Airworthiness Manual Chapter 525 Appendix O - Canadian Aviation Regulations (CARs)

From: Transport Canada

Preamble

Subchapters

  • A (525.1-525.2),
  • B (525.21-525.255),
  • C (525.301-525.581),
  • D (525.601-525.899),
  • E (525.901-525.1207),
  • F (525.1301-525.1461),
  • G (525.1501-525.1587)
  • H (525.1701-525.1733)

Appendices

A, B, C, D, E, F, G, H, I, J, K, L, M, N, O

APPENDIX O

Supercooled Large Drop Icing Conditions

(effective 2021/04/08)

This Appendix consists of two parts. Part I defines this Appendix as a description of supercooled large drop icing conditions in which the drop median volume diameter (MVD) is less than or greater than 40 μm, the maximum mean effective drop diameter (MED) of Appendix C of this chapter continuous maximum (stratiform clouds) icing conditions. For this Appendix, supercooled large drop icing conditions consist of freezing drizzle and freezing rain occurring in and/or below stratiform clouds. Part II defines ice accretions used to show compliance with the aeroplane performance and handling qualities requirements of Subchapter B of this chapter.
(effective 2021/04/08)

Part I—Meteorology

In this Appendix icing conditions are defined by the parameters of altitude, vertical and horizontal extent, temperature, liquid water content, and water mass distribution as a function of drop diameter distribution.
(effective 2021/04/08)

  • (a) Freezing Drizzle (Conditions with spectra maximum drop diameters from 100μm to 500μm):
    • (1) Pressure altitude range: 0 to 22,000 feet MSL.
    • (2) Maximum vertical extent: 12,000 feet.
    • (3) Horizontal extent: Standard distance of 17.4 nautical miles.
    • (4) Total liquid water content.
    • Information Note: Liquid water content (LWC) in grams per cubic meter (g/m3) based on horizontal extent standard distance of 17.4 nautical miles.
    • (5) Drop diameter distribution: Figure 2.
    • (6) Altitude and temperature envelope: Figure 3.
      (effective 2021/04/08)
  • (b) Freezing Rain (Conditions with spectra maximum drop diameters greater than 500μm):
    • (1) Pressure altitude range: 0 to 12,000 ft MSL.
    • (2) Maximum vertical extent: 7,000 ft.
    • (3) Horizontal extent: Standard distance of 17.4 nautical miles.
    • (4) Total liquid water content.
    • Information Note: LWC in grams per cubic meter (g/m3) based on horizontal extent standard distance of 17.4 nautical miles.
    • (5) Drop Diameter Distribution: Figure 5.
    • (6) Altitude and temperature envelope: Figure 6.
      (effective 2021/04/08)
  • (c) Horizontal extent. The liquid water content for freezing drizzle and freezing rain conditions for horizontal extents other than the standard 17.4 nautical miles can be determined by the value of the liquid water content determined from Figure 1 or Figure 4, multiplied by the factor provided in Figure 7, which is defined by the following equation:

S = 1.266 – 0.213 log10(H)

Where:

S = Liquid Water Content Scale Factor (dimensionless) and

H = horizontal extent in nautical miles
(effective 2021/04/08)

Figure 1 – Appendix O, Freezing Drizzle, Liquid Water Content
(effective 2021/04/08)

appendix_o_image1
Figure 1 – Appendix O, Freezing Drizzle, Liquid Water Content

The diagram determines the value of liquid water content for freezing drizzle environments for horizontal extents other than the standard 17.4 nautical miles. The horizontal axis represents ambient temperature from -30 degrees Celsius to 5 degrees Celsius. The vertical axis represents liquid water content from 0 grams per cubic meter to 0.6 grams per cubic meter. The diagram starts on the horizontal axis from -25 degrees Celsius to 0 degrees Celsius ambient temperature. One vertical line is drawn from -25 degrees Celsius to 0.18 gram / m3 with a continuation to 0.29 gram / m3. A second vertical line is drawn from 0 degrees Celsius to 0.27 gram / m3 with a continuation to 0.44 gram / m3. A line is drawn from 0.18 gram / m3 to 0.27 gram / m3 to limit the freezing drizzle environment for drops of a median volume diameter (MVD) greater than 40 microns (light gray area). A line is drawn from 0.29 gram / m3 to 0.44 gram / m3 to limit the freezing drizzle environment for drops of a median volume diameter (MVD) less than 40 microns (dark and light gray area).

