AIRWORTHINESS DIRECTIVE

View image in the official source

View image in the official source
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

The Limitations Section of the aircraft's Aircraft Flight Manual (AFM) by incorporating the following:

"WARNING"

Severe icing may result from environmental conditions outside of those for which the aircraft is certificated.

Flight in freezing rain, freezing drizzle, or mixed icing conditions (super cooled liquid water and ice crystals) may result in:

ice build-up on protected surfaces and exceed the capability of the ice protection system, or

ice forming aft of the protected surfaces.

This ice may not be shed using the ice protection systems, and may seriously degrade the performance and controllability of the aircraft.

During flight, severe icing conditions that exceed those for which the aircraft is certificated shall be determined by the visual cues described below. If one or more of these visual cues exists, immediately request priority handling from Air Traffic Control to facilitate a route or an altitude change to exit the icing conditions. The cues are:

unusually extensive ice accumulation on the airframe and windscreen in areas not normally observed to collect ice, and/or

accumulation of ice on the lower surface of the wing aft of the protected area, and/or

accumulation of ice on the engine nacelles and propeller spinners farther aft than normally observed.

THE FOLLOWING WEATHER CONDITIONS MAY BE CONDUCIVE TO SEVERE IN-FLIGHT ICING:

Visible rain at temperatures below 0 degrees Celsius ambient air temperature;
Droplets that splash or splatter on impact at temperatures below 0 degrees Celsius ambient air temperature.

PROCEDURES FOR EXITING A SEVERE ICING

ENVIRONMENT: (These procedures are applicable to all flight phases from take-off to landing.)

Monitor the ambient air temperature.

While severe icing may form at temperatures as cold as -18 degrees Celsius, increased vigilance is warranted at temperatures around freezing when visible moisture is present.