Contrail temperature

[Unregistered]

At altitude what temperature is needed for jet fuel exhaust to freeze and create a contrail?

Thanks and hello to all!

[Mick]

about -40F, or -40C. The actual physics are quite complex. See::

http://journals.ametsoc.org/doi/full...C%3E2.0.CO%3B2

[Unregistered]

So about -43 to -53 depending on humidity and pressure at say 35,000 to 40,000 ft. Wow I didn't realize it had to be that cold. Cool, learning Something new everyday.
Thx!

[firepilot]

There are different methods of preventing jet fuel icing. Prist is an additive for that, but also there can be heat exchangers that warm the jet fuel.

The BA 777 that had the crash landing, had an issue where ice in the jet fuel, traveled downstream and clogged the fuel filters.

[Mick]

So about -43 to -53 depending on humidity and pressure at say 35,000 to 40,000 ft. Wow I didn't realize it had to be that cold. Cool, learning Something new everyday.
Thx!

The thing is, it's ALWAYS cold enough at some altitude. The real variable is the relative humidity, which needs to be above 60% (approximately, it varies).