De-icing?

[Rush2112]

OK, this is not, repeat not, a whinge or whine, or trying to be smart, but I am genuinely thirsting for information on when it is necessary: we don't often get de-iced leaving from Changi.

Many years ago I was on a Swissair flight leaving Zurich late at night, mid December, and I can believe it was pretty cold outside, as I could see the snow, so could easily see why the plane would need de-icing.

However, on Wed last (25th) I was on SQ321 ex LHR @2205, and it was a bit chilly but I know the temp was about 8C when I got out of the taxi 3 hours before that. I was slightly surprised then when the push back was delayed by 40 mins while they de-iced the plane.

So I suppose the question is, at what temp do you need to de-ice? Clearly above "freezing" point, I realise!

[Di_Vosh]

G'day Rush,

At my airline (Turboprop regional in Oz) we must Deice if there is ice/frost/snow on the aircraft (in the opinion of the ground engineer OR the Pilot - i.e. to NOT deice, both must agree that it isn't necessary). The actual temp isn't relevant for us; it is the presence of ice, frost or snow that matters.

Having said that, we don't do it much either, as the weather in Oz is pretty good. There are probably only 2 days per year that it's required at any of our capital cities (frost). It happens a lot more at some of our regional airports, and we have two airports that service our ski fields in winter (Cooma and Mt Hotham) where it happens more often.

Other airlines may have different procedures.


I'll add this bit as well (Not quite what you asked for, but anyway).

Ice protection (anti-ice) is different.

We must put the Ice Protection on when there is either:

A): Visible moisture (e.g. in cloud or rain) and the outside temperature is 5 degrees C or less when airborne

B): Same as above but 10 degrees C or less when on the ground

C): If on the ground (again 10 degrees or less) and there is standing water/slush/snow which could get ingested into the engine intakes.

Cheers,

DIVOSH!

[Don Coyote]

Rush2112,

Most airlines operate a clean wing policy so if any ice or contamination is on top of the wing then it must be removed.

In the cruise the temperature can be as low as -51 deg which cold soaks the wing and the fuel inside the wing. When you land any moisture can condense and form ice on the top of the wing. In warmer climates this disappears quite quickly but in colder temperatures such as you had at LHR then it might be a bit slow to melt and therefore require a de-ice.

Hope that helps

[Rush2112]

:ok: Great, thanks to you both.

Hopefully I can continue to generally avoid colder climes...

[leewan]

we don't often get de-iced leaving from Changi.
Correction. You will NEVER get deiced in Changi.;) It's hot as hell in there

[Rainboe]

You bet 'you don't often get de-iced leaving Changi'! Probably not till the next Ice-age!

[TURIN]

RUSH2112 (excellent album by the way)

Put a bottle of Gin or Vodka in the freezer for a few days, take it out and watch as the frost develops on the bottle. That is exactly what happens to a cold soaked wing full (or even parially full) of fuel.

If your a/c is on the ground for a while IE several hours, and the a/c is re-fuelled with warm fuel then the ice will slowly melt. Usually.

If on the other hand you are on a quick turnaround and not uplifting much fuel then the ice will not melt unless the sun is belting down or the outside air temp is +(insert Changi local here) degrees.

Hope this helps.

PS, Hemispheres is a better album IMO. :ok:

[leewan]

re-fuelled with warm fuel then the ice will slowly melt
Sometimes, chunks of ice will fall off the underside of the wing, but mostly it will start to "rain". And for some reason, i've noticed this ice forming is more common in Airbus than boeings. Especially the A330, near the inboards. And Changi's average day temp is around 24 deg celsius to 31 deg celsius.