Why does the engine fan seem to be rotating the other way?

Source: YouTube, 2018

Why does the engine fan seem to stop for a while and then rotate the other way when it’s spooled up?

The fan blades are spinning so fast that when you look at it or take a video it seems to stop and spin the other way and keep doing that. It like an optical illusion because of how fast its spinning. Dont worry it’s going the right way still


Indeed, i believe its called ‘stroboscopic effect’

Its to do with how many ‘frames’ our eyes and brain can process before it starts filling in the blanks and gives the illusion that the blades are moving backwards, same effect can be seen on car wheels

No doubt someone here will give a very detailed scientific explaination 🙂


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If you can handle the “bot voice” here is a short video on it

I’d say you handled the explanation pretty well already! I’ve noticed that with props and fans but never stopped to question why, so thanks!

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