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An aircraft at high altitude passed by faster and higher than normal, about 50% faster when compared to others in this recording. 2 mins later it appeared that half of the contrail developed right angle pulses evenly spaced along the contrail. It took about 7 minutes to clear. Is this normal? I have complete video. 2 pics attached.

Pulses begin to appear

Aircraft passing

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    $\begingroup$ A contrail is a cloud-like stream behind a high altitude jet aircraft, a con trail is what police dogs follow to capture an escaped prisoner. $\endgroup$ Commented Jul 17, 2022 at 15:13
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    $\begingroup$ But... What if the prisoner has hijacked a high altitude jet? Eh? Think about that one? Ha! $\endgroup$
    – John K
    Commented Jul 17, 2022 at 16:24
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    $\begingroup$ I know I know, High Altitude Jet Tracking Dogs... $\endgroup$
    – John K
    Commented Jul 17, 2022 at 16:25
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    $\begingroup$ Clearly one of the mind-control-chemical sprayers had a partially clogged nozzle. 😎 $\endgroup$ Commented Jul 17, 2022 at 17:00
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    $\begingroup$ it's the lizard people sending coded messages $\endgroup$
    – RedSonja
    Commented Jul 18, 2022 at 6:55

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This phenomenon--which is not all uncommon-- is 100% meteorological. On a day when conditions favor this, you'll notice this happening in most or all of the contrails visible, or at least in most or all of the contrails in a given altitude range.

You shouldn't assume that just because the phenomenon appears to involve only one side of the contrail, that one of the (presumably two total) engines is operating differently than the other. If there is a wind shear, then parts of the contrail that ascend or descend will also move laterally relative to the main body of the contrail. In the photo, the "puffs" appear to be descending relative to the main body of the contrail. I believe I've also seen cases where the puffs appeared to be ascending, but would have to check old notes or photos to be sure.

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    $\begingroup$ Sounds reasonable, but how do you know this? $\endgroup$
    – user22445
    Commented Jul 17, 2022 at 18:22
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    $\begingroup$ Inferred due to fact that on days when it happens, it appears to involve nearly all the contrails that are visible. $\endgroup$ Commented Jul 17, 2022 at 18:25
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In 1992, Aviation Week reported on sightings of unusual contrails which were called "donuts on a rope" because they had evenly spaced puffs along a central line. The article speculated that they are the result of a "pulsed detonation wave engine", a propulsion technology which offers high efficiency at hypersonic speed.

Since then, there have been many sightings of such contrails and in many cases they were caused by conventional airplanes. The "donuts on a rope" speculation has been discredited as exactly this.

If you google for "donuts on a rope", you will find many more pictures and sometimes even a breathless comment that someone has spotted the airplane behind the black "Aurora" program. However, I am at a loss to explain how those contrails are made.

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  • $\begingroup$ @RobertDiGiovanni I prefer not to engage in speculation because I have no detail knowledge here. $\endgroup$ Commented Jul 19, 2022 at 7:56
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    $\begingroup$ Good references, thanks. $\endgroup$ Commented Jul 19, 2022 at 9:28
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When an object passes through a fluid, it can leave a Kármán vortex street. The vortex street is a common occurrence, but it is only visible when the humidity is just right.

enter image description here

Your picture shows the contrail disturbed by the plane's vortex street. The picture is taken from an odd angle that hides some the structure of the vortex.

Here is another example.

enter image description here

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Contrails are the same as the steam that comes out of you car's exhaust on a cold morning. It's condensed or crystallized water as a byproduct of burning gasoline or kerosene.

Therefore, I would say it's some kind of fuel control or airflow issue with one of the engines. The contrails are ice crystals from moisture in the engine exhaust. Certain temperatures and exhaust moisture levels will produce the contrail - drop below a threshold, and the contrail stops.

The puffs suggest that one of the engines has some oscillation in fuel flow or mass airflow, and the oscillation is taking the moisture level in the exhaust above and below the contrail formation threshold with each cycle. It may or may not be noticeable to the crew, and may not even be a problem, as in engine malfunction, just a phenomenon that occurs when conditions hit a sweet spot.

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    $\begingroup$ Took the words righ out of my keyboard. $\endgroup$
    – Jpe61
    Commented Jul 19, 2022 at 11:43
  • $\begingroup$ It’s quite possible that this kind of ‘standing wave’ or more accurately resonant airflow isn’t established until some distance behind the aircraft and so would be undetectable on the aircraft (and unlikely to be observed in a wind tunnel). $\endgroup$
    – Frog
    Commented Jul 22, 2022 at 22:05
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I’m going to speculate that the hot exhaust gases quickly cool and the water content freezes into small ice crystals. Steam turning into ice contracts significantly and so clumps of water vapour may be pulled together into blobs that are visible from the ground, under certain conditions. Under other conditions the ice crystals may remain more or less amorphous, although I can’t immediately say what conditions would favour the one over the other.

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  • $\begingroup$ This is very plausible. $\endgroup$
    – Jpe61
    Commented Jul 22, 2022 at 11:57
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SR-72 I observed this phenomenon as you care to call it from a high altitude aircraft traveling northward over California. I call it high altitude because I was able to view an airliner at altitude, we're talking what 30,000 ft or so and the contrail in question was far above it also it's rate of speed well having no instrumentation to rely on I can only say was let's just say it was moving pretty fast. Incidentally Edwards Air Force bas is to the north of me. I also observed two other high altitude contrails that strangely enough exhibited none of the unique properties being discussed here. So let's speculate a little bit, higher than normal altitude higher than normal speed unusual contrail, interesting at the very least and wouldn't it just be grand.

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    $\begingroup$ Not an answer. These are anecdotal ramblings. $\endgroup$ Commented Dec 5, 2023 at 1:37
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    $\begingroup$ This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review $\endgroup$
    – Bianfable
    Commented Dec 5, 2023 at 8:35
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    $\begingroup$ As pointed out in one of the answers this type of contrail has been seen with many types of aircraft including regular airliners. Possibly you saw this type of contrail in a high altitude military jet but there doesn't seem to be any definitive evidence that the phenomenon is based on the type of aircraft. $\endgroup$ Commented Dec 5, 2023 at 13:42

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