Vapour trails from aircraft in winter

[RedKestrel]

I was flying career mode in Battle of Moscow today and on my last mission I noticed that all of the aircraft were trailing vapour.

I don't think I've seen it before in the campaigns. And I only saw it once out of about 6 missions I flew today.

So what gives? Is this a new effect, or something that I haven't seen yet because it only happens when the temperature is low enough or something?

[Field-Ops]

It happens once you break a certain altitude. Temperature also has a great affect on what altitude it starts happening. The colder it is, the lower the altitude is for you to see it. But its been in the game for a while. Most fighting takes place at lower altitudes so its no real surprise to me that someone had not seen it yet. 

[RedKestrel]

2 minutes ago, Field-Ops said:

It happens once you break a certain altitude. Temperature also has a great affect on what altitude it starts happening. The colder it is, the lower the altitude is for you to see it. But its been in the game for a while. Most fighting takes place at lower altitudes so its no real surprise to me that someone had not seen it yet. 

This was happening at all altitudes, right down to treetop level. Temperature was -24 if I remember correctly, so maybe it was triggered by the extreme cold.

[[APAF]VR_Spartan85]

1 hour ago, RedKestrel said:

This was happening at all altitudes, right down to treetop level. Temperature was -24 if I remember correctly, so maybe it was triggered by the extreme cold.

Down on tree top level??  Cool

[-TBC-AeroAce]

Contrail height is all about the dew point

[Yogiflight]

Play 'Fire and Ice' and you will see plenty of it, at tree top level.

[ShamrockOneFive]

I was going to check but for some reason the mission editor is crashing on me right now. Does IL-2 model humidity or is it locked in at a single value?

[RedKestrel]

12 hours ago, 19//Rekt said:

Contrails...water vapor in the exhaust condenses and then flash freezes when it hits the cold air.

 

From Wikipedia:

 

The main products of hydrocarbon fuelcombustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into a cold environment, and the local increase in water vapor can raise the relative humidity of the air past saturation point. The vapor then condenses into tiny water droplets which freeze if the temperature is low enough. These millions of tiny water droplets and/or ice crystals form the contrails. The time taken for the vapor to cool enough to condense accounts for the contrail forming some distance behind the aircraft. At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation. The exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to condense rapidly. Exhaust contrails usually form at high altitudes; usually above 8,000 m (26,000 ft), where the air temperature is below −36.5 °C(−34 °F). They can also form closer to the ground when the air is cold and moist.

Oh yeah, I know roughly how they work in real life. I was just unsure it has been modeled in the game at such low altitudes. The formation of contrails must be controlled by the temperature at a given altitude in-game as well, which is really cool.

[unreasonable]

14 hours ago, RedKestrel said:

This was happening at all altitudes, right down to treetop level. Temperature was -24 if I remember correctly, so maybe it was triggered by the extreme cold.

 

I am a week or so into "Counter Attack" in early December and not seen this yet, but so far not no temperatures below about -12C IIRC. (A few close shaves but iron-man still going after 30+ hours).  So far I have only seen vapour trails at about 3km altitude.  I remember playing MP on Stalingrad maps where the vapour trail altitude was about 4.5km.   If you set up a mission on Moscow winter map with temperature at -40C (lowest allowed) you get trails down to ground level, so I am sure you are right about the cause.

 

 

Edited July 30, 2018 by unreasonable