Disappearing gas tank

[cubflier]

Most folks who have them wind up filling them all the time, and as a consequence are flying really heavy a lot.

Mike

I don't want to be disagreeable here but I have experiences to the contrary.

I've had Atlee tanks for 13 years and only fill them when I need the range that 61 gallons yields or am just using them to haul fuel. I also know a few people including some old time guides that have the tanks and none of us ever fill them up except when the situation warrants.

The only situation where I have heard of pilots flying consistently with topped off tanks is the state owned cubs that have them installed. I think this has more to do with policy/procedure.

The people I know that fly the Atlee tanks carry similar fuel levels same that you would expect of a standard tank cub owner with one exception. The tanks at the low end of fuel level are difficult to accurately assess.

I'm not trying to sell the tanks and think anyone that decides to install them should talk around since this is a long term commitment with various pros and cons to consider.

Jerry

 

[Christina Young]

Jerry / Mike,
The very few (i.e. 2) people who I have personally spoken with that have the Atlee tanks love them. The advantages are obvious. Of the drawbacks, so far we have mentioned 2: fuel gauges inaccurate when tanks are low, and some people fill them all the time when they don't need to thus flying around heavy a lot.

Are there any other drawbacks?

 

[Steve Pierce]

Are there any other drawbacks?

Installing them correctly to eliminate cracks.

I agree with Crash on the siphon hose. We use them to fuel and defuel in my shop on occasion and they are a lot easier than balancing and pouring out of a can.

 

[Jerry Gaston]

I didn't read all of the thread comments but was wondering why not use the belly tank that has 50# storage and 18 gal fuel capacity. That way when you don't need the extra fuel you don't fill the aux tank but it sure is handy when going x-country. I purchased one and it has proven very useful for all situations and it even increased my cruise speed 3-4 mph.and I don't have gas cans sitting around in the back seat.

 

[Cubdude]

The wife and I were headed out on a 6 week adventure, from Lafayette La to the Kenai peninsula, Alaska. We got about 100 miles north of Lafayette and the 0-320 started losing RPM. On went carb heat, no change. Swiched tanks, no help. Got to full throttle and started looking for a place to put down, we were at 1800 rpm max now. We had filed so Houston center starts asking about souls on board, fuel etc. I said I was rather busy, in the soup and looking for the ground. I switched to the tower at Alexandria La, found them with the GPS and broke out of the overcast. Two things happened then, I saw the airport under me and the engine quit. We dead sticked to the 7000' ex-military runway and nearly were run over by all the equipment the tower had sent out. So there we were, 100 miles from home,not even completing the first leg of our 8500 mile trip. Friends at England Jet Center converged on the cub and started pulling cowling off. The head man walked behind the wing and said that I had lost a fuel cap. I climbed up on a ladder and saw that the tank had been sucked in on top of itself. It then registered with me why it happened. The night before, trying to make everything perfect before the big trip, I cut out new fuel tank gaskets using the old ones as patterns, the second or third time I had done that over the time I owned the Cub. Yes,the gaskets get bigger each time you cut on the traced line and I had finally closed off the venting of the tank. What a dummy! We carefully inflated the tank with an air hose and flew 8400 miles, 53 landings in the next 6 weeks without a single additional problem. Great trip! Bill S.

Were you in the soup in a supercub?

 

[Crash]

Jerry / Mike,
The very few (i.e. 2) people who I have personally spoken with that have the Atlee tanks love them. The advantages are obvious. Of the drawbacks, so far we have mentioned 2: fuel gauges inaccurate when tanks are low, and some people fill them all the time when they don't need to thus flying around heavy a lot.

Are there any other drawbacks?

When I installed two new Atlee Dodge tanks in my PA-14 I had to mark the sight gauges for 1/4, 1/2, 3/4 & FULL. I took the plane outside and with an accurately marked five gallon can I poured in one can, nothing, the ball didn't move off the bottom. Poured in a second can, same thing. Poured in half of the third can and the ball finally came off the bottom. That is 12.5 gallons in the tank before the ball even moved. The plane in three point could have 24 gallons in the tanks and show empty on the sight gauges. Thats 144 lbs of weight you didn't know you had on board before take off. I find that they are usually always over filled because you don't know what's in them.

Second: When the tanks are full the plane flys and feels heavy, very heavy. Atlee built these tanks for Alaska Polar Bear guides of the 60's and early 70's who were working in extreme conditions and long distances. Most Cub drivers will never need this much fuel between fuel stops. Crash

 

[sharp]

I have clear tubing sight gauges and think I get better readings than the conventional SC sight gauges in the metal housing w/balls. The tubing is marked with a permanent marker for reference. It's not perfect but works good for me.
Sharp

 

[stevensonjr]

Hi Cubdude, yes, we were in the soup on a instrument flight plan. My traveling Cub had a horizon, 2 radios, 2GPS's, glideslope and an ADF.

