Contrails

[R1nger]

I know wew have some knowledgeable people on the group so my question is : In what circumstances are contrails formed?
We can have blue skies with trails everywhere you look but on other days there may only be tiny trails or even none at all.
Flight level is obviously a factor but why FL250 one day but only FL360 and above on other days. Often trails between FL280 to FL380 but not showing at FL400+.
Do we have a met expert who can explain how FL, Temp & humidity interact to cause the trails.

[bizfreeq]

Plenty of info on Google but as I have done it for you, try this:

https://www.faa.gov/regulations_policie ... trails.pdf

[R1nger]

Cheers Mark, excellent data. Now all I need is a source to tell me the height range and intensity on a daily basis

[T_J]

See following link. It can get quite in-depth. Hopefully of use?

https://contrailscience.com/contrail-forecast/

https://www.metabunk.org/threads/why-we ... ther.8003/

https://www.metabunk.org/threads/relati ... tion.8084/

https://www.metabunk.org/threads/calcul ... eria.7196/

[DavieB]

My favourite contrails pic https://i0.wp.com/theaviationist.com/wp ... azione.jpg

[R1nger]

Hi T_J, lots of good bedtime reading there.
I think the real answer is to look up and see what the trail situation is like on the day.
Or have a tame met-man with weather balloons and all the other kit on standby

[STN RAMP RAT]

Eurocontrol are trying to phase them out

https://www.eurocontrol.int/article/red ... g-contrail

[Nighthawke]

That will put paid to a lot of dot-spotting! But if it's better for the environment then so be it.

[R1nger]

I wonder what Gary Powers thinks about it?

[Arthur Tee]

As a former RAF Flight Ops Assistant, I remember we used to get the Contrail Levels from the Met Forecaster whilst operating the E-3D's out of Aviano over the Former Yugoslav Republic.
Rather embarrassingly I had to tell a particular Captain that he was opting to fly at a level which would expose his position to the enemy.
He thought the CFM-56 engines were 'low bypass' - and was rather shocked to find a humble Corporal telling him they were 'High Bypass'!
Fortunately a 'senior' Flight Engineer was present to support me!

It pays to be an Anorak

Arthur

[T_J]

Hi T_J, lots of good bedtime reading there.
I think the real answer is to look up and see what the trail situation is like on the day.
Or have a tame met-man with weather balloons and all the other kit on standby

Thanks for the reply. There certainly is a lot of info out there.

The US put a lot of effort into contrail avoidance and mitigation.

Contrail Avoidance and Mitigation Techniques

https://contrailscience.com/contrail-av ... echniques/

A lot of people don't realise that contrails are not just produced by the engines. Upper wing surfaces can
also generate contrails. If the conditions are correct then these can produce sheets of contrails. Some times you can get combinations
of engine and aerodynamic contrails.

https://contrailscience.com/aerodynamic ... contrails/

USAF KC-10 producing aerodynamic contrails.

https://www.youtube.com/watch?v=t22wy4c-A-A

https://www.youtube.com/watch?v=VaQ2_yHeNSM

This following video shows Airbus at different altitudes. The lower Airbus is producing aerodynamic contrails with the higher Airbus
producing engine contrails. If the conditions are correct then both types of contrails can persist.

Aerodynamic contrails caused a bit of a UFO flap in Chile during 2014. Footage filmed from a Chilean Navy helo.

https://www.metabunk.org/threads/explai ... 6830.8306/