Standard 624.56 – RVSM Requirements – Canadian Aviation Regulations (CARS)

Last amendment to standard: 2025/01/31

(effective 2025/01/31)

Definitions:

• (a) Group aircraft: Aircraft comprising a Group must be of nominally identical design and build with respect to all details that could influence the accuracy of the altitude-keeping performance. The following conditions should be met:

  1. Aircraft should be approved by the same Type Certificate (TC), TC amendment, or Supplemental Type Certificate (STC), as applicable.

  2. For derivative aircraft, it may be possible to use the database from the parent configuration to minimize the amount of additional data required to show compliance. The extent of additional data required will depend on the nature of the changes between the parent aircraft and the derivative aircraft.

  3. The static system of each aircraft should be installed in a nominally identical manner and position. The same SSEC should be incorporated in all aircraft of the Group.

  4. The avionics units installed on each aircraft to meet the minimum RVSM equipment requirements (see paragraph A.4) should be manufactured to the manufacturer’s same specification and have the same equipment part number and software part number (or version and revision).

     Note: Aircraft which have avionics units which are of a different manufacturer or equipment part number, software part number (or version and revision) may be considered part of the Group if the applicant demonstrates to the appropriate Transport Canada office this standard of avionic equipment provides identical or better system performance.

  5. The airframe manufacturer or design organization produced or provided the RVSM data package.

• (b) Non-Group aircraft: If an airframe does not meet the conditions of a Group aircraft or is presented as an individual airframe for approval, then it must be considered as a Non-Group aircraft for the purposes of RVSM approval.

General:

• (1) The aircraft shall meet the following eligibility requirements in respect of aircraft performance:

  • (a) Altimetry System Error (ASE):

    • (i) The requirements in the basic RVSM envelope are as follows:

      1. At the point in the basic RVSM envelope where ASE mean reaches its largest absolute value, the absolute value should not exceed 80 ft (25 m).

      2. At the point in the basic RVSM envelope where ASE mean plus ASE3 SD reaches its largest absolute value, the absolute value should not exceed 200 ft (60 m).

    • (ii) The requirements in the full RVSM envelope are as follows:

      1. At the point in the full RVSM envelope where ASE mean reaches its largest absolute value, the absolute value should not exceed 120 ft (37 m).

      2. At the point in the full RVSM envelope where ASE mean plus of ASE3 SD reaches its largest absolute value, the absolute value should not exceed 245 ft (75 m).

      3. If necessary, for the purpose of achieving RVSM approval for an aircraft group, an operating restriction may be established to restrict aircraft from conducting RVSM operations in areas of the full RVSM envelope where the absolute value of ASE mean exceeds 120 ft (37 m) and/or the absolute value of ASE mean plus ASE3 SD exceed 245 ft (75 m).

    • (iii) The standard for aircraft submitted for approval as Non-Group aircraft, is as follows:

      1. For all conditions in the basic RVSM envelope:

         Absolute value of Residual SSE + worst case avionics ≤ 160 ft (50m)

      2. For all conditions in the full RVSM envelope:

         Absolute value of Residual SSE + worst case avionics ≤ 200 ft (60m)

         Note: Worst-case avionics means that combination of tolerance values, specified by the manufacturer for the altimetry fit into the aircraft, which gives the largest combined absolute value for avionics errors. For most systems, this may not be a fixed value over time.

  • (b) Altitude keeping

    • (i) An automatic altitude control system shall be required and be capable of controlling altitude within ±65 ft (±20 m) about the acquired altitude when operated in straight and level flight under nonturbulent, non-gust conditions.

      Note: Aircraft types for which application for type certification or major change in type design is made on or before April 9, 1997, which are equipped with automatic altitude control systems with flight management system (FMS)/performance management system inputs allowing variations up to ±130 ft (±40 m) under nonturbulent, non-gust conditions do not require retrofit or design alteration.

      The methodology described above for Group approval is statistical in nature. This is the result of the statistical nature of the risk analysis and previous statistical statements made when developing RVSM. In the context of a statistical method, a statement that, “Each individual aircraft in the Group must be built to have ASE contained within ±200 ft,” does not mean every airframe should be calibrated with a trailing cone or equivalent to demonstrate ASE is within 200 ft. Such an interpretation would be unduly onerous. However, if any aircraft is identified as having an error exceeding ±200 ft, then it should receive corrective action.

