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Last weekend, while watching the second world war film "Fury" with a friend, there was a scene near the end with a large set of bombers flying overhead, leaving large contrails. That seemed wrong to me, as I'd thought that contrails were a jet thing, but the friend I was watching it with thought it was right. (Was a lovely shot though, accurate or not!)

That has me wondering - do propeller planes generate contrails like jets do? And if so, is it only turborops that would, or is it something all propeller planes can create?

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Yes they can. That image from wikipedia showing B-17s is more descriptive

B-17 contrail

Contrails originate from condensation of vapor coming from internal combustion engines, regardless of being turboprop, turbojet/turbofan or cylinder engine. Vapor is a byproduct of the hydrocarbon (fuel) being combusted with the atmospheric oxygen.

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    $\begingroup$ Just an addition, some contrails form due to lower pressure areas at certain angles/speeds of flight. Wingtip contrails and propeller contrails are good examples. $\endgroup$ – Alexus Jul 30 '15 at 22:36
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    $\begingroup$ @Alexus Yes but in most cases it comes from combustion and it's more prominent and visible from long distances as you can see from the image in my answer. Also OP asked _ do propeller planes generate contrails like jets do?_ The effect you describe can happen on a jet engine but will never be visible as a trail behind it. $\endgroup$ – Stelios Adamantidis Jul 31 '15 at 5:48
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    $\begingroup$ @Alexus, the low pressure "vapes" you describe is a very fleeting phenomenon compared to the persistence of exhaust contrails. $\endgroup$ – Michael Hall Apr 12 at 1:47
  • $\begingroup$ @MichaelHall Sure, but they are a real thing. $\endgroup$ – Alexus Apr 13 at 19:05
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"Contrails" is a contraction of "condensation trails" (as opposed to "chemtrails" - a contraction of "chemical trails" [think "trails" left by an agricultural crop duster aircraft as it makes an application pass over a field]).

All other things excluded, condensation trails can occur when specific conditions in the atmosphere occur - certain levels of moisture (visible or not), the mass of air that contains that moisture moving from one area of pressure to a lower area of pressure, and that mass of air moving at a velocity that is commensurate with producing a change-of-state of the moisture in that mass from a non-visible state to a visible state.

When non-visible-moisture-laden air moved rapidly from a high-pressure area to a low-pressure area a rapid change of air temperature takes place due to the expansion of the space between air molecules. In cool air water molecules clump closer together than they are in warm air, sometimes to the point that the moisture actually becomes visible.

All other things being equal, the faster the velocity of the moving air mass from the high-pressure area to the low-pressure area the more likely visible moisture will appear. That is one reason you can see visible moisture coming off the propellers of the C-130's in the photos which have been submitted to this website. The propeller tips are moving at nearly the speed of sound, their angle-of-attack relative to the air in front of them is such that they move a huge amount of air past them at a very high speed. The amount of moisture in the air is such that when it undergoes a compression/de-compression cycle as it passes the tip of the propeller blade is is quickly compressed then de-compressed and then is appears as vapor behind the propeller.

As one contributor has already explained "contrails" can also come from exhaust systems of piston-driven aircraft. Those "contrails" come from basically the same events - i.e., compression and then rapid de-compression of moisurized air. The most-often seen photographs/movies which show this effect are usually of B-29 aircraft. Most piston engines cannot operate at altitudes higher than about 20,000 feet because the air is too "thin" to sustain combustion in their cylinders. B-29's, like many other late-WW 2 aircraft - were equipped with "superchargers" - in effect very powerful "fans" which pulled in atmospheric air, compressed it, then sent it into the fuel/air intakes, thus providing sufficient oxygen to sustain the fuel burn in the cylinders. That "compressed" air naturally contained moisture - some of which did not completely get enough heat/pressure in the cylinders to be destroyed. It subsequently re-formed as condensation after it left the exhaust stack - only with a vengeance because of the extreme temperature shock it experienced going from the high temperature/pressure of the combustion cylinder to the sub-zero temperatures of altitude at the high altitude these bombers were flying at.

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  • $\begingroup$ Welcome to Aviation.SE! $\endgroup$ – Rhino Driver Jul 31 '15 at 6:47
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    $\begingroup$ This is excellent, apart from the last few sentences. Internal combustion engines are not an environment where water breaks down chemically. The contrails from engines are not because water enters the engine and "is not destroyed"; they're because fuel enters the engine and is burnt to produce water, carbon dioxide, and small amounts of other substances. Roughly speaking, every kilo of fuel that's burnt produces a little over a kilo of water and three kilos of carbon dioxide. $\endgroup$ – David Richerby Jul 31 '15 at 9:05
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    $\begingroup$ "chemtrails" is more usually reserved for the conspiracy theorists who claim that contrails are actually "secret mind control chemicals" sprayed from aircraft by <name your Evil American Agency>... $\endgroup$ – jwenting Jul 31 '15 at 10:28
  • $\begingroup$ RE: response by David Richerby $\endgroup$ – JT1000 Aug 1 '15 at 4:24
  • $\begingroup$ Perhaps a bit misleading to to refer to WW2 contrails only being possible in 'late war aircraft'. Think of the photographs of the Battle Of Britain showing trails all over the sky as spitfires & 109s fought over Britain in 1940. $\endgroup$ – Rob Oct 11 '17 at 8:05
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Yes they do. They can however have different types of contrails. Some come from propeller blade tips, while others are from engines themselves.

Here are a few examples:

Video of A Hercules C-130: C-130 Contrails

C-130 Contrails From: Contrail Science

C-130 Contrails From: Airliners.net

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    $\begingroup$ These are only short, because no water gets added in them, so they evaporate again as the vortex slows. Note that they basically don't extend aft of the wing on your second picture. Why they seem to extend further in the first picture is that as the pressure returns to normal, the exhaust plumes add the water to keep it condensed. $\endgroup$ – Jan Hudec Jul 31 '15 at 8:41
  • $\begingroup$ These are not what are usually meant by the word "contrails", i.e., long-lasting trails of condensation behind the aircraft. $\endgroup$ – David Richerby Jul 31 '15 at 8:55
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    $\begingroup$ You are correct, @DavidRicherby, but they make for some incredible pictures! $\endgroup$ – FreeMan Jul 31 '15 at 12:21
  • $\begingroup$ @FreeMan You area also correct. :-) $\endgroup$ – David Richerby Jul 31 '15 at 13:06
  • $\begingroup$ @DavidRicherby Technically, these also are contrails, as they are condensation, and they are trails behind the wing(which we can assume the propeller to be a wing of it's own type) :) $\endgroup$ – Alexus Aug 4 '15 at 16:51
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Almost all fighter and bomber aircraft had supercharges from the very start of WW2. So all of them would produce contrails at high altitude. 30,000 feet was no problem to most of these early piston engines aeroplanes. The comment about the B-29 being one of the few that produced contrails was very misleading.

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