Motivations: aircraft safety in snowfall

Different processes occurring in cold atmospheric conditions are a challenge for the aviation industry.
The risk of aircraft icing in supercooled- or mixed-phase clouds is a well-known example. Ice crystal icing, often associated with flying in high-altitude regions near deep convective systems, leads to the ingestion of ice crystals by jet engines and subsequent power loss or engine damage. Snowfall has also been reported to induce in-flight power interruptions on certain engines, while at ground level, snow accretion on aircraft is an additional threat for takeoff.

Helicopter flight tests in snowy conditions. Credits: F. Dezitter
View from the Safire ATR-42 cockpit. Credits: F. Dezitter

To comply with certification requirements addressing these risks, aircraft and helicopter manufacturers need to substantiate that each engine and its air inlet system can safely operate in snow, both falling and blowing, without adverse effect on engine operation. Concerning snowfall and blowing snow, the Federal Aviation Administration (FAA) in the Advisory Circular AC29-2C and Acceptable Means of Compliance AMC25.1093 prescribes temperature conditions to be tested between -9°C and +2°C; there are however no validated engineering tools (test facilities and numerical tools) available to support the design of air inlet systems by assessing the risk of snow accretion or accumulation in this temperature range. Demonstration is thus performed at the end of the program development during certification flights, and any issue found at this stage of the development can lead to significant delays and costs. There is therefore a clear need to better characterize the microphysical properties of snowfall, to support the development of engineering tools and de-risk design before in-flight demonstration.

ICE GENESIS work package 5

Within work package 5 (WP5) of the ICE GENESIS project, the major objective is to quantify the microphysical properties of individual snow crystals as well as entire snow crystal populations (per volume of air). These properties include for example 3D size, crystal mass, mass-size relation, fractal dimension, differentiation dry and wet snow, number and mass size distributions. These data will then serve to specify snow properties to be generated in icing wind tunnels (WP7) and simulated in numerical tools (WP10).