According to their pattern, they have been nicknamed by aviation enthusiasts as ‘the comma’, ‘the swirl’, ‘the typhoon’, ‘the spiral’ ‘the apostrophe’, ‘the wobbly ball’ and even ‘the wobbly crescent’. We are talking about those white ‘shapes’ which adorn the spinners on the majority of commercial jet engines. The ‘spinner’ is the cone which stands in the middle of the front of the engine, around which fan blades depart. ‘Spinner spirals’ may be a good way to call them.

Their function is all but decorative, although any aviation geek could tell you how funny (and hypnotic) is to watch them when engines run at low power. Instead, they are of extreme importance for the safety of ground crews on the airport aprons to know immediately if an engine is running. One could say: jet engines are very loud… but at crowded airports, ground personnel may be surrounded by several aircraft in close proximity with engines screaming. Making things worse, ground crews wear hearing protection to suppress the deafening noise.

So… spinner spirals are attention getters, making it easy to identify a running engine with just a quick glance. Even a smaller engine at idle can have a hazard zone of up to 10 feet (3 meters), while bigger engines have a larger hazard zone. Within this zone, objects (and humans) can be sucked into the engine. It is absolutely critical that ground crews can identify a running engine and stay away from it.

Nonetheless, not all jet engines are fitted with spinner markings: the Embraer ERJ regional jets family (170, 175, 190, 195), for example, have ‘naked’ spinners and also a few Boeing 757s, 787s and 747-8s have been spotted without the swirls.

Which is your favourite, or most-effective, spinner spiral? Let the Guru know!