Ice shape deposit
obtained in a wind tunnel on a leading edge of a wing
When a plane flies through a supercooled1 droplets cloud, ice accretion occurs on the front parts of structure (wings, tail plane, air intakes). The ice deposit can cause, on the one hand, very important aerodynamic airfoil degradations, on the other hand, engines extinction due to ice ingestion coming from air intakes. In order to avoid icing, the pilot can supply de-icing2 or anti-icing3 protection system, when encountering icing conditions.
Based on icing wind tunnel tests, studies run at ONERA led to very accurate numerical codes, predicting the ice shape deposit.
Supercooled water : Liquid water below freezing temperature
Because of their small size (between 10 and 40 µm) the water droplets in clouds can stay in a liquid state at a temperature as low as -30°C.
De-icing : protection system against ice, removing ice that has already formed on the surface .
Several methods can be used :
pneumatic systems : tubes covering areas to be protected are periodically inflated thus splitting up ice deposit, which sheds.
thermal systems : helicopter rotor blade leading edges and some air intakes are fitted out with electrical resistances.
Anti-icing : Protection system preventing ice formation on the surface. Hot air is taken from the first engine stages and circulate inside wings leading edges.
