Is there generally pilot and airplane design awareness of jet fuel freezing issues? Or is it impossible?

Question

Are pilots of commercial jet planes conscious of the risk of fuel freezing? Do they monitor the outside air temperature and/or fuel temperature gauges to ensure their fuel is not at risk of freezing? Or is the general belief that the freezing point of jet fuel is so low that it is basically impossible for it to freeze during normal operation? Do most pilots of jets even know the freezing point of jet fuel?

In passenger jet design, is fuel freezing a factor? Are fuel lines insulated? Heated? Are there systems to monitor fuel temperature and alert the crew if the fuel gets close to the freezing point? If not, is it because it is considered impossible for the fuel to get cold enough to freeze?

Thanks in advance for helpful, knowledgeable answers.

Answer 1

Yes it can freeze. Or at least gels up to the point where its unusable. It's the water in the fuel that's the problem though and most jet aircraft have fuel heaters to take care of that. Yes we have fuel tank temp. gages and such to monitor it. And no, I'll bet most of us don't know the freezing point of jet fuel anymore than we know the melting point of a turbine blade. Neither a melting turbine blade or freezing jet fuel has ever been much of a problem in aviation. If you're worried I can't help you. But I'm not and somehow I've survived four decades making safe use of kerosene.

Answer 2

yes jet fuel can freeze. the fuel temp is monitored and if it comes within 3 degrees of freezing we get a warning ie at -44 degrees for jet A-1 and -37 degrees for jet A. the fuel is heated before going into the engine, the heater actually uses the engine's oil to heat up the fuel and in turn cools the oil, one of the rare instances where you get 2 for the price of 1.

Answer 3

There is a rumor that this may have been one of the possible reasons for the 777 crash in England after a polar route flight where the temperatures were very low.  Read this excerpt from the most recent report:  

"During the flight there was a region of particularly cold

air, with ambient temperatures as low as -76ºC, in the

area between the Urals and Eastern Scandinavia. The

Met Office described the temperature conditions during

the flight as ‘unusually low compared to the average,

but not exceptional’. The lowest total air temperature

recorded during the flight was ‑45ºC, and the minimum

recorded fuel temperature was -34ºC. The specified

fuel freezing temperature for Jet A-1 is not above

‑47ºC; analysis of fuel samples taken after the accident

showed the fuel onboard the aircraft complied with the

Jet A-1 specification and had a measured fuel freezing

temperature of -57ºC. The aircraft was operated within

its certified flight envelope throughout the flight."

The whole report can be found here:  http://www.aaib.gov.uk/cms_resources/S3-...

That should show you how seriously everyone takes it.

Answer 4

Besides all that has been already mentioned( wing heating etc.) A special additive called "prist" is also added. It acts as an Icing Inhibitor.

Here's more about it:

http://en.wikipedia.org/wiki/Prist

Answer 5

most commercial aircraft have there wings sumped every week to remove water from there wings to prevent the water from freezing and causing problems. Then the fuel goes thru what they call a fuel oil cooler to heat the fuel up on the engine. The fuel is heated and the oil is cooled down. Some aircraft producers route there hydraulic lines into the fuel tank to cool the hydraulics down and heat the fuel up.The fuel lines are non insulated except in the passenger compartment where they double walled to serve the same purpose as a double wall oil tanker but in reverse if it leaks it woudn`t get in the passenger compartment. Most aircraft have some sort of gauge to tell the engine inlet fuel temp . When it comes to the 777 crash it can`t see that the fuel froze up due to the fact Boeing routes it`s hydraulic lines thru the fuel tank to cool hydraulics and heat the fuel. I believe the pilot was flying the aircraft and mad a mistake.

Answer 6

Yup, not only pilots are aware but aircraft manufacturer (design) as well that is why in the engine there is a fuel/oil heat exchanger where the cold fuel passes and gets heated by the hot oil while oil gets cooler via heat transfer. This heated fuel then goes to the pump then to the fuel spray nozzles.

Fuel booster pumps - the one that ensures a positive fuel flow from the tank to the engine are submerged in the tanks for lubrication and cooling (of the pump) in the same way pre-heating or heat transfer to the tank ensuring fuel heating too.

Not sure on the value (Training manual only use as reference) but a -20 or -40 deg C on the fuel temperature gage , pilots have to switch on their fuel heater  as part of their oper. procedure.