for a change to a type certificated appliance are those recorded in the TCDS. This requirement also applies to repair design approvals under subsection 513.07(2).
     
  5. Subsection 511.13(3) through (5), and 513.07(3) through (5), pertain to changes for which earlier standards provide adequate standards. Earlier standards may be used when the change is not significant. In cases where design changes involve features that have no associated standards in the existing certification basis, the Minister will review the proposed certification plan to ensure adequacy of the airworthiness standards against the proposed design change and may require compliance with Special Conditions - Airworthiness.
     
  6. Subsection 511.13(3) and 513.07(3) allow the applicant to show compliance with earlier standards when the Minister, or a ministerial delegate, determines the change is not significant. Paragraph 511.13(3)(a) and (b), and 513.07(3)(a) and (b), pertain to changes that meet the criteria where the change is significant. Subsection 511.13(4) and 513.07(4) allow the use of earlier standards for significant changes for areas of the product not affected by the change and for cases where compliance with the latest standards would not contribute materially to the level of safety or would not be practical. Note that subsection 511.13(5) and 513.07(5) specify that the earlier standards may not precede the corresponding requirements recorded in the TCDS.
     
  7. Subsection 511.13(6) and 513.07(6) provide an exception to the requirements of subsection 511.13(1) and 513.07(1), respectively. An applicant for a change to an aircraft (other than rotorcraft) of a maximum weight of 2720 kg (6,000 lbs) or less, or to a non-turbine rotorcraft of a maximum weight of 1360 kg (3,000 lbs) or less, may show that the changed product complies with the standards recorded in the TCDS. The applicant may elect to comply with the later standards. However, if the Minister, or a ministerial delegate, finds that the change is significant in an area, the Minister may designate compliance with a later amendment to the standards recorded in the TCDS that apply to the change and any other requirement that the Minister finds is directly related.
     
  8. Subsection 511.13(7) and 513.07(7) allow the application of Special Conditions-Airworthiness when the proposed certification basis does not provide standards with respect to a proposed change that has novel or unusual design features.
     
  9. Subsection 511.13(8) and 513.07(8) specify the applicable airworthiness standards for aircraft certified in the restricted category as those that provide a level of safety appropriate for the special purpose operations.
     
  10. Subsection 511.13(9) and 513.07(9) allow voluntary compliance with a subsequent amendment to the standards in effect on the date of application for the proposed change to the type design, provided any related amendments are also included.
     
  11. Subsection 511.13(10) and 513.07(10) allow for re-establishing the certification basis when the Minister extends the effective period of an application, prescribed by section 511.06 and 513.06. The effective periods prescribed under section 511.06 and 513.06 are consistent with the requirements for a new type certificate.

4.0 Establishing the Certification Basis of Changed Products (Steps 1 to 4)

The administrative burden for the applicant is to demonstrate, and the Minister, or a ministerial delegate, to find, that a change to a product is significant or not significant, and to determine the resulting certification basis. The certification basis can vary depending on the magnitude and scope of the change. Figure 1 provides a flowchart of the process to determine the applicable certification basis for a proposed design change under section 511.13 or 513.07 of the CARs, following a determination that the proposed design change is not substantial under section 511.14 or 513.14 of the CARs, respectively. The steps below correspond to the Figure 1 flowchart and present a streamlined approach in making this determination. In addition to assisting in the determination of significance, this guidance will help establish the appropriate amount of co-ordination required between the applicant and the Minister.

Classifications of typical changes are provided in the tables of Appendix A. For instructions on how to use the Appendix A tables, proceed to step 4 below. In cases where the classification in Appendix A is not applicable, or not immediately obvious for the proposed change, the following steps should be used in conjunction with Figure 1 to determine the appropriate certification basis for the changed product.

For a change to an appliance for which a type certificate has been issued, the applicable standards will continue to be the requirements recorded in the TCDS. This requirement also applies to the approval of repair design under subsection 513.07(2) of the CARs.

