Original Posted By: "Gene & Tammy"
I just installed a new fuel valve, gascolator screen and fuel hoses on my plane, and decided I needed to test the fuel flow rate when I was done. I have an 18.3 gallon nose tank, and I expected the flow rate to be far more than adequate. It appears to be adequate, but is not as high as I hoped, so I'd like to get the opinion of more experienced people to determine what I need to do, if anything.I have an A-75. The chart indicates a maximum full throttle demand of about 6.3 gallons per hour. Of course, my burn rates in cruise are higher than what they should be according to the same table, so I think the actual max rate is probably also higher. For that reason, I'd be happy with a rate of at least 9-10 GPH, just for a safety margin. It took about 38 minutes to drain 5 gallons of fuel, a flow rate of about 7.9GPH. I started with 5 gallons of fuel, then when it got to four gallons, I noticed the flow rate had decreased substantially. I added another 5 gallons, and this increased the flow rate and it appeared to remain near constant as it drained from 9 gallons to 5 gallons. Obviously what I am trying to simulate is a full throttle climb with minimum useable fuel.A few questions:1. - What is the MINIMUM acceptable flow rate for an A-75?2. - Does the carburetor/needle assembly affect the flow rate? I tested the rate by simply disconnecting the hose from the carb, and keeping the hose at the same height as the carb inlet. Would the needle lower the fuel rate?3. - Is ~7GPH adequate for an A-75 in your opinion?Something to consider for builders...because my tank is so low relative to the carb, I don't get adequate fuel pressure when the fuel level is low. As a result, I have about 4 gallons of fuel that is unusable, not because it won't reach the sump, but because of pressure. So I am always carrying around 25lbs of fuel for no reason other than to make the fire bigger after a crash. Somewhere before I have seen a specification for a minimum height of the tank outlet above the carburetor. Mine does not meet that spec, hence the reason for a large amount of unuseable fuel. The bottom of my tank is about 2"-3" above the carb when sitting on the ground.Of course before I fly it, I intend to do an extended ground run at full throttle to verify that flow is adequate. Any thoughts or shared experience on the subject would be appreciated.Thanks,Steve RuseNorman, Ok ________________________________________________________________________________
Pietenpol-List: Fuel Flow Rates
Re: Pietenpol-List: Fuel Flow Rates
Original Posted By: "Steve Ruse"
Steve, the two questions I have is what size hose and do you have a vented cap? I have also seen problems with fuel valves not opening all the way even though the handle indicates it is full open.Gene----- Original Message -----
Steve, the two questions I have is what size hose and do you have a vented cap? I have also seen problems with fuel valves not opening all the way even though the handle indicates it is full open.Gene----- Original Message -----
Re: Pietenpol-List: Fuel Flow Rates
Original Posted By: "Gene & Tammy"
The fuel lines are 1/4" Aeroquip 666 (666-4), but the ID is only .188. There are two 16" lines, one from the tank to the gascolator and one from the gascolator to the carb. The ID of that hose is only .188, which initially caused me concern, but the company I ordered them from (www.aircrafthose.com) assured me that was fine for a gravity feed system, and that I should use it instead of a larger hose since those fittings were what were on my carb and gascolator.The valve does open all the way, I just installed it and checked it before installation. It is a new miniature 1/4" valve from Aircraft Spruce.http://www.aircraftspruce.com/catalog/a ... ifv.phpThe cap is a cub-style cap with a cork float. It is only vented via the small opening around the 1/8" float rod and the tube it passes through. Removing the cap did not cause a noticeable different in the flow rate, so I don't believe it is a vacuum problem.Thanks for any input,Steve----- Original Message -----
The fuel lines are 1/4" Aeroquip 666 (666-4), but the ID is only .188. There are two 16" lines, one from the tank to the gascolator and one from the gascolator to the carb. The ID of that hose is only .188, which initially caused me concern, but the company I ordered them from (www.aircrafthose.com) assured me that was fine for a gravity feed system, and that I should use it instead of a larger hose since those fittings were what were on my carb and gascolator.The valve does open all the way, I just installed it and checked it before installation. It is a new miniature 1/4" valve from Aircraft Spruce.http://www.aircraftspruce.com/catalog/a ... ifv.phpThe cap is a cub-style cap with a cork float. It is only vented via the small opening around the 1/8" float rod and the tube it passes through. Removing the cap did not cause a noticeable different in the flow rate, so I don't believe it is a vacuum problem.Thanks for any input,Steve----- Original Message -----
Re: Pietenpol-List: Fuel Flow Rates
Original Posted By: "gcardinal"