Figure 2 – Appendix O, Freezing Drizzle, Drop Diameter Distribution
(effective 2021/04/08)

appendix_o_image2
Figure 2 – Appendix O, Freezing Drizzle, Drop Diameter Distribution

The diagram determines the drop diameter distribution in freezing drizzle conditions. The diagram is displayed on a logarithmic scale starting on the horizontal axis from 0 diameter in microns to 1000. The vertical axis represents “Cumulative Mass” and is drawn from the 0 diameter micron to limit the freezing drizzle environment for drops of a median volume diameter (MVD) of less than or for greater than 40 microns. A first curve is drawn through the actual points from 0 to 1 cumulative mass to show the freezing drizzle drop diameter distribution of a median volume diameter (MVD) less than 40 microns. A second curve is drawn through the actual points from 0 to 1 cumulative mass to show the freezing drizzle drop diameter distribution of a median volume diameter (MVD) greater than 40 microns.

Figure 3 – Appendix O, Freezing Drizzle, Temperature and Altitude
(effective 2021/04/08)

appendix_o_image3
Figure 3 – Appendix O, Freezing Drizzle, Temperature and Altitude

The diagram determines the altitude and temperature envelope in freezing drizzle conditions. The horizontal axis represents pressure altitude from 0 to 25,000 feet. The vertical axis represents ambient temperature from -30 degrees Celsius to 5 degrees Celsius. The freezing drizzle envelope starts from 0 feet pressure altitude on a horizontal line from -25 degrees Celsius to 22,000 feet pressure altitude. At 22,000 feet, the line becomes vertical till -20 degrees Celsius. At this point, the line becomes a negative slope that extends upward till 12, 000 feet pressure altitude. At 12,000 feet, the line continues to the left on horizontal along the 0 degrees Celsius line to reach the 0 feet pressure altitude. The gray shaded area is the envelope.

Figure 4 – Appendix O, Freezing Rain, Liquid Water Content
(effective 2021/04/08)

appendix_o_image4
Figure 4 – Appendix O, Freezing Rain, Liquid Water Content

The diagram determines the value of liquid water content for two freezing rain environments for horizontal extents other than the standard 17.4 nautical miles. The freezing rain environments are made up of supercooled large drops whose median volume diameter (MVD) is less than or greater than 40 microns. The horizontal axis represents ambient temperature from -30 degrees Celsius 0 to 5 degrees Celsius. The vertical axis represents liquid water content from 0 grams per cubic meter to 0.6 grams per cubic meter. The diagram starts on the horizontal axis from -30 degrees Celsius to 5 degrees Celsius ambient temperature. One vertical line is drawn from -13 degrees Celsius to 0.21 gram / m3 with a continuation to 0.25 gram / m3. A second vertical line is drawn from 0 degrees Celsius to 0.26 gram / m3 with a continuation to 0.31 gram / m3. A line is drawn from 0.21 gram / m3 to 0.26 gram / mm3 to limit the freezing rain environment for drops of a median volume diameter (MVD) greater than 40 microns (light gray area). A line is drawn from 0.25 gram / m3 to 0.31 gram / m3 to limit the freezing rain environment for drops of a median volume diameter (MVD) less than 40 microns (dark and light gray area).

Figure 5 – Appendix O, Freezing Rain, Drop Diameter Distribution
(effective 2021/04/08)

appendix_o_image5
Figure 5 – Appendix O, Freezing Rain, Drop Diameter Distribution

The diagram determines the drop diameter distribution in freezing rain conditions. The freezing rain environments are made up of supercooled large drops whose median volume diameter (MVD) is less than or greater than 40 microns. The diagram is displayed on a logarithmic scale starting on the horizontal axis from 0 diameter in microns to beyond 1000. The vertical axis represents “Cumulative Mass” and is drawn from the 0 diameter micron to limit the freezing rain environment for drops of a median volume diameter (MVD) of less than or for greater than 40 microns. A first curve is drawn through the actual points from 0 to 1 cumulative mass to show the freezing rain drop diameter distribution of a median volume diameter (MVD) less than 40 microns. A second curve is drawn through the actual points from 0 to 1 cumulative mass to show the freezing rain drop diameter distribution of a median volume diameter (MVD) greater than 40 microns.

