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Which fuel tank to select for T.O. and Landings?

This is a great thread. I have never cared right or left and never had any problems, the only time I have run dry is in the air (usually in Texas or Oklahoma). I like the "use the one with the most fuel" option, but this has caused me to pause...

sj
 
which tank

As a matter of habbit I run the right tank dry leaving only the left to use. Cross country of coarse and at altitude. I'll read my late model owners manual and see what it says. What year is your machine?
 
PA-12 Tanks

Not a PA-22 expert, but I do have a PA-12 Owner's Manual (I think for hte headerless models) that states:

1. LEFT TANK-MAIN valve must be on all the time during flight (See Figure 2).
2. RIGHT TANK-AUXILIARY valve may be off until the fuel is used from the tank to check fuel consumption or it may be turned on at the beginning of flight, thus using fuel from both tanks simultaneously.
3. RIGHT TANK-AUXILIARY valve should be turned off during refueling to prevent feed-back from one tank to the other.

The original fuel system diagram shows rear feeds only and then a front cross vent between tanks for headerless aircraft. On the "older" models with the header tank the drawing shows the right tank rear feed going direct to the header tank, the left tank rear feed going to a valve, then teeing in with the right line to the header tank, then a valve between the header tank and the gascolator.
 
This is an interesting topic for me as I had an "interesting" experience while bringing my SC home to Michigan from Northern Maine after I bought it. It may explain what happened, You all tell me as I have never been able to figure it out for sure. About 5 miles out from the airport in Batavia New York where I was landing to buy fuel the engine stopped. It seemed pretty evident that the problem was fuel starvation. I had been watching the fuel usage closely and had run the left tank drying about 45 minutes prior. I was on the right tank with still about 1 1/4 inches of fuel showing in the sight gauge. I switched to the left just to see if I could get a little more from it, got just a little sputter as I turn toward a grass strip I had just passed. Then back to the right tank, all the time I keep looking back up at the sight gauge as I'm having trouble believing that it is still showing fuel but can't use it. I did the rudder fuel slosh thing and the fuel moved up and down in the sight gauge, but I just got an occational few seconds of power as I approached the strip. As I explained to the nice man at the house why I left the SC sitting in the middle of his airstrip rather than bring it up to the hangar, he offered to gather up some fuel cans and we drove over to the airport and got some fuel. In trying to figure this out I took the sight gauge apart to see if there was some kind of restriction in it that would not allow it to empty completely at times, everything was fine with it. I have tried and been able to fly the right tank empty and the sight gauge shows empty. So now I leave fuel in the left and drain the right first. My fuel system is original.
 
Gas.

Hi Gerald. In my opinion, you have stated a textbook case, of the stock fuel system and why the proceedure to empty the right at altitude. There is a problem however. And that is that it should have taxied to the barn with no problem as soon as the tail was lowered. In fact that is how you get yourself out of this situation usually. Let me go back. The original problem comes from the nose down attitude when letting down for landing while on the right tank. The hardest thing to do with the airport in sight is to slow down and raise the nose into a slowflight descent. But that will usually keep the engine running. In your case, if the engine quit and wouldn't restart in 3 point, I suspect that the right gage is mounted a bit too low and giving a bad reading. You may have really been out of gas. I do this test every time I rehang the wings or work on a tank. Raise the tail to a descent attitude and drain the fuel from the tank into a container. ( at the gascolator ). Then lower the tail to level flight, and drain it again. Then lower it to climb attitude and drain it again. That is the best way I know to get the answers for your airplane. Works for me. :) Jerry.
 
I think.......as with all gravity flow systems.......that if you visualize the fuel in regard to the aircraft attitude and know that if the carb is higher than the fuel you are going to eventually starve the engine. sj and I can attest to that........we made a wide extended left turn with minimum fuel in the left tank trying to look at some moose while in Canada last winter. Eventually the engine coughed an told us to switch tanks. Makes me wonder if, in that situation, that fuel from the header tank actually flows in reverse back to the main tank.......anybody know?
 
