---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Thu 09/19/13: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:56 AM - Re: Fuel return line one-way-valve (Frans Veldman) 2. 09:43 AM - Re: Fuel return line one-way-valve (Raimo Toivio) 3. 11:01 AM - Re: Fuel return line one-way-valve (Frans Veldman) 4. 02:29 PM - Re: Fuel return line one-way-valve (rparigor@suffolk.lib.ny.us) 5. 02:59 PM - Re: Fuel return line one-way-valve (Frans Veldman) ________________________________ Message 1 _____________________________________ Time: 01:56:40 AM PST US From: Frans Veldman Subject: Re: Europa-List: Fuel return line one-way-valve On 09/19/2013 07:07 AM, rparigor@suffolk.lib.ny.us wrote: > The 914 returns a lot of fuel to the tank compared to the 912S. By I have a 914 AND I have a one-way-valve in the fuel return line. No problems, although with the engine at idle the fuel pressure tends to climb to the upper edge of the green zone of my fuel differential pressure gauge. But maybe that would even be the case without the one way valve. At anything else than idle the fuel pressure is in about the middle of the green zone. > I think I remember reading it may > not be a great idea to let fuel (especially auto fuel) cascade as I > think it may somehow accelerate spoiling the fuel? Did you ever hear of > this? I have the same fear. Remember the returning fuel has an increased temperature (might even be hot) due to its travel through the heated engine bay, pumps, pressure regulator, etc! That's the reason why we have a fuel return line after all; by keeping more flow in the system than the engine requires we prevent vapor lock. Fuel consists of many components, and they all vaporize at a different rate. It doesn't feel right to have hot fuel cascading downwards from the top of the tank, splattering around, having its components vaporize partly, then condensing against the cold tank walls, and dripping into the fuel pool again. Also the surrounding oxigen together with the high temperature of the return fuel vapor might oxidize some of the fuel components at an increased rate. We all know that fresh fuel is different than "old" fuel and elevated temperatures and lots of contact with oxigen might play a role in this "aging" process. My feeling is that it is healthier to arrest the returning fuel immediately on arrival in a pool of cold fuel without letting it get into contact with air and oxigen first. For what it is worth, I try to use Mogas as much as possible, even when flying in the French Alps (around FL100), have done this dozens of times (Ilona's parents live there so we tend to visit them often with our little aircraft) and I never had any problems with the fuel. Maybe it just helps to keep the fuel temps down and not inviting too much interaction with oxigen molecules. > I suppose could put a dip tube to the bottom of the tank to > prevent this? So then what would be the point to route the fuel to the top of the tank first while there is a shorter route to the same spot? > On the 914 you don't want much in the way of back pressure > as it can cause problems with proper functioning of the fuel pressure > regulator. One more reason to feed the fuel back at the underside of the tank. Shorter hose, and less elevation of the fuel required to deliver it where it ends up anyway. Of course, a one way valve gives some resistance, but apparently it is not too much. A valve can fail, but the most dangerous fail is when it remains shut. If this happens, you will discover it during engine start up. With the low fuel demand during that stage there is much return flow, and if the valve stays shut it will quickly flood the engine (apart from your fuel pressure needle pegging against the stop) Once open, it seems utterly unlikely that the valve will spontaneously close against the fuel pressure during flight. Once open, it will stay open as long as fuel pressure is pushing against it and holding it there. It gives some piece of mind that there is not an unclosable fuel hose going to the engine bay. If the hose breaks, the fuel flow will stop by itself. Frans ________________________________ Message 2 _____________________________________ Time: 09:43:58 AM PST US From: "Raimo Toivio" Subject: Re: Europa-List: Fuel return line one-way-valve Hi Frans, you are absolutely as right ******as usually********* (ask Ilona about these stars ;) but still I am brave enough to consider that fuel will not be significantly "aged" when dropping or in fact spraying it from top of the tank. That spray will contact air just a split second during the drop distance from 0 to max say 40 cm. Notice you will use this fuel in hours or at least mix it soon to the fresh fuel when refueling again. Anyway - if you have a manual tap or an automatic one-way-valve - there is no reason to instal it (a return line) to the top of the tank. BTW have you any idea what=B4s a typical fuel temperature rise from the tank outlet to