Advisory Circular (AC) No. 521-007

Part Design Approvals

Issuing Office: Standards Document No.: AC 521-007
File Classification No.: Z 5000-34 Issue No.: 01
RDIMS No.: 5612108-V33 Effective Date: 2012-03-16


  1. This Advisory Circular (AC) is provided for information and guidance purposes. It describes an example of an acceptable means, but not the only means, of demonstrating compliance with regulations and standards. This AC on its own does not change, create, amend or permit deviations from regulatory requirements, nor does it establish minimum standards.

1.1 Purpose

  1. The purpose of this document is to provide guidance in applying for and obtaining a part design approval (PDA) in accordance with Subpart 521 of the Canadian Aviation Regulations (CARs). It is to be used in conjunction with  AC 521-004.

1.2 Applicability

  1. This document applies to:

    1. applicants for and holders of a  PDA;

    2. Transport Canada Civil Aviation (TCCA) personnel;

    3. delegates; and

    4. the aviation industry.

  2. This AC does not apply to products approved by a Canadian Technical Standard Order (CAN-TSO) design approval.

1.3 Description of Changes

  1. Not applicable.


2.1 Reference Documents

  1. It is intended that the following reference materials be used in conjunction with this document:

    1. Aeronautics Act (R.S., 1985, c. A-2);

    2. Part I, Subpart 4 of the Canadian Aviation Regulations (CARs)— Charges;

    3. Part II, Subpart 1 of the CARsIdentification of Aircraft and Other Aeronautical Products;

    4. Part V, Subpart 21 of the CARsApproval of the Type Design or a Change to the Type Design of an Aeronautical Product;

    5. Part V, Standard 561 of the CARsApproved Manufacturers;

    6. Advisory Circular (AC) 500-016—Establishing the Certification Basis of Changed Aeronautical Products;

    7. AC 521-002—Type Certification requirements of Aircraft, Engines and Propellers;

    8. AC  521-004—Changes to the Type Design of an Aeronautical Product;  

    9. Maintenance and Manufacturing Staff Instruction (MSI) 53—Review of Supplemental Instructions for Continued Airworthiness;

    10. Notice of Proposed Amendment (NPA) 2010-021Approval of the Type Design or a Change to the Type Design of an Aeronautical Product; and

    11. Transport Canada Form 26-0469Design Change Approval Application.

2.2 Cancelled Documents

  1. Not applicable.

  2. By default, it is understood that the publication of a new issue of a document automatically renders any earlier issues of the same document null and void.

2.3 Definitions and Abbreviations

  1. The following definitions are used in this document:

    1. Aeronautical Product: an aircraft, aircraft engine, aircraft propeller or aircraft appliance or part, or a component part of any of those things, including any computer system and software (Ref. Aeronautics Act andSection 521.01 of the  CARs).

    2. Certification Basis: refers to the applicable standards as established in Section 521.157 of the CARs, as appropriate, including any special conditions—airworthiness (SCA), findings of equivalent level of safety, and exemptions applicable to the product to be certified.

    3. Conformity with the Certification Basis: demonstrating compliance with all of the applicable standards and requirements of the certification basis.

    4. Delegate: any person or class of persons authorized under the authority of Subsection 4.3(1) of the Aeronautics Act to perform functions on behalf of the Minister, subject to the requirements in Chapter 505 of the Airworthiness Manual (AWM).

    5. Manufacturer Certificate: a document issued to a Canadian holder in accordance with Subpart 561 of the CARs, and includes the associated limitation record.

    6. Original Equipment Manufacturer (OEM) Part: a part supplied by the type certificate holder, or a vendor to the type certificate holder, that is in compliance with the specifications of the type certificate for the aeronautical product (including the configuration of that part).

    7. Part Design Approval (PDA): a document that is issued by the Minister to record approval of the type design of a replacement part identified by a part number or by some other means of identification unique to the part, for use on an aeronautical product that is identified by type or model. (Ref. Subsection 101.01(1) of the  CARs).

    8. Parts Manufacturer Approval (PMA): an approval issued by the Federal Aviation Administration (FAA) for the production of modification or replacement parts, which includes materials, parts, processes and appliances. For a replacement part, it is both a design and a production approval. For a modification part (i.e. parts approved via an FAA Supplemental Type Certificate (STC)), it is a production approval only.

    9. Replacement Part: a part intended to be installed in the place of a part specified in the type design of an aeronautical product.

    10. Standards of Airworthiness: design requirements as defined in the AWM. For design changes, the standards of airworthiness may also be listed on the type certificate data sheet (TCDS).