It's just not as simple as visuallizing where the gas is going to be in the tanks while tipping the plane around in a hanger. A aircraft in flight has so many constantly changing forces being applied to it, anything can be happening to that fuel. You can be completely inverted on the top of a loop, still pulling positive g's and completely coodinated, and the fuel system is not going to know it is upsidedown. You can be in a 90 degree bank turn, if you are coodinated, same thing. you can be straight and level, but have the plane all crossed up, and you can unport a tank. When low on fuel, just try to fly as coodinated as possible.

Think of it like when you were a kid with a pail of water, and spun the pail around at arms length, or in a loop up over your head. As long as you applied the proper forces to the pail, the water stayed in the bottom. Your fuel system is no different.
 
Ok, I think I got it! No spinning around with a pail when you have low fuel...

You may need the pail afterwards if you do too much spinning around also...

Maybe I don't quite have it yet? :eek:

sj
 
Ok....then try this sj.....

It's like walking back to your tent after an evening of Crown and lies. If you remember to stay coordinated you can manage the trip just fine. If you don't pay attention to your attitude then you tip over.
 
Ahhh, now I have it. There are probably also cigar burns involved...

sj
 
Now you've got it, it's all about proper coodination, no matter how bad your attitude is.

Just remember not to lean to far to the left sj....or all hell starts breaking loose.
 
Gas.

Hi Mark. OK I guess we will have to agree to disagree. I don't do loops and I don't swing my airplane around by the handle. What I have done is make a long (COORDINATED, STRAIGHT IN) descents in smooth air and run out of gas on the right tank with 3 gallons left in it. As long as the port is in the rear of the tank and the gas is in the front (due to my descent attitude) it will continue to run out of gas with gas in the tank. If I level off or raise the nose, I can use the other three gallons. These are the simple, straight, descending, coordinated facts. The last time I rebuilt the wings, I canted the tanks in the wings so the leading edge of the tank was as high and the trailing edge was as low as I could get them. It helped, but the situation still exists and will untill ports are installed in the front and rear of the tank. I'm sure the left one would do the same thing, I just run the right one dry because of the header position. People who never run the tanks lower than 3 or 4 gallons should not have a problem unless, as you say they fly majorly uncoordinated or do long steep descents. :-? Jerry.
 
AS ALWAYS GOOD INFO ON THESE SITES! ALWAYS CHECK YOUR SITE GAUGES 1/4 TANK IN 3 POINT VARIES TANK TO TANK,BIG TIRES, 3 INCH GEAR, THOSE MARKS ARENT USUALLY TRUE ESPECIALLY LOW ON FUEL. YOU WANT TO RUN 1/2 INCH LINES THEY ARE STILL PROBABLY RESTRICTED TO 3/8 GOING INTO THE CARB, GASCOLLATOR,HEADER TANKS AND THE FUEL VALVE. ARE YOU RUNNING ON BOTH PARKED ON A SLOPE THE FUEL WILL CROSS OVER USALLY TO HE LOW SIDE. MOST GUYS I KNOW RUN 4-7 GALS IN THE RIGHT (45 MIN RESERVE FOR DAY VFR ACCORDING TO FARS) AND WHAT THEY NEED IN THE LEFT TANK. BURSTING HEADER TANKS NOT TO COMMON ESPECIALLY USING ATLEE DODGE HEADERS, ACTUALLY KNOW OF ACCIDENTS SOME REAL BAD WITH NO BURSTING.MOST FIRE/FUEL PROBLEMS IN CRASHES USUALLY OCCUR CATCHING THE LEFT WING AND STILL HAVING THE ELECTRICAL IN THE WING ROOT INSTEAD OF ON THE PANEL FLY LOW FLY SLOW FLY SAFE
 
Lets look at what happens in the long steep coodinated descent Jerry.

