Maintenance and Manufacturing Policy Letters (MPL)

Subject: Number: MPL 36
Approved Maintenance Organizations for Re-certification of Parts Revision No: 1
  Number of Pages: 7
File No: AARP-5009-0-36 Issue Date: February 2, 2006

1. Purpose

1.1 The purpose of this letter is to clarify the intent of extending priviledges to Approved Maintenance Organizations (AMOs) to re-certify parts and establish a process for controlling these approvals.

2. Background

2.1 On March 1, 2002 changes to Canadian Aviation Regulation 573 and associated standards, specifically 571 Appendix H, introduced a new means of documenting and certifying parts of varying provenance and criticality. The changes associated with the revision of the parts approval process enables the use, after appropriate evaluation, of parts for which the certification or known history no longer conforms to traditional standards. These rules are the result of the rule making process utilizing the Canadian Aviation Regulatory Advisory Committee (CARAC) and the diligent work in the Maintenance and Manufacturing Technical Committee and Parts Working Group. The changes were put forward 3-5 years ago and have already been implemented with some AMO’s.

2.2 A series of presentations by headquarters personnel was conducted for Maintenance and Manufacturing Inspectors across most of the Transport Canada Centre (TCC) to present the rule changes and introduce the concept of re-certification privileges for qualified AMOs. Presentations have also been offered at AME symposiums across Canada. As a result of those sessions, some concerns were raised over the nature of an AMO that would qualify for approval to exercise this process, and the standardization of approvals.

2.3 It should be clearly understood that an AMO who wishes to re-certify undocumented parts is simply wishing to expand their capability as an AMO and this type of capability should not be considered an approval on its own merit, but more as a process under an existing AMO approval. As a result, a Notice of Proposed Amendment (NPA) has been developed to introduce changes to STD 573.02 (11) to remove the reference to having this capability identified in the limitations set out in the AMO certificate. This capability is to be described and controlled in the limitations section of the AMO’s Maintenance Policy Manual (MPM) and is to be directly linked to existing capabilities (ratings) held by the AMO. Additional changes to 573.02 (11) have been added to include the requirement for an AMO to identify which types of aeronautical products it is capable of evaluating in its MPM.

2.4 An additional NPA has been drafted to further clarify the requirement for AMO’s to establish applicable procedures based on the criticality of the aeronautical products being re-certified and the ability to correctly identify the part through any part markings. The applicable procedures will vary depending on the types of products they intend to re-certify and the proposed methods to be used to evaluate the part.

2.5 The Appendix H process in Std. 571 has been amended to help clarify some of the steps in the process. A new step has been added between step 5 (documentation process) and step 7 (evaluation). The new step 6 (Determine part Criticality) was added to clarify the need for an AMO to take the part criticality into consideration when developing and applying the evaluation part of this process. Critical parts would require a more detailed evaluation based on the use of design data versus a more simplified evaluation for a non- critical part, which could be evaluated based on Instructions for Continuing Airworthiness (ICA) data and/or comparison data. 

2.6 Step 9 (Material Analysis), is a continuation of the evaluation process (Step 7), which has been expanded to help clarify the need to determine any material processes which may have been applied to a part. Some parts will need to be tested to determine material type, material condition and/or any other special processes, which may have been applied to the part.   

3. Policy Statement

3.1 The intention of Transport Canada (TC) is to extend this privilege to qualified AMOs who have identified a  need to re-certify undocumented parts and have demonstrated that they hold the necessary capability to  evaluate the type of parts identified in their MPM revision, based on their current AMO rating’s. TC does  recognize that this is a process that most AMO’s will want to have, but in general most AMO’s will be limited to very specific types of parts and to very specific types of testing and evaluation in relation (once again) to  their AMO ratings and capabilities. For example; a component AMO may only be capable to re-certify undocumented parts based on Instructions for Continued Airworthiness (ICA) data, while another AMO may  be able to re-certify parts based on ICA data, design data and special processes, due to their engineering  capability and existing AMO limitations. The method of applying for this privilege is through the submission of a Maintenance Policy Manual (MPM) amendment, which shall include the details with which the organization  intends to administer their process.

3.2 It was recognized that a great deal of interpretation could be applied, as the level of evaluation would have to be balanced against the knowledge of the part history.  (i.e. the less one knows about the history and genuine origin of the part, the more evaluation may be involved, and vice versa). For this reason a generic procedure was not possible. However, by applying the standards as a series of questions at each stage of a process, an inspector should be able to review a MPM to determine that each element of the standards are met. This may involve consultation with the Aircraft Certification Branch for some interpretation of the processes proposed. The planning and design aspects are crucial elements in the approval process and particular attention needs to be paid to these areas in the MPM. This is not to mean that entire procedures are to be placed in the MPM, but that the overruling policy is clearly explained and auditable. For control purposes AMO’s are to identify which types of products are eligible for re-certification by their organization  and that they be incorporated into the limitations section of their MPM.  

