WHY is there a SPIRAL in a JET ENGINE? Explain by CAPTAIN JOE


Dear friends and followers. Welcome back to my channel for a short video about the little swirl You can see on most jet turbine engines now once they spin they look pretty cool But do they have a specific purpose and you’ll be surprised how many different shapes and sizes are out there? So let’s get spinning Now let’s imagine you’re sitting in a terminal gazing out of the window and the incoming aircraft is taxiing towards the gate position I’m sure you’ve spotted these before which looked like one of those spinning things Fortune tellers used to mesmerize their clients Obviously that’s not their purpose and alongside the fact that they don’t have an industrial name So let’s call them spinner spirals for today’s video now The spinner itself is an aerodynamically shaped Cone or dome in the center of the fan covering the fan blade mounds many engine manufacturers like Pratt & Whitney General Electric CFM and rolls-royce Have been painting spinners with the catchy swirls for decades the practice even goes back as far as World War two When the spirals were painted on the propeller cones So the primary reason for painting designs on engine spinners is for safety of the ground personnel Now working near a running jet engine is extremely dangerous and for example at Boeing 737 engine running at idle power has a hazard zone of nine feet to the front and the sides of the engine This means that even at idle thrust, a human that walks within the hazard area, or any loose objects, Risk being sucked up Into the engine and when the engine is above idle thrust, the hazard zone increases to 14 feet or more Now not to speak of even larger hazardous zones of a Boeing 777 For example, therefore it’s absolutely critical that the ground personnel can identify A running engine and stay away from it Even though jet engines are incredibly loud a running engine may not be obvious to ground personnel Airport aprons often have several airplanes in close proximity with engines screaming next to each other Therefore ground personnel have to wear hearing protection to suppress the deafening noise and making matters worse It can be hard to see that the engine is running Especially during nighttime operation as the black-and-gray fan blades become translucent when they’re spinning Therefore spinning spirals make it a lot easier to identify a running engine and besides that Ground personnel can check if the airplane’s red anti-collision light is still flashing: this indicates that the pilots have received a start up clearance and will start the engines very soon and On arrival at the gate the light is turned off by the pilots after the engines are shut off and spiral down After which it is safe to approach the engines from either side. for the same safety reason the tips of propeller blades on propeller driven airplanes like the Dash Q400 are painted in bright colors to be more visible to the human eye and you won’t believe how many Incidents have happened in the past involving jet engines and ground personnel Do the spirals scare away birds? Now that’s a difficult question to answer and many rumors have arisen around this question Birds and aircraft engines are a bad combination Bird ingestion and bird impact casue expensive damage to the engines and the birds are not happy about it either. For years It’s been speculated that spinner spirals might startle or frighten birds away from the engine during taxi, takeoff and landing. Doing the research on this topic I found numerous explanations that made sense in my opinion However, I’m not an ornithologist but birds have the tendency to seek shelter in holes and caves. As spinning turbine Imitates a black hole so birds may be more likely to fly towards them Therefore the flickering image of the spiral startles the birds to fly near the engine Inlet. Japan’s All Nippon Airways ANA, for example, completed a year-long study. In 1986, the airline painted wobbly balls Styled eyes on the engines spinners of some of the aircraft the airline found a small reduction in bird Impacts on those airplanes so they added the markings to the rest of their fleet If you consider the cost of the $40 spinner paint job compared to ten million dollar engine replacement You would have all the spinners painted if you thought it would be even only a minor reduction in bird strikes. This has then led to many different shapes and styles that engineers and Airlines have tested on their planes. Here, for example You see the apostrophe on the Boeing 747-400 by Cathay Pacific, the most common one the G-swirl on a Boeing 777 by Emirates, the longer spiral on a Singapore Boeing 777, the typhoon or hurricane on the Philippine Airlines Airbus A330 and a few more which were really hard to find: the horseshoe the wobbly crescent, and the comma. I personally think they look cool and I like them for this safety benefit for the ground personnel as their job is dangerous enough I can’t really say if they straddle birds or not I’ve experienced numerous bird strikes with spinner spirals when without. I personally think the most effective way to Scare birds are with the landing lights, or by the airport ranger who fires a shotgun every now and then to scare the birds I’m not kidding. They really do that. And one more thing, there’s a bit of a legend that the Germans use their massive spinner spirals on the Messerschmitt fighter plane to confuse or distract allied Gunners I doubt that because at higher rpm the markings are more of a blur than an optical illusion Lighting conditions and the viewing angle would have had to be perfect for the Gunners who were confused by the spinner markings. The purpose for the spinner markings in world war II was the same as it’s now: Safety of ground personnel! That’s it for today. Thanks very much for your time I hope you enjoyed this video and don’t forget a good pilot is always learning! See you next week, all the best: your captain Joe.

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