Here's What Those White Spirals Inside Airplane Engines Are For - White Spirals Inside Airplane Engines.jpg

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If you’ve ever traveled on a commercial airplane, there’s a likely chance you’ve
noticed those little white swirls in the center of those engines on the wings.
It may seem straightforward: to keep people on the ground advised when the
turbofan is spinning, right? But that doesn’t explain everything.

To learn more about nosecone spirals—also called spinner spirals, spinner
swirls, or nosecone swirls—I emailed Boeing, whose spokesman responded with:

....the nosecone spirals serve two purposes: one is to scare birds and the other
is to identify when the engine cone is spinning.

This agrees with what Rolls Royce—a leading maker of jet engines—had to say as
well. They described how the swirls fend off birds, saying:

"Our aerospace engines have swirls painted onto their spinners in order to
indicate when the engine is rotating while on the ground. In flight these swirls
flicker as the engine rotates at high speed, scaring birds and allowing them to
fly clear of the engine.

So to warn ground crews and to ward off birds—seems plausible. But while two
solid sources like Boeing and Rolls Royce being in agreement might make you
think we’re done here, there’s actually quite a bit of conflicting information
on all this.

There’s a lot of conflicting information about the swirl’s value as a
bird-strike prevention mechanism. For example, Boeing’s representative told me
that one of the swirl’s functions is to “scare birds,” but if you look at this
article in Boeing’s own Aero Magazine, co-written by a Ph.D. in Aviation System
Safety and a safety pilot, it says that’s not true.

In its “Common Misconceptions About Bird Strikes” section, the article includes
“airplane colors and jet engine spinner markings help to repel birds.”

Adding to confusion, despite Rolls Royce’s press release suggesting that the
swirl’s “flicker” when it rotates repels birds, online aviation blog AeroSavvy
says it received the following statement from Rolls Royce:

"The nose cone (both in terms of strength and angle) is designed to reduced bird
impact damage to the engine and reduce ice build-up. The spirals are there as a
warning to ground crew when taxiing… In flight, the spirals could not be seen by
birds as the rotation of the engine would be too fast.

So it appears that both Boeing and Rolls Royce contradict themselves on this
point.

I’ve come across plenty of other sources, including this Luftahansa Chief Pilot,
that say the swirls help keep the fowls at bay.

But unfortunately, as AeroSavvy points out, aside from a study mentioned in the
New York Times about a Japanese airline that seems to have reduced bird strikes
by painting “eyes” on Boeing 747 and 767 aircraft—and another small study on
zebra-pattern propellors that appeared to have reduced bird strikes in
Norway—there’s really not a lot of conclusive, hard research proving the spinner
swirl’s worth as a bird strike preventer.



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