 

[mvivion]

Crash makes my point better than I can. This is precisely the issue I've seen with cubs.

This is particularly bad when you get into a Cub you aren't familiar with, ie haven't flown a lot, and therefore don't really know what sort of fuel burn to expect.

You can have ten gallons of fuel, distributed between the two tanks in these tanks and not even be able to tell you have gas, or worse, have virtually no fuel and think you have ten gallons.

Has anyone ever figured out how to calibrate a stick or their sight gauges accurately enough on these tanks to be able to tell the difference between 30 gallons and 35? How about 30 and 40? Five gallons is 30 pounds. That's a lot, especially on floats.

The same issue applies with the Cessna 185 or 206 with long range tanks. Unless you have a fuel computer, its really hard to tell where you're at. And, computers rely on your ability to accurately meter fuel going into the tanks. Got a good meter on your remote fuel stash?

Anyway, as Crash said, they are good products, but designed for someone who REALLY needs a LOT of gas, and carrires it on most if not all flights.

Personally, I think the combo belly tanks/pods are the greatest thing since sliced bread.

The 24 gallon tanks also make sense, particularly for the 180 hp aircraft. Don't they have a fairly significant unuseable fuel quantity, though?

MTV

 

[aktango58]

A good tip: NEVER pour the bottom of the can into your plane.

Just look into the bottom of a year old can. A speck of dirt from the gas nossel that filled it each time builds lots of junk in the bottom. Look in year old cans.

It is lots cheaper to leave some cans you can not fit that buy the $660 one. Also, up here I have bears eat my cans every couple of years.

Christine, I highly recomend running Avgas in Alaska. We talk about cans being contaminated, some of the village supplies....

just a thought.

 

[Christina Young]

Christine, I highly recomend running Avgas in Alaska. We talk about cans being contaminated, some of the village supplies....

Thanks. I HATE avgas. It's nasty stuff. The O-320 was never certified for it. And it causes all sorts of lead fouling issues with my engine. I have to lean a lot at even low altitudes (when I shouldn't have to) or else my engine starts running rough. I simply don't have that problem with autogas.

 

[behindpropellers]

Christine, I highly recomend running Avgas in Alaska. We talk about cans being contaminated, some of the village supplies....

Thanks. I HATE avgas. It's nasty stuff. The O-320 was never certified for it. And it causes all sorts of lead fouling issues with my engine. I have to lean a lot at even low altitudes (when I shouldn't have to) or else my engine starts running rough. I simply don't have that problem with autogas.

Sounds like you have a carb heat issue to me, is it turning all of the way off?

Tim

 

[Christina Young]

No carb heat issue. I only use the carb heat when I throttle below 2000 RPM.

It is a lead fouling issue. The engine starts running rough, and you can determine which set of plugs are fouling by switching to one mag or the other.

If it was a carb heat issue, the engine would run equally rough on either mag. And it wouldn't be dependent on whether you're using avgas or autogas either.

The O-320 was NEVER certified for avgas.

Which engine do you have?

 

[Jerry Gaston]

Christina I'm with you I have been using auto gas for over 4.5 years and love it . If you read the EAA research you'll discover that auto gas has alot less additives and the only thing your getting with avgas is long term storage benefits.

 

[aktango58]

Well, I taint no engineer, nor do I profess to be a mechanic, but......

Certified or not, Avgas is refined more, has less suspended moisture, and will usually have a better filter before the nossel.

car gas today IS NOT THE SAME STUFF USED WHEN THESE ENGINES WERE DESIGNED!!!!!

The base metals have been changed and removed from car gas more than avgas to meet 'emission standards'. Stand behind a buick and take a wiff as it is running, pew

As the base metals have changed/been removed, there is less internal lubrication for valves etc, hence some of the drop in octane and increas in engine knock on older engines.

My 1974 motor cycle had a bad habit of running like a scalded cat every trip to Canada due to the increased base metal component of fuel. I even got to where I would adjust the carb if I was there more than a day. What a treat.

Of course, back in the states, guess.

Long way around to say adjust the mixture. Don't get too busy on the argument between the two fuels if your plane is set with a rich mixture, pull the knob while flying. I have to do that anyway, except in dead of winter, (always set it for the most rich setting needed). It has more to do with your engine needing LESS fuel/air ratio due to the better burning of aviation fuel; it seems that a poorly adjusted carb on your plane has given you the idea that a lesser fuel is better. Avgas is a better performer, more power, less varnishing, less water.