4.1 Step 1 of Figure 1 - Identify the Proposed Change to an Aeronautical Product

The applicant must, as a first step, identify the proposed change to the aeronautical product. An applicant for a change to a type certificate must consider all previous related design changes to the aeronautical product. Changes to a product can include physical design changes, changes to an operating envelope, and/or performance changes. The change may be a single change, or a collection of changes.

For each change, it is important that the effects of the change on other systems, components, equipment, or appliances of the product are properly assessed. The characteristics affected by the change are not only physical changes. The intent is to encompass all aspects where there is a need for re-evaluation, that is, where the substantiation presented for the product being changed should be reviewed, updated, or re-written. All other areas of the aircraft are considered to be unchanged or not affected by the change.

4.2 Step 2 of Figure 1 - Is the Change Substantial?

Section 511.14 and 513.14 of the CARs require that an applicant obtain a new type certificate if the scope and nature of the proposed change in design, configuration, power, power limitations (engine), or weight are so extensive that a substantially complete investigation of compliance with the applicable standards is required. A new type certificate could be required for either an extensive change to a previously type certificated product or for a new design derived through a series of design changes from a previously type certificated product. The need for a new type certificate may be obvious when the change is first considered or may need a more extensive evaluation through application of section 511.13 or 513.07 of the CARs.

A "substantially complete investigation" of compliance is required when most of the existing substantiation is not applicable to the changed product. The question of whether a change is substantial must be addressed at the beginning of the process. However, if at any point while developing the certification basis, it becomes clear that the proposed change is a substantial change, the process ceases to be an amendment process under section 511.13 and CAR 513.07 of the CARs and becomes a new type certificate process under section 511.05 of the CARS.

If it is not initially clear that a new type certificate is required, Appendix A provides some examples of substantial changes to aid in this classification.

In considering the above, a substantial change will require a new Type Certificate; section 511.14 and 513.14 of the CARs apply. If the change is not substantial, section 511.13 or 513.07 of the CARs apply.

4.3 Step 3 of Figure 1 - Will the Latest Standards Be Used?

Where the latest standards are used, the intent of section 511.13 and 513.07 of the CARs has been met including the case where the applicable standards have not changed since the previous update of the certification basis or where the applicant elects to comply with the latest amendments.

4.4 Step 4 of Figure 1 - Is the Proposed Change Significant?

Significant changes are product level changes, and by their very nature distinct from the vast majority of major changes. In general, these changes either are the result of an accumulation of changes or occur through an isolated extensive major change rising to the product level that makes the changed product distinct from others.

Additionally, subsection 511.13(3) and 513.07(3) of the CARs define a significant change based on whether or not one or more of the three criteria applies:

  1. the general configuration is not retained;
     
  2. the principles of construction are not retained; and
     
  3. the assumptions used for certification of the product do not remain valid. In many cases, a significant change will involve more than one of these criteria and will, by its very nature, be obvious and distinct from other product improvements or production changes.

The applicant may use the tables in Appendix A and the criteria described in Section 6 as guidance to make the classification of significance.

Previous relevant design changes of the product can trigger one or more of the criteria listed in paragraph 511.13(3)(a) and (b), or 513.07(3)(a) and (b) of the CARs for the proposed design change. When assessing the design change, either singularly or collectively, the cumulative effect of previous relevant design changes must be considered. These design changes may have been incorporated through earlier changes in the type certificate on areas related to the current proposed change and the associated areas, systems, components, equipment, or appliance. The collective result may be a product considerably different from the latest updated certification basis for the product or model. Two examples of previous relevant aeroplanes design changes address those incremental increases in weight or thrust that, while individually not significant (e.g., 2%, 4%, 5% discrete increases), can, through a series of changes, achieve a significant product level change.

