---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Sun 04/07/13: 14 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:21 AM - Re: Rotax Fly Dat (Peter Jeffers) 2. 03:30 AM - Re: Rotax Fly Dat (Alan Carter) 3. 07:14 AM - Re: Rotax Fly Dat (Richard Girard) 4. 07:17 AM - Re: Rotax Fly Dat (Richard Girard) 5. 09:32 AM - Re: Re: Fuel return line (Sacha) 6. 11:09 AM - Re: Re: Fuel return line (FLYaDIVE) 7. 01:44 PM - Re: Rotax Fly Dat (Alan Carter) 8. 02:26 PM - Re: Re: Fuel return line (GRAHAM SINGLETON) 9. 02:55 PM - Re: Fuel return line (Alan Carter) 10. 03:02 PM - Re: Re: Fuel return line (Bob Harrison) 11. 03:39 PM - Re: Re: Fuel return line (Sacha) 12. 03:46 PM - Re: Re: Fuel return line (Sacha) 13. 04:21 PM - Re: Re: Fuel return line (rayj) 14. 11:33 PM - Re: Re: Fuel return line (Bob Harrison) ________________________________ Message 1 _____________________________________ Time: 01:21:26 AM PST US From: " Peter Jeffers" Subject: RE: RotaxEngines-List: Rotax Fly Dat Hi Alan, If your Flydat is an old unit then this defect you refer to is because it thinks you have exceeded some limit or other. If this is so you need to have the unit reset by a Rotax specialist who will have the necessary software to interpret the parameters stored and advise you of any required special checks that may need to be carried out. More recent FlyDats do not do this as having the screen going blank during and immediately after start is not very clever. I hope this helps and also hope it does not involve you in too much expense. Pete -----Original Message----- From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Alan Carter Sent: 07 April 2013 00:29 Subject: RotaxEngines-List: Rotax Fly Dat Hello All I have a Rotax FlyDat on my 914, I notice it has a small battery located on the back side. Master switch on, Flydat cycles, shows temp,and hours, turn the key ,Starting the engine and display recycles nothing showing till after its completed its cycle, then come in with all the temps and pressures. But during the vital starting stage I have nothing showing.???? Alan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=397987#397987 ________________________________ Message 2 _____________________________________ Time: 03:30:29 AM PST US From: "Alan Carter" Subject: Re: RotaxEngines-List: Rotax Fly Dat Hi Peter. Many thanks, I have had the problem since i purchased the plane, and the last owner said he had it also, so its been like it for a long time. I thought it might be something to do with the battery, but have heard a slight event can trigger this, sometime as simple as out of limit temperature. I must admit i rarely scan the thing, its down the bottom out of sight, and the LCD are not easy to see, for me a red needle on a gauge pointing in the correct known position would be better. But i does work, one day i was climbing out and the red warning light on the panel came one, too slow a climb, nose to high, water temp out of limits. I will have to get the blood thing reset as i would be nice to see it during start up, I'm really not a bad pilot, but this is probably the main time i would be watching it as its tucked away down by my knees . Regards Alan -----Original Message----- From: Peter Jeffers Sent: Sunday, April 07, 2013 9:16 AM Subject: RE: RotaxEngines-List: Rotax Fly Dat Hi Alan, If your Flydat is an old unit then this defect you refer to is because it thinks you have exceeded some limit or other. If this is so you need to have the unit reset by a Rotax specialist who will have the necessary software to interpret the parameters stored and advise you of any required special checks that may need to be carried out. More recent FlyDats do not do this as having the screen going blank during and immediately after start is not very clever. I hope this helps and also hope it does not involve you in too much expense. Pete -----Original Message----- From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Alan Carter Sent: 07 April 2013 00:29 Subject: RotaxEngines-List: Rotax Fly Dat Hello All I have a Rotax FlyDat on my 914, I notice it has a small battery located on the back side. Master switch on, Flydat cycles, shows temp,and hours, turn the key ,Starting the engine and display recycles nothing showing till after its completed its cycle, then come in with all the temps and pressures. But during the vital starting stage I have nothing showing.???? Alan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=397987#397987 ________________________________ Message 3 _____________________________________ Time: 07:14:39 AM PST US Subject: Re: RotaxEngines-List: Rotax Fly Dat From: Richard Girard Check the power going to the FlyDat during start up. Most likely it is falling below some preset level at which the FlyDat cannot function. Since it has happened from day one, the fault may be in your electrical architecture and not the unit itself. Rick Girard On