the tank inlet? My guess is it is just couple of degrees only or even zero - flow rate is so high. Anyway - thanks you helped me/us to understand that return line potential danger IN TIME (and to do something to it). Among us is living at least one person who would have been very happy about that extra valve during his awful incident (IMHO). Funny, we (me & my wife) feel comfortable over the shoreless sea or in the most thickiest cloud but so far we cannot even think about flying VFR over hostile & high terrain like Ilona=B4s parent=B4s Alps. I understand it=B4s just our lack of information. And also lack of turbo, oxygen and BRS... Raimo HA-MDO http://www.flyfinland.fi/view/10153/ OH-XRT http://www.flyfinland.fi/view/9490/ -----Alkuper=E4inen viesti----- From: Frans Veldman Sent: Thursday, September 19, 2013 11:55 AM Subject: Re: Europa-List: Fuel return line one-way-valve On 09/19/2013 07:07 AM, rparigor@suffolk.lib.ny.us wrote: > The 914 returns a lot of fuel to the tank > compared to the 912S. By I have a 914 AND I have a one-way-valve in the fuel return line. No problems, although with the engine at idle the fuel pressure tends to climb to the upper edge of the green zone of my fuel differential pressure gauge. But maybe that would even be the case without the one way valve. At anything else than idle the fuel pressure is in about the middle of the green zone. > I think I remember reading it may > not be a great idea to let fuel (especially auto > fuel) cascade as I > think it may somehow accelerate spoiling the > fuel? Did you ever hear of > this? I have the same fear. Remember the returning fuel has an increased temperature (might even be hot) due to its travel through the heated engine bay, pumps, pressure regulator, etc! That's the reason why we have a fuel return line after all; by keeping more flow in the system than the engine requires we prevent vapor lock. Fuel consists of many components, and they all vaporize at a different rate. It doesn't feel right to have hot fuel cascading downwards from the top of the tank, splattering around, having its components vaporize partly, then condensing against the cold tank walls, and dripping into the fuel pool again. Also the surrounding oxigen together with the high temperature of the return fuel vapor might oxidize some of the fuel components at an increased rate. We all know that fresh fuel is different than "old" fuel and elevated temperatures and lots of contact with oxigen might play a role in this "aging" process. My feeling is that it is healthier to arrest the returning fuel immediately on arrival in a pool of cold fuel without letting it get into contact with air and oxigen first. For what it is worth, I try to use Mogas as much as possible, even when flying in the French Alps (around FL100), have done this dozens of times (Ilona's parents live there so we tend to visit them often with our little aircraft) and I never had any problems with the fuel. Maybe it just helps to keep the fuel temps down and not inviting too much interaction with oxigen molecules. > I suppose could put a dip tube to the bottom of > the tank to > prevent this? So then what would be the point to route the fuel to the top of the tank first while there is a shorter route to the same spot? > On the 914 you don't want much in the way of > back pressure > as it can cause problems with proper functioning > of the fuel pressure > regulator. One more reason to feed the fuel back at the underside of the tank. Shorter hose, and less elevation of the fuel required to deliver it where it ends up anyway. Of course, a one way valve gives some resistance, but apparently it is not too much. A valve can fail, but the most dangerous fail is when it remains shut. If this happens, you will discover it during engine start up. With the low fuel demand during that stage there is much return flow, and if the valve stays shut it will quickly flood the engine (apart from your fuel pressure needle pegging against the stop) Once open, it seems utterly unlikely that the valve will spontaneously close against the fuel pressure during flight. Once open, it will stay open as long as fuel pressure is pushing against it and holding it there. It gives some piece of mind that there is not an unclosable fuel hose going to the engine bay. If the hose breaks, the fuel flow will stop by itself. Frans browse Un/Subscription, FAQ, http://www.matronics.com/Navigator?Europa-List Forums! List Admin. ________________________________ Message 3 _____________________________________ Time: 11:01:01 AM PST US From: Frans Veldman Subject: Re: Europa-List: Fuel return line one-way-valve On 09/19/2013 06:43 PM, Raimo Toivio wrote: > you are absolutely as right > > ******as usually********* > > (ask Ilona about these stars ;) I will do! > but still I am brave enough to consider that fuel will not be > significantly "aged" when dropping or in fact spraying it from top of > the tank. That