Do you need to turn off the engine and cut off the power supply when refueling an airplane or helicopter?

The car must have stalled, but the power didn't stop. Powered by APU or ground power supply. This is usually the case, and so is the small plane I have seen.

There are many restrictions on refueling of civil aviation aircraft.

No refueling in the hangar. You can't refuel in windy and thunder weather. Hot work shall not be carried out within 0/5m from the plane/KLOC-. Don't turn on the weather radar and use high-frequency communication when refueling. When refueling, it is not allowed to operate ground power supply equipment, fill oxygen or replace oxygen cylinders. Do not use mobile phones, flashlights or walkie-talkies within 3 meters of the fuel filler or vent. ..... many rules.

By the way, the reason why the car must be closed has been mentioned above. Why can't you cut off the power? Because pressure refueling needs to open the shutoff valve, and the valve is closed when there is no electricity, so there must be electricity. Also, usually refueling is pressure refueling, and you can refuel with only battery power. It doesn't matter whether the APU or external power supply supplies power. Generally, the aircraft is powered by APU and refueled by tanker of CAO.

In addition to pressure refueling, there is gravity refueling. That can be cut off, but it is rarely used. It's usually pressure refueling.