On 5 Dec 2003 01:17:22 -0800, (Koopas Ly)
wrote:

1. Is the fuel port inboard on the C172?
2. Does selecting "both" draw fuel from both tanks, even if one is empty?

I have an oblique answer to this question. I'm building an airplane
that seats four and is a high wing monoplane. The fuel tanks are in
the wing root, just like most high wing Cessnas. The plans show that
the fuel outlets should be placed near the wingroot but in different
locations fore and aft from each other. One tank has an outlet near
the wingroot by the trailing edge, the other tank has the outlet near
the wingroot but towards the leading edge.

The wings have dihedral so the fuel wants to flow to the wingroot and
the two differently located outlets are specifically designed that way
for low fuel situations. If you are low on fuel and you nose down for
descent, the leading edge outlet will flow fuel while the trailing
edge outlet may be unported (dry). If you have to go around, the
trailing edge outlet will flow fuel while the leading edge outlet may
be unported.

This is a gravity feed system. An option is to install a header tank
ahead of the instrument panel to augment the somewhat small wing
tanks.

The designer implied that this is a standard aviation design (the
different locations for the fuel outlets).

Corky Scott

PS, in addition