Have you considered buying a piece of 3/8th hose and seeing what you get. It should be a whole lot more. I have just about the same tank (17 gal nose tank) with 3/8th hose. I don't recall the flow rate but it is much higher than yours. If you need, I can run another test, using my tank, in a few days when I have the time.As a side note, I doubt if the last 4 gal in your tank is unuseable, if it is above the carb while in flying attitude. You may not be able to fly at full throttle thru all 4 gals but it could get you to a safe place to land. I never fly with less than an hours worth left over, just for safety. One of the main reason for airplane crashes is running out of gas.Just my two cents worthGene________________________________________________________________________________
Have you considered buying a piece of 3/8th hose and seeing what you get. It should be a whole lot more. I have just about the same tank (17 gal nose tank) with 3/8th hose. I don't recall the flow rate but it is much higher than yours. If you need, I can run another test, using my tank, in a few days when I have the time.As a side note, I doubt if the last 4 gal in your tank is unuseable, if it is above the carb while in flying attitude. You may not be able to fly at full throttle thru all 4 gals but it could get you to a safe place to land. I never fly with less than an hours worth left over, just for safety. One of the main reason for airplane crashes is running out of gas.Just my two cents worthGene________________________________________________________________________________
Re: Pietenpol-List: Fuel Flow Rates
Original Posted By: "Gene & Tammy"
3/8" tubing from a center section fuel tank resulted in a flow rate of 19 gph on NX18235.Greg Cardinal----- Original Message -----
3/8" tubing from a center section fuel tank resulted in a flow rate of 19 gph on NX18235.Greg Cardinal----- Original Message -----
Re: Pietenpol-List: Fuel Flow Rates
Original Posted By: hvandervoo(at)aol.com
OZ and Corky's "Arsenal of Democracy"- http://www.flysquirrel.net/piets/arsenal.jpgIt was too windy and gusty to fly yesterday, but the flag did fine. Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Subject: Re: Pietenpol-List: Fuel Flow RatesDate: Tue, 27 May 2008 09:24:15 -0400
OZ and Corky's "Arsenal of Democracy"- http://www.flysquirrel.net/piets/arsenal.jpgIt was too windy and gusty to fly yesterday, but the flag did fine. Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Subject: Re: Pietenpol-List: Fuel Flow RatesDate: Tue, 27 May 2008 09:24:15 -0400
Pietenpol-List: Fuel Flow Rates
Original Posted By: Steve Ruse
To some of Steve's comments and questions->I have an 18.3 gallon nose tank, and I expected the flow rate to be far more> than adequateThe nose tank on 41CC is 16 U.S. gallons, more or less. Flow is adequate, butread on.> I have an A-75. The chart indicates a maximum full throttle demand of about> 6.3 gallons per hour.41CC currently has an A65, which should consume 4 gallons/hr., but I'm preparingto install an A75 on it so this discussion is of interest to me.>Of course, my burn rates in cruise are higher than> what they should be according to the same tableBurn rates for the A65 on my airplane seem to be pretty much spot-on with the 4GPH figure.>I started with 5 gallons of fuel, then when it got to four gallons, I noticedthe flow rate> had decreased substantially.I've noticed that with anything less than 6 gallons in my tank and with the taildown, flowrate is quite low and probably would only sustain idling or low powersettings. In fact, it is not possible to get the final 4 or so gallons outof the system without raising the tail to level flying attitude because thefuel outlet and shutoff valve are lower than the carb float level, or at leastthe static head is insufficient to flow much fuel through the restrictions atthat point. I have determined this both by repeatedly draining the tank on theground, and by having had the engine quit due to fuel starvation in the flareto landing with the fuel indicator down to the "red" (the top inch of my floatrod is painted red). Valuable lesson, but one that I don't care to learnagain.> 1. - What is the MINIMUM acceptable flow rate for an A-75?I don't know but am interested to know what you find out.> 3. - Is ~7GPH adequate for an A-75 in your opinion?Since you're opening it up to opinions, I'd have to say "yes". I can't imagine10HP jumping the fuel consumption from 4 to 7 gal./hr.>I have about 4 gallons of fuel that is unusable, not because it> won't reach the sump, but because of pressure. So I am always carrying> around 25lbs of fuel for no reason other than to make the fire bigger after> a crash.Well, I guess that's one way of looking at it, but you're in good company... I'dsay quite a few of us have the identical setup and the only sure-fire way tomake all of your fuel usable is to put it in the wing. I consider the final4 gallons in my tank unusable except in level flight in emergency circumstances,and probably the final 6 gallons are only usable in the tail-low attitude,as you've found by testing and I've confirmed by... "testing" ;o) It's nice toknow that I can use that fuel if I really, really have to... but the engineWILL quit the moment the tail comes down if I'm into that last 4 to 6 gallons.That still gives me 2 to 3 hrs.' flight time, which is still longer than I wantto sit in the airplane in flight.When I had the tank out of the airplane during repairs, I carefully poured singlegallons one by one into the tank to check the markings Corky had put on thefloat rod and was very puzzled at why he shorted himself the final few gallons'capacity. The float rod wouldn't move off the peg until there were a coupleof gallons in the tank but I figured he was just being conservative. Nossir...he knew what he was doing and I should never have tested the limits of anold Cajun's smarts but I did, and maybe I'm a little smarter now, too.