    11. Type Design:

      1. the drawings and specifications, and a listing of those drawings and specifications that are necessary to define the design features of an aeronautical product in compliance with the standards applicable to the aeronautical product;

      2. the information on dimensions, materials and manufacturing processes that is necessary to define the structural strength of an aeronautical product;

      3. the approved sections of the aircraft flight manual, where required by the applicable standards of airworthiness;

      4. the airworthiness limitations section of the instructions for continued airworthiness specified in the applicable chapters of the AWM; and

      5. any other data necessary to allow, by comparison, the determination of the airworthiness and, where applicable, the environmental characteristics of later aeronautical products of the same type or model.

        (Ref: Section 101.01 of the  CARs).


  1. With the implementation of Subpart 521 of the CARs, new documents have been created to support the regulations. All guidance material such as Staff Instructions (SIs), ACs, and Policy Letters that supported the previous CARs including Chapters 511, 513, 591 and 593 of the Airworthiness Manual (AWM) have been reviewed and the relevant material included in the 521 series ACs and  SIs.

  2. This AC is organized to mirror the Sections and Subsections of Subpart 521 of the CARs, Division VII, so that they can be read in conjunction with Subpart 521 of the CARs.

  3. Although Subpart 521 of the CARs introduced a change in terminology in the English version from “compliance” to “conformity” this AC will be using “compliance” wherever possible to minimize confusion in this document.

    Note:  In December 2010, a Notice of Proposed Amendment (NPA) to Subpart 521 of the CARs (NPA 2010-021) was introduced to revert the terminology “conform” and “conformity” back to “comply” and “compliance”.

  4. The PDA was introduced to allow the approval of replacement parts where the design of that replacement part represents a negligible change to the fit, form and function of the part it is intended to replace. The replacement part must meet the applicable airworthiness requirements as stated in the type certificate data sheet (TCDS) of the OEM product. In addition, the replacement part does not enhance the functionality of the part it is intended to replace, nor of the aeronautical product on which the part is installed.


  1. The requirements that must be fulfilled to obtain a PDA for a replacement part are defined in Division VII— Part Design Approvals and Division IV — Changes to a Type Design of Subpart 521 of the CARs. This AC should be used in conjunction with AC 521-004.

  2. Section 521.301 of the CARs defines to whom and what this division applies.

  3. Section 521.303 of the CARs defines the requirements of an applicant for a  PDA.

  4. Sections 521.304, 521.305 and 521.157 to 521.160 of the CARs define what actions are required by an applicant for a part design approval document. 

  5. Sections 521.306, 521.307 and 521.161 of the CARs define the requirements of the design approval issuance and subsequent revision.


5.1 Application — Section 521.301

  1. Section 521.301 of the CARs applies to applicants and holders in respect of a replacement part for an aeronautical product.

  2. The actions and requirements of the applicant may be undertaken by a person acting as their representative.  However, such an arrangement in no way divests the applicant of their responsibilities to the  CARs.

  3. Any Canadian individual or organization may apply for a PDA. Canadian design approval documents are not issued directly to foreign applicants. Refer to Division XI of Subpart 521 of the CARs for more information on foreign aeronautical products.

5.2 Eligibility Requirements — Section 521.302

  1. Section 521.302 of the CARs requires the applicant to have or have access to the required technical capabilities specific to the replacement part under consideration. An applicant could meet this requirement by:

    1. Having a level of knowledge and capability appropriate for the replacement part; or

    2. Showing that an arrangement exists for the applicant to have access to a level of knowledge and capability appropriate for the replacement part.

  2. The intended holder is required to control the design of the replacement part.  A licensing agreement with the type certificate holder is not considered ‘control’ of the replacement part.

  3. For more detailed information on how the Minister determines technical capability, refer to AC 521-002.
5.2.1 Replacement Part Eligibility Criteria
  1. In order to qualify for a PDA, a replacement part shall meet the following criteria:

    1. It shall not be a standard or a commercial part, as defined in Subpart 101 of the  CARs;

    2. It shall not create a new airworthiness limitation, as defined in Subpart 101 of the CARs, nor shall it replace a part that has existing airworthiness limitations;

    3. The part being replaced cannot be the subject of an Airworthiness Directive;

    4. The part design shall meet the applicable airworthiness standards for the OEM part being replaced. It shall be a part from an aeronautical product approved by a type certificate;

    5. It shall not require an Instruction of Continued Airworthiness (ICA) that differs from the original ICA unless use of the original ICA would result in an unsafe condition;