• (2) The aircraft shall meet the following eligibility requirements in respect of aircraft equipment for RVSM Operations:

  • (a) Two Independent Altitude Measurement Systems. Each system should be composed of the following elements:

    • 1) Cross-coupled static source/system, provided with ice protection if located in areas subject to ice accretion;

    • 2) Equipment for measuring static pressure sensed by the static source, converting it to pressure altitude and displaying the pressure altitude to the flight crew;

    • 3) Equipment for providing a digitally coded signal corresponding to the displayed pressure altitude, for automatic altitude reporting purposes;

    • 4) SSEC, if needed to meet the performance requirements of paragraphs 1(a)(i) and 1(a)(ii), or 1(a)(iii), as appropriate; and

    • 5) The equipment fit should provide reference signals for automatic control and alerting at selected altitude. These signals should preferably be derived from an altitude measurement system meeting the full requirements of this document, but must in all cases meet the requirements of paragraphs 2(i) and 2(k).

  • (b) One Secondary Surveillance Radar (SSR) Altitude Reporting Transponder. If only one is fitted, it should have the capability for switching to obtain input from either altitude measurement system.

  • (c) An Altitude Alert System. The altitude alert system should be capable of operation from either of the two required independent altitude measurement systems.

  • (d) An Automatic Altitude Control System. The automatic altitude control system should be capable of operation from either of the two required independent altitude measurement systems.

  • (e) The altimetry system of an aircraft shall of all those elements involved in the process of sampling free stream static pressure and converting it to a pressure altitude output. The elements of the altimetry system fall into two main groups:

    • 1) Airframe plus static sources, including the area around the static sources in the system design that must be maintained.

    • 2) Avionics and/or instruments.

  • (f) The following altimetry system outputs are significant for RVSM operations:

    • 1) Pressure altitude (Baro Corrected) display, including the area around the static sources in the system design that must be maintained.

    • 2) Pressure altitude reporting data.

    • 3) Pressure altitude or pressure altitude deviation for an automatic altitude control device.

  • (g) The total altimetry system accuracy should satisfy the requirements of (1)(a)(i) and (1)(a)(ii) or (1)(a)(iii), as appropriate.

  • (h) If the design and characteristics of the aircraft and altimetry system are such that the requirements of paragraphs (1)(a)(i) and (1)(a)(ii) or (1)(a)(iii), are not satisfied by the location and geometry of the static sources alone, then suitable SSEC should be applied automatically within the avionic part of the altimetry system. The design aim for SSEC, whether aerodynamic/geometric or avionic, should be to produce a minimum residual SSE, but in all cases it should lead to satisfaction of the standards of paragraphs 1(a)(i) and 1 (a) (ii), or 1(a)(iii), as appropriate.

  • (i) The aircraft altimetry system shall provide an output to the aircraft transponder such that if the requirements of paragraphs (1)(a)(i) and (1)(a)(ii) or (1)(a)(iii), are not satisfied by the location and geometry of the static sources alone, then suitable SSEC should be applied automatically within the avionic part of the altimetry system. The design aim for SSEC, whether aerodynamic/geometric or avionic, should be to produce a minimum residual SSE, but in all cases, it should lead to satisfaction of the standards of paragraphs (1)(a)(i) and (1)(a)(ii) or (1)(a)(iii), as appropriate.

  • (j) During the RVSM approval process it must be verified analytically that the predicted rate of occurrence of undetected altimetry system failures does not exceed 1 x 10-5 per flight hour. All failures and failure combinations whose occurrence would not be evident from cross cockpit checks, and which would lead to altitude measurement/display errors outside the specified limits, need to be assessed against this budget. No other failures or failure combinations need to be considered.

  • (k) The altitude deviation warning system should signal an alert when the altitude displayed to the flight crew deviates from selected altitude by more than a nominal value. For aircraft for which application for type certification or major change in type design is on or before April 9, 1997, the nominal value shall not be greater than ±300 ft (±90 m). For aircraft for which application for type certification or major change in type design (e.g., STC) is made after April 9, 1997, the nominal value should not be greater than ±200 ft (±60 m). The overall equipment tolerance in implementing these nominal threshold values should not exceed ±50 ft (±15 m).

  • (l) As a minimum, a single automatic altitude control system should be installed which is capable of controlling aircraft height within a tolerance band of ±65 ft (±20 m) about the acquired altitude when the aircraft is operated in straight and level flight under nonturbulent, non-gust conditions.