Figure 6 – Appendix O, Freezing Rain, Temperature and Altitude
(effective 2021/04/08)

appendix_o_image6
Figure 6 – Appendix O, Freezing Rain, Temperature and Altitude

The diagram determines the altitude and temperature envelope in freezing rain conditions. The horizontal axis represents pressure altitude from 0 to 25,000 feet. The vertical axis represents ambient temperature from -30 degrees Celsius to 5 degrees Celsius. The freezing rain envelope starts at 0 pressure altitude on a line from -13 degrees Celsius to 12,000 feet pressure altitude. At 12,000 feet, the line is drawn horizontal along the 0 degrees Celsius line to reach the 0 feet pressure altitude. The gray shaded area is the envelope.

Figure 7 – Horizontal Extent, Freezing Drizzle and Freezing Rain
(effective 2021/04/08)

appendix_o_image7
Figure 7 – Horizontal Extent, Freezing Drizzle and Freezing Rain

The diagram shows the factor needed to multiply by to determine the liquid water content for freezing drizzle and freezing rain conditions for horizontal extents other than the standard 17.4 nautical miles when multiplied by the value of the liquid water content determined from Figure 1 or Figure 4. The diagram is displayed on a logarithmic scale starting on the horizontal axis representing cloud horizontal extent from 1 to over 100 nautical miles. The vertical axis represents the liquid water content scale factor from 0 to 2. At 1 (100) nautical mile, the line is drawn starting slightly above 1.2 along a negative slope defined by a liquid water content scale factor of 0.8 using the equation below.

The Figure 7 factor is defined by the following equation:

S = 1.266 – 0.213 log10(H)

Where:

S = Liquid Water Content Scale Factor (dimensionless) and

H = horizontal extent in nautical miles

Part II - Airframe Ice Accretions for Showing Compliance with Subchapter B of this Chapter

(effective 2021/04/08)

