Maintenance and Manufacturing Policy Letters (MPL)


Subject:

Number:

MPL 20

Progressive Maintenance Schedules - Cycles Longer that 12 Months

Revision No:

1

Number of Pages:

2

File No: AARP-5009-0-20

Issue Date:

November 9, 2001

1. Purpose

1.1 The purpose of this letter is to ensure consistent interpretation of General Operating and Flight Rules Standards 625 Appendix D paragraph (4).

2. Background

2.1 General Operating and Flight Rules Standards 625 Appendix D paragraph (4) states:

"The progressive maintenance schedule shall provide for a complete inspection of the aircraft, to at least the same extent as the schedule contained in Appendix B, within each 12 month period."

This has been interpreted as a requirement that all tasks of a progressive schedule must be completed within each 12 months. That interpretation has been challenged by operators who wish to use a manufacturer's recommended progressive schedule that programs a cycle of tasks over a longer period than is practical to fly in a year. Examples include the Beech King Air, and DHC-6 Emma programs.

The requirement for a "complete inspection of the aircraft" only applies to programs approved in accordance with Appendix "B", which is meant to ensure that the aircraft as a whole is evaluated at least annually. It is not considered acceptable for any significant part of an aircraft to operate for several years without inspection.

Maintenance programs based on a Maintenance Review Board Report (MRB) or Manufacturer's recommendations, are routinely approved with tasks, such as C or D check tasks, that are not intended to be accomplished in a single year. Those schedules actually do involve relatively frequent inspections of the complete aircraft, in that the lower level checks are completed within a year, while only the more in-depth tasks are carried out at longer intervals. It was never intended that small aircraft progressive schedules be restricted to tasks that are all intended to be accomplished each year.

STD 625 Appendix B states at paragraph (5):

"The depth of inspection of each item on the schedule shall be determined by the person performing the inspection, and shall be consistent with the general condition and operating role of the aircraft."

Progressive schedules are in compliance with the annual requirements of Appendix D if:

  1. within each year a mix of detailed and less detailed tasks covers the entire aircraft; and
     
  2. the depth of inspection is "consistent with the general condition and operating role of the aircraft".

3. Policy

3.1 Progressive maintenance schedules may be approved in accordance with General Operating and Flight Rules Standards 625 Appendix B (4) if the applicant establishes that a package of tasks that constitute an inspection of the complete aircraft is to be completed within each 12 month period. Appendix B effectively defines the minimum areas that constitute a complete aircraft inspection. The Principal Maintenance Inspector (PMI) must be satisfied that the depth of inspection will be consistent with the operating role of the aircraft.

4. Effective Date

4.1 This policy comes into effect immediately.

5. Expiry

5.1 This policy expires on November 9, 2003 or upon publication of a revision to the General Operating and Flight Rules Standards 625, which ever occurs first.

6. HQ Contact

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

Brian Whitehead, AARPC
Aircraft Maintenance & Manufacturing Branch
E-mail: whitehb@tc.gc.ca
Phone:      (613) 941-8371
Facsimile: (613) 952-3298

D.B. Sherritt
Director,
Maintenance and Manufacturing

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