>Somewhere before I have seen a specification for a minimum height> of the tank outlet above the carburetor. Mine does not meet that spec,> hence the reason for a large amount of unuseable fuel. The bottom of my> tank is about 2"-3" above the carb when sitting on the ground.I'll bet that spec is in Tony Bingelis' books somewhere, as well as in Evans' LightplaneDesigner book. I'll check tonight, but I'll bet the number will surpriseyou.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Date: Tue, 27 May 2008 10:00:50 -0400
To some of Steve's comments and questions->I have an 18.3 gallon nose tank, and I expected the flow rate to be far more> than adequateThe nose tank on 41CC is 16 U.S. gallons, more or less. Flow is adequate, butread on.> I have an A-75. The chart indicates a maximum full throttle demand of about> 6.3 gallons per hour.41CC currently has an A65, which should consume 4 gallons/hr., but I'm preparingto install an A75 on it so this discussion is of interest to me.>Of course, my burn rates in cruise are higher than> what they should be according to the same tableBurn rates for the A65 on my airplane seem to be pretty much spot-on with the 4GPH figure.>I started with 5 gallons of fuel, then when it got to four gallons, I noticedthe flow rate> had decreased substantially.I've noticed that with anything less than 6 gallons in my tank and with the taildown, flowrate is quite low and probably would only sustain idling or low powersettings. In fact, it is not possible to get the final 4 or so gallons outof the system without raising the tail to level flying attitude because thefuel outlet and shutoff valve are lower than the carb float level, or at leastthe static head is insufficient to flow much fuel through the restrictions atthat point. I have determined this both by repeatedly draining the tank on theground, and by having had the engine quit due to fuel starvation in the flareto landing with the fuel indicator down to the "red" (the top inch of my floatrod is painted red). Valuable lesson, but one that I don't care to learnagain.> 1. - What is the MINIMUM acceptable flow rate for an A-75?I don't know but am interested to know what you find out.> 3. - Is ~7GPH adequate for an A-75 in your opinion?Since you're opening it up to opinions, I'd have to say "yes". I can't imagine10HP jumping the fuel consumption from 4 to 7 gal./hr.>I have about 4 gallons of fuel that is unusable, not because it> won't reach the sump, but because of pressure. So I am always carrying> around 25lbs of fuel for no reason other than to make the fire bigger after> a crash.Well, I guess that's one way of looking at it, but you're in good company... I'dsay quite a few of us have the identical setup and the only sure-fire way tomake all of your fuel usable is to put it in the wing. I consider the final4 gallons in my tank unusable except in level flight in emergency circumstances,and probably the final 6 gallons are only usable in the tail-low attitude,as you've found by testing and I've confirmed by... "testing" ;o) It's nice toknow that I can use that fuel if I really, really have to... but the engineWILL quit the moment the tail comes down if I'm into that last 4 to 6 gallons.That still gives me 2 to 3 hrs.' flight time, which is still longer than I wantto sit in the airplane in flight.When I had the tank out of the airplane during repairs, I carefully poured singlegallons one by one into the tank to check the markings Corky had put on thefloat rod and was very puzzled at why he shorted himself the final few gallons'capacity. The float rod wouldn't move off the peg until there were a coupleof gallons in the tank but I figured he was just being conservative. Nossir...he knew what he was doing and I should never have tested the limits of anold Cajun's smarts but I did, and maybe I'm a little smarter now, too.>Somewhere before I have seen a specification for a minimum height> of the tank outlet above the carburetor. Mine does not meet that spec,> hence the reason for a large amount of unuseable fuel. The bottom of my> tank is about 2"-3" above the carb when sitting on the ground.I'll bet that spec is in Tony Bingelis' books somewhere, as well as in Evans' LightplaneDesigner book. I'll check tonight, but I'll bet the number will surpriseyou.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Date: Tue, 27 May 2008 10:00:50 -0400
RE: Pietenpol-List: New $100 dollar breakfast location For Ohio Piets!!