Sun, Apr 7, 2013 at 5:29 AM, Alan Carter wrote: > alancarteresq@onetel.net> > > Hi Peter. > Many thanks, I have had the problem since i purchased the plane, and the > last owner said he had it also, so its been like it for a long time. > I thought it might be something to do with the battery, but have heard a > slight event can trigger this, sometime as simple as out of limit > temperature. > I must admit i rarely scan the thing, its down the bottom out of sight, > and the LCD are not easy to see, for me a red needle on a gauge pointing in > the correct known position would be better. > But i does work, one day i was climbing out and the red warning light on > the panel came one, too slow a climb, nose to high, water temp out of > limits. > I will have to get the blood thing reset as i would be nice to see it > during start up, I'm really not a bad pilot, but this is probably the main > time i would be watching it as > its tucked away down by my knees . > > Regards > Alan > > > -----Original Message----- From: Peter Jeffers > Sent: Sunday, April 07, 2013 9:16 AM > To: rotaxengines-list@matronics.**com > Subject: RE: RotaxEngines-List: Rotax Fly Dat > > > pjeffers@talktalk.net> > > Hi Alan, > If your Flydat is an old unit then this defect you refer to is because it > thinks you have exceeded some limit or other. If this is so you need to > have > the unit reset by a Rotax specialist who will have the necessary software > to > interpret the parameters stored and advise you of any required special > checks that may need to be carried out. > More recent FlyDats do not do this as having the screen going blank during > and immediately after start is not very clever. > I hope this helps and also hope it does not involve you in too much > expense. > > Pete > > -----Original Message----- > From: owner-rotaxengines-list-**server@matronics.com > [mailto:owner-rotaxengines-**list-server@matronics.com] > On Behalf Of Alan > Carter > Sent: 07 April 2013 00:29 > To: rotaxengines-list@matronics.**com > Subject: RotaxEngines-List: Rotax Fly Dat > > > > Hello All > I have a Rotax FlyDat on my 914, > I notice it has a small battery located on the back side. > Master switch on, Flydat cycles, shows temp,and hours, > turn the key ,Starting the engine and display recycles nothing showing till > after its completed its cycle, then come in with all the temps and > pressures. > But during the vital starting stage I have nothing showing.???? > > Alan > > > Read this topic online here: > > http://forums.matronics.com/**viewtopic.php?p=397987#397987 > > -- Zulu Delta Mk IIIC Thanks, Homer GBYM It isn't necessary to have relatives in Kansas City in order to be unhappy. - Groucho Marx ________________________________ Message 4 _____________________________________ Time: 07:17:14 AM PST US Subject: Re: RotaxEngines-List: Rotax Fly Dat From: Richard Girard Dang, I hit send and not return. Anyway, one solution might be to install a small battery, say a 2AH SLA to drive the FlyDat and connect it to the system through a diode so that the starter cannot draw it down, but the system can keep it charged. Rick On Sun, Apr 7, 2013 at 9:14 AM, Richard Girard wrote: > Check the power going to the FlyDat during start up. Most likely it is > falling below some preset level at which the FlyDat cannot function. Since > it has happened from day one, the fault may be in your electrical > architecture and not the unit itself. > > Rick Girard > > > On Sun, Apr 7, 2013 at 5:29 AM, Alan Carter wrote: > >> alancarteresq@onetel.net> >> >> Hi Peter. >> Many thanks, I have had the problem since i purchased the plane, and the >> last owner said he had it also, so its been like it for a long time. >> I thought it might be something to do with the battery, but have heard a >> slight event can trigger this, sometime as simple as out of limit >> temperature. >> I must admit i rarely scan the thing, its down the bottom out of sight, >> and the LCD are not easy to see, for me a red needle on a gauge pointing in >> the correct known position would be better. >> But i does work, one day i was climbing out and the red warning light on >> the panel came one, too slow a climb, nose to high, water temp out of >> limits. >> I will have to get the blood thing reset as i would be nice to see it >> during start up, I'm really not a bad pilot, but this is probably the main >> time i would be watching it as >> its tucked away down by my knees . >> >> Regards >> Alan >> >> >> >> -----Original Message----- From: Peter Jeffers >> Sent: Sunday, April 07, 2013 9:16 AM >> To: rotaxengines-list@matronics.