    6. The replacement part shall represent a negligible change to the fit, form and function of the OEM part, and should be operated, installed and maintained in the same way. Changes to the part design that enhance its utility must be approved as an  STC;

    7. The design or installation of the replacement part shall not result in a major modification to the product (i.e. a major change in the type design of the part, as defined in Subpart 101 of the  CARs);

    8. It shall not, either as a single PDA or when combined with other PDAs, result in a replacement part:

      1. that when assembled, rises to the level of an aeronautical product which could be approved using a type certificate, a CAN-TSO Design Approval, an FAA Technical Standard Order Authorization (TSOA) or Letter of Design Approval (LODA); or

      2. that consists of a major component of an aeronautical product, including wings, fuselages, empennage assemblies, landing gears and any other component, the failure of which may affect the airworthiness of the aeronautical product.

    9. The means of compliance to the design standards shall be with test and computation. It is not sufficient to have an OEM drawing or to demonstrate that the proposed replacement part has the same dimensions.

5.2.2 Supplemental Type Certificate or Repair Design Certificate conversion to Part Design Approval
  1. A holder of an STC or a Repair Design Certificate (RDC) obtained prior to October 2000 as an approval for a replacement part, may request issuance of a PDA to replace the STC or RDC that they had been issued. The applicant need not demonstrate compliance again, nor should TCCA review again. However, all other eligibility criteria for PDA issuance shall be met.


6.1 Application for a Part Design Approval — Section 521.303

  1. The applicant applies for a PDA by completing Form 26-0469 - Design Change Approval Application, (or alternate TCCA accepted form or process).

  2. The application is to be accompanied by:  

    1. a part design description;

    2. a proposed certification basis;

    3. a certification plan per Section 521.155 of the CARs; and

    4. Identification of the part for which PDA application is being made, including the:

      1. OEM part number for the part to be replaced;

      2. Identity of the type certificated aeronautical products where the part will be installed; and

      3. Type, model, series, type certificate number and serial number(s) of the aeronautical products as appropriate;

    5. Identification of the certification basis in the TCDS of the corresponding OEM product.

  3. Application can be made for a PDA for a replacement part, which may have more than one component, and which may be applicable to one or more aeronautical products. When applying for a single PDA for an assembly of components, there shall be an interrelationship between those components and the associated aeronautical product, for example overhead bins for installation on transport category aircraft; accessory parts for one type of reciprocating engine; control cables for normal/utility aircraft.

  4. For additional details of the application process including submittal procedures, refer to AC 521-004.

6.2 Certification Basis — Section 521.304

  1. PDAs will have a certification basis as defined by Subsection 521.158(2) of the  CARs.


  1. SI 521-004 provides information on establishing means of compliance and TCCA’s level of involvement.


8.1 Compliance with Certification Basis — Section 521.305

  1. Section 521.305 of the  CARs:

    1. requires the applicant to comply with Section 521.160 of the CARs in regards to compliance with the certification basis; and

    2. defines the effective period of an application for the approval of a replacement part as per Section 521.156 of the  CARs.

      Note: Section 521.160 of the CARs will point the applicant back to Section 521.44 of the CARs with respect to Inspections and Tests. More information on Inspections and Tests can be found in  AC 521-002.

8.2 Data Package

  1. The complexity of the data package will vary depending on the nature of the part and its relationship to the aeronautical product on which it will be installed. However, the minimum documentation that is required prior to issuance of a PDA include:

    1. A certification plan referred to in Phase I outlining how compliance is to be demonstrated for each part of the affected design requirements;

    2. A declaration attesting to the compliance demonstration of the product design with the certification basis;

    3. Master Drawings and/or a Master Drawing List;

    4. Production drawings and specifications necessary to define the configuration of the part;

    5. Maintenance Staff Instruction (MSI) 53 is used to determine if the OEM ICA may be used. If this is not adequate, the applicant shall justify to TCCA why a new ICA is required;

    6. Part marking information as required by Section 201.10 of the CARs; and

    7. Any other data requirements requested by the Regional Aircraft Certification office, which may include:

      1. Test plans and reports;

      2. A complete drawing package;

      3. Manufacturing processes and controls; and

      4. An eligibility list describing the parts and the aeronautical products on which they may be installed.

8.3 Part Design Approval - Part Marking

  1. Replacement parts produced under a PDA must be marked in a manner that will enable persons to identify key information about the replacement part. The issuance of the PDA authorizes (and requires) the PDA holder to mark the replacement parts in accordance with the approved design. Therefore, identifying marks are to be included in the design data and reviewed as part of the engineering approval to establish that the location and process of identification does not degrade airworthiness compliance.