    Note: Aircraft types for which application for type certification is on or before April 9, 1997, which are equipped with automatic altitude control system with FMS/performance management system inputs that allow variations up to ±130 ft (±40 m) under nonturbulent, non-gust conditions do not require retrofit or design alteration.

    Note: If specific tuning is needed for a “legacy” autopilot to meet performance standards in RVSM airspace, this gain scheduling or tuning must not negatively impact the way the autopilot performs in other phases of flight and at non-RVSM altitudes. For example, it is common for older systems to be tuned to meet RVSM tolerance, only to realize they no longer have acceptable vertical performance on a coupled approach.

  • (m) Where an altitude select/acquire function is provided, the altitude select/acquire control panel must be configured such that an error of no more than ±25 ft (±8 m) exists between the display selected by the flight crew and the corresponding output to the control system.

• (3) The aircraft is equipped with a navigation system that meets the following accuracy requirements:

  • (a) the standard deviation of lateral track errors shall be less than 6.3 NM (11.7 km);

  • (b) the proportion of total flight time spent by the aircraft 30 NM (56 km) or more off the cleared track shall be less than 5.3 x 10^-4;

  • (c) the proportion of total flight time spent by the aircraft between 50 and 70 NM (93 and 130 km) off the cleared track shall be less than 13 x 10^-4;

  • (d) with at least two fully serviceable Long Range Navigation Systems (LRNSs) capable of providing to the flight crew a continuous indication of the aircraft position relative to desired track. A LRNS may be one of the following:

    1. one Inertial Navigation System (INS);

    2. one Global Navigation Satellite System (GNSS); or

    3. one navigation system using the inputs from one or more Inertial Reference System (IRS) or any other sensor system complying with the MNPS requirement.

  • (e) All navigation data provided to flight crews, including but not limited to charts, flight plans, master documents, and track messages, must be presented in a format that ensures error-free use within the cockpit environment that must be clearly legible under the worst cockpit lighting conditions.

• (4) The operator shall ensure that the aircraft meets the following continued airworthiness maintenance requirements:

  • (a) Maintain all RVSM equipment in accordance with the component manufacturer’s maintenance requirements and the performance requirements outlined in the approved data package.

  • (b) Any modification, repair, or design change that in any way alters the initial RVSM approval shall be subject to a design review by persons approved by the Minister.

  • (c) Refer any maintenance practices that may affect the continuing RVSM approval integrity (e.g., the alignment of pitot/static probes, dents, or deformation around static plates) to the Minister or persons delegated by the Minister.

  • (d) Built-in Test Equipment (BITE) testing is not an acceptable basis for system calibrations, (unless it is shown to be acceptable by the airframe manufacturer with the Minister’s agreement) and should only be used for fault isolation and troubleshooting purposes.

  • (e) Some aircraft manufacturers have determined that the removal and replacement of components utilizing quick disconnects and associated fittings, when properly connected, will not require a leak check. While this approach may allow the aircraft to meet static system certification standards when properly connected, it does not always ensure the integrity of the fittings and connectors, nor does it confirm system integrity during component replacement and reconnections. Therefore, a system leak check or visual inspection should be accomplished any time a quick disconnect static line is broken.

    Note: If both quick disconnects are broken for any reason, a leak-check must be done.

  • (f) Maintain airframe and static systems in accordance with the airframe manufacturer’s inspection standards and procedures.

  • (g) If necessary, to ensure the proper maintenance of airframe geometry for proper surface contours and the mitigation of altimetry system error, surface measurements or skin waviness checks should be made to ensure adherence to the airframe manufacturer’s RVSM tolerances. Perform these tests and inspections as established by the airframe manufacturer. Perform these checks following repairs, or alterations that affect RVSM by having an effect on airframe surface and airflow.

  • (h) The maintenance and inspection program for the autopilot should ensure continued accuracy and integrity of the automatic altitude control system to meet the height-keeping standards for RVSM operations. This requirement will typically be satisfied with equipment inspections to ensure the equipment is serviceable.

  • (i) Where the applicant demonstrates the performance of existing equipment is satisfactory for RVSM approval, Transport Canada should verify that the existing maintenance practices are also consistent with continued RVSM approval integrity. Examples include:

    1. Altitude alert.

    2. Automatic altitude control system

    3. Air traffic control (ATC) altitude reporting equipment (ATC transponder and altitude reporting equipment and use).

    4. Altimetry systems.