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Ever wondered why there is a white spiral on a jet engine cone?

A Rolls Royce Trent Engine on Boeing 777-300

A Rolls Royce Trent Engine on Boeing 777-300

Most people who have flown have looked at the engine as they walked past and the keen-eyed will have noticed the white spiral painted on the (usually black) cone. but why is it there?

The most common reason people think is that its to scare birds away but whilst the “flickering” effect it produces may be a deterrent for birds, that isnt the actual reason its there.

Known as “The Comma” the white swirl is an indicator that the engine is turning and is vital for the safety of ground crews working in the vicinity of an engine.

A CFM Leap Engine on a Boeing 737 Max

Engine manufacturer SAFRAN, which produces the CFM56 & Leap engines along with GE, says that staff on the ground must keep 3 metres away from Boeing 737 engine even running at idle. At full power that exclusion extends to 5 metres otherwise, they risk being pulled over or sucked into the engine.

This means that if you are near a jet engine and you see a swirl then your safe, if its a blurred white circle, stand back!

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