Staff Instruction (SI) No. 513-004

Alternate Maximum Certified Weight Approval

Internal documents and documents hyperlinked and stored on
Transport Canada's intranet mentioned in this document
are available upon request. See Contact Office below.

Issuing Office: Standards    
Activity Area: Qualifying SI No. 513-004
File No.: 5009-32-2 Issue No. 01
RDIMS No.: 2538345-V5 Effective Date 2008-01-31


1.1  Purpose

The purpose of this Staff Instruction (SI) is to provide guidance on the approval of lower alternate maximum certified weight limits, by Limited Supplemental Type Certificates (LSTC), for use by operators that have configuration control and aircraft dispatch release systems that will ensure that the flight crew knows and complies with the weight limits under which they are to operate the aircraft.

1.2  Applicability

This document is applicable to Transport Canada Civil Aviation (TCCA) Headquarters and Regional personnel.

1.3  Description of Changes

Not Applicable.


2.1  Reference Documents

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

    1. Part V, Subpart 13 of the Canadian Aviation Regulations (CAR)—Approval of Modification and Repair Designs; and
    2. Chapter 513 of the Airworthiness Manual (AWM)—Approval of Modification and Repair Designs.

2.2  Cancelled Documents

Not applicable.

2.3  Definitions and Abbreviations

The following definitions and abbreviations are used in this document:

  1. Alternate Maximum Certified Weight means anyone of the following common use terms that are generally defined in the Aircraft Flight Manual (AFM):

    1. Maximum Ramp Weight (MRW);
    2. Maximum Takeoff Weight (MTOW);
    3. Maximum Landing Weight (MLW); and
    4. Maximum Zero Fuel Weight (MZFW).


  1. There have been requests to approve lower Maximum Certified Weight limits of aircraft in airline service for commercial reasons relating to the reduction in operating fees.
  2. TCCA has determined that this may be accomplished through the LSTC process. In general, an Aircraft Flight Manual Supplement (AFMS) is required which details the changes in limitations, procedures and performance associated with the change in Maximum Certified Weight limits.


  1. In accordance with the certification requirements, maximum certified weights are established where structural, performance and other requirements (e.g. noise) are met. Terms in common use are MRW, MTOW, MLW and MZFW. In general, there are defined values of these maximum certified weights due to structural reasons, which are specified in the limitations section of the AFM. The operating weights may be less than the maximum certified weights as established by the performance limitations derived from the AFM performance section based on such factors as altitude, temperature and runway length considerations.
  2. There are no certification or safety issues associated with operating at lower values of the maximum certified weights except that the AFM limitations are to be revised accordingly. This can be accomplished by issuing an LSTC as the means to approve for an AFMS to the basic AFM.


5.1  General

  1. The maximum certified weight limits in the basic AFM should be reviewed. Depending on the aircraft, the weight limits may be defined as appropriate to a model series, aircraft within a model series that include modification(s) to increase the maximum certified weights, and/or individual serial numbers of aircraft within a model series. Hence, the applicability of the AFMS should be clearly specified in the General or Introduction section of the AFMS.
  2. Since the approval is expected to be via the issue of an LSTC, the serial numbers of applicable aircraft shall be listed.
  3. The AFMS should not refer to an individual airline or an individual airline procedure since the certification is applicable to the aircraft design.

5.2  Limitations Section

  1. The AFMS must not permit any aircraft to have a maximum certified weight that exceeds that defined for the aircraft in the basic AFM.
  2. The AFMS can define more than one Alternate Maximum Certified Weight configuration. However in order to prevent confusion, the basic AFM maximum certified weight configuration should not be listed as an Alternate Maximum Certified Weight configuration.
  3. Each defined Alternate Maximum Certified Weight configuration may contain only one value of the MRW, MTOW, MLW and/or MZFW.
  4. Where the basic AFM contains a weight and balance diagram, which illustrates centre of gravity limitations as a function of aircraft weight and shows the maximum certified weights, this diagram must be revised to show the revised weights for each defined Alternate Maximum Certified Weight configuration.
  5. The AFMS must contain a statement similar to the following:

    "At the specified Alternate Maximum Certified Weights, the aircraft configuration must be controlled and the aircraft dispatched under an appropriate operator's flight release system (or equivalent flight planning, maintenance or dispatch procedures), that ensures that the flight crew knows and operates within the authorized weight limitations."

5.3  Operating Procedures Section

Normally, there are no changes required to the Operating Procedures section of the AFM. Hence, the AFMS should state that there are no changes to the procedures contained in the basic AFM.

5.4  Performance Section

  1. The Performance section of the AFM should be reviewed to determine whether the basic AFM maximum certified weight limits are specified or otherwise referenced. If so, appropriate information for the Alternate Maximum Certified Weights should be included in the Performance section of the AFMS.
  2. If computerized AFM performance data programs have input data limitations or validity checks for the basic aircraft maximum certified weights, the programs should be revised to reflect Alternate Maximum Certified Weights or alternatively, the AFMS should specify how to account for the Alternate Maximum Certified Weights.
  3. There is no credit permitted for the effect of Alternate Maximum Certified Weights on noise data.

5.5  AFMS and AFM Appendices

Existing AFMS and Appendices to the AFM should be reviewed to ensure that there are no incompatibilities between the information contained in them and the AFMS for the Alternate Maximum Certified Weights. If so, the AFMS should contain an appropriate applicability statement that specifies compatible Supplements and Appendices.


For more information please contact:
Policy Standards Coordinator (AARTC)

Phone:       613-990-8234
Facsimile:   613-996-9178

Suggestions for amendment to this document are invited and should be submitted via the Transport Canada Civil Aviation Issues Reporting System (CAIRS) at the following Internet address:

or by e-mail at:

Original signed by

D.B. Sherritt
Director, Standards
Civil Aviation

Date modified: