Heat: protecting a drone’s battery and eyes in hot air and near hot equipment

Heat has two faces. One is hot ambient air — summer outdoors, desert solar plants, the inside of operating buildings. The other is flying near hot objects — furnaces, piping, flare stacks, stack exhaust. Both raise the temperature of batteries, motors and electronics, and thin the air so propellers make less lift. Radiant heat from hot surfaces warms the aircraft beyond the air temperature, just as a car bonnet heats up in the sun.

The answers are to shield the aircraft from heat, measure without getting close, and measure heat correctly. Many aircraft specify a maximum operating temperature of around 40–50 °C, so beyond that you need heat shielding or a different time of day. The key sensor is the thermal infrared camera, which finds hot spots on solar panels, damaged furnace refractory and failing pipe insulation from a distance.

Heat is common in energy and industry: solar PV plants in summer, operating process plants and plant piping, chimneys with live exhaust, boilers and furnaces still hot after shutdown, and pipelines across deserts and summer plains. The costlier it is to shut down and cool an asset, the stronger the demand to inspect it hot.

• Check the maximum operating temperature: confirm limits for aircraft and battery, and assume the aircraft runs hotter than the air temperature in sun or near equipment.
• Keep batteries in the shade: never leave them in a hot vehicle or direct sun. Do not fly an overheated battery until it has cooled.
• Set approach distance by temperature: for each hot asset, decide how close the aircraft can tolerate the radiant heat, and use zoom inside that line.
• Read the exhaust flow: check the wind at stacks and flares and approach from upwind. Never plan a path through the plume.
• Standardise thermal imaging conditions: record time, irradiance, wind, viewing angle and emissivity settings, so results can be compared with last time.
• Protect people from heat stress: build rest, water and shade for pilots and observers into the flight plan. Heat-dulled judgement leads to accidents.

Aviation law does not address heat directly, but plants and stacks often cluster hazardous materials, hazardous-area classifications and high-pressure gas equipment. Where heat meets flammable gas, an overheating battery can trigger fire or explosion. Flights at operating plants presuppose the operator’s safety-management procedures and permits.

Outdoor inspections fall under aviation rules according to height and distance from people and objects. Related: explosive atmospheres, dust & smoke, wind & turbulence, world regulations.

• Inside operating furnaces: neither people nor aircraft can enter at those temperatures. Drone inspection still mostly happens after shutdown and cooling.
• Absolute temperature: thermal cameras excel at comparison, but stating an accurate temperature needs emissivity and reflection corrections that are hard to standardise on site.
• Heat versus explosion protection: explosion-protected aircraft are sealed and trap heat. Few aircraft can work in hot hazardous areas.
• Midday in hot countries: where air temperature nears aircraft limits, the flying window shrinks and rarely coincides with the strong sun PV thermography needs.

Power stations and plants host docks with heat-tolerant aircraft that repeat thermal surveys at fixed times and under the same conditions, without stopping operations. Temperature changes are compared automatically with past records, and only places running “hotter than usual” reach a person. The days spent cooling furnaces for inspection have shrunk sharply. That is the editors’ outlook.