Document ID: chunk:federal_register_of_legislation:F2009L03768:body:0:p3
Version: federal_register_of_legislation:F2009L03768
Segment Type: other
Provision Reference: 
Character Range: 5908–7212

performance degradation possibly due to abnormal ice accretion can be calculated.  When the performance degradation passes given thresholds, the APM annunciates warning signals by triggering up to two different levels of alerts while on climb/descent and three levels of alerts on cruise to the flight crew to make them aware of potential severe icing conditions degrading the aircraft performance.
   It is recognised that, although the ice protection system of the aeroplane is compliant with the current certification envelope for flight into known-icing conditions, the possible unsafe condition originating from a prolonged exposure to severe icing environment will be annunciated by the alert(s) provided by the APM, which has proved to be reliable during its in-service experience.
   Because the APM warning will only indicate the significant aerodynamic penalties, the current AFM Emergency Procedures for severe icing remain totally valid and applicable.  No relief to the pilot procedures concerning the current visual cues to detect severe icing conditions can result from this Directive because APM function provides flight crews with objective indications which complement and enhance the situation awareness.

James Coyne
Delegate of the Civil Aviation Safety Authority

2 September 2009