Wing de iceing
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Wing de iceing
I'm working for a major which went through a merger a few years back. It's interesting to see the different "cultures" and the preferences/techniques/habits from the other outfit.
Some things are a little perplexing but I dare say that some of the things I do are equally curious to the F/Os I fly with (the ones from the other outfit).
Here's one I'd like comments on. Maybe I've been missing something.
Quite often I am asked if I "want to heat up those wings" prior to entering cloud which we both anticipate will produce wing ice. For the last 20 years I've been content to turn on wing a/i just prior to entering cloud, assuming that the leading edges reach effective temperature very quickly. Apparently there is a feeling from the f/o that one needs to turn wing a/i on earlier to reach effective temperature before entering cloud. Maybe he's right although I (unsurprisingly) doubt it.
Any comments from those who know how quickly the leading edges reach effective temperature?
Some things are a little perplexing but I dare say that some of the things I do are equally curious to the F/Os I fly with (the ones from the other outfit).
Here's one I'd like comments on. Maybe I've been missing something.
Quite often I am asked if I "want to heat up those wings" prior to entering cloud which we both anticipate will produce wing ice. For the last 20 years I've been content to turn on wing a/i just prior to entering cloud, assuming that the leading edges reach effective temperature very quickly. Apparently there is a feeling from the f/o that one needs to turn wing a/i on earlier to reach effective temperature before entering cloud. Maybe he's right although I (unsurprisingly) doubt it.
Any comments from those who know how quickly the leading edges reach effective temperature?
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What type?
Anyhow every type I've flown uses the wing heat as a DE-icer rather than an ANTI-icer. So let the ice build up bit , switch on and then switch off again when its gone, let it build up , repeat.
Boeing do say you can use as an anti but then they never seem to pick up wing ice.
Anyhow every type I've flown uses the wing heat as a DE-icer rather than an ANTI-icer. So let the ice build up bit , switch on and then switch off again when its gone, let it build up , repeat.
Boeing do say you can use as an anti but then they never seem to pick up wing ice.
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Without more info on your aircraft type, or the wing de-icing (there's the clue) system, I can only offer the SOPs with which I am familiar, explain the reasons behind them and my experience of their application (A320/321 and B737).
Wing de-icing should usually be used as just that, de-icing the wing leading edges after some ice build-up has already taken place. In continuous icing conditions, it should therefore be used intermittently, at a frequency according to the rate of ice accretion.
The reason for this is if super-cooled water droplets, as can be present in Cu clouds above the freezing layer, strike a significantly warm leading edge (as you advocate providing), they don't freeze immediately, but run some way back over the wing before freezing. This can mean that any ice build-up that does occur instead forms as clear ice behind the de-iced leading edge (so you can't then get it off, except by descending into warmer air) and causing the nasty aircraft behaviour and loss of performance which we are concerned about.
I expect there to be a deal of debate regarding the above info, as usual - but for my company, operating in temperate European conditions, it is the accepted procedure.
Engine Anti-ice is different - that remains on all the time in icing conditions and is concerned with avoiding ice build-up on the engine cowls, which can affect intake airflow and engine damage if chunks detach. Any water run-back from warm cowls gets warmed-up somewhat fairly promptly!
Wing de-icing should usually be used as just that, de-icing the wing leading edges after some ice build-up has already taken place. In continuous icing conditions, it should therefore be used intermittently, at a frequency according to the rate of ice accretion.
The reason for this is if super-cooled water droplets, as can be present in Cu clouds above the freezing layer, strike a significantly warm leading edge (as you advocate providing), they don't freeze immediately, but run some way back over the wing before freezing. This can mean that any ice build-up that does occur instead forms as clear ice behind the de-iced leading edge (so you can't then get it off, except by descending into warmer air) and causing the nasty aircraft behaviour and loss of performance which we are concerned about.
I expect there to be a deal of debate regarding the above info, as usual - but for my company, operating in temperate European conditions, it is the accepted procedure.
Engine Anti-ice is different - that remains on all the time in icing conditions and is concerned with avoiding ice build-up on the engine cowls, which can affect intake airflow and engine damage if chunks detach. Any water run-back from warm cowls gets warmed-up somewhat fairly promptly!
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I use to fly a B-707 and I confirm that in our manuals it's written to use the wing anti ice as a de icer rather than a anti icer. The only situation when you can keep the wing anti ice on and use it as a anti icer is with flaps extended during the approach.
But in the last 10 years I used it only may be 10 times.
LAF
But in the last 10 years I used it only may be 10 times.
LAF
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From the airbus 320/321 supplementary procedures:
•Wing anti-ice
WING ANTI ICE may either be used to prevent ice formation, or to remove ice
accumulation from the wing leading edges.
WING ANTI ICE should be selected ON, whenever there is an indication that airframe
icing exists. This can be evidenced by ice accumulation on the visual ice indicator
(located between the two cockpit windshields), or on the windshield wipers.
So can be used as either anti-ice or de-ice; as has been said above the clue is in the name and its labelled wing anti-ice.
•Wing anti-ice
WING ANTI ICE may either be used to prevent ice formation, or to remove ice
accumulation from the wing leading edges.
WING ANTI ICE should be selected ON, whenever there is an indication that airframe
icing exists. This can be evidenced by ice accumulation on the visual ice indicator
(located between the two cockpit windshields), or on the windshield wipers.
So can be used as either anti-ice or de-ice; as has been said above the clue is in the name and its labelled wing anti-ice.