All that aside: every time I have had to run car gas I develop serious carb ice up here. Winter, summer, spring, Fall. Carb heat helps, but when you lose the engine at level off when you pull the power back 300 rpm....

Yes, the EAA and many say it is just as good. Well, all you you bring your car gas on up here and lets see what happens when it sits the winter in your carb.......

(my opinion, not certified, just certifiable)

(I have snow machines, chain saws, generator, and a few outboards, fuel varnish/contamination is a BIG issue with me)

 

[AIRWOLF]

OK Christina I have been waiting for someone else to take the bait and ask but nobody has so hear goes. Why do you say that the O-320 was never certified for avgas. I just looked at the data plate on one and it states "avgas min. grade (Oct.) 80" as far as having to lean I never saw that as a problem. If I burn less fuel I can stay in the air longer.

 

[mvivion]

AIRWOLF,

Thank you, I also was waiting for someone to point that out.

Christina, your engine is set up too rich. You should be able to run a 320 on avgas, with reasonable leaning with very little lead fouling issues. Install fine wire plugs at least in the lower holes, which should be the ones leading first (correct?) and that also should help.

I think what you were trying to say is that the O-320 was certified to run on 80--87 avgas, and that 100 LL is still a little lead heavy for it. Nonetheless, you should be able to run 100 LL in it.

I ran half and half for a long time, but avgas in Alaska is really crappy stuff. Seems like it is simply the dregs of whatever they have left over after making jet fuel or something. I've had some good avgas in Alaska, and some really bad stuff. So, be careful up there. I always mixed the stuff to at least get some lead in the fuel.

You are aware that your valves are designed to have SOME lead in the fuel, right? The fact that auto gas has NO lead now may be long term problematic in engines that are designed to burn leaded fuels.

In other words, have someone set the mixture of your plane, experiment with leaning, and put some 100 LL in it sometime, maybe a little at a time.

MTV

 

[Ursa Major]

I ran half and half for a long time, but avgas in Alaska is really crappy stuff. Seems like it is simply the dregs of whatever they have left over after making jet fuel or something. I've had some good avgas in Alaska, and some really bad stuff.

MTV

Mike do you mean Mogas (being crappy)? I've never had an issue with 100LL Avgas in Alaska - maybe I've been lucky.

 

[Steve Pierce]

Christina, Which dash number carb do you have? There is a leaner carb for the O-320 which in my experience has worked better on fouling issues.

 

[mvivion]

Duh!! THere I go.....No, I meant that autogas is all over the place in quality and additives in Alaska. I've never had any issues with avgas there, but it of course, does contain a lot of lead, and many engines , as Christina points out don't care for that much lead.

MTV

 

[Christina Young]

OK Christina I have been waiting for someone else to take the bait and ask but nobody has so hear goes. Why do you say that the O-320 was never certified for avgas. I just looked at the data plate on one and it states "avgas min. grade (Oct.) 80" as far as having to lean I never saw that as a problem. If I burn less fuel I can stay in the air longer.

Sorry, I meant it was never certified for 100LL avgas. You can't get 80 anymore.

 

[Christina Young]

Christina, Which dash number carb do you have? There is a leaner carb for the O-320 which in my experience has worked better on fouling issues.

Steve, I don't know. My carb was replaced a couple of years ago with a new one. I'll have to check. The previous carb was shot and choked almost to the point of not running when the carb heat was pulled on. I do know that my mechanic set this new carb on the lean side, and he verified that it is the right one for my engine.

Mike, I do use avgas every now and then for the lead, maybe 25% of the time. The lead fouling issues are dramatic, I have to lean a lot. No problems of course with autogas.

The Franklin in my Stinson is even worse with 100LL. It was designed from the beginning (before WWII) to run on unleaded gas. Almost any avgas at all without TCP will send it back to my mechanic's hangar.

 

[bob turner]

What I want to know is: how does the Super Cub tank vent system work? Assuming the caps are vented ( a good assumption, given the number of holes that are required to be drilled in them) doesn't the lower pressure on the top of the wing make feeding less efficient? A ram tube on top was the old solution to that, and on a lot of airplanes, the tanks have a vent somewhere other than the top of the wing, with non-vented caps.

 

[tamarack]

Christina,

FWIW, the two dash common O-320 dash numbers on the carb are the -12 and -32. Additionally there are two different induction ports in the sump just above the carburetor. The curved induction port uses the -12 carb and the straight port uses the -32 carb. I don't know of any way to verify which port is installed other than pulling the carb and looking straight up.

A curved or venturi-like port with the -32 carb can cause the engine to run rich. It should be noticeable during shut-down.

In the past two years I have recieved two overhauled carburetors that had the float setting too high, thus running too rich; and one carburetor that had the bowl halves come loose after only a few hours of running, also running too rich.

Vickie