  • (a) General. The most critical ice accretion in terms of aeroplane performance and handling qualities for each flight phase shall be used to show compliance with the applicable aeroplane performance and handling qualities requirements for icing conditions contained in Subchapter B of this chapter. Applicants shall demonstrate that the full range of atmospheric icing conditions specified in Part I of this Appendix have been considered, including drop diameter distributions, liquid water content, and temperature appropriate to the flight conditions (for example, configuration, speed, angle of attack, and altitude).
    • (1) For an aeroplane certified in accordance with 525.1420(a)(1), the ice accretions for each flight phase are defined in part II, paragraph (b) of this Appendix.
    • (2) For an aeroplane certified in accordance with 525.1420(a)(2), the most critical ice accretion for each flight phase defined in part II, paragraphs (b) and (c) of this Appendix, must be used. For the ice accretions defined in part II, paragraph (c) of this Appendix, only the portion of part I of this Appendix in which the aeroplane is capable of operating safely must be considered.
    • (3) For an aeroplane certified in accordance with 525.1420(a)(3), the ice accretions for each flight phase are defined in part II, paragraph (c) of this Appendix.
      (effective 2021/04/08)
  • (b) Ice accretions for aeroplanes certified in accordance with 525.1420(a)(1) or (2).
    • (1) En route ice is the en route ice as defined by part II, paragraph (c)(3), of this Appendix, for an aeroplane certified in accordance with 525.1420(a)(2), or defined by part II, paragraph (a)(3), of Appendix C of this chapter, for an aeroplane certified in accordance with 525.1420(a)(1), plus:
      • (i) Pre-detection ice as defined by part II, paragraph (b)(5), of this Appendix; and
      • (ii) The ice accumulated during the transit of one cloud with a horizontal extent of 17.4 nautical miles in the most critical of the icing conditions defined in part I of this Appendix and one cloud with a horizontal extent of 17.4 nautical miles in the continuous maximum icing conditions defined in Appendix C of this chapter.
    • (2) Holding ice is the holding ice defined by part II, paragraph (c)(4), of this Appendix, for an aeroplane certified in accordance with 525.1420(a)(2), or defined by part II, paragraph (a)(4), of Appendix C of this chapter, for an aeroplane certified in accordance with 525.1420(a)(1), plus:
      • (i) Pre-detection ice as defined by part II, paragraph (b)(5), of this Appendix; and
      • (ii) The ice accumulated during the transit of one cloud with a 17.4 nautical miles horizontal extent in the most critical of the icing conditions defined in part I of this Appendix and one cloud with a horizontal extent of 17.4 nautical miles in the continuous maximum icing conditions defined in Appendix C of this chapter.
      • (iii) Except the total exposure to holding ice conditions does not need to exceed 45 minutes.
        (effective 2021/04/08)
    • (3) Approach ice is the more critical of the holding ice defined by part II, paragraph (b)(2), of this Appendix, or the ice calculated in the applicable paragraphs (b)(3)(i) or (ii) of part II, of this Appendix:
      • (i) For an aeroplane certified in accordance with 525.1420(a)(2), the ice accumulated during descent from the maximum vertical extent of the icing conditions defined in part I of this Appendix to 2,000 feet above the landing surface in the cruise configuration, plus transition to the approach configuration, plus:
        • (A) Pre-detection ice, as defined by part II, paragraph (b)(5), of this Appendix; and
        • (B) The ice accumulated during the transit at 2,000 feet above the landing surface of one cloud with a horizontal extent of 17.4 nautical miles in the most critical of the icing conditions defined in part I of this Appendix and one cloud with a horizontal extent of 17.4 nautical miles in the continuous maximum icing conditions defined in Appendix C of this chapter.
      • (ii) For an aeroplane certified in accordance with 525.1420(a)(1), the ice accumulated during descent from the maximum vertical extent of the maximum continuous icing conditions defined in part I of Appendix C to 2,000 feet above the landing surface in the cruise configuration, plus transition to the approach configuration, plus:
        • (A) Pre-detection ice, as defined by part II, paragraph (b)(5), of this Appendix; and
        • (B) The ice accumulated during the transit at 2,000 feet above the landing surface of one cloud with a horizontal extent of 17.4 nautical miles in the most critical of the icing conditions defined in part I of this Appendix and one cloud with a horizontal extent of 17.4 nautical miles in the continuous maximum icing conditions defined in Appendix C of this chapter.
          (effective 2021/04/08)
    • (4) Landing ice is the more critical of the holding ice as defined by part II, paragraph (b)(2), of this Appendix, or the ice calculated in the applicable paragraphs (b)(4)(i) or (ii) of part II of this Appendix:
      • (i) For an aeroplane certified in accordance with 525.1420(a)(2), the ice accretion defined by part II, paragraph (c)(5)(i), of this Appendix, plus a descent from 2,000 feet above the landing surface to a height of 200 feet above the landing surface with a transition to the landing configuration in the icing conditions defined in part I of this Appendix, plus:
        • (A) Pre-detection ice, as defined in part II, paragraph (b)(5), of this Appendix; and
        • (B) The ice accumulated during an exit manoeuvre, beginning with the minimum climb gradient required by 525.119, from a height of 200 feet above the landing surface through one cloud with a horizontal extent of 17.4 nautical miles in the most critical of the icing conditions defined in part I of this Appendix and one cloud with a horizontal extent of 17.4 nautical miles in the continuous maximum icing conditions defined in Appendix C of this chapter.
      • (ii) For an aeroplane certified in accordance with 525.1420(a)(1), the ice accumulated in the maximum continuous icing conditions defined in Appendix C of this chapter, during a descent from the maximum vertical extent of the icing conditions defined in Appendix C of this chapter, to 2,000 feet above the landing surface in the cruise configuration, plus transition to the approach configuration and flying for 15 minutes at 2,000 feet above the landing surface, plus a descent from 2,000 feet above the landing surface to a height of 200 feet above the landing surface with a transition to the landing configuration, plus:
        • (A) Pre-detection ice, as described by part II, paragraph (b)(5), of this Appendix; and
