The first thing I think I was every taught being around airplanes was to always assume those probes were hot!You have the right idea though, basically keep off until you are ready to taxi and turn them off after vacating.I'm not sure of any Boeing or airline procedure exactly, but I think it's good practice to keep them on if there's a good chance of accumulating snow/moisture on the probes...like if it was 2-3 degrees and raining or that really wet snow.

A note in my company manual says that having the pitot heat on too early can mess with the FMC planning. We don't turn it on until after start.

Ok, thanks for your input guys!

This is great, multiple RW guys covering this subject. Charles, do you fly for delta? Just guessing based on where you live.

Hi and sorry if that was mentioned before, at cruise altitude when it's -40 to -50 or through descend or climb phases when temperature is low and lots of clouds, I understand that engine anti ice won’t be necessary due to engine heat, but how about the wings and flying surface?Regards

Remember that you need two things for ice to accumulate on an aircraft:1 - Water2 - ColdnessWater + coldness = ice.If it's -40 to -50 (or even as "high" as -10), chances are the water is already ice, and will not stick to the airframe. There are minor exceptions here and there, but in general if it's less than -10, it's too cold to freeze to the plane.

Edited February 8, 201214 yr by scandinavian13

My bad, when it's -40 there wont be any water present, I got it now thank you Kyle

To be honest, I didn't really get it until someone mentioned that to me, either - you're welcome!

I will typically switch them off a little bit after we have left icing conditions and then switch them on again if any of the criteria described before is encountered again.

This is great, multiple RW guys covering this subject. Charles, do you fly for delta? Just guessing based on where you live.

I fly for one of Delta's "red-headed step children" out of ATL.

What is the correct positions for the packs and isolation valve when parked at the gate with external air conditioning unit connected?

NGX Manual Vol. 1, SP.2.1 (PDF Page 177 and 178).Note that the difference between TAT (Total Air Temperature) and SAT (Static Air Temperature) is this:TAT is the temperature of the air allowing for compressibility (as air is compressed against a moving aircraft for example, it warms up - see Boyle's Gas Law and Bernoulli).SAT is the temperature of the air outside the aircraft as measured at the airport for example and reported by ATIS.TAT is used when talking about icing as the SAT may be -1 °C but TAT could be +12 °C so rain (NOT freezing rain!) won't be much of an issue. If however TAT was +5 °C and the aircraft encountered rain, the air is cold enough that it could start accruing ice on the leading edges of wings, tail, air intakes etc.. and could cause serious problems, so at this point the anti-ice systems are switched on to prevent the start of build-up on the aircraft surfaces (anti-ice is not to be confused with de-ice - there is a subtle distinction in that one prevents ice build up to begin with, whilst the other removes ice build-up after the ice already started accumulating).If you start to get ice build up with anti-ice on you have no option but to get the hell out of whatever it is you are flying into that is causing it. Usually requires descending to warmer air as well as turning around and flying out of the conditions (if that is possible).Best regards,Robin.

The answer has already been mentioned but thanks anyway and I know 99% of what you need to know are somewhere in the documentation and I did try to find it before posting but sometimes it's not that easy to find what you're looking for and if someone with more knowlede then can give you a quick and simple answer I think that's great.

Just mentioning it - it wasn't an RTFM post. Ultimately there is no right/wrong way, just don't do things that are prohibited! :) The rest are SOPs.The difference between a good pilot and a great pilot? A good pilot knows what you can do, a great pilot knows what you can't do. If the answer is "that is what is done", you didn't understand the question.Best regards,Robin.

:(

I'm no expert on the subject, but I do know as you descend into warmer air, you'll get a TAI warning (on the CDU) when you're in temps above 10 degress celcius. So you'll turn them off before you land in most cases I think, unless you're in a cold winter setting.