I fly a ragwing 170 which,as every good 170'er knows,came originally equipped with two Cessna 120/140 fuel tanks (25 gallons) in the RH wing and one (12.5 gal) in the LH wing. Mine has been modified,as many others have,with a second LH tank for a total of 50 gallons.
My airplane consistantly feeds fuel faster out of the RH tanks than the LH tanks--in other words,I might burn 12 gallons out of the RH side & only 5 or 6 out of the LH tanks. Do any other ragwing owners notice a similar tendency?
I just came up with a possible theory--since the factory installed RH tankage is double the LH tankage,maybe they installed bigger fuel line(s) coming from the RH side so that the RH & LH systems would remain at approximately the same level. It wouldn't do to have the LH system run dry while the RH system still was half full. Since I have the added tank on the LH side,making the LH & RH systems equal capacity,the level on that side is therefore going down slower than on the RH side.
My IPC doesn't seem to indicate any difference in the fuel lines from the LH & RH systems,and I've never measured the lines myself.
Any thoughts on the subject?
Eric
ragwing fuel feed
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
I have the standard set up with 2 on the right and 1 on the left. My left tank always went down first, and having just done the wings, we found the one vent cross tube delibertly plugged. We are going to origional and I still have the unvented recessed caps. I am anxious to see how it now behaves with equal flow. The lines on mine are the same size from the tanks through the door posts to the selector valve on the firewall. I also have both curved vents on top.
John - 48 n3833v
John - 48 n3833v
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zero.one.victor
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Larry Holtz
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Ragwing Fuel Feed
On short flights and around the pattern mine seems to feed about even, but on long a crosscountry things are different. If it is feeding from the left tank and I have to start some aliron to keep things level I switch to the right tank for a while. But when I switch back to both, it continues to feed from the right tank faster than the left. I have the original setup.
Larry
Larry
Uneven fuel feeding has been addressed elsewhere, but the short-story version is this:
If your right fuel cap is vented, you might find that tank appears to feed faster than the left when the selector valve is in "Both". This is a false appearance in most cases. What actually happens is that the vented right tank will not only feed the engine, but it will also feed the left tank via the vent line. Fuel from the left tank is replaced by fuel crossing over from the right tank, therefore the left tank appears to not feed as quickly as the right. This is even more pronounced with a partially blocked "gooseneck", due to a siphoning action.
If your right fuel cap is vented, you might find that tank appears to feed faster than the left when the selector valve is in "Both". This is a false appearance in most cases. What actually happens is that the vented right tank will not only feed the engine, but it will also feed the left tank via the vent line. Fuel from the left tank is replaced by fuel crossing over from the right tank, therefore the left tank appears to not feed as quickly as the right. This is even more pronounced with a partially blocked "gooseneck", due to a siphoning action.
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russ murri
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fuel
Eric
I use fuel out of right tank faster also.I have the 50 gal set up also. My question to you is how long do you fly without adding fuel I am not comfortable after about 4 hrs. If I am local I will refuel at about this much time. still have 20 gal or more at that time. on trips my bladder is good for 2 to 3 hrs thats not the issue. do you run the tanks down to less than the 20 gal range? Thanks Russ
I use fuel out of right tank faster also.I have the 50 gal set up also. My question to you is how long do you fly without adding fuel I am not comfortable after about 4 hrs. If I am local I will refuel at about this much time. still have 20 gal or more at that time. on trips my bladder is good for 2 to 3 hrs thats not the issue. do you run the tanks down to less than the 20 gal range? Thanks Russ
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zero.one.victor
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George: I have never seen a ragwing 170 with vented cap(s). They have a different style cap than the A & B models. They also have different style caps than the 120/140,even thought they use 120/140 fuel tanks--leftovers? The only venting is via the cabin-top gooseneck.
Russ: Most of my flying is local. I usually start off with mostly full tanks,in the neighborhood of 40 gallons or a bit more. On a trip,I will top it off before leaving home,but still generally don't go more than about 4 hours (approx 32 gallons burned) without gassing. Usually if I'm flying with another plane they need gas by then so I just go ahead & gas up too. I think running out of gas is about the stupidest & most preventable type of emergency to have. The old expression "the only time you can have too much gas is when you're on fire" comes to mind,as well as "the 3 most useless things:runway behind you,altitude above you,and fuel left back in the gas truck."
Eric
Russ: Most of my flying is local. I usually start off with mostly full tanks,in the neighborhood of 40 gallons or a bit more. On a trip,I will top it off before leaving home,but still generally don't go more than about 4 hours (approx 32 gallons burned) without gassing. Usually if I'm flying with another plane they need gas by then so I just go ahead & gas up too. I think running out of gas is about the stupidest & most preventable type of emergency to have. The old expression "the only time you can have too much gas is when you're on fire" comes to mind,as well as "the 3 most useless things:runway behind you,altitude above you,and fuel left back in the gas truck."
Eric
Yes, Thanks, Eric, I did know this particular post applied to ragwings, but uneven fuel flow caused by siphoning action can occur to any airplane with a common vent line, so I mentioned this phenomena categorically. But to be accurate, the AD note and the Service Letter SE 77-6 regarding vented caps only applied to sn's 18730 and above (and also excluded sn 609 which had an experimental fuel system.)
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zero.one.victor
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I admit, it's a stretch of the imagination, but both Cessna and CPA have supposedly confirmed this event. Fuel flows from both tanks equally (more or less) to the engine. But the fuel is normally replaced by atmosphere. In the scenario suggested, ...instead of air replacing the fuel used from the left tank,...fuel is siphoned from the right tank through the common vent line to the left tank, thereby replacing the fuel which was consumed by the engine. Therefore, the left tank remains full until that siphon/suction is broken by sufficiently-developed differential vent pressure. The left tank now contains more fuel than the right tank, and both tanks continue to feed the engine more or less equally. This scenario is most common in under-wing vented systems, but has also been observed in systems such as 170's, etc., with the over-cabin vent.zero.one.victor wrote:George,the logic and mechanics of your whole explanation of siphoning from one tank to another because of the common vent eludes me. Can you clarify what's allegedly going on?
Eric