        • (B) The ice accumulated during an exit manoeuvre, beginning with the minimum climb gradient required by 525.119, from a height of 200 feet above the landing surface through one cloud with a horizontal extent of 17.4 nautical miles in the most critical of the icing conditions defined in part I of this Appendix and one cloud with a horizontal extent of 17.4 nautical miles in the continuous maximum icing conditions defined in Appendix C of this chapter.
          (effective 2021/04/08)
    • (5) Pre-detection ice is the ice accretion before detection of flight conditions in this Appendix that require exiting per 525.1420(a)(1) and (2). It is the pre-existing ice accretion that may exist from operating in icing conditions in which the aeroplane is approved to operate prior to encountering the icing conditions requiring an exit, plus the ice accumulated during the time needed to detect the icing conditions, followed by two minutes of further ice accumulation to take into account the time for the flight crew to take action to exit the icing conditions, including coordination with air traffic control.
      • (i) For an aeroplane certified in accordance with 525.1420(a)(1), the pre-existing ice accretion shall be based on the icing conditions defined in Appendix C of this chapter.
      • (ii) For an aeroplane certified in accordance with 525.1420(a)(2), the pre-existing ice accretion shall be based on the more critical of the icing conditions defined in Appendix C of this chapter, or the icing conditions defined in part I of this Appendix in which the aeroplane is capable of safely operating.
        (effective 2021/04/08)
  • (c) Ice accretions for aeroplanes certified in accordance with 525.1420(a)(2) or (3). For an aeroplane certified in accordance with 525.1420(a)(2), only the portion of the icing conditions of part I of this Appendix in which the aeroplane is capable of operating safely shall be considered.
    • (1) Take-off ice is the most critical ice accretion on unprotected surfaces, and any ice accretion on the protected surfaces, occurring between the end of the take-off distance and 400 feet above the take-off surface, assuming accretion starts at the end of the take-off distance in the icing conditions defined in part I of this Appendix.
    • (2) Final take-off ice is the most critical ice accretion on unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, between 400 feet and either 1,500 feet above the take-off surface, or the height at which the transition from the take-off to the en route configuration is completed and VFTO is reached, whichever is higher. Ice accretion is assumed to start at the end of the take-off distance in the icing conditions defined in part I of this Appendix.
    • (3) En route ice is the most critical ice accretion on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, during the en route flight phase in the icing conditions defined in part I of this Appendix.
    • (4) Holding ice is the most critical ice accretion on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, resulting from 45 minutes of flight within a cloud with a 17.4 nautical miles horizontal extent in the icing conditions defined in part I of this Appendix, during the holding phase of flight.
    • (5) Approach ice is the ice accretion on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, resulting from the more critical of the:
      • (i) Ice accumulated in the icing conditions defined in part I of this Appendix during a descent from the maximum vertical extent of the icing conditions defined in part I of this Appendix, to 2,000 feet above the landing surface in the cruise configuration, plus transition to the approach configuration and flying for 15 minutes at 2,000 feet above the landing surface; or
      • (ii) Holding ice as defined by part II, paragraph (c)(4), of this Appendix.
    • (6) Landing ice is the ice accretion on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, resulting from the more critical of the:
      • (i) Ice accretion defined by part II, paragraph (c)(5)(i), of this Appendix, plus ice accumulated in the icing conditions defined in part I of this Appendix during a descent from 2,000 feet above the landing surface to a height of 200 feet above the landing surface with a transition to the landing configuration, followed by a go-around at the minimum climb gradient required by 525.119, from a height of 200 feet above the landing surface to 2,000 feet above the landing surface, flying for 15 minutes at 2,000 feet above the landing surface in the approach configuration, and a descent to the landing surface (touchdown) in the landing configuration; or
      • (ii) Holding ice as defined by part II, paragraph (c)(4), of this Appendix.
    • (7) For both unprotected and protected parts, the ice accretion for the take-off phase shall be determined for the icing conditions defined in part I of this Appendix, using the following assumptions:
      • (i) The airfoils, control surfaces, and, if applicable, propellers are free from frost, snow, or ice at the start of take-off;
      • (ii) The ice accretion starts at the end of the take-off distance;
      • (iii) The critical ratio of thrust/power-to-weight;
      • (iv) Failure of the critical engine occurs at VEF; and
      • (v) Crew activation of the ice protection system is in accordance with a normal operating procedure provided in the aeroplane flight manual, except that after beginning the take-off roll, it must be assumed that the crew takes no action to activate the ice protection system until the aeroplane is at least 400 feet above the take-off surface.
        (effective 2021/04/08)
  • (d) The ice accretion before the ice protection system has been activated and is performing its intended function is the critical ice accretion formed on the unprotected and normally protected surfaces before activation and effective operation of the ice protection system in the icing conditions defined in part I of this Appendix. This ice accretion only applies in showing compliance to 525.143(j) and 525.207(h).
    (effective 2021/04/08)
  • (e) In order to reduce the number of ice accretions to be considered when demonstrating compliance with the requirements of 525.21(g), any of the ice accretions defined in this Appendix may be used for any other flight phase if it is shown to be at least as critical as the specific ice accretion defined for that flight phase. Configuration differences and their effects on ice accretions must be taken into account.
    (effective 2021/04/08)
  • (f) The ice accretion that has the most adverse effect on handling qualities may be used for aeroplane performance tests provided any difference in performance is conservatively taken into account.
    (effective 2021/04/08)

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