**com >> Subject: RE: RotaxEngines-List: Rotax Fly Dat >> >> >> pjeffers@talktalk.net> >> >> Hi Alan, >> If your Flydat is an old unit then this defect you refer to is because it >> thinks you have exceeded some limit or other. If this is so you need to >> have >> the unit reset by a Rotax specialist who will have the necessary software >> to >> interpret the parameters stored and advise you of any required special >> checks that may need to be carried out. >> More recent FlyDats do not do this as having the screen going blank during >> and immediately after start is not very clever. >> I hope this helps and also hope it does not involve you in too much >> expense. >> >> Pete >> >> -----Original Message----- >> From: owner-rotaxengines-list-**server@matronics.com >> [mailto:owner-rotaxengines-**list-server@matronics.com] >> On Behalf Of Alan >> Carter >> Sent: 07 April 2013 00:29 >> To: rotaxengines-list@matronics.**com >> Subject: RotaxEngines-List: Rotax Fly Dat >> >> >> >> Hello All >> I have a Rotax FlyDat on my 914, >> I notice it has a small battery located on the back side. >> Master switch on, Flydat cycles, shows temp,and hours, >> turn the key ,Starting the engine and display recycles nothing showing >> till >> after its completed its cycle, then come in with all the temps and >> pressures. >> But during the vital starting stage I have nothing showing.???? >> >> Alan >> >> >> >> >> Read this topic online here: >> >> http://forums.matronics.com/**viewtopic.php?p=397987#397987 >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> > > > -- > Zulu Delta > Mk IIIC > Thanks, Homer GBYM > > It isn't necessary to have relatives in Kansas City in order to be unhappy. > - Groucho Marx > > -- Zulu Delta Mk IIIC Thanks, Homer GBYM It isn't necessary to have relatives in Kansas City in order to be unhappy. - Groucho Marx ________________________________ Message 5 _____________________________________ Time: 09:32:08 AM PST US From: "Sacha" Subject: RE: RotaxEngines-List: Re: Fuel return line Roger, Thanks! Makes sense... Regards, Sacha ________________________________ Message 6 _____________________________________ Time: 11:09:01 AM PST US Subject: Re: RotaxEngines-List: Re: Fuel return line From: FLYaDIVE Sacha: You have some great thought provoking questions. I hope some are provoked. Fire sleeves or One piece Molded Teflon fuel lines are the way to go. You always want to do all you can to keep extra heat from fuel and oil lines. BUT! Where did this Old Wives Tail of Vapor Lock come from? It is a BUNCH OF BUNK! The "T" fitting does NOTHING for Vapor Lock... High Pressure does NOTHING to prevent Vapor Lock. Well, almost nothing - It corrects Pilot/Builder error. Vapor Lock happens ON THE GROUND and is experienced usually at start up and sometimes in the air, immediately during or after rotation. Vapor Lock can occur with MoGAs or AvGas. It is more of a POOR PILOT SHUTDOWN PROCEDURE that anything else. And since we are talking Home Built Planes and Self Proclaimed Engineers - - Builder error. So, what does the "T" fitting do? Well, the history goes way back to the 1960's... Electric home made Fuel Pumps were being used on Carbureted engines. And the engines were FLOODING like crazy. Flooding, Fires, Poor Starts (if at all), Dying when the throttle was floored and Low HP. All because of TOO MUCH Fuel Pressure Pushing the Carburetor's intake valve off the seat and flooding the carb. So, how do you get more fuel to the carb so it does not go LEAN? You do a whole lot of pressure testing and engineering - BUT! These were HOME MADE FUEL PUMPS - And Manufacturer made Carbs. Transducers were not around then. It was too costly to try to figure out how many GPH and How much Fuel Pressure would work,and what size spring to use... Too many variables. The QUICK and EASY and VERY Effective solution... Put a "T" fitting in the line and the excess pressure and excess fuel is returned to the fuel tank. The Carb takes what it needs - Has a steady supply of fuel and does NOT go lean no matter how fast you hit the throttle. No Smoke and Mirrors, No ridiculous Vapor Lock theories. But, hell, this is aviation so everybody just re-invents the wheel with their own ideas. In simple terms: It is better and easier to KNOW you have too much fuel than to take the chance of going lean and destroying an engine or not enough power to clear the trees. What are the 4 most useless things to a pilot? We all know the first 3: 1 - The Gas left on the ground. 2 - The runway behind you. 3 - Are airspace above you . The fourth - 4 - The Gas you can't get out of your tanks. Barry On Sat, Apr 6, 2013 at 2:36 PM, Sacha wrote: > > Hi Roger > I can see why hot fuel would exacerbate vapor lock problems and this > conversation has convinced me to firesleeve my fuel lines. But why does a > return line improve the situation. And I would have thought higher fuel > pressure would lower the incidence of vapor lock (as it increases the temp > at which fuel vaporizes). Can you shed more light on why higher fuel > pressure is bad? > Regards, > Sacha > > -----Original Message----- > From: owner-rotaxengines-list-server@matronics.com > [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Roger > Lee > Sent: