Aero-fabricators aux fuel system

[ablight]

Group

I have a 7CCM newly restored. The airplane had an Aero-fabricators aux fuel system installed years ago (337), so it now has two wings tanks, plus the main tank in the nose. The paperwork that I have for the kit has a very crude hand drawn set of drawings and a nice pretty set of CAD like drawings that are dated some time after the aux fuel system was installed. So my point is that these drawing were probably acquired after the previous owner bought an early kit and installed it.

Well, the fuel system is set up just like the crude drawing except the fuel from both wing tanks drain into the main tank at the orginal location that the factory aux fuel tank emptied into. The kit literature says it was for a 7AC (with out any wing tanks), my airplane came from the factory with a wing tank so the main tank had the wing fuel access point. The 7AC wing fuel kit was designed to empty into the main through the primer acces not the 7CCM wing fuel access point.

Now my question, The fuel from the wings drains into the main very slowly, if at all. We have checked the lines, valve, etc... All 3 caps are vented. Can anyone shed any light on this kit first and second any ideas on how to make the fuel drain better, is the location of the main tank access a factor (can't imagine it makes a difference)? Also, the newer of the two drawings that I have shows a tank shut off for each wing tank, were as my install is like the crude drawing only one valve shutoff in the panel for both tanks. Thanks..Andy

[Don Eide]

Andy,

You say your fuel caps are vented. Are they the flange vented caps that Wag Aero sells with its tanks, part # E482-000 ?

If so what you need is a ram air pressure cap. A cap that has a tube sticking out the top and bent forward. I have seen Luscombe's, Piper's and Taylorcrafts all use the ram air pressure cap. I have two 13gal wing tanks in my modified 7AC. I use NON vented caps and a vent system that uses two forward facing pressure vent tubes all tied together to pressurize my tanks.

How large is the tubing between your tanks? Small tubing = small fuel flow. I know my system is different, but ALL my tubing is 3/8".
Hope some of this helps.

[Bob Eilers]

I have the two five gallon wing tanks that empty into the main. I can select "off", or "right", or "left". I have developed the habit of timing the fuel transfer. In my aircraft, it will generally take 20 minutes to completely drain a five gallon wing tank.

[ablight]

Don and Bob, thanks for the info. Don, my fuel lines are 3/8 I believe. Bob, your fuel valve - is it in the panel? Mine is in the panel and I do not have a right or left position. Only on or off. Is your aux fuel system the areo-fabricators system?

Also, I have been looking for the caps with the ram air inlets (tubes), I can't find them anywhere. Is there a source for these? Cheers...Andy

[Guest]

Andy, Bend about 4 inches of 1/4 inch copper tubing into a question mark shape ( ? ). Drill a small hole in the top of the cap and solder the ram tube on, paint red. You can cut the opening of the ram tube at a 45 degree angle for a finished look. Start with a very small drill hole in the cap, check your fuel flow, enlarge if needed.