Trailspotter
Senior Member.
Better late than never. I've just stumble upon an eight month old airliners.net thread describing the most unusual contrail:
The planefinder.net playback suggests the photos were taken at about 18:10 BST (17:10 UTC)
As none of the proposed explanations in the airliners.net discussion sounds convincing, I suggest here a new plausible explanation.
Apart of the gaps, the two dashed trails look very much like a typical pair of hybrid contrails, the parallel linear trails formed by the parts of exhaust contrails entrained into the plane wake vortices. In non-persistent conditions, the hybrid contrails will outlast the ordinary exhaust contrails, but they eventually will break up due to the Crow instability:
The parallel dashed trails occur fairly close to the plane and therefore the gaps in them cannot be attributed to the Crow instability. It is the most likely that the vortices are still intact in the gaps between the dashes, but, for some reason, they did not entrain any exhaust condensation in these segments.
Such gapped hybrid contrails may be specific to the A380 aircraft. It appears that only a portion of its exhaust contrails can be entrained into the wake vortices at a considerable distance behind the aircraft. Depending on atmospheric conditions, it can happen that exhaust contrail is entrained only on one side, like in the following popular video:
In the beginning, there is just one linear trail on the port side, behind fairly symmetrical exhaust contrail, whereas the second trail on the starboard side appears later (from 0:39). As the camera zooms out, we can see a gap in the starboard trail and a segment of weaker density in the port trail, staggered relative the gap:
It is possible that, in the presence of some kind of an atmospheric wave, the entrained portions of exhaust contrail will alternate between the sides, like in the OP images and, in a lesser extent, in the following cockpit video:
As none of the proposed explanations in the airliners.net discussion sounds convincing, I suggest here a new plausible explanation.
Apart of the gaps, the two dashed trails look very much like a typical pair of hybrid contrails, the parallel linear trails formed by the parts of exhaust contrails entrained into the plane wake vortices. In non-persistent conditions, the hybrid contrails will outlast the ordinary exhaust contrails, but they eventually will break up due to the Crow instability:
The parallel dashed trails occur fairly close to the plane and therefore the gaps in them cannot be attributed to the Crow instability. It is the most likely that the vortices are still intact in the gaps between the dashes, but, for some reason, they did not entrain any exhaust condensation in these segments.
Such gapped hybrid contrails may be specific to the A380 aircraft. It appears that only a portion of its exhaust contrails can be entrained into the wake vortices at a considerable distance behind the aircraft. Depending on atmospheric conditions, it can happen that exhaust contrail is entrained only on one side, like in the following popular video:
In the beginning, there is just one linear trail on the port side, behind fairly symmetrical exhaust contrail, whereas the second trail on the starboard side appears later (from 0:39). As the camera zooms out, we can see a gap in the starboard trail and a segment of weaker density in the port trail, staggered relative the gap:
It is possible that, in the presence of some kind of an atmospheric wave, the entrained portions of exhaust contrail will alternate between the sides, like in the OP images and, in a lesser extent, in the following cockpit video:
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