Thursday, 04 April, 2013 19:43 > To: rotaxengines-list@matronics.com > Subject: RotaxEngines-List: Re: Fuel return line > > --> > > Hi John, > > Here's the issues. > Many of the planes from yesteryear wasn't a problem. They were open air > engines so hot fuel lines weren't an issue and the old style fuel pump > didn't have enough excess pressure to be an issue. Come up to date with > many > of the newer LSA and Experimental aircraft with nice tight cowls and then > throw in on top of that too many owners fail to install the fuel and oil > lines in fire sleeve then heat inside the cowl makes a night a day > difference. Vapor lock. I see it alot now days with tight cowls. Fire > sleeve > not only protects from fire, but helps with excessive heat too. Now comes > along the new Rotax fuel pump that puts out more pressure and then add on > top of that someone who likes to run an electric pump all the time which > adds > .5 -1.0 psi more and the fuel then can't be controlled by the float needle > valve and it pukes out the vents all over a hot engine, on hot exhaust > manifolds because some didn't bother to install carb drip trays and now we > have an issue. Now add that owners haven't rebuilt or replaced an older > float needle valve and now we definitely puke fuel and the engine runs > rough. > Just a side note* Exposed fuel lines outside of fire sleeve tend to > deteriorate faster than fire sleeved fuel lines. > > > So the bottom line is application is everything and sooner or later your > old > pump will die and the new pump is all that is available. It's so easy to > add > the re-circulation line and never have to look back. On any flight the > float > needle valve can start leaking then you have the issue too. > > -------- > Roger Lee > Tucson, Az. > Light Sport Repairman - Maintenance Rated Rotax Repair Center - Heavy > Maint. > Rated Home 520-574-1080 TRY HOME FIRST Cell 520-349-7056 > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=397863#397863 > > ________________________________ Message 7 _____________________________________ Time: 01:44:14 PM PST US Subject: RotaxEngines-List: Re: Rotax Fly Dat From: "Alan Carter" Hi Richard. I think it is as Peter said, but not in these words, Its part of the Rotax design feature, to show a message Saying Service, then goes blank and recycle and come back online after the engine has started, A stupid idea, and can only be reset by a Rotax computer, Which is a nice little earner. What was life like before Flydat, It works, does its job, but a bit of common sense needed. In the summer maybe i can fly in somewhere and get it reset, the engine done many hours so reasonable confident all is well. But i do plan to have it reset, and see for myself just what triggers it, should it happen to me. Alan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=398083#398083 ________________________________ Message 8 _____________________________________ Time: 02:26:33 PM PST US From: GRAHAM SINGLETON Subject: Re: RotaxEngines-List: Re: Fuel return line Vapour lock certainly does occur. I know of several instances, one of which resulted in a written off aircraft. It happens when the-=0Aengine driven fuel pump-gets heated-by-the engine oil and then heats the fuel. Low fuel flow rate such as -when-taxiing or waiting for air traffic on the ground=0Acan vaporize the fuel, especially Mogas.-The fuel return -Rot ax recommend keeps more fuel flowing through the system which-helps-coo l the pump and ensures cold fuel when you need it for high power.-=0AMost -carburetor-installations in cars have a fuel-return-line for the s ame reasons.=0AGraham=0A=0A________________________________=0A From: FLYaDI VE =0ATo: rotaxengines-list@matronics.com =0ASent: Sund ay, 7 April 2013, 19:08=0ASubject: Re: RotaxEngines-List: Re: Fuel return l ine=0A =0A=0ASacha:=0A=0AYou have some great thought provoking questions. -I hope some are provoked.=0AFire sleeves or One piece Molded Teflon fuel lines are the way to go.=0AYou always want to do all you can to keep extra heat from fuel and oil lines.=0ABUT! -Where did this Old Wives Tail of V apor Lock come from? -It is a BUNCH OF BUNK!=0AThe "T" fitting does NOTHI NG for Vapor Lock... High Pressure does NOTHING to prevent Vapor Lock. -W ell, almost nothing - It corrects Pilot/Builder error.=0AVapor Lock happens ON THE GROUND and is-experienced usually at start up and sometimes in th e air,-immediately-during or after rotation.=0AVapor Lock can occur wit h MoGAs or AvGas.=0AIt is more of a POOR PILOT SHUTDOWN PROCEDURE that anyt hing else.=0AAnd since we are talking Home Built Planes and-Self Proclaim ed-Engineers - - Builder error.=0ASo, what does the "T" fitting do? -We ll, the history goes way back to the 1960's... -Electric home made Fuel P umps were being used on-Carbureted-engines. And the engines were FLOODI NG like crazy. -Flooding, Fires, Poor-Starts (if at all), -Dying-wh en the throttle was floored and Low HP. -All because of TOO MUCH Fuel Pre ssure Pushing the-Carburetor's-intake valve off the seat and flooding t he carb.