On

the

subject of using fuel as a coolant - in the FA-18 Hornet the fuel is

used to

cool the accessory drive units on each engine (generator, hyd pump,

fuel

pump).  From there the fuel is circulated through the relatively

small

and

thin internal wing tanks to radiate the gained heat.  Unfortunately,

I

can't

think of a good use for this concept in our homebuilt aircraft.  :(

Mike Amos

I tried circulating the return fuel from the pressure regulator through

a

heat exchanger in the oil pan to help cool it.  Worked, but not enough
volume of fuel to make it worth while (oil temp down 2 degrees at

cruise).

The temperature rise in my wet wing fuel tanks was not even measurable.

I

may revisit the idea with a separate higher volume pump.  The idea of

"drag

free" oil cooling really appeals to me.  A clean airplane has about 30%

drag

in cooling (does not apply to you jet jocks) so if oil cooling is 33% of
cooling on a rotary, that means a potential of 10% drag reduction.  Aero
engineers would sell their mothers for 10% of drag.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

 O.K. This is from memory which in my case can be somewhat cloudy. But I

remember the F-16 having a Heat exchanger in the fuel system. It used fuel
to cool either engine oil or hydraulic fluid. I don't remember which for
sure. Could a heat exchanger be put in a main fuel tank. Or maybe it could
be installed in  some sort of sump or header tank to keep it immersed in
fuel? Would this work better than having the heat exchanger in the hot oil
pan?
James Phillips

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