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Header Tanks

arcticairalaska

Registered User
Fairbanks, Alaska
There is value to the fact that cubs have header tanks. There is function other than being able to get most of the fuel out of each tank.
If one flies where the potential for ice crystals in fuel exists. [Underground fuel tanks [warm fuel] and cold ambient temperatures -20's & -30's.]
As the fuel cools down in the wing tanks any entrained moisture will turn to crystals. The same principal as cloud formation. The front header tank is in the warmest part of the aircraft and should be your reserve fuel in most conditions. When the crystals begin to clog the screen in your gascolator and the engine starts to starve for fuel then switch to the left tank and look for a place to land and clear the screen of crystals. It takes a very small amount of ice crystals to clog a screen. I have seen screens completely stopped up after a three hour flight. I have seen one aircraft totaled due to this fuel stoppage.
Sandy
 
Interesting post, I have been thinking of going to the header-less system but I think I will take another look at it, thanks Sandy

DW
 
How many headerless aircraft have come out of the sky because of the scenario you described? Interesting theory but question the data.

I'd rather not have two mini napalm bombs in the cockpit with me if I can avoid it.
 
Something I read on this site spooked me about header tanks- it was fire related. In a crash - are the stock header tanks apt to rupture? I'm tying to make my super cub as safe as possible - what's my weak link now. (I know it's probably me - but we don't need to go there!!).
I had the slotted wings put on, a cross brace in the cabin I bought a helmet, 31 inch tires, & extended gear.
how about the gascolator also? If I land hard and mash up the front end - is the gascolator apt to rupter?
cliff in Maine
 
OVEREASYGUY
Buy a Steve's Aircraft Gascolator money well spent.
 
I think the fear of gas splashed all over the cockpit due to ruptured header tanks is somewhat overplayed. It's a good sales pitch, I suppose.

The stock header tanks are not as sturdy as Atlee Dodge's replacements. If you are concerned about the eventuality of burst header tanks, first, don't crash with so much enthusiasm that it would cause a header tank to burst. Second, replace your stock header tanks with a set of Atlee's.

I agree with Sandy's assessment of this issue. I too think the header tanks have value, and the problem he describes is real.

Probably not an issue if you live and fly only in Florida, but..

MTV
 
I just made a new header tank for my 12 and I can guarantee you that if you rupture it you won`t have to worry about it bursting. I pressure tested mine to 150 psi and then drove an F-150 ford pickup over it. The tanks and fuel lines may break but the header won`t.
 
I still have the same question I originally posted. Another item not realized is the headerless system fuel lines pass through the same area the original header tanks did. So if you think the fuel tank is warm in the front header area then so are the same fuel lines, with or without header.
 
In a super cub the front header tank has two lines that come from the left tank. One of which comes through the fuel selector, so the warm fuel may even thermal-cycle.
The military has lots of information on ice crystals and fuel that was generated from WW II. This is why there is heated fuel systems on aircraft that spend time at altitudes where temperatures are at the -30 and -40 range.
Sandy
 
Even if you heat the fuel to 60 deg. F and your gascolator is -20 I doubt the fuel is going to melt the crystals in it.

Tim
 
I think the warm fuel combined with the warm air coming out of the bottom of the cowling just might do the trick. When I have as much time flying Cubs in extremely cold weather as Sandy does, (in my dreams!) I'll have more definitive opinions. Before I'm accused of believing everything I hear or read, let me say I am not that gullible. However, I do listen carefully to the words of successful long-time experience. I suspect there is more to Sandy's words than simple conjecture. We need to hear more from him.

On another note we recently removed the stock header tanks from my Cub and replaced them with the AD tanks. I'm fairly sure they had never been out of the airplane before. The rear tank had been kinked where the clamp closes on it to the point where I couldn't believe that 33 years of vibration hadn't produced a leak. The wrinkle was covered by the clamp. You never know what you're going to find.
 
You're flying a plane with 36 gallons of fuel located about 18 inches from your head, and your worried about a 1 gallon fuel tank located 24 inches from your lap!
OK.
If you think the damn thing is gonna burn up, you need to take up bicycle riding. No fuel. :angel:
 
I fell 100 feet straight down in a PA16. The airplane ended up lawn darted in the ground with the tail straight up in the air. The engine mount broke and pierced the firewall and the 12 gallon nose tank. 12 gallons of fuel dumped on the hot muffler and by the grace of God didn't catch fire. I didn't know this at the time. My concern was the fuel in the wing tank that was dumping out the fuel filler cap and running towards the hot engine.

As far as I am concerned the headerless system is convenient, turn the fuel on and fly. Sometimes I am complacent and forget to switch tanks.

I have turn the end out of the original header tanks removing them. They are considerably lighter and thinner than the heavy duty tanks from Univair and F. Atlee Dodge. If you are replacing your header tanks be sure and check the part numbers per your serial number. The rear header tank is different depending on serial number. Atlee has one and Univair the other.
 
A couple of interesting thoughts;

1. I know a fellow who crashed a PA-12 (modified) due to a fuel problem. He told me he researched fuel-type problems and compared PA-12s and PA-18 systems. His data told him there were roughly twice as many fuel problems with a PA-12 system as PA-18 fuel systems. His take on it was either the super cub pilots are a lot more smarter than PA-12 pilots (not!), or, there was something intrinsically different. He felt the old system used by PA-18 was probably hard to beat. The PA-12 system usually has a low spot where moisture can collect and they lacked the header systems.

2. Another friend supposedly "imploded" a headerless vented cap as a result of icing plugging up the small forward facing vent line. There was fuel starvation from the plugged tank on that particular side. I don't know if it is true; I think there are usually crossfeed vents present but I don't know that for certain.

I like to have something that is SIMPLE, where I can control which side fuel is used from. My brother's C-150 (on "both") usually drains most of one tank before the other tank is drained which would drive me nuts flying over remote country with no safe places to land. I like to know before hand that both tanks will drain normally and are not fouled. I switch every 30 minutes so I can always spot an unexpected problem with plenty of fuel on-board since I get about 2 hours per side.
 
The stock PA12 has two fuel valves and if I remember correctly there aren't fittings in both the front and rear of each tank.

Stock PA18 system is pretty simple and fool proof.

The headerless system has a vent on both caps and they are vented together. This is part of the FAA requirements on this type system. There has to be two ways of venting the system. I have flown the headerless system in a pretty good rain shower and didn't get any water in the tanks. Was the iced over vent flown in freezing rain?
 
The later 12's with the sideways header had 3 valves. Your average pilot today can't handle operating a single engine plane with one valve without screwing it up, wonder why there are so many accidents.... I wouldn't change my stock 18 system for anything, I like having complete control over the system.
 
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