-=0ASo, how do you get more fuel to the carb so it does not go LE AN? -You do a whole lot of pressure testing and engineering -- BUT! - These were HOME MADE FUEL PUMPS - And Manufacturer made Carbs. -Transduce rs-were not around then. -It was too costly to try to figure out how ma ny GPH and How much Fuel Pressure would work,and what size spring to use... -Too many variables.=0AThe QUICK and EASY and VERY-Effective-solutio n... -Put a "T" fitting in the line and the excess pressure and excess fu el is returned to the fuel tank.=0AThe Carb takes what it needs - Has a ste ady supply of fuel and does NOT go lean no-matter-how fast you hit the throttle.=0ANo Smoke and Mirrors, No-ridiculous Vapor Lock-theories. -But, hell, this is aviation so everybody just re-invents the wheel with their own ideas. -=0A=0AI ________________________________ Message 9 _____________________________________ Time: 02:55:17 PM PST US Subject: RotaxEngines-List: Re: Fuel return line From: "Alan Carter" Hi All. My 914 has two fuel pumps, one pump has to run all the time as i think the 914 has no engine drive pump, Why? These pumps are mounted well away from the engine in the belly of the fuselage, so cooling of the pumps is good, Has there been any problems with vapor lock on the 914, using Mogas. Alan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=398092#398092 ________________________________ Message 10 ____________________________________ Time: 03:02:04 PM PST US From: "Bob Harrison" Subject: RE: RotaxEngines-List: Re: Fuel return line Thanks Graham .........I was beginning to think I was having a bad dream ! Me too over the M1 from Halfpenny Green back to Wickenby, mind you it was Jabiru originated but no one will convince me anything else and nothing else found after exhaustive checks and re-checks. As far as I'm concerned there was no BS involved. To say there's no such thing is misleading in the extreme. The return line must go back into the Europa Tank via the reserve supply side ensuring only the coolest fuel goes forward. Best regards Bob Harrison. (Survived 1000 hours but would never boast about that before a flight ! Also only about half of that was with the Jabiru.) From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of GRAHAM SINGLETON Sent: 07 April 2013 22:25 Subject: Re: RotaxEngines-List: Re: Fuel return line Vapour lock certainly does occur. I know of several instances, one of which resulted in a written off aircraft. It happens when the engine driven fuel pump gets heated by the engine oil and then heats the fuel. Low fuel flow rate such as when taxiing or waiting for air traffic on the ground can vaporize the fuel, especially Mogas. The fuel return Rotax recommend keeps more fuel flowing through the system which helps cool the pump and ensures cold fuel when you need it for high power. Most carburetor installations in cars have a fuel return line for the same reasons. Graham _____ From: FLYaDIVE Sent: Sunday, 7 April 2013, 19:08 Subject: Re: RotaxEngines-List: Re: Fuel return line Sacha: You have some great thought provoking questions. I hope some are provoked. Fire sleeves or One piece Molded Teflon fuel lines are the way to go. You always want to do all you can to keep extra heat from fuel and oil lines. BUT! Where did this Old Wives Tail of Vapor Lock come from? It is a BUNCH OF BUNK! The "T" fitting does NOTHING for Vapor Lock... High Pressure does NOTHING to prevent Vapor Lock. Well, almost nothing - It corrects Pilot/Builder error. Vapor Lock happens ON THE GROUND and is experienced usually at start up and sometimes in the air, immediately during or after rotation. Vapor Lock can occur with MoGAs or AvGas. It is more of a POOR PILOT SHUTDOWN PROCEDURE that anything else. And since we are talking Home Built Planes and Self Proclaimed Engineers - - Builder error. So, what does the "T" fitting do? Well, the history goes way back to the 1960's... Electric home made Fuel Pumps were being used on Carbureted engines. And the engines were FLOODING like crazy. Flooding, Fires, Poor Starts (if at all), Dying when the throttle was floored and Low HP. All because of TOO MUCH Fuel Pressure Pushing the Carburetor's intake valve off the seat and flooding the carb. So, how do you get more fuel to the carb so it does not go LEAN? You do a whole lot of pressure testing and engineering - BUT! These were HOME MADE FUEL PUMPS - And Manufacturer made Carbs. Transducers were not around then. It was too costly to try to figure out how many GPH and How much Fuel Pressure would work,and what size spring to use... Too many variables. The QUICK and EASY and VERY Effective solution... Put a "T" fitting in the line and the excess pressure and excess fuel is returned to the fuel tank. The Carb takes what it needs - Has a steady supply of fuel and does NOT go lean no matter how fast you hit the throttle. No Smoke and Mirrors, No ridiculous Vapor Lock theories. But, hell, this is aviation so everybody just re-invents the wheel with their own ideas. I ________________________________ Message 11 ____________________________________ Time: 03:39:11 PM PST US From: "Sacha" Subject: RE: RotaxEngines-List: Re: Fuel return line Barry/Graham/Roger, I'm no expert, but I'm going to try and summarize the arguments here. There is no question that Vapour Lock does occur and that it can be a serious problem. I plan to fly in a hot climate with mountainous terrain (i.e. at altitude), hence my concern. To summarize what I'm hearing: - High fuel temp is bad because is causes fuel to vaporize easily (so don't shut down your engine suddenly and then try to restart it without cooling it as the fuel lines will likely be heat soaked) - High fuel pressure is good to the extent that o a) it increases the temp at which fuel vaporizes (though IMO this effect would be marginal as the Vaporization Temp varies as 1/log Pressure) and o b) if a fuel return line is fitted, the fuel pump mixes the warmer fuel in the lines under the cowling with cooler fuel from the fuel tanks/gascolator (unless you left your plane out in the sun and your wings are painted in a dark colour in which case fuel in your tanks might be quite warm?). - Very high fuel pressure is bad because it can cause the carbs to flood, hence the advisability of fitting a fuel return line If one encounters vapour lock during flight, what is the best way of dealing with it, assuming one has sufficient altitude? Reduce throttle and descent at a decent airspeed to cool the engine? Sacha From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of GRAHAM SINGLETON Sent: Sunday, 07 April, 2013 22:25 Subject: Re: RotaxEngines-List: Re: Fuel return line Vapour lock certainly does occur. I know of several instances, one of which resulted in a written off aircraft. It happens when the engine driven fuel pump gets heated by the engine oil and then heats the fuel. Low fuel flow rate such as when taxiing or waiting for air traffic on the ground can vaporize the fuel, especially Mogas. The fuel return Rotax recommend keeps more fuel flowing through the system which helps cool the pump and ensures cold fuel when you need it for high power. Most carburetor installations in cars have a fuel return line for the same reasons. Graham _____ From: FLYaDIVE Sent: Sunday, 7 April 2013, 19:08 Subject: Re: RotaxEngines-List: Re: Fuel return line Sacha: You have some great thought provoking questions. I hope some are provoked. Fire sleeves or One piece Molded Teflon fuel lines are the way to go. You always want to do all you can to keep extra heat from fuel and oil lines. BUT! Where did this Old Wives Tail of Vapor Lock come from? It is a BUNCH OF BUNK! The "T" fitting does NOTHING for Vapor Lock... High Pressure does NOTHING to prevent Vapor Lock. Well, almost nothing - It corrects Pilot/Builder error. Vapor Lock happens ON THE GROUND and is experienced usually at start up and sometimes in the air, immediately during or after rotation. Vapor Lock can occur with MoGAs or AvGas. It is more of a POOR PILOT SHUTDOWN PROCEDURE that anything else. And since we are talking Home Built Planes and Self Proclaimed Engineers - - Builder error. So, what does the "T" fitting do? Well, the history goes way back to the 1960's... Electric home made Fuel Pumps were being used on Carbureted engines. And the engines were FLOODING like crazy. Flooding, Fires, Poor Starts (if at all), Dying when the throttle was floored and Low HP. All because of TOO MUCH Fuel Pressure Pushing the Carburetor's intake valve off the seat and flooding the carb. So, how do you get more fuel to the carb so it does not go LEAN? You do a whole lot of pressure testing and engineering - BUT! These were HOME MADE FUEL PUMPS - And Manufacturer made Carbs. Transducers were not around then. It was too costly to try to figure out how many GPH and How much Fuel Pressure would work,and what size spring to use... Too many variables. The QUICK and EASY and VERY Effective solution... Put a "T" fitting in the line and the excess pressure and excess fuel is returned to the fuel tank. The Carb takes what it needs - Has a steady supply of fuel and does NOT go lean no matter how fast you hit the throttle. No Smoke and Mirrors, No ridiculous Vapor Lock theories. But, hell, this is aviation so everybody just re-invents the wheel with their own ideas. I ________________________________ Message 12 ____________________________________ Time: 03:46:05 PM PST US From: "Sacha" Subject: RE: RotaxEngines-List: Re: Fuel return line My fuel return line only goes back to the gascolator. but I'm hoping it's enough as it is at the bottom of the cowling and should get decent cooling from the airflow. I read Transport