The assessment of a proposed design change together with any previous relevant design changes is based on whether any of the three criteria are triggered. Subsection 511.13(3) and 513.07(3) of the CARs state that changes that meet one of the three criteria are considered significant. The examples of significant and not significant changes in Appendix A are predicated upon more than 10 years of international certification experience. The concept of having only three criteria fits these examples and it is therefore considered that no other criteria apply. Therefore, only when one or more of the three criteria is affected is the design change considered significant. The starting point to begin accumulating previous relevant design changes is the time the latest applicable standards were applied in the affected area, system, component, equipment, or appliance.

Typically, a change to a single area, system or component will not result in a product level change. However, there may be distinct cases where the change to a single system or component may result in a significant change due to its effect on the product level certification assumptions.

Figure 1: Establishing the certification basis of changed products

Figure 1: Establishing the certification basis of changed products

Notes:

  1. In the vast majority of cases, the applicant will proceed to Step 4 as the initial step in the process. See Section 4 for guidance.
  2. For excepted products under subsection 511.13(6) and 513.07(6) of the CARs, see Section 7.
  3. For Special Conditions-Airworthiness under subsection 511.13(7) and 513.07(7) of the CARs, see Section 8.

5.0 Using the Criteria to Determine Significance at the Product Level (STEP 4)

Typically, a significant product level change would result in a model change if approved by an amendment to the type certificate, or if approved through an STC the change would be equivalent in level to that of an amended type certificate. Note that applications for a new model not associated with hardware changes, i.e. commercial considerations, are not an indication of a significant change under section 511.13 or 513.07 of the CARs. All changes are considered in light of the change itself and its classification.

The following, defined in section 3, build upon the criteria identified in the regulations and provide additional guidance on how to apply the criteria when classifying product level changes. In cases of doubt, and to ensure a consistent outcome, the applicant is encouraged to seek the advice of the Minister:

  1. Changes Where the General Configuration Is Not Retained (Significant Change to General Configuration);
     
  2. Changes Where the Principles of Construction Are Not Retained (Significant Change to Principles of Construction); and
     
  3. Changes That Invalidate the Assumptions Used for Certification (Significant Change to the Assumptions Used for Certification).

Examples may include:

  1. Change of an aircraft from an unpressurized to pressurized fuselage;
     
  2. Change of operation of a fixed wing aircraft from land based to water based; and
     
  3. Operation envelope expansions that are outside the existing design parameters and capabilities.

Note:

Merely operating a product to an expanded envelope for which it was originally designed is generally not a significant change. In this case, the assumptions used for certification of the basic product remain valid and the results can be applied to cover the changed product with predictable effects or can be demonstrated without significant physical changes to the product.

The above criteria are used to determine if a change is significant. In applying the criteria and the examples in Appendix A, the applicant must concentrate on the change itself. Consideration of only the latest standards is not a reason to cause a classification of significance under section 511.13 or 513.07 of the CARs.

aeroplanes, small aeroplanes, rotorcraft, and engines/propellers that meet the definition of significant change for each product line. The Appendix tables can be used in one of two ways:

  1. To classify a proposed change that is listed in the table; or
     
  2. In conjunction with the three criteria, to help classify a proposed change not listed in the table.

If, based on Appendix A and/or the criteria of subsection 511.13(3) or 513.07(3) of the CARs, the change is classified as:

  1. Significant - The applicant will comply with the latest standards for the certification of the changed product. The applicant can use the exceptions provided in subsection 511.13(4), or 513.07(4) of the CARs to show compliance with earlier standards. The final certification basis may consist of a combination of the latest and earlier or existing standards for the change; or
     
  2. Not significant - The applicable standards are those contained in the existing certification basis. The applicant may elect to comply with later standards.

Note:

In cases where no standards are defined in the existing certification basis for the design change but are available on later standards, the applicable later standards will be made part of the certification basis.

Making the Classification - A classification of significant or not significant can be made through application of subsection 511.13(3) or 513.07(3) of the CARs, in one of two ways:

  1. By delegation, where appropriate procedures are in place to support a classification of significant or not significant by a delegate. The Minister may accept the not significant determination without further evaluation and rely on the delegates design control system and the Minister's oversight system to monitor and validate decisions; or
     
  2. By the Minister accepting the determination of significant relevant to a major modification based on the applicant's data submission.

