From kls Fri Sep 13 03:03:31 1996 Newsgroups: sci.aeronautics.airliners Path: bounce-back From: Bob Falkiner Subject: Re: Do fuel valves ice jam due to water in fuel? Approved: kls@ohare.Chicago.COM Sender: kls@ohare.Chicago.COM References: Organization: RJF Home Date: 13 Sep 96 03:03:31 Message-ID: Patrick Roberts wrote: > > gerwocii@aol.com (GERWOCII) wrote: > > >It is my understanding that the fuel is heated. At what point this occurs > >I do not know. If it is heated this would prevent and water condesation > >from freezing. > > Most Jets I've worked on heat the fuel on the engine with a bleed air > heat exchanger. Ussally just before the fuel contol unit. it varies by the design. usually fuel heaters are on the filter (engines are certified up to 200 ppm water - a necessity when temperatures drop from houston ambient to -56C at altitude as some condensation is inevitable) mil fuel has a de-icer glycol type compound added at 0.15 vol%. some biz jets are certified with de-icer which lowers the weight for heating equipment. others use fuel to cool avionics etc and pick up heat. but in any case, there is no way to prevent some degree of condensation with these kinds of temperature ranges - just different ways of dealing with it.