Canada's piece on using Mogas in aviation and they say that vapor lock problems can occur more easily if you use winter fuel (which has a lower vaporization temp) in the warmer months. Not sure if there are different grades of fuel in winter/summer in the UK - certainly doesn't seem like there is any need for "summer" fuel this year so far. :-( From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Bob Harrison Sent: Sunday, 07 April, 2013 23:01 Subject: RE: RotaxEngines-List: Re: Fuel return line Thanks Graham .........I was beginning to think I was having a bad dream ! Me too over the M1 from Halfpenny Green back to Wickenby, mind you it was Jabiru originated but no one will convince me anything else and nothing else found after exhaustive checks and re-checks. As far as I'm concerned there was no BS involved. To say there's no such thing is misleading in the extreme. The return line must go back into the Europa Tank via the reserve supply side ensuring only the coolest fuel goes forward. Best regards Bob Harrison. (Survived 1000 hours but would never boast about that before a flight ! Also only about half of that was with the Jabiru.) From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of GRAHAM SINGLETON Sent: 07 April 2013 22:25 Subject: Re: RotaxEngines-List: Re: Fuel return line Vapour lock certainly does occur. I know of several instances, one of which resulted in a written off aircraft. It happens when the engine driven fuel pump gets heated by the engine oil and then heats the fuel. Low fuel flow rate such as when taxiing or waiting for air traffic on the ground can vaporize the fuel, especially Mogas. The fuel return Rotax recommend keeps more fuel flowing through the system which helps cool the pump and ensures cold fuel when you need it for high power. Most carburetor installations in cars have a fuel return line for the same reasons. Graham _____ From: FLYaDIVE Sent: Sunday, 7 April 2013, 19:08 Subject: Re: RotaxEngines-List: Re: Fuel return line Sacha: You have some great thought provoking questions. I hope some are provoked. Fire sleeves or One piece Molded Teflon fuel lines are the way to go. You always want to do all you can to keep extra heat from fuel and oil lines. BUT! Where did this Old Wives Tail of Vapor Lock come from? It is a BUNCH OF BUNK! The "T" fitting does NOTHING for Vapor Lock... High Pressure does NOTHING to prevent Vapor Lock. Well, almost nothing - It corrects Pilot/Builder error. Vapor Lock happens ON THE GROUND and is experienced usually at start up and sometimes in the air, immediately during or after rotation. Vapor Lock can occur with MoGAs or AvGas. It is more of a POOR PILOT SHUTDOWN PROCEDURE that anything else. And since we are talking Home Built Planes and Self Proclaimed Engineers - - Builder error. So, what does the "T" fitting do? Well, the history goes way back to the 1960's... Electric home made Fuel Pumps were being used on Carbureted engines. And the engines were FLOODING like crazy. Flooding, Fires, Poor Starts (if at all), Dying when the throttle was floored and Low HP. All because of TOO MUCH Fuel Pressure Pushing the Carburetor's intake valve off the seat and flooding the carb. So, how do you get more fuel to the carb so it does not go LEAN? You do a whole lot of pressure testing and engineering - BUT! These were HOME MADE FUEL PUMPS - And Manufacturer made Carbs. Transducers were not around then. It was too costly to try to figure out how many GPH and How much Fuel Pressure would work,and what size spring to use... Too many variables. The QUICK and EASY and VERY Effective solution... Put a "T" fitting in the line and the excess pressure and excess fuel is returned to the fuel tank. The Carb takes what it needs - Has a steady supply of fuel and does NOT go lean no matter how fast you hit the throttle. No Smoke and Mirrors, No ridiculous Vapor Lock theories. But, hell, this is aviation so everybody just re-invents the wheel with their own ideas. I http://www.matronics.com/Navigator?RotaxEngines-List http://forums.matronics.com http://www.matronics.com/contribution ________________________________ Message 13 ____________________________________ Time: 04:21:15 PM PST US From: rayj Subject: Re: RotaxEngines-List: Re: Fuel return line I don't know if this applies to Rotax engines. There is another way a carbureted engine can vapor lock. Back in the 50s and 60s some automotive engines had the carb bolteddirectly to the intake manifold, without an insulating spacer. The heat from the engine block could be conducted to the carb and cause the combination of fuel draw through the venturi and the fuel evaporation out of the bowl to exceed what the needle valve could let it in. The fuel bowl would get low and the engine would stop. Then the heat soaking of the stationary fuel in the lines in the engine compartment would start. Some times it took 20-30 min or more with the hood open to be