fuel temp control in wing tanks

[max lenz]

heard b717 is only jet enabling control of fuel temp in wings by controlled backfeeding of warm fuel from engine, probably from oil cooler.
would appreciate this feature on other planes where cold soaked fuel after long flights leeds to unnecessary stress for pilots for things like:
- resulting fuel temp in different wing sections after refuelling;
- resulting fuel temp after switching on fuel pumps;
- check for build up of clear ice during approach;
- antiicing required when dry wing but rain expected during taxi-out.

who knows more about:
- efficiency of engines with or without fuel heating feature;
- plans of manufacturers to introduce wing fuel temp control

thanks
max

[GlueBall]

I have never gotten "stressed" over low fuel temperature in the wings as fuel is continually circulated by pumps and warmed by the oil/heat exchanger prior to injection into the combustion chamber. But I know that the freezing point for Jet A begins at -37C, and for Jet A1 at -40C. These are threshold temperatures where crystals begin to form, but it doesn't mean that if you're cruising for 9 hours at a Flight Level at -56C ambient temperature that all the fuel in the wings will turn into a solid. It's just as if you were to take a blender full of water into freezing conditions; the water will slowly begin to freeze at 0C, but if you were to run the motor on the blender the water won't begin to gradually freeze until it's at a much lower temperature.

[Flight Detent]

Hi all,
As we speak, this and many other fuel system upgrades are being developed for the B737.

Cheers

[Capt Fathom]

Boeing Article on Cold Fuel (http://www.boeing.com/commercial/aeromagazine/aero_16/polar_story.html#3)
fuel is continually circulated by pumps and warmed by the oil/heat exchanger prior to injection into the combustion chamber
Problem is...once the fuel turns to wax, it won't go through the pumps!:(

[max lenz]

allthough problems with cold fuel during flight may be a concern as well I`m trying to talk here about ground operations and this was the reason for my stress:
between 99 and 01 was flying on F100 between HEL and CDG and many times we were the first who requested deicing in CDG, because the cold wing had built up clear ice on top during approach through rain.
sometimes airport deicing staff just refused to show up and we had to heat up the wings with warm air from airconditioning unit (a procedure approved by Fokker).
that`s why I still would like to upgrade the fuel system of e.g. F100...

[m&v]

But Max,surely the,on ground,fuel temp didn't go to 0degrees once you'd taken on warm fuel??How long did the aircraft stand to allow the fuel to meet ambient(zero degrees)....If thats the case don't fuelup, with warm fuel, until just prior to Boarding??:bored:

[max lenz]

F100 has a collector tank which is from wing root to about 1.5m outwards. it is allways kept full. after HEL-CDG during winter estimated fuel temp was minus 5 to minus 10 degrees. refuelling with "warm" fuel was done as well via this tank but experience showed with fuel pumps off allmost no mixing took place as warm fuel went up and spilled to outer tanks via stringers.
in worst case this resulted in melting up of ice initially but when fuel pumps were switched on just before engine start as required by SOPs resulting mixing temperature could cool down upper side of wing below freezing again resulting in new ice build up if there was rain.
leaving fuel pumps on during transit stops helped as with this procedure temp of upper wing skin could only rise with outside temp above freezing but fleet manager didn`t like me not following SOP here and controlling fuel temp above freezing could make us both happy...

[Md-driver]

This is a wwell knomn problem for airlines flying a lot in cold conditions. A flight in January from scandinavia to say Milano with fuel already below 0deg C when fueling and after a 2 1/2 hour flight the fuel in the wing tanks is sometimes as low as -20deg C. Upon arrival in Milano with say 5-10 deg OAT and drizzle will certainly give you a problem especially if you are carrying some extra fuel. Try to find a de-icing crew who is ready to de-ice one aircraft per day.
Clear ice is a serious problem for F-100, DC-9,MD-80 aircraft.
After having seen this fenomenon many times I can say that it often is not enough with just fueling up the aircraft, as is the case on your return flight when the fuel uplifted in scandinavia is below or just above freezing.

The first aircraft to have warm fuel return to tank from the oilcoolers was as far as I know the MD-90, the larger sister of the MD-95 (B-717).

Merry Christmas to you all.

[Dan Winterland]

747s have some fuel warming in the form of the return lines to the hyd resevoirs being fed through a system of pipes in the fuel tanks. This is primarily for hyd fluid cooling and with low fuel levels you can see the hyd temps in the number 1 and 4 systems rising.

JT9 powered 747s have additional fuel heat other than that provided by the oil cooler/fuel warmer. It's necessary for most situations when you go tank to engine for the outboard engines.

The 747-400gives you an eicas warning LOW FUEL TEMP when the temp in tank number one reduces to -40. I saw it once flying accross Siberia returning from Hong Kong. We had to accelerate to increase kinetic heating as descending wasn't an option. It was a reasonablt common scenario and we carried extra fuel for this eventuality.