If you are travelling frequently or if you are interested in aircraft design, you may have noticed a spiral painted on the center of the aircraft engine. Have you ever wondered what is it for? Although this spiral looks like a decorative aircraft detail, it is more than just a design element. This spiral was painted as an important safety measure.
Ground Crew warning
The primary function of the spiral is to warn the ground crew working around the aircraft that the engine is on and to ensure nobody comes up too close to the running engine. Working near a running jet engine is extraordinarily dangerous and it is important that the ground crew members can identify a running engine and stay away from it.
How is the spiral working? If the engine is off, you can clearly see the spiral in the center. When the engine is running, you will see a white almost transparent blur or a hypnotizing swirl, depending on the rotation speed of the engine.
You may know that aircraft engines make noise when they are on. And now you may be wondering how ground crew can’t hear the deafening roar of a running jet engine? Firstly, the ground crew wear the hearing protection. Secondly, there may be several aircraft engines running at the same time, thus it is not always obvious which engine is running and which isn’t.
Protection from birds
Another reason for the painted spiral is to prevent the aircraft engine from the bird strike. The idea is the same as warning the ground crew – spinning spiral notifies of the danger.
There are several studies and publications on the impact of the spiral on reducing the bird crash number, thus the opinion on this issue differs. While proponents state that the rotating spiral repels the birds from flying into the running engine, opponents claim that the engine is rotating at a high speed and it is too fast for the birds to see the spiral. The discussions continue and the theory of the spiral is still not proven scientifically. However, birds avoid planes in general before they see the spirals on the engines due to the noise produced by engines and aircraft aerodynamic.
Although, the spiral may not affect birds, it has a huge impact on the ground handling crew work environment. Even the smallest detail in aviation is designed for the safety.