able to start the engine again. Raymond Julian Kettle River, MN. "And you know that I could have me a million more friends, and all I'd have to lose is my point of view." - John Prine On 04/07/2013 04:25 PM, GRAHAM SINGLETON wrote: > Vapour lock certainly does occur. I know of several instances, one of > which resulted in a written off aircraft. It happens when the > engine driven fuel pump gets heated by the engine oil and then heats > the fuel. Low fuel flow rate such as when taxiing or waiting for air > traffic on the ground > can vaporize the fuel, especially Mogas. The fuel return Rotax > recommend keeps more fuel flowing through the system which helps cool > the pump and ensures cold fuel when you need it for high power. > Most carburetor installations in cars have a fuel return line for the > same reasons. > Graham > ------------------------------------------------------------------------ > *From:* FLYaDIVE > *To:* rotaxengines-list@matronics.com > *Sent:* Sunday, 7 April 2013, 19:08 > *Subject:* Re: RotaxEngines-List: Re: Fuel return line > > Sacha: > > You have some great thought provoking questions. I hope some are > provoked. > Fire sleeves or One piece Molded Teflon fuel lines are the way to go. > You always want to do all you can to keep extra heat from fuel and oil > lines. > BUT! Where did this Old Wives Tail of Vapor Lock come from? It is a > BUNCH OF BUNK! > The "T" fitting does NOTHING for Vapor Lock... High Pressure does > NOTHING to prevent Vapor Lock. Well, almost nothing - It corrects > Pilot/Builder error. > Vapor Lock happens ON THE GROUND and is experienced usually at start > up and sometimes in the air, immediately during or after rotation. > Vapor Lock can occur with MoGAs or AvGas. > It is more of a POOR PILOT SHUTDOWN PROCEDURE that anything else. > And since we are talking Home Built Planes and Self > Proclaimed Engineers - - Builder error. > So, what does the "T" fitting do? Well, the history goes way back to > the 1960's... Electric home made Fuel Pumps were being used > on Carbureted engines. And the engines were FLOODING like crazy. > Flooding, Fires, Poor Starts (if at all), Dying when the throttle > was floored and Low HP. All because of TOO MUCH Fuel Pressure Pushing > the Carburetor's intake valve off the seat and flooding the carb. > So, how do you get more fuel to the carb so it does not go LEAN? You > do a whole lot of pressure testing and engineering - BUT! These were > HOME MADE FUEL PUMPS - And Manufacturer made Carbs. Transducers were > not around then. It was too costly to try to figure out how many GPH > and How much Fuel Pressure would work,and what size spring to use... > Too many variables. > The QUICK and EASY and VERY Effective solution... Put a "T" fitting > in the line and the excess pressure and excess fuel is returned to the > fuel tank. > The Carb takes what it needs - Has a steady supply of fuel and does > NOT go lean no matter how fast you hit the throttle. > No Smoke and Mirrors, No ridiculous Vapor Lock theories. But, hell, > this is aviation so everybody just re-invents the wheel with their own > ideas. > > I > * > > > * ________________________________ Message 14 ____________________________________ Time: 11:33:03 PM PST US From: "Bob Harrison" Subject: RE: RotaxEngines-List: Re: Fuel return line Hi! Alan/all The Jabiru incident to which I refer was with their engine mounted fuel pump plus another electrical pick up pump. But of course in my ultimate bad dream, actually a nightmare! The Jabiru 3300 I had fitted was never without overheating problems ...... then take it up on Mogas in a stinking hot summer day to about 5,000ft and it lets you know the limits of using Mogas. With the 914 Rotax I would never fly hot and high with Mogas, I think the recommended limits are about 2,000ft and 20deg C Ambient but having said that someone more clever than me will likely correct me ! But the 914 on 100ll and two electrical pumps took me safely to 17,500ft over Mont Blanc with Ivor Phillips as a "two ship" last August. Outside ambient at that height was approx 4deg C but at -2deg\C per 1000ft the ambient at ground was very hot. (as an aside had the Jabiru been the "donkey" it used to struggle at less than 50ft per minute climb at 13,000ft like "watching paint dry" even without vaporisation !) Sorry about that chaps I couldn't refrain any longer ! Bob Harrison. G-PTAG -----Original Message----- From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Alan Carter Sent: 07 April 2013 22:55 Subject: RotaxEngines-List: Re: Fuel return line --> Hi All. My 914 has two fuel pumps, one pump has to run all the time as i think the 914 has no engine drive pump, Why? These pumps are mounted well away from the engine in the belly of the fuselage, so cooling of the pumps is good, Has there been any problems with vapor lock on the 914, using Mogas. 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