Ice accumulation on aircraft is one of the dangerous causes that can change aerodynamics, lose lift and lead to catastrophic accidents.

On November 1, a Learjet 60 commercial jet crashed into the ground almost vertically at high speed and exploded violently on the route in Palm Beach County, Florida, USA, killing all 9 people.

The recording of radio communication with the air traffic control station shows that a few minutes before the accident, the flight crew announced the discovery of ice accumulating on the plane, the outside air temperature was -47 degrees Celsius and moderate air turbulence appeared, causing the plane to sway up and down with an amplitude of about 210 m. According to data on the ADS-B Exchange aviation tracking platform, the plane dropped more than 8,000 meters in just one minute, before the data was cut off. Florida Governor Ron DeSantis described the fall as "like a rocket hitting the ground".

Historically, many accidents involving ATR propeller aircraft were caused by severe ice accumulation on the wing surface, causing a sudden decrease in lift force, leaving the crew unable to save the situation.

Danger from ice accumulation

According to the Pilot Institute, ice can build up on airplanes quickly. As long as there is visible moisture (clouds, dew, rain) and a cold surface of 0°C or below, water droplets will freeze immediately when they touch the fuselage. These two conditions are easily encountered when aircraft operate at high altitudes, forming one of the oldest and most persistent hazards in aviation.

Airplane wings work thanks to their designed shape, but ice that sticks to them will change this shape. When it accumulates on the leading edge of the wing, ice will disrupt the flow of air, reducing lift (pulling the aircraft up) and increasing drag (holding the vehicle back).

The rough ice surface alone is enough to increase drag by 50%. If the ice is thicker and more jagged, this number could potentially double. Overall, the tape can reduce lift by up to 30% and increase drag by 40%. These serious impacts can easily cause the aircraft to suddenly stall (lose lift and fall freely).

Ice doesn't just stick to the lifting surfaces of airplanes like wings. It increases weight, shifts the center of gravity, and causes vibrations, making the vehicle difficult to steer if it grips unevenly on the propeller or control surface. If the wind measuring tube (pitot tube) is clogged, the speedometer will display incorrectly, leading to an actual accident.

Ice can block the air intake, causing the engine to lack air, and worse, reduce power or cause the engine to completely shut down in mid-air. In particular, the engine can freeze even in fairly warm weather. Carburetor icing has occurred at air temperatures up to 25°C, because the reduced pressure inside cools the air to the point of freezing moisture, despite the higher temperature outside.

Aeroxplorer reports that each type of ice/frost affects aircraft to a different extent. Clear ice forms when a plane experiences freezing rain. Rainwater spreads and then freezes into a fine, heavy and long-lasting film that is difficult to see with the naked eye and clean up.

Cloudy ice occurs because microscopic supercooled water droplets in stratus clouds freeze immediately upon contact with an aircraft. They create a rough, milky white coating that accumulates very quickly on the leading edges of airplane wings.

Mixed ice is a combination of the above two types, not only has the heavy weight of clear ice, but also creates great resistance for the aircraft like opaque ice. The last type of frost is the most invisible but can still reduce wing lift, causing the plane to not reach the speed needed to take off normally.

Ice treatment measures

Most large jets use thermal anti-icing systems: hot air from the engine's compressor is routed through perforated tubes (called piccolo tubes) that run along the leading edges of the wings and tail of the plane. This keeps surface temperatures above freezing, causing water to evaporate upon contact instead of freezing into ice. Some systems operate by complete evaporation, eliminating every drop of water, while others let the water flow backward.

Smaller parts require a different approach. The pitot tube, angle of attack sensor and static pressure port use electric heaters because hot air is not feasible for such a small size. For example, the Boeing 787 places thermoelectric heating coils directly into the composite wings.

On aircraft that do not have enough power for either method, a "wing exudation" system pumps a glycol-based liquid through a grille on the leading edge of the wing, helping to lower the freezing point of the water adhering to it, preventing ice from forming. According to The Conversation, glycol is very effective in lowering the freezing point of water, making it difficult for water to freeze or maintain that state on surfaces. Propylene glycol and ethylene glycol are the two most commonly used, typically making up 30-70% of anti-freeze solutions.

Airlines also sometimes use anti-icing coatings to prevent new ice from forming and caking on outer surfaces. Smaller aircraft may use inflatable rubber strips called "pneumatic boots" on their wings, which are inflated as needed to break up ice buildup at the leading edge.

Crew are trained to activate the anti-icing system as soon as the temperature drops to 10°C or below with visible humidity, as doing so after ice appears will result in a slower and less effective de-icing process. When the plane has problems such as the heating system not being hot enough, a valve being broken or a pump malfunctioning, the vehicle can easily freeze. In that situation, the pilot cannot continue flying as before but must fly higher, lower or change direction to completely escape the ice area.

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