At this point, the determination of significant or not significant has been made. For significant changes, if the applicant proposes to show compliance with an earlier requirement, the procedure outlined in Section 7 should be used.

6.0 Showing Compliance with Earlier Standards (Steps 5 and 6)

For a design change that has been determined to be significant, subsection 511.13(4) and 513.07(4) of the CARs provide the exceptions from the requirement of subsection 511.13(1) and 513.07(1) of the CARs, respectively, to meet the latest standards for design changes.

Subsection 511.13(4) and 513.07(4) of the CARs identify conditions under which an applicant may show that the changed product complies with earlier standards or with the existing certification basis and, therefore, would not be required to comply with latest standards. The earlier standards with which the applicant intends to show compliance may not precede the amendment levels of the standards in the existing certification basis. An applicant may propose to show compliance with earlier standards or with the existing certification basis for areas not affected by the change, and areas affected by the change for which compliance with the latest standards would not contribute materially to the level of safety or would not be practical. It is incumbent upon the applicant to demonstrate to the Minister that compliance with the latest standards does not materially contribute to the level of safety, or is not practical.

Steps 5 and 6 described in section 7.4 and 7.5 should be used in conjunction with Figure 1, when an applicant wishes to comply with earlier standards for a significant change.

6.1 Step 5 of Figure 1 - For every area, is the area affected by the proposed change?

A not affected area is any area, system, component, equipment, or appliance that is not affected by the proposed product level change (paragraph 511.13(4)(a) or 513.07(4)(a) of the CARs). For a product level change, it is important that the effects of such change on other systems, components, equipment, or appliances of the product are properly assessed because areas that have not been changed may be affected. If the significant change does not affect the area, then the certification basis for that area need not be revisited.

In assessing affected areas, it may be necessary to identify secondary changes resulting from a product level change. The secondary changes may be changes in both physical aspects and/or performance characteristics that are part of, but consequential to, the overall product level change. Secondary changes may be evaluated to the existing certification basis for the product being changed; however, care should be taken to ensure that affected areas are not overlooked. The intent is to encompass all aspects where there is a need for re-evaluation.

The following aspects of a product level change should be considered:

  1. Physical aspects - The physical aspects include, but are not limited to, structures, systems, equipment, components and appliances (physical aspects can cover both "hardware" and "software"). When evaluating the physical aspects, it is necessary to make a distinction between the product level change and the resulting secondary changes. An example of a secondary changes may be the lengthening and re-routing of the various aeroplane circuits because of the fuselage plug.
     
  2. Performance/functional characteristics - The less obvious aspect of the word "areas" covers general characteristics of the type certificated product such as performance features, handling qualities, emergency provisions, fire protection, structural integrity, aero elastic characteristics, or crashworthiness. These characteristics may be affected by a product level change. For example, adding a fuselage plug could significantly affect performance and handling qualities.

All areas affected by the proposed design change must comply with the latest standards, unless the applicant can demonstrate that compliance with the latest standards would not contribute materially to the level of safety or would not be practical. Step 6 provides further explanation.

6.2 Step 6 of Figure 1 - Are the latest standards practical and/or do they contribute materially to the level of safety?

Paragraph 511.13(4)(b) or 513.07(4)(b) of the CARs addresses:

  1. Not contribute materially to the level of safety - Compliance with the latest standards could be considered "not to contribute materially to the level of safety" if the change to type design and/or the relevant experience demonstrates a level of safety comparable to that provided by the latest standards, or if compliance may compromise the existing level of safety for that particular changed product. The applicant must provide sufficient justification to allow the Minister to make this determination. This exception could be applicable in the situations described in the paragraphs below:

    1. Design - This provision gives the opportunity to consider the consistency of design. For example, when a small fuselage plug is added, additional seats and overhead bins are likely to be installed, and the lower cargo hold extended. These additional seats, bins, extended lower cargo hold and structural plug may be identical to the existing parts. Applying the latest standards only to the changed parts may not contribute materially to the level of safety, as the entire design as modified may not necessarily be any safer than the original design. It may also be inappropriate to require compliance with the latest standards for the entire fuselage, seats, bins, doors and cargo holds. For this reason, compliance of the new fuselage structure, seats, bins and cargo hold area with the standards in effect when the original fuselage, seats, bins and cargo hold area were certified may be acceptable.