Original Posted By: "Cuy, Michael D. (GRC-RXD0)[ASRC]"
Fuel lines and fittings on 41CC are AN6 (3/8").Oscar ZunigaNX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Subject: RE: Pietenpol-List: New $100 dollar breakfast location For Ohio Piets!!Date: Tue, 27 May 2008 12:25:57 -0500
Fuel lines and fittings on 41CC are AN6 (3/8").Oscar ZunigaNX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Subject: RE: Pietenpol-List: New $100 dollar breakfast location For Ohio Piets!!Date: Tue, 27 May 2008 12:25:57 -0500
Re: Pietenpol-List: Fuel Flow Rates
Original Posted By: FTLovley
________________________________________________________________________________Date: Tue, 27 May 2008 19:09:49 -0500
________________________________________________________________________________Date: Tue, 27 May 2008 19:09:49 -0500
Pietenpol-List: Fuel Flow Rates
Original Posted By: "Gordon Bowen"
Some info from Tony Bingelis' books: From "Sportplane Builder", he shows a gravityfeed system that is almost a precise schematic/sketch of what's installedon 41CC, from fuel tank cap to carb inlet. In the text he gives rules of thumbfor gravity feed systems but almost discounts the calculated minimum statichead as being unrealistic by saying that there are many, many proven designsout flying with nowhere near that amount of head. The more realistic rules ofthumb that he gives are to figure a minimum flowrate in takeoff configurationas 1.2 lbs. per HP-hr. or 150% of the takeoff fuel consumption rate.For a nominal 75 takeoff horsepower engine, the 1.2 lb./HP-hr gives 15 gallonsper hour minimum flow. I couldn't find takeoff fuel consumption specs on theA75 but cruise consumption is given as 4.8 gal./hr. so for simplicity let's use6 gal./hr. at takeoff power. Using that, the 150% gives a minimum requiredflow of 9 gal./hr. so there are two numbers that you can use to check against.Looking in "Tony Bingelis on Engines", he has a schematic/sketch very similar tothe one from the earlier "Sportplane Builder" but in this one he clearly labelsa minimum of 17" (0.5 psi static head) between the bottom of the fuel tankand the fuel inlet to the carb.My airplane does not have 17". I'll have to measure it (or estimate it) next timeI have the cowling off but I'd be surprised if it's half that.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________
Some info from Tony Bingelis' books: From "Sportplane Builder", he shows a gravityfeed system that is almost a precise schematic/sketch of what's installedon 41CC, from fuel tank cap to carb inlet. In the text he gives rules of thumbfor gravity feed systems but almost discounts the calculated minimum statichead as being unrealistic by saying that there are many, many proven designsout flying with nowhere near that amount of head. The more realistic rules ofthumb that he gives are to figure a minimum flowrate in takeoff configurationas 1.2 lbs. per HP-hr. or 150% of the takeoff fuel consumption rate.For a nominal 75 takeoff horsepower engine, the 1.2 lb./HP-hr gives 15 gallonsper hour minimum flow. I couldn't find takeoff fuel consumption specs on theA75 but cruise consumption is given as 4.8 gal./hr. so for simplicity let's use6 gal./hr. at takeoff power. Using that, the 150% gives a minimum requiredflow of 9 gal./hr. so there are two numbers that you can use to check against.Looking in "Tony Bingelis on Engines", he has a schematic/sketch very similar tothe one from the earlier "Sportplane Builder" but in this one he clearly labelsa minimum of 17" (0.5 psi static head) between the bottom of the fuel tankand the fuel inlet to the carb.My airplane does not have 17". I'll have to measure it (or estimate it) next timeI have the cowling off but I'd be surprised if it's half that.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________
RE: Pietenpol-List: Fuel Flow Rates
Original Posted By: "Phillips, Jack"
Subject: Pietenpol-List: More photos-front seat shoulder harness attachMore photos Dan HelsperPoplar Grove, IL.**************Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence" on AOL Food. (http://food.aol.com/tyler-florence?vide ... 0000000002)________________________________________________________________________________Subject: RE: Pietenpol-List: Fuel Flow RatesDate: Wed, 28 May 2008 07:30:15 -0400
Subject: Pietenpol-List: More photos-front seat shoulder harness attachMore photos Dan HelsperPoplar Grove, IL.**************Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence" on AOL Food. (http://food.aol.com/tyler-florence?vide ... 0000000002)________________________________________________________________________________Subject: RE: Pietenpol-List: Fuel Flow RatesDate: Wed, 28 May 2008 07:30:15 -0400
Re: Pietenpol-List: Fuel Flow Rates
Original Posted By: Ben Williams
Pietenpol-List: Fuel Flow Rates
Original Posted By: "Dick Navratil"
>> ________________________________________________________________________________
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> Pietenpol-List: Fuel Flow Rates
Original Posted By: "Gene & Tammy"
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> Pietenpol-List: Fuel Flow Rates
Original Posted By: Oscar Zuniga
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