• Icing: Ice formation on aircraft

    One of the main ‘enemies’ on flight.

Although the general public may be unaware, for a pilot, the formation of ice in flight is one of the main enemies to combat. It may not be the case, but ice covering the wing engines or propellers can have serious consequences.

Don’t be afraid, though! Aeroplanes have systems to fight ice and we tell you all about it in our post about de-icing. The topic today is finding out about ice formation on aircraft, types of ice that can be formed and everything relating to ice formation on an airplane.


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What is icing on aircraft

As we said earlier, icing is the formation of ice or the freezing of some surfaces of an aeroplane, such as wings, propeller blades, carburetor or pitot probe, amongst others.

Some of the consequences of ice formation are:

  • The aeroplane’s weight increases because of the weight of great ice sheets.
  • Sustentation generated by the wings is significantly reduced.
  • Resistance increases, reducing aerodynamics.
  • It can cause problems in control surfaces or engines.

And why is ice formed on aircraft?

Two requirements for ice formations are the visible humidity and temperatures between 10ºC and -15ºC, even though ice can be formed at 30ºC. You don’t believe this? We will go on to explain it later, for now, let’s take a look at the different types of ice.

  • Photo: By Olivier Cleynen on Wikimedia Commons

Types of ice formation on aircraft

Different types of ice can be found on aeroplanes and we can classify it according to its appearance and the temperature at which it has formed:

Clear ice

It is formed at temperatures between 0º and -10º C and is the most dangerous icing.

Clear ice is formed when large water droplets impact upon the leading edge and freeze slowly. A sheet of transparent ice forms on the top part of the wing. It is termed extrados.

This type of ice is especially dangerous as it totally changes the shape of the leading edge, which in turn, reduces the wing’s sustentation capacity. Even though it may not seem so, ice is very heavy and affects the total weight of the aircraft.

Rime ice

It is formed at lower temperatures than clear ice, at approximately -15ºC and is the result of the practically instant freezing of small water droplets that hit the leading edge.

Mixed ice

It’s a mix of the two previous ones, which combine instantly supercooled water droplets and the large one that do so progressively.

Frost

Frost is sometimes formed when aeroplanes are left overnight outside the hangar. To put it in other words, it occurs on ground when water vapour in the air first condenses upon contact with the plane’s fuselage and then freezes.

Ice formation on fuselage.

Ice on a propeller.

Clear ice on the wing edge.

Parts of the aircraft mostly affected by icing

Propellers

Propellers are one of the parts of a plane mostly affected by icing as they’re generally located at the nose of the aeroplane and thus, one of the first parts to come into contact with supercooled water droplets.

We must remember a propeller is basically a blade turning to generate thrust force so if it becomes loaded with ice, thrust will decrease, increasing resistance and the aeroplane will lose speed.

Carburetor

Some aviation engines have a carburetor, and if you’re wondering what it is, it’s the piece that mixes fuel and air before it reaches the cylinders for combustion. This mixture must be as homogenous as possible, and does so through Venturi’s effect.

Without going into too much detail, as we’ve already explained all in the linked post, Venturi´ effect makes the mixture cool to a great extent, it is, therefore possible, to experience ice in the carburetor at outdoor temperatures of up to 30ºC.

Pitot probe

Another element that habitually suffers from icing is the pitot’s probe. This part of the aeroplane measures total pressure and static pressure, essential factors for an anemometer and altimeter to function correctly. You can read more about this in our post about the speed of aeroplanes.

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