What is that SPIRAL in the Jet Engine?

what is the use of this thing?. The spiral II white thing behind me and why are you not allowed to work under the wings while you're boarding the aircraft stay tuned.

So, what is the reason that we have those spirals painted on the spinner of a jet engine well the history of the spiral actually goes back to the Second World War when the first propeller aircrafts that were using during battle actually started to have these spiral markings.

They also started to paint the tips of the propeller for the same reason and you might have guessed it by now the reason for these markings are safety for ground personnel okay that's the primary reason it does have some more reasons and I'll get to that in a second but a the reason that there is a spiral marking is that it's actually showing the direction of the turning engine and it's also showing how fast the engine is turning.

If it wasn't you know painted as a spiral you wouldn't really get a sense of how fast it's turning and how fast an engine is turning is really important to know in order to kind of assess the ingestion risk of a running engine and you Justin is when when you get sucked in potentially sucked into an engine so when we stop with an aircraft when we taxi into stand .

There's going to be a lot of different personnel that is going to attend to the aircraft there's going to be people who is doing catering who is unloading and loading baggage and also fueling the aircraft and they will all be looking for signs that it is safe to approach the aircraft now the first sign that they will get is that we the pilots have turned off the anti-collision light and we turn off the anti-collision light when the m2 drops below 20 percent alright now if you want to know more about the different lights that we have in the 737 I did a video on that a few months back so check that out anyway .

So, when we see that m2 is dropped below 20 percent we turn off the anti-collision light now the engines would still be spinning at a fairly high speed by then okay and a an engine that's running only on idle trusts can suck a person into the engine if it coming in you know closer than about nine feet.

Okay an engine that's running a slightly higher trust can suck in someone that's far away as 14 feet and even further than that so that's about four five meters away so once the anti-collision light is out the ground personnel should be looking at the engine to see that swirl because as the engine is winding down one it's spinning really really fast .

It's impossible for the human eye to determine the shape of that spiral but as it's slowing down you will eventually start to see the spiral and when you see the spiral - combined with the fact the intercalation like this out then the engine is turning slowly enough for you to approach the aircraft now..

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