      1. However, it may also be the case that the extent of the fuselage change may be large relative to the original certificated structure, seats, bins, doors and cargo compartment, and/or the change may require a new compliance substantiation that is comparable with that required for a new model aeroplane. Here, it would be expected that the proposed certification basis would encompass the standards in effect on the date of application, for the entire fuselage, seats, bins, doors and cargo hold.
      2. In the examples above, it would be incumbent upon the applicant to show that compliance with the latest standards would not contribute materially to the level of safety.
    2. Service experience

      1. This provision permits the use of relevant service experience, such as fleet hours, to demonstrate that compliance with the latest standards would not contribute materially to the level of safety, and as such, the use of earlier standards may be appropriate. Appendix C provides additional guidance on the use of service experience, along with examples.
      2. There may be cases for rotorcraft and small aeroplanes where sufficient and relevant data may not be available because of the reduced utilisation and the different amount and type of data available. In such cases, other service history information may provide sufficient data to justify the use of earlier standards, such as: warranty, repair and parts usage data; accident, incident and service difficulty reports; service bulletins; airworthiness directives; or other pertinent and sufficient data collected by the manufacturers, authorities, or other entities.
      3. The service experience levels necessary to demonstrate the appropriate level of safety as they relate to the proposed design change would have to be reviewed and agreed to by the Minister.
    3. Other exceptions - Compliance with later standards will not be required where the amendment to a standard is of an administrative nature and has been made only to correct errors or omissions, consolidate text or clarify an existing standard.
  2. Not Practical - Compliance with the latest standards may be considered not practical (or impractical) if the applicant can substantiate that it would result in additional resource requirements that are not commensurate with the safety benefits. The additional resource requirements could include those arising from design changes required for compliance, and the effort required to demonstrate compliance, but would not include resource expenditures for prior product changes.

    1. Substantiating data and analyses must support an applicant's position that compliance is not practical, and the Minister must agree with this position. In evaluating an applicant's position and substantiating data regarding impracticality, the Minister may consider other factors (e.g. the costs and safety benefits for a comparable new design).
    2. A review of transport category projects showed that in certain cases, where earlier standards were allowed, design changes were made to comply nearly with the latest standards. In these cases, the applicant successfully demonstrated that full compliance would require a substantial increase in the outlay of resources with a very small increase in the level of safety. These cases reflect an appropriate application of impracticality to a changed product.
    3. A proposal that a product design change would not be practical can be used in cases where compliance with the latest standards would contribute materially to the level of safety, but this contribution may not be commensurate with the associated additional resource expenditures.
    4. Appendix B provides additional guidance and examples for determining impracticality.

This completes the systematic process used in the determination of the certification basis for the changed product.

7.0 Excepted Products

An applicant for a change to the type design of an aircraft (other than rotorcraft) of a maximum weight of 2720 kg (6,000 pounds) or less, or to a non-turbine rotorcraft of a maximum weight of 1360 kg (3,000 pounds) or less, may show that the changed product complies with the standards recorded in the TCDS. The applicant may elect to comply with later standards. If the Minister, or a ministerial delegate, finds that the change is significant in an area, the Minister may specify compliance with an amendment to the standards recorded in the TCDS that applies to the change and any requirement that the Minister finds is directly related. Beginning with the existing certification basis, the Minister will step through each progressive amendment of the standards to determine the appropriate amendment level for the change. It is incumbent on the Minister to find that compliance with the specified amendment or requirement would contribute materially to the level of safety of the changed product, or would be practical. However, the Minister may also allow compliance with an earlier amendment to that standard initially specified, or with the existing certification basis, depending on the proposed design change.

