Jet Engines

[mvspring]

Why do a lot of jet engines have the little white spiral in the center of them? Here is a picture of one with the spiral.

http://www.geae.com/lrgcom/cf6/cf6_comm_home.html

 

[firstthird]

birds

I'm pretty sure it is to keep the birds out. Apparently as it rotates the spiral makes the center appear to 'wobble' and that provides an illusion of motion so that birds know to get out of the way seeing as 2 pound masses and turbine blades spinning at some god-awful high rpm don't mix well. I think the problem is when a plane is coming straight at you the only motion is it getting bigger and bigger, which apparently isn't enough for your average bird to realize it is about to be smushed.

I'm not a mech though but that is what they told us out at aviation safety school in Monterey (I think, it's been a few years)

 

[Brother Francis]

Same reason propeller/rotor tips are painted. It is to alert ground crew that the engine is running so they don't walk into it.

 

[avbug]

Hermano Fransisco was correct. The purpose of painting the fan hubs is to alert ground personnel to a turning engine; it's a safety feature.

The birds couldn't give a stuff.

 

[Timebuilder]

Some birds have really good eyesight, but I doubt that they can see that swirl on the hubs as anything more than a blur at cruise engine speeds.

Who knows if they can make a decision if they see it turning at ground idle? If anything, it might look like a tasty snake wriggling in the nacelle....

 

[crosscut]

Some birds have really good eyesight, but I doubt that they can see that swirl on the hubs as anything more than a blur at cruise engine speeds.

Who knows if they can make a decision if they see it turning at ground idle? If anything, it might look like a tasty snake wriggling in the nacelle....

How about them mismatched radomes (such as a black radome on a perfectly white airplane)? Is that another safety consideration? - so that ground personnel doesn't keep bumping into airplanes; or is that to keep the birds away? - after all, if they [birds] have hard time seeing the wriggling snake, they’ll, for sure, see the one-eyed monster getting bigger and bigger at 80% of the speed of sound; or is that a maintenance shortcut? It must have something to do with keeping the birds out of harms way – I’m sure.

 

[jetexas]

The Germans in WWII would paint the whirly spirals on the spinners of fighters such as the ME-109. It was supposed to mess up an enemies 'lead' when they fired.

 

[jdog78]

I think delta has been guilty lately of having mismatched radomes, engine cowlings, etc., because they've changed their color schemes so much. I've seen a few delta birds with those hodgepodge colors
The black radomes you've seen are usually found on older aircraft. I have read that some sort of protective black paint or rubber coating was applied to the nose to protect sensitive equipment up front from lightning strikes and what not. Modern aircraft don't need it anymore...i think chines are the modern nose protection. But some airlines may actually paint their noses because they like the way it looks or to match the colors of their newer aircraft with older ones.
I'm no expert so don't take my word for it.

john