Why do they turn off cabin lights when aircarft take off?
Answers:
So that your eyes adjust to the lower light levels in case of an emergency/crash where you have to evacuate the aircraft in the dark. They should do this on landing as well.
The idea that they are turned off to reduce the strain on the aircraft engines is a myth. Most jet airliners only use about 92% of thrust for takeoff anyway.
to stop them from stalling the engine
If the plane doesn't make it off the runway the lit bulbs might ignite the fuel that is being sprayed all over you.
Erm. to make sure they don't attract the huge mutant moths?
So that the people waving goodbye at the airport can't see how scared the passengers are as they are trying to exit the plane.
It reduces the load on the generators, This lets you have more power to create thrust from the jet pipe or propeller as its not being sapped by the electrics.
Jono is right it's a safety measure to aid in possible evacuation.
So if something happens and you crash, you are use to it being dark already. Just a safety thing.
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