Airframe Anti-Ice / De-Ice on Avro RJ

[inthetops]

Hi, I remember to have been told, that the Manufacturer of the Avro RJ
did state a time-limit during which it is still safe do fly and pick up
airframe ice before switching the Airframe Anti-Ice system on.

Does somebody know where this is written? or if it is still:confused: true?
I have the number of 6 minutes in my head, but I am not sure!

thanks

[renard]

Our SOP's are:
1. Icing in descent - Inner wind de-ice is seclected on for one minute after ice detect light has extinguished.

2. When holding in icing conditions, Inner wing de-ice should be on for 1 minute at 8 to 10 minute intervals.

3. Inner wing de-ice must be on if airframe anti-ice is on before selecting flap18

[PEI_3721]

I doubt that there is any time at which it is considered safe to pick up ice and continue flight before selecting anti icing.
The design of the 146 / RJ anti-icing system is to be ‘evaporative’, thus preventing any ice formation. However, this does not guarantee that the system will cope with all conditions and thus the crew is required to check for ice, use de-icing, and/or leave icing conditions. E.g. “severe icing is where the rate of accumulation is such that de-icing/anti-icing equipment fails to reduce or control the hazard - immediate diversion from the flight path is necessary” (UK AIP).

The 146 / RJ de-icing system is to reinforce the anti-icing system in specific configurations / flight conditions (high lift wing) and to remove any residual ice when exiting icing conditions, re the period of 1 min as above.
The 146 / RJ has been demonstrated as safe to fly with ice on the airframe, but in such circumstances, abnormal / emergency – system failure etc, there are large speed additives and possibly other considerations.
Always follow the procedures and advice in the AFM / QRH. IIRC the section on flight in icing conditions is very comprehensive and often revised to keep up to date with current rules and knowledge.