National Aeronca Association Bulletin Board

A friend has an approved wing tank setup for an O-200 powered 7AC. He recently got two Aeronca fuel caps from Aircraft Spruce - P/N 05-06357. Bargains, since I have no idea where to get authentic caps.

However, my Decathlon caps are non-vented, causing me to wonder about vented caps in the low pressure area of the wing. I am encouraging him to check the paperwork to find out if the system is internally vented.

What do you use on your wing tanks? My Cub needs a forward facing ram tube to feed reliably.

The venting / non-venting set up can be confusing and a nightmare if you get a hole in the system somewhere. I had problems in my 7CCM and talked to Bill Pancake. I had the correct vented nose cap and unvented wing cap and had terrible transfer problems especially after installation of VGs. Turned out I had a hole in the wing tank that caused part of the problem and the vent tube on the wing was not cut on the required angle, which I immediately did. Then I put holes in my caps and braised brass tubes on them bend in a circular arch forward and never had another problem.

Bob

Bob,
I use the non-vented caps for the wing. make sure the nose tank will vent in both directions. Most of the new vented caps only vent air into the tank not allow it to escape. If the air can't escape the fuel will not transfer. If you put on the vent style caps get them high enough out of the low pressure area.
Paul

I have the Wag Aero 5 gallon fuel tanks in both wings of my 0200/L16. Even though the caps that came with the tank kit are vented the tanks had a "difficult time" transferring to the nose tank. If I remember correctly the left tank would transfer but the right one not so I'm thinking it's due to the prop wash over the wing. Anyway, I drilled the cap and installed a forward facing vent.....end of problem. Now one more thing: because the original caps are vented if the tanks are full to the top the pressurizing tends to push a small amount of fuel out the original cap vents over the wing. I have a set of non-vented caps that I intend to modify with the vent tubes but haven't gotten around to it yet.
Mike

My wing tank set-up is the 13 gallon factory installation. This uses an additional vent from the tanks to the bottom of the wing. If you have another approved installation use what they supply for the modification. The W/A set-up is a different breed of cat. The last one I installed came with a well worn STC from the 1960's as the "STC approved" installation. With this, you will need to have your specific installation approved by the FAA via Form 337.
Paul