  2. For a PDA granted on an assembly of parts, each component of that assembly shall be identified by a distinct part number traceable to a general assembly or top-level drawing, and shall comply with part marking criteria specified in Section 201.10 of the CARs. This will allow the PDA holder to release individual components for repair of an overall assembly.

  3. Except as noted in section 8.3(4) of this AC, each replacement part, or component of a part assembly, shall be permanently and legibly marked, in the same location or on the same data plate, with the following information:

    1. The legal name, trade mark, or symbol identifying the PDA holder;

    2. The manufacturer’s approval number and PDA approval number; and

    3. The part number as identified in the applicable type design data. The replacement part must be numbered such that it is distinguishable from the specific type certificate holder’s part number. Using a prefix or suffix may meet this requirement, as long as it does not cause confusion with the part marking practices of the type certificate holder or other PDA holders. The PDA document identifies the type-approved part number with which the applicant’s part is interchangeable.

  4. If the part is too small or it is otherwise impractical to mark, the required information may be placed on the authorized release certificate referred to in Section 561.10 of the Standard accompanying the replacement part or its container.

8.4 Analyses, Inspections and Tests

  1. Although the PDA part is intended to be equivalent to the OEM part for which it is intended to replace, arguments of identicality are not considered an acceptable means by which compliance with the certification basis is determined.  Considerations that may be an acceptable means of demonstrating compliance with the associated airworthiness standards should include:

    1. Demonstration that the design of the replacement part represents a negligible change to the form, fit and function of the OEM part that it is to replace, and that it does not enhance the functionality of the OEM part or the intended aeronautical product on which it is intended to be installed. As a minimum, this includes a validation of the replacement part dimensions, materials and processes;

    2. Conduct all tests, analyses and inspections necessary to demonstrate compliance with the applicable airworthiness standards. Comparative analyses may contribute towards meeting this requirement, but shall not be used alone. Test and computation are the only means by which an applicant may demonstrate compliance with the applicable airworthiness standards:

      1. Test means testing related to the criticality and complexity of the replacement part. If required, the component testing shall be designed to test the performance and durability of the part to the extent required by the applicable airworthiness standards.  Certification testing (as opposed to developmental testing) include protocols such as conformity inspections of the test article and acceptance of a proposed test plan that should be discussed and agreed to by the regional engineer before proceeding with the testing. The tests must be supported by appropriate analysis and engineering assessment to both the next higher assembly, and the aeronautical product as a whole of the consequences should the part fail to perform its intended function;

      2. Computation means demonstration by analysis that the design of the part meets the requirements of all applicable airworthiness standards.  This analysis should discuss how the part meets these requirements and address elements such as material composition, condition, fabrication, configuration, and interface with other parts.

    3. Ensure that the form and fit of the replacement part complies with that of the OEM part, that no interference with mating or adjacent hardware occurs, and that the part performs its intended function;

    4. Demonstrate that the replacement part can be manufactured and installed on the aeronautical product in compliance with pertinent drawings and/or instructions; and

    5. Demonstrate that the operating and maintenance instructions provide adequate information for safe operation and continuing airworthiness of the product.


9.1 Issuance of a Part Design Approval— Section 521.306

  1. Section 521.306 of the CARs defines the requirements for the issuance of a  PDA.

  2. The applicant must provide a signed undertaking signed by the intended holder to assume the responsibilities of a design approval document holder. More information on this item is provided in AC 521-004.

  3. The issuance of a PDA signifies that the technical design data for a replacement part is approved and the approval forms part of the aeronautical product type design, when the replacement part is incorporated.

  4. Although Aircraft Certification Delegates may contribute towards the design, they do not have the authority to issue PDAsPDAs shall only be approved and issued by appropriately authorized TCCA employee.


10.1 Change to a Part Design Approved in a Part Design Approval — Section 521.307

  1. A change to a PDA that is classified as a major change (not minor) shall be applied for as either a new PDA (replacement part that does not modify the baseline aeronautical product), or shall be applied for as an STC that is separate from the original PDA, the new change being a modification of the baseline aeronautical product. 

  2. Minor changes shall be dealt with in accordance with Section 521.154 of the  CARs.


  1. Not applicable.


  1. Not applicable.


Suggestions for amendment to this document are invited, and should be submitted to:

Chief, Aircraft Certification Standards (AARTC) via the following e-mail address:

Original signed by

Jacqueline Booth
A/Director, Standards Branch
Civil Aviation
Transport Canada

Transport Canada documents or intranet pages mentioned in this document are available upon request.