Cold and icing: what happens when batteries weaken and propellers ice up

Cold has two effects. The first is on the battery: lithium-ion chemistry slows when cold, and under high current the voltage sags sharply. Even fully charged, flight time shrinks, and in the worst case voltage collapses in the air. The second is icing: around and below freezing in fog, cloud or drizzle, supercooled droplets freeze the instant they hit propellers and airframe. Once the propeller shape is spoiled, lift drops, vibration rises and the aircraft can lose the ability to fly within minutes.

The answers are to warm the battery before and during use, avoid ice or escape it quickly, and adapt operations to the cold. Some aircraft have self-heating batteries, and products and research for heated propellers and airframes are emerging. But the most reliable defence against icing is still not to fly in icing conditions.

Cold and icing are unavoidable on winter ridges, coasts and in cold regions. Wind turbines on ridges and in cold climates face blade icing that is itself a subject of inspection. Pipelines across snowfields at high latitudes must be patrolled over long distances, winter included. Both are places where climbing and walking are hardest on people in winter.

• Check the minimum operating temperature: confirm the lower limits for aircraft and battery, and add margin at height where wind chill bites.
• Warm the battery before flight: carry it in an insulated case and check its temperature before take-off. Hover briefly after launch and confirm the voltage is stable before starting the inspection.
• Avoid icing conditions: do not enter freezing fog, cloud, drizzle or sleet. Assume ridges are colder and cloudier than the ground.
• Flying over snow: downward sensors may be useless over pure white snow. Rely on GNSS position hold and keep ample height.
• Move equipment without condensation: when coming back from the cold into a warm vehicle or building, let the aircraft acclimatise inside its case.
• Allow for short days: winter daylight is short. In Japan night flight needs approval, so plan to finish before sunset.

No aviation rule addresses cold itself, but winter brings conditions that push you towards night flight (which needs approval in Japan) and beyond-visual-line-of-sight operation. Snow or fog that hides the aircraft breaks the visual-line-of-sight assumption. At wind turbines, ice thrown or shed from blades can strike people on the ground, so place take-off points and crew outside the ice-fall zone.

Related: wind & turbulence, height, water, spray & humidity, world regulations.

• Continuous flight in icing: anti-icing aircraft are appearing, but small drones cannot yet fly long and confidently through icing conditions.
• Long patrols in extreme cold: batteries lose performance and snowfields offer nowhere to land and wait. Cold-region pipeline patrols still lean heavily on crewed aircraft and ground crews.
• Local icing forecasts: there is not yet a good way to predict, before flight, cloud and fog that sit only on a ridge or around a turbine.
• Winter-proof autonomous docks: docks that stay clear of snow, do not freeze and keep batteries warm are still mostly at the trial stage in cold regions.

Beside cold-region turbines and pipelines stand snow-proof docks where drones wait on warmed batteries. Icing risk is judged automatically from on-site weather sensors and forecasts: the aircraft stays down when it is dangerous and seizes every clear spell. Far fewer people freeze while climbing towers or trudging across snowfields in winter. That is the editors’ outlook.