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Old 04-07-2018, 08:17 PM   #1
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Default The 747 Rainbow Challenge.

This is a 747 making it's own rainbow arch. It's an amazing photograph where a number of things have to be in the right place at the right time. A rainstorm must have left water vapor (mist) in the atmosphere, the sun, aircraft and camera all have to be in just the right place and just the right moment.

The arch is formed over and behind the wings. The tremendous vacuum produced by the wings creates a drop in air pressure and temperature that literally rips water (condensation) out of the air. The sunlight then refracts of the water droplets to form a rainbow.

Note the contrails forming off the winglets and the heat waves behind the engines. Amazing.

I did some research. I might be wrong but I believe the 747 is the only aircraft capable of doing this. I haven't found the effect in any pictures of other aircraft.

So here is the ORR.net 747 Rainbow Challenge... I think this is the only aircraft capable (or at least, documented) of making it's own rainbow arch. The challenge is to prove me wrong, find another aircraft doing the same thing. No need for a 24 hour rule. Jump on it!

No, it's not my image. Found it on the 'net. But that is a really interesting image, a KLM climbing out of Heathrow.
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Old 04-08-2018, 06:28 PM   #2
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This is a striking and beautiful image, but I don't think we're seeing a rainbow produced by an airplane.

The rainbow, if that's what it is, appears to be in the cloud ahead of the airplane. Notice that there's a white puff, clearly part of the cloud, over the starboard wing between engines 3 and 4, that is between us and the colored arc, so that it obscures that part of the arc. So the arc can't be as near to us as the airplane is.

Also, what contrails? I see the aircraft's winglets sticking up, as they do on all 747s, but no contrails. There's a light flare, likely from the bright sunlight reflecting off the starboard winglet. I think the flare is probably produced within the camera lens.

Contrails are almost always below the wing that's causing them (and below the flight path of the airplane). That's because they're floating in the air that has been pushed downward by the wing. That's how the wing produces lift, by pushing air downward. Many airplanes can produce contrails at high angles of attack and especially at low speed. The F4U Corsair of WW2 was especially notable in that regard, during hard (high G) pulls in aerial maneuver. But I think there ain't no contrails in this photo anyway.

Oh, well, what do I know anyway?

Still, it's a lovely and serendipitous photo, for sure.
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Old 04-08-2018, 07:34 PM   #3
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Quote:
Originally Posted by NN5I View Post
This is a striking and beautiful image, but I don't think we're seeing a rainbow produced by an airplane.

The rainbow, if that's what it is, appears to be in the cloud ahead of the airplane.

<snip>

Also, what contrails? I see the aircraft's winglets sticking up, as they do on all 747s, but no contrails.

<snip>

Still, it's a lovely and serendipitous photo, for sure.
I think the wings are creating a vapor cloud (which reflects the rainbow colors) as apposed to a rainbow in the distance because the rainbow appears to stop, very neatly, at the wings, If the rainbow were in the cloud ahead, that would be unlikely. At least some of the distant rainbow would be under the wing.

Each winglet appears to be trailing a thin white ribbon, the one on our right being much larger, that remind me of those silly ribbons you see in the Olympic Gymnastics. (Why do they do that?) Anyway, the "ribbon thingy" is there at the winglet tip. I don't know if the correct name is "contrail" but they seem to be made of water vapor, so i don't know what else to call them.

For the puffy white cloud over engines 3 and 4, I think both the aircraft and the rainbow are both on the other side of the small cloud. The aircraft has just taken off and it and the clouds are both very close to the ground, the rain shower having just ended. I think he has just finished retracting the landing gear.

I did a Google search on "747 rainbow" and this was one of the results. I couldn't find pictures of other aircraft "making rainbows" - only 747s - and there were several. This was the best of the bunch, IMHO. Yeah, it's a neat picture.
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