Originally Posted by
Jump Complete
I wonder if the OP is confusing ‘Icing’ conditions with ‘Freezing’ conditions? I am currently mid-way through line training on the 737NG (having come from regional jets and turbo-props.) Our fleet is a mix of ‘mid-life’ (up to 20 year old, and new aircraft.)
Probe heats aren’t automatic on ours.
We have supplementary procedures for freezing (temp 3•C or less, wet runway and / or visible moisture) as distinct from ‘icing conditions’ mentioned by the OP. We performed them yesterday. Freezing conditions supplementary procedures include turning the probe heats on before start, and performing a 70% N1 runup for 30 seconds on the seconds on the runway before brakes release and TOGA being pressed.
But clearly, I appreciate different operators have varied definitions and procedures, so obviously, go with what’s in your manuals (or ask a Trainer to clarify.)
I'm not confusing the definition of icing conditions and freezing conditions, but our manual clearly directs crew to do a 30 second engine run up in case of freezing conditions, but for the use of pitot static heat (or probe on the NG), it is not clear, at least to me, when to start them on during my preflight flow. I asked a LTC and a TRI, and the general consensus seems to be also in freezing conditions.