3.3 It is expected that an inspection of an AMO’s facilities may be required to verify that the capabilities exist to conduct the procedures proposed by the MPM submission. This would be conducted only after the regional inspectors have satisfied themselves the procedures in the MPM amendment are acceptable, but before further processing of the amendment is conducted at a higher level. It will be the individual inspectors who will review the material submitted and inspect the facilities to determine whether the AMO is capable of carrying out the process proposed in the MPM amendment package.

3.4 The region will be responsible for establishing the review procedures within the regional framework.  It is recommended that each region establish a core of knowledgeable persons to act as a committee of specialists to review the first several MPM amendment packages. The regional committee will act as a reference source and standardization team to review the packages for content and ensure that all issues have been addressed prior to approval being granted to a requesting AMO. Where necessary this committee will consult with headquarters on the establishment of further guidance material.

3.5 For the sake of national consistency, copies of the first two packages from each region will be forwarded to headquarters contact, listed below, for a secondary review prior to approval being granted. The headquarters secondary review will be a quality assurance and standardization function to ensure the intentions of the rule changes are being met. These will be complete in the sense that an inspector has reviewed the information and satisfied him/herself that it meets the requirements, an inspection to verify the capability of the organization has been conducted, the regional committee has reviewed it for consistency in the region and it is recommended for approval. After final acceptance by headquarters, verification will be sent to the regional committee. With a recommendation from the regional committee the Principle Maintenance Inspector can approve the amended MPM package thereby approving the re-certification privileges for the qualified AMO.

3.6 The policy letter applies to existing organizations approved to re-certify undocumented parts in accordance with CAR Std. 571 Appendix H. This policy letter also applies to any new applicant for the issue of re-certification of undocumented parts approval.

3.7 The Appendix contained in this policy letter contains Notice’s of Proposed Amendments to the CAR’s and STD’s applicable to the re-certification of undocumented parts process. 

4. Effective date

4.1 This policy comes into effect immediately.

5. Expiry

5.1 This policy expires two years from the date of release of the regulations, at such time as the rules themselves change or this MPL is superceded.

6. HQ Contact

6.1 The responsible officer indicated below may be contacted for information regarding this MPL

Jeffrey Phipps
Chief, Standards & Procedures AARPE
Aircraft Maintenance & Manufacturing
Phone:      (613) 952-4386
Facsimile: (613) 952-3298

D.B. Sherritt
Maintenance and Manufacturing


Appendix to MPL 36 - Approved Maintenance Organizations for Re-certification of Parts


  1. undocumented part” means a part lacking sufficient certification or history to make it eligible for installation on an aircraft without submitting it to a recertification process.

Approved Maintenance Organizations for Re-certification of Parts

Condition .01 (1) An AMO may evaluate undocumented parts of the kinds associated with ratings held, provided that:

  1. the AMO identifies what aeronautical products it is capable of evaluating in its MPM; and

  2. the AMO establishes applicable procedures, in its MPM, to perform the process outlined in Standard 571, Appendix H; taking into consideration the criticality and origin of the part and the ability to correctly identify the part through any markings.

  3. the AMO obtains approval for the procedures required in paragraph (b) in accordance with section 573.10 of the CARs.

Standard 571 Appendix H - Process to Evaluate Undocumented Aircraft Parts

  1. Parts at receiving: Retain all historical documents, tags, invoices, and packing slips for evaluation.

  2. Part Identification: Verify that the part has certification or sufficient documentation, or both as applicable, to ascertain that it is a genuine part (i.e. nomenclature, part number, serial number, time in service) and that the part corresponds to that documentation. If the part appears to be a used part, verify that the identity of the aircraft from which the part was removed is documented. Verify that the technical records indicate that the applicable Airworthiness Directives and equivalent applicable directives issued by a foreign civil aviation authority have been accomplished.

  3. Stores: Complete incoming stock procedures and place in stores by following the procedures described in the company Maintenance Policy Manual (MPM).

  4. Exceptions: Section 571.09 of the CARs limits the installation of used life limited parts to those for which the technical history is available. Therefore, parts of the following kinds that are considered undocumented at step 2, are not be further evaluated under this appendix:

    1. life-limited parts that are subject to limits on flying hours, landings, operating cycles or calendar time in service, or combinations thereof;

    2. parts that are required to be rejected in accordance with the instructions for continued airworthiness following an abnormal occurrence; or

    3. parts that are eligible for use in multiple applications with different operational limitations, or different limits on the time in service, which if exceeded would require rejection of the part.

  5. Documentation and evaluation: Record and retain evidence of all tasks accomplished throughout the process of ascertaining the conformity of the part. Detail each step of the process up to and including the determination of conformity. 

