Fuel Type

[OKD]

Hi guys...

Just a quick question...

What type of jet fuel to be used if a 744 flies from a freezing LHR to say SIN (hot and humid weather) OR VICE-VERSA?

I remember that I read somewhere in the PS manuel which explained different type of jet fuel for different weather / temperature conditions.

How does this actually work (choosing jet fuel)?

Impart some knowledge into me please? :mrgreen:

[Jeroen Hoppenbrouwers]

You look what is for sale at the airport where you are and that is what you get  

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

"Jet A specification fuel has been used in the United States since the 1950s and is only available in the United States, whereas Jet A-1 is the standard specification fuel used in the rest of the world."

[John H Watson]

You look what is for sale at the airport where you are and that is what you get

This is basically correct.

When aircraft arrive from the USA (carrying JetA), we have to ensure that the next 3 flights do not go on long sectors near the poles. Alternatively, engineers transfer as much (remaining) JetA fuel from the wings into the CWT as possible (using the wing fuelling station controls and cockpit pump switches), then top up the rest of the aircraft with JetA1. Most of the fuel in the CWT is usually burnt off by the time the aircraft gets close to the poles.

Rgds
JHW

[Jeroen Hoppenbrouwers]

By the way, is it still the captain's credit card that smokes after fueling, or is the bill sent to the company and paid later? How much money is typically involved in fueling up a 744 on a typical leg (no tankering) nowadays?

[OKD]

So that's why sometimes when there is a warning of "fuel temp", we need to descend to a lower altitude for warmer air, as my understanding is that some ac do not have the systems to warm up the fuel?

What about if the fuel is typically for "cold cold" temp, but flies to hot and humid ap? Is there any procedure or notes to take in this situation?

[Lasse]

haha no Jeroen, all it takes is a signature now a days...
I think Jet A1 price now is about 0.79 EUR ltr so then its just to do the math... Specific gravity depending on temperature around 0.796 kg/l

Freezing point for Jet A1 is -47 degrees. however since there are not temp censers in all the tanks a 3 degree buffer is in the limitation sections to account for difference in tank temperature. So for Jet A1 -44 is the limit.
Most jet aircrafts warms up the fuel entering the engine by using it to cool down engine oil...So the concern in all this is freezing fuel in the tank...

Normally its not a problem staying within that limit. But extreme cold temperatures can occur and the fuel cools quicker than normally. It that case non normal checklist list must be applied.
Software are available to predict fuel temperature. So dispatchers can look into if an alternate route should be used...

Max temperature is 49 degrees. Thats very seldom that the temperature come up there since cold fuel is pumped in the wings during the turnaround.

So a quick rule of thumb is +-40 then you need to pay attention to the fuel temperature...

[Phil Bunch]

It's amazing to me that upper level temperatures can be predicted in advance of a polar or other cold flight with sufficient accuracy (that is within a few degrees of the target critical temperature).   I assume they don't usually have the option to drop down to a lower altitude for an extended period of time in order to prevent fuel freezing - the fuel economy would seemingly become too degraded at lower altitudes.

I seem to recall that the friction of the air on the skin of the airliner is part of the calculations and planning.

Perhaps part of the story is that previous flights and/or their central offices presumably record various temperatures along the route through satellite data links, etc.