National Aeronca Association Bulletin Board

I am doing a 7AC conversion to 7DC. The FAA is going by the book on the conversion (Service Ltr #14) for the new airworthiness certification. The SL#14 states that the present main fuel tank must be replaced with a "modernized new" (1949) type fuel tank.
I don' t have the log book from '46-'50.
How do I identify the tank as a "new" one (which I assume that it is) and how do I convince the FAA.
I have searched Aeronca.com for the Factory drawing for part 7-778 and have come up empty.
Thank you

ralphmag wrote:I am doing a 7AC conversion to 7DC. The FAA is going by the book on the conversion (Service Ltr #14) for the new airworthiness certification. The SL#14 states that the present main fuel tank must be replaced with a "modernized new" (1949) type fuel tank.
I don' t have the log book from '46-'50.
How do I identify the tank as a "new" one (which I assume that it is) and how do I convince the FAA.
I have searched Aeronca.com for the Factory drawing for part 7-778 and have come up empty.
Thank you

Ralph

I think the new style has a sump low spot in the bottom of the tank.

This is another post here at NAA

The service letter conversion to a 7DC is for a -8. You have to convert the airplane then get the engine STC from Lasher or the B..W... guy. You can make it a DC, by the Lasher STC, which includes the -12 approval. Same with a BCM, if you have a -12 in it. You also need the new style
tank, with the sump in it.


Also send the NAA a note asking about the drawing, they have some also.

nationalaeroncaassociation@yahoo.com

Mike K

Unless I'm mistaken, I don't think it's much of a sump. Mostly just a low spot in the tank were the pickup tube and screen are screwed in. Seems the 7AC tanks are fairly flat. If I get out to the shop this afternoon, I'll take a picture of my BCM tank. I think that's what you're looking for or at least someone can let us know for sure.

Mike Berg

Here's a photo of the tank I have from my L16. Not too clear, though and the sump is the big round spot slightly to the right. The other fittings are for the primer line hookup and, apparently someone has plumbed another fitting for an auxiliary fuel tank.

It isn't much of a sump, probably less than 1/2 inch, and maybe not what you're looking for. I thought it was larger. It does seem my 7AC tank is about the same. Someone else might spring in with more information.

Mike Berg

Mike
Thanks for the photo.
I'll take a look at mine.
I'm still waiting for my CD from the FAA with the 337 details from the early years.
Ralph

If you have the tank out, a lot of people have placed the bottom on a shot bag, then cut off the rounded end of a broom handle and formed their own sump, by hammering the broom handle to shape it. You also have to cut a larger hole in the plywood support. I wish I could get to the photo I have, but it is on my crashed computer.

I know. I know, this is a chief tank. (for Joe A) Champ is same, but a little smaller. Still a tear drop sump that holds @ a quart, or slightly less.

Jody,

Nice photo and wonder where that happened? Clearly not stock but very good idea and makes sure that you get every last drop and if you are low in fuel helps in case the fuel is sloshing around.

Joe

home made sump

Ralph,
Refresh my memory: did you say on a previous post some time ago that you have 13 gallon wing tanks? If I'm interpeting SL14 correctly, the 13 gallon (26 total) wing tanks are an approved alternate system. I have a friend who is rebuilding a BCM (L16) and he only has 13 gallon wing tanks or no nose tank.

I stopped at the airport today and looked at the tank on a fuselage that I recovered for someone else and it has the sump in it. Not as deep as Jody's picture, but bigger than the picture I sent and has a bigger hole in the plywood to accomadate the sump. It's pretty obvious. I knew I'd seen it somewhere (the mind is a terrible thing to waste).

Mike Berg

Mike
I have the main tank that came with the plane (7AC) when I bought it.
I have placed 2- 5 gallon wing tanks from Wag. I also have the more shallow sump on the main tank.
Ralph

Ralph, Looking over the paperwork that came with my Wag Aero kit, it looks like its' STC'd for 7AC, 7BCM and 7CCM. Doesn't say anything in the instructions about a sump in the main tank. On the other hand, it doesn't say anything about a model 7DC either so maybe that's the problem. If you're already adding extra fuel I can't imagine what the problem is, but what do I know .

Mike

According to the FAA's formula for fuel burn/quantity, only 12 gallons is needed for a C-85. Cubs with 85's are approved with their 12 gallon tanks. We have 13. Why they wanted the sumped tanks in the service letter is beyond me. Most guys I know make their own sumps.

Jody Wittmeyer wrote:
I know. I know, this is a chief tank.

You know those Chief do look bad, here is a L-16 even with the Sump looking real good.



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The sump is flush at the firewall then slopes reward to the panel.

Have a few more if someone wants them

Mikek

Mikek wrote: You know those Chief do look bad, here is a L-16 even with the Sump looking real good. Mikek

Bad mouth them all you Champ owners want, but the Chief is still faster, funny looking fuel tank sump or not!

Joe