For a change that contains novel or unusual design features, the Minister will apply Special Conditions-Airworthiness. The level of safety to be achieved by the Special Conditions-Airworthiness will be equivalent to the level of safety of the certification basis that the Minister has established for the changed product.

The exception for products under subsection 511.13(6) and 513.07(6) of the CARs apply at the aircraft level only. Design changes to engines and propellers installed on these excepted aircraft are assessed as separate products using subsection 511.13(1) through (4) or 513.07(1) through (4) of the CARs.

8.0 Special Conditions - Airworthiness

Subsection 511.13(7) or 513.07(7) of the CARs allows for the application of Special Conditions-Airworthiness, or amendments to existing special conditions, to address novel or unusual design features in the changed design. The objective is to achieve for the significant change a level of safety consistent with that provided by the latest standards. The application of Special Conditions-Airworthiness to a design change is not in itself a reason for the change to be classified as either a substantial change or a significant change. When the change is not significant, the Special Conditions-Airworthiness must be consistent with the level of safety of the certification basis that the Minister has established for the changed product.

9.0 Effective Period For An Application To Change A Certificate

The intent of section 511.06 and 513.06 of the CARs is to ensure that at the time, a changed product is certificated, no more than three or five years as appropriate to the product, has elapsed from the date of application. This is to ensure that the certification basis for the changed product is as current as practical. This is consistent with the requirements for a new type certificate and prescribes the process of updating the certification basis if these limits are exceeded.

10.0 Restricted Category Aircraft

10.1 Special Purpose Operations

For aircraft certificated in the restricted category under subsection 511.11(5) of the CARs, the application of the latest standards may not normally be considered to contribute materially to the level of safety or be practical for its intended use. As such, continued compliance with the existing certification basis may also be allowed. However, if the existing certification basis does not provide an appropriate level of safety for its intended use, the application of later standards would be considered. The intended role of a restricted category aircraft should be the main consideration when establishing the applicable airworthiness requirements for a proposed design change. Restricted category aircraft perform aerial work that are considered special purpose operations and are certified to a level of safety considered appropriate to the role or function of the aircraft. It is recognized that certain airworthiness standards applied on a "standard" aircraft may be deemed unnecessary or prohibitive, i.e. inappropriate, for the special purpose operation of the restricted category aircraft. The airworthiness requirements applicable to a design change on a restricted category aircraft should be those later amendments that bring practical safety benefit for the intended role of the aircraft.

10.2 Ex-Military aircraft

For aircraft that have been issued a type certificate in the restricted category (or special purpose) based on its military service record, an appropriate equivalent civil certification basis should be established for the proposed design change. The applicable airworthiness standards should be determined with the recognition that the aircraft has not been type certificated to civil aircraft airworthiness standards. Therefore, a change to an aircraft of this type may not realize a safety benefit by complying with later standards. The goal is to maintain a level of safety at least equivalent to the original design and appropriate for the intended role of the aircraft.

11.0 Documentation

All changes that result in a revision to the product's certification basis must be reflected on the TCDS. Similarly, the certification basis must be noted on all STCs, in detail or by reference to the TCDS for that STC.

12.0 Headquarters Contact

For more information please contact:

Policy Standards Coordinator (AARDH/P)
Phone: (613) 990-3923
Facsimile: (613) 996-9178
E-mail: AARDH-P@tc.gc.ca

Original signed by Maher Khouzam

Maher Khouzam
Chief, Regulatory Standards
Aircraft Certification Branch

Appendix A - Classification of Changes
Appendix B - Procedure for Evaluating the Practicality of Applying the Latest Standards to a Changed Product
Appendix C - The Use of Service Experience in the Certification Process

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