  6. Determine Part Criticality: An evaluation of the part must be made to determine the part criticality.  For example:

    1. critical parts such as engine components, power train drive components, flight controls, and primary structural parts whose failure or malfunction could cause a catastrophic failure; or

    2. non-critical parts are those that typically can be identified through their part markings whose failure or malfunction would not cause a catastrophic failure, but instead a possible loss of system redundancy.

  7. Evaluation:  The intent of the evaluation process is to determine the eligibility of the part through the identification of the part and the ability to determine its attributes. Can the origin of the part be confirmed (i.e. was the part received from an aircraft, a maintenance organization, manufacturer, or other source? Is there sufficient documentation to ascertain that it is the proper part such as packing slip, manufacturer’s identification tag, identity of component from which the part was removed. Can the part nomenclature, part number, serial number, manufacturer’s identification marks or stamps found on the part be confirmed? The more information that is known about a part will enable the evaluator to confirm whether a part conforms to its type design or not.

    Depending on the criticality of the part, the type of data used during the evaluation process will differ.  For example:

    7 (a) Non-critical parts will be evaluated in accordance with applicable ICAs or equivalency data.  Equivalency data is determined by a process of material and dimensional analysis, which can then be used with known authentic parts to determine eligibility, which essentially becomes a fit, form and function test.

    7 (b) Critical parts will require a higher level of evaluation based on design data, OEM drawings, and other associated specifications, in order to determine the attributes of the part.  For primary structure the attributes of the part must be identified and as a result the organization will be required to obtain the manufacturers data as applicable.

    Note: attributes are the characteristics, qualities or properties of the part as identified by the OEM, such as material type, material strength, and special processes used during the manufacturing process.

    Note: part conformity is based on the data associated with the appliance type certificate, TSO, or aircraft type certificate, as applicable.

  8. Is there sufficient data to confirm conformity: is there sufficient information obtained during the evaluation of the part in the previous step, using the appropriate data based on part criticality to confirm conformity. Parts, which are lacking sufficient information, may require additional evaluation through material analysis to determine the attributes of the part. Parts that can be correctly identified through their markings etc. and have sufficient data available to evaluate the characteristics, qualities or properties of the part may not require material analysis to determine conformity.

  9. Material Analysis Processes: When a part is no longer in production and type design data is no longer available, and/or the source of the part is unknown, material analysis maybe necessary in order to determine the attributes of the part.  Typically material analysis will determine the material type, material strength, and any special processes applied during manufacturing, which are considered to be part of the design approval process. 

    Note: When the type design data is no longer available, the data resulting from the material processes could be used to determine part eligibility for a particular design.

    In comparison, when the source of the part is unknown the material process data could be used in comparison to the OEM design data in order to determine eligibility of the part.

  10. Conformity: Verify that the part conforms to all applicable characteristics published in the OEM drawings or other associated specifications, ICAs, or equivalency data, as necessary.  If the part conforms it is now considered to be eligible for installation only once the airworthiness of the part has been determined in step 11.

  11. Testing and Repair: The objectify of this step is to determine the Airworthiness of the part by the processes identified in the applicable ICAs, which will confirm the serviceability of the item.  These processes could be as simple as a bench check, dimensional inspection, visual inspection, and/or, as complex as an overhaul or major repair.

    Note: Parts that have not been evaluated in step 7 cannot be certified using a test and/or repair procedure in step 11.  Only once eligibility has been determined through evaluation can the part be subjected to step 11 using published ICA data to complete the re-certification process.  All repairs must be performed in accordance with the appropriate specified or approved data as necessary.

  12. Acceptability: The part is acceptable for certification when it meets all the requirements of the type design or instructions for continued airworthiness and approved procedures including inspection, overhaul and testing. Ensure that all Airworthiness Directives and equivalent directives issued by a foreign civil aviation authority applicable to the part are complied with.

  13. Certification and supporting documents: If the part has been found acceptable under paragraph 12, fill out and sign a maintenance release, meeting the requirements of section 571.10 of the CAR's, and provide any other supporting documentation that may be required such as calibration records and test results, and ensure the certification documents accompany the part. Where a part has been accepted pursuant to Appendix H of this standard, the certification statement shall include the following words.

    “This part has been determined to conform to the approved type design, or to be acceptable under section 571.13 of the CAR’s”

    Note: An AMO will only be able to determine part eligibility and airworthiness in accordance with their AMO capabilities, which are based on their applicable AMO rating(s) and limitation(s).

  14. Reject: Ensure that any part that has reached its life limit or that is identified as ineligible (step 10), or unairworthy (step 12), is rendered unusable or kept segregated from airworthy parts, in accordance with section 571.09 of the CARs.

Flow Chart

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Flow Chart

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