Snowflake Arizona, Broken Sunrise Contrail, [Likely FedEx 806]

Mick West

Administrator
Staff member

upload_2015-9-19_22-50-5.png


upload_2015-9-19_22-49-30.png

https://www.facebook.com/video.php?v=10205155232663724

Interesting sunrise contrail, not sunset like most of this type of thing. Less commonly observed, mostly because people are still in bed. Here the contrail develops in sections as it passes through bands of moisture. You can see those bands of moisture reflected somewhat in the bands of cloud (although the clouds are probably not at the exact same altitude).

The biggest misconception with this type of thing is that it's fly "vertically" (like, straight down). It's not, it's just flying in a way so that the contrail is lined up with the camera. For more on this illusion, see:
http://contrailscience.com/contrails-are-usually-horizontal/

Arizona is in the MST time zone (no summer time), that is UTC-7, so this is 1300 to 1400 UTC on 9/19/2015. Without a precise time it's hard to say which plane it was. At around that time there's three FedEx planes playing over Snowflake heading east. FDX806 was the highest at 37,000 to 39,000ft, and this seems like the most likely candidate. It's a twin engined 777, quite a large plane, which matches the visual appearance of the contrail quite well (although I would not entirely rule out a trijet).

One thing to remember when looking at contrails like this, with the forced perspective, is that the angle of the trail doe not indicate the direction of travel, as it will usually be blown from it by the wind, and the perspective greatly magnifies this effect. It looks like the viewer is to the south of the trail (which is descending to the east), but Snowflake itself is actually to the North of the GPS track (attached).

 

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deirdre

Senior Member.
neat footage. i understand it, but good luck explaining this one to the chemmies :)


its cool too toward the end, it shows how the digital cameras react to light conditions when she shows the sun itself.. you can watch the camera try to reajust. cool.
out3.PNG
 

Trailblazer

Moderator
Staff member
I wonder if the position of the sun could help narrow it down? Correcting for altitude (1732m), sunrise for Snowflake was at 5.59am on a bearing of 86.6 degrees.

I looked at this same video before I was aware of this thread, and I thought it was probably FedEx 691. That would have been in the right position at around 6.10 to 6.15am. The sun looks as though it has only just risen, so I'm erring towards this earlier flight. It's hard to know where the true horizon is, though.
 

Mick West

Administrator
Staff member
I wonder if the position of the sun could help narrow it down? Correcting for altitude (1732m), sunrise for Snowflake was at 5.59am on a bearing of 86.6 degrees.

I looked at this same video before I was aware of this thread, and I thought it was probably FedEx 691. That would have been in the right position at around 6.10 to 6.15am. The sun looks as though it has only just risen, so I'm erring towards this earlier flight. It's hard to know where the true horizon is, though.

You could be correct. It's a 767, and I'd favored 806 because it was a 777 - I'd got the impression that all the other planes were MD-80s. With the viewpoint at the main intersection in Snowflake (77 and 277, Main and Ramsey), then as 691 approaches the horizon the track matches the trail and the sun very well.



Then when 806 approaches the horizon it passes from right to left under the sun.


However in the video the sun (to the right of the trail) appears to be visible over a small hill, which suggests maybe a bit later than actual sunrise.


So I'm leaning more towards 691, but ideally we need a better viewpoint and time.
 

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