Amazing Places

The Spiral on Airplane Engines Serves an Important Purpose

If you've ever gazed out an airport window at the planes taxiing around — and if you've ever been on hour three of a five-hour delay, you know you have — you've probably noticed the spiral shape on the nosecones of the airplane engines. What exactly is such a whimsical design doing on such an industrial piece of machinery? It serves an important purpose, in fact.

Look Into My Nosecone

The spiral's many reasons for being are a little controversial, but there is one that everyone agrees on: It alerts ground crews as to when the engines are spinning. Think about a ceiling fan; even though its blades are perfectly visible at rest, turn it on and they become a seemingly motionless blur. The same thing happens to engine turbines. At their high rotation rates, all visible movement stops and they turn into a deep and dangerous black hole. The spiral, meanwhile, turns into a bright white flicker that's easy to spot.

Though you'd think crews could distinguish between the silence of a stopped engine and the deafening roar of a live one, there are a few reasons they often can't. Take it from KLM Royal Dutch Airlines: "Well, there could be several engines running at once near ground crew, plus they wear hearing protection. If five engines are singing in your ears, it isn't always obvious which is running and which isn't." Knowing one from the other is literally a matter of life and death. A Boeing 787 Dreamliner, for example, has a "hazard area" of 15 feet (5 meters) around its engine. That's because if you get any closer — perhaps because you didn't know the engine was on — you could literally be sucked into the deadly blades, as several news outlets have reported happening.

United Airlines jetliner at gate, Juan Santamaria International Airport.
Airplane engine and ground services staff making the last checks before the flight.

What About Birds?

A less airtight reason? Some say it's there to protect birds. Boeing names this as a purpose, as does Rolls Royce. There isn't a lot of science to back that up, but it's possible. As KLM says, "Instead of a black hole, [birds] see the spinning spiral as a white disk, which might warn them to get away from the black hole that would lead to their untimely demise." It can only help, right?

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Written by Ashley Hamer March 24, 2017

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