spray will contact air just a split second during the > drop distance from 0 to max say 40 cm. Well, ever noticed in the shower how much the water cools down in the same distance? It is pure interaction with the surrounding air... > Notice you will use this fuel in > hours I often park my airplane with the tank about half filled. > BTW have you any idea whats a typical fuel temperature rise from the > tank outlet to the tank inlet? My guess is it is just couple of degrees > only or even zero - flow rate is so high. I don't know. But even it it were at room temperature I wouldn't think that repeatedly cascading it down would do any good to its composition. > Anyway - thanks you helped me/us to understand that return line > potential danger IN TIME (and to do something to it). Among us is living > at least one person who would have been very happy about that extra > valve during his awful incident (IMHO). It was at that moment of the incident I was installing the fuel hoses and indeed considered that I didn't want to go that same route. > Funny, we (me & my wife) feel comfortable over the shoreless sea or in > the most thickiest cloud but so far we cannot even think about flying > VFR over hostile & high terrain like Ilonas parents Alps. This gets interesting. The places we feel incomfortable is when flying in Scandinavia. With an almost blank GPS screen, and hours of flying above just rocks, ice and maybe some trees (if you are not too far north) beneath you. I've never observed an almost blank GPS screen, except in Scandinavia, and I've never seen such strectched areas where you can't find a landing area of 200 meters without hitting at least a car sized rock. At our return flight from the North cape, at about 2am in daylight conditions (for you not amazing but for the majority of pilots it is) we were flying above terrain that looked very hostile and didn't change for two hours. In these two hours we didn't see any road, house, or whatever human structure. We felt very alone and wondered if in case we would have to carry out a forced landing (between the endless rocks) whether anybody would ever find our remains. Don't get me wrong, I found it absolutely beautifull, very serene, the midnight sun, the small amount of haze, the reddish sky, the blueish light surrounding you and the absolute silence (radio contact got lost very soon). Even while the engine was dutyfully whirring you could sense the silence around you. And then to see a moon rise just in front of you. Priceless. Then the Alps. Chances are big that if you look down at any spot you will find an airfield beneath you. The mountains look agressive, but so much cultivated that there is always some pasture, road, or anything within gliding distance. There are plenty of shallow slopes. I guess it is difficult to land uphill but of course it means that once in the landing flare you will very quickly come to a halt. If in doubt, just land uphill and gently fall down when your speed reaches zero just above the tree tops. I haven't seen much of these escape possibilities in Scandinavia. The terrain, although filled with enormous rocks, is most of the time very shallow. And even if you were to survive such a landing, you will freeze to death, eaten by wolves or bears (no beers unfortunately!) before someone finds you. If something is left at all. Anyway, you are invited. If you want to go to the Alps, just let us know. We can guide you in and probably offer some accommodation. Frans ________________________________ Message 4 _____________________________________ Time: 02:29:12 PM PST US Subject: Re: Europa-List: Fuel return line one-way-valve From: rparigor@suffolk.lib.ny.us Hi Frans Thx. for the reply. If there is a trauma to the return line, we want the break or leak to occur upstream of the 1 way return valve (closder to the fuel pressure regulator). Did you do anything to stack the cards in favor when the engine gets ripped off that the 1 way return valve stays connected to the fuel tank? Ron Parigoris ________________________________ Message 5 _____________________________________ Time: 02:59:51 PM PST US From: Frans Veldman Subject: Re: Europa-List: Fuel return line one-way-valve On 09/19/2013 07:00 PM, rparigor@suffolk.lib.ny.us wrote: > Hi Frans > > Thx. for the reply. > > If there is a trauma to the return line, we want the break or leak to > occur upstream of the 1 way return valve (closder to the fuel pressure > regulator). > > Did you do anything to stack the cards in favor when the engine gets > ripped off that the 1 way return valve stays connected to the fuel tank? Good to mention this! I have the one way valve very close to the fuel outlet. The rest of the hose is securely tied to the aircraft at numerous places before it enters the cowling. I'm quite confident that if the engine gets ripped off the one way valve stays connected to the fuel tank. Frans ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.