Approach in heavy ice condition

[PEI_3721]

‘Heavy Ice’

Standard Definitions (UK AIP 8.3.2 ‘Airframe Icing’):-

It should be noted that the following icing intensity criteria are reporting definitions; they are not necessarily the same as forecasting definitions because reporting definitions are related to aircraft type and to the ice protection equipment installed and do no involve cloud characteristics. For similar reason, aircraft icing certification criteria might differ from reporting and/or forecasting criteria.

Trace - Ice becomes perceptible. Rate of accumulation slightly greater than rate of sublimation. It is not hazardous even though de-icing/anti-icing equipment is not utilized, unless encountered for more than one hour.

Light - The rate of accumulation might create a problem if flight in this environment exceeds 1 hour. Occasional use of de-icing/anti-icing equipment removes/prevents accumulation. It does not present a problem if de-icing/anti-icing equipment is used.

Moderate - The rate of accumulation is such that even short encounters become potentially hazardous and use of de-icing/anti-icing equipment, or diversion is necessary.

Severe - The rate of accumulation is such that de-icing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.

It appears that the thread is discussing severe icing conditions and therefore these should be avoided, or if already in the conditions, leave them as soon as possible (diversion from route/altitude).

If the approach is being flown in less than severe conditions then follow the manufacturer’s recommendations; do not change procedures on myth or mistaken belief, i.e. “delay flaps extension, as ice can build up”.