Scientists from the US Naval Research Laboratory (NRL) are researching solutions that would enable aircraft to avoid potentially hazardous icing conditions from a safe distance.

Ice accumulates on aircraft in the air due to a weather phenomenon called supercooled liquid clouds.

NRL Remote Sensing Division electrical engineer Ian Adams said: “Clouds composed of supercooled liquid can cause aircraft to ice over quickly because the liquid water droplets are below the freezing point, and will freeze after contact with aircraft surfaces.”

Adams also noted that supercooled liquid clouds cannot be easily detected through conventional ground-based or airborne weather radars, as the equipment fails to provide information on the temperature of clouds and precipitation. The supercooled droplets are also too small to be detected by radar technology.

Both Adams and NRL colleague Justin Bobak are researching the feasibility of a new passive millimetre-wave radiometer, which would be beneficial for manned as well as unmanned aircraft.

Adams states the forward-looking passive sensor can be particularly used when size, weight, and power requirements do not allow for the installation of any de-icing tool.

The researchers commenced their investigation by observing of arctic mixed-phase cloud structures in order to develop a computer-simulated instrument response in the form of a forward-looking sensor.

Simulations were performed by using atmospheric radiative transfer simulator (ARTS), which provides advanced radiative transfer models equipped with 3D capabilities.

"Clouds composed of supercooled liquid can cause aircraft to ice over quickly because the liquid water droplets are below the freezing point."

Adams added: “So far, the model shows a strong signal at two distances when compared with a clear sky scenario.

“It shows supercooled liquid layers not visible to ground-based radar.”

It is hoped the researchers will be able to increase the set of atmospheric conditions modelled with further simulation work.

The researchers are also collaborating with a team from NRL Electronics Science and Technology division and NRL’s Optical Sciences division to find out the possibility of using graphene in the detectors in order to reduce weight, size and power to ensure compatibility with small unmanned aerial vehicles (UAVs).

Image: Crew chief with Marine Heavy Helicopter Squadron 464 brushes snow and ice off of a CH-53 Super Stallion during a deployment for training exercise aboard Camp Dawson, West Virginia, US. Photo: courtesy of US Naval Research Laboratory.