The gas will slosh forward a little. This will vary depending on angle, speed, and drag. For instance, a Cub with extra large flaps down, and maybe ailerons drooped will induce more drag, so the gas in it's tanks will move forward more than a stock Cub with flaps out. If running on the right, the rear header is way up high (if it's installed), and gives the engine 1/2 gallon of fuel to run on even if the main tank completely unports and stays that way. In this steep descent the engine is probably at idle, or close to it, and should run a while on 1/2 gallon of fuel. If running on the left, you have the 1/2 gallon in the forward header, plus whatever may trickle down through the small header vapor return line.

I have also run the right header vapor return line to the bottom of the gage instead of the top. That way you may get a trickle of extra fuel from the sight gage (midtank) if the rear outlet unports.

It's true the large amounts of thrust and drag (hanging on the prop/steep descents) throws a wrench in the coodinated theory, but that is covered by the "When low to the ground and low on fuel, don't do anything stupid" rule.
 
It did not occur to me to try to start the engine post landing........probably to busy kissing the ground. :eek:
 
Gas.

Hi Mark. I see what the difference is. I don't come back on the power on a long descent. Hell, it's the only time I get to go fast. :lol: Jerry.
 
With the fuel sight gauges in upside down you can see your little red ball until it can't wiggle anymore.
 
Yes, I sent him these options and he chose his own, which I think is better than anything I sugguested. I just thought such a prominent guy needed a moniker...

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In response to Mark's assertion that a high drag configuration will cause the fuel to flow further to the front of the tank, this is true only to the extent that the attitude of the plane changes.

True, the fuel will slosh to the front of the tank momentarily due to the initiation of the draggy configuration, but then it will achieve stasis, and level off.

With the tank low on fuel, the fuel pickup in the rear only of the right tank will allow the tank to unport, causing fuel exhaustion. The header tank will allow the engine to run for a bit (which is why these things came with header tanks), but if sustained, it'll cough.

The Atlee 30 gallon tanks are nerve-wracking, in my experience, since they are so much bigger, and harder to determine how much gas you actually have left.

As to adding a fuel pickup to the front of the right tank, this would fix the descent unporting problem, but not the climb issue.

As has been noted several times here, none of this makes any difference if you have lots of gas on board. Problem comes when you are used to flying around with bunches of gas, then get in a situation where you are a little thin on gas.

In that instance, try to make sure that the left tank has the most fuel in it.

And, the two operative concepts above all are as noted above:

Know your airplane and its systems

and

Don't do anything stupid close to the ground, including running low on gas.

Just remember, during at least two points in every flight, you will be close to the ground. One of those points is usually where you have the least fuel on board.

Mike V
 
diggler said:
Your site gage could be in upside down also but thats another thread.

that was something I was going to bring up. My 55 SC had the thick part of the Aluminum tube at the bottom hence when the ball disappears I have 15-20 minutes left. My 75 has the thin part at the bottom, and will run out of gas with the ball still showing. Seems I've seen more old ones(50's) with the thick part at the bottom and more newer (70's) with the thin part at the bottom.Was this original or did a lot of older ones just accidently get switched??? I got used to the thick at the bottom and like it better that way.
 
I didn’t know a site gauge could lie, but I have seen my right one lie.

I was in a left “turn about a point” when my engine sputtered and started to die. I was running on the right tank, and I had been checking the gauge, and it had been showing a 1/4 tank or better. I switched to the left tank, and the engine snapped back to life.


On the way back to the airport, 10 miles, I was sloshing the fuel around, and the right tank gauge was reading as it normally would with 1/4 - 1/3 tank of fuel sloshing around.


I was thinking that it must be contamination or a venting issue; however, after landing, gauge now showing empty (nose high so not unusual), I took the cap off and it made no suction sound. Next I went to sump the tank, and I found that there wasn’t enough fuel left to fill the fuel tester.

So I guess this can happen





Sent from the other side
 
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