De-icing

[Navy_Adversary]

Last night in PRG it was extremely cold with snow squalls, the Captain told the pax of EZY 6504 that we would have to de-ice the aircraft before departure.
A lady alongside me asked why the aircraft has to be de-iced on the ground yet is OK when flying in temperatures of minus 50C at 35000 feet?

I was unable to explain, can anyone:8

[Farmer 1]

Good question.

The ice and snow on the aircraft is extra weight, which is not good for the aircraft. Also, the ice deforms the aerofoil shape of the wings, and can cause substantial loss of lifting ability. On both accounts, the ability of the aircraft to take off within the length of the runway would be very much reduced.

At 35,000 feet, the aircraft is travelling at high speed, so if it did encounter rain, most of it would wash off immediately. However, supercooled water hitting the wings is still a problem.

[Navy_Adversary]

Cheers Farmer
I think an ATR went down in the USA several years ago because of icing.
Myself I would have thought the two big aircraft manufacturers could have included some form of heating within the moving surfaces.
I realise it is not as simple as that otherwise it would already be operative.

Not sure how the military cope, 2 F3s on QRA, sorry be up in 10 mins need to de-ice, OK they are sheltered but I am not sure what happens with US carrier aircraft in artic conditions, not much room for de-icing on the carrier deck.

[North Stand Tier3]

FYI Navy Adv,the a/c does not pick up ice over the aerofoil in flt due to its motion,so little can cling to the surface as long as all contaminants are removed prior to t/off.However the leading edges do build up ice when flying in icing conditions,ie moisture in the air and sufficiently low temps(below +10',I believe).For this reason the leading edges can be heated to prevent ice formation - anti-icing - or have rubber boots fitted that are inflated on a timed cycle to break up the ice with the airflow then removing it - de-icing.Engine intakes are anti-iced too to prevent ice formation while props are de-iced electrically with deposits being flung off by centrifugal forces.
Hope this helps!

[Scoob]

An aircraft does not normally pick up ice in very cold conditions below about -15 C because the moisture in the air is already ice and therefore does not freeze onto the airframe. The worst ice is usually found at or just below freezing temperatures. They deice a plane before it departs because it is covered in heavy ice/snow etc and the deice or anti ice equipment on the plane cannot remove it. In flight the majority of the airframe is kept ice free using anti ice equipment. In case you are wondering anti ice equipment prevents the formation of ice by heating surfaces or dispersing alcohol over surfaces. Deice equipment removes ice already on the airframe usually by inflating rubber boots to crack the ice off and then it is removed by the airflow. You need to let quite a bit of ice accumulate on the deice equipment before using it.

[Scoob]

If you look at an airliner eg 737 the leading edges of the wing, tail, horiz stab are a different color and shiny, that is the anti ice bits that are heated. Also on the engine cowling. If you look at a turboprop (small turboprop) or piston, they have black where the 737 has the shiny bits, that is the deice stuff, rubber boots that inflate. Obviously not all small planes have them but then you cannot fly in iceing conditions.

[North Stand Tier3]

Scoob,no tail anti-ice on 737 Classic or 320 family-don't know about the bigger stuff but predominantly T-tails that have tail anti-ice systems.