On Feb 23, 9:49*am, wrote:
IIRC on similar thread(s) the idea was put forth that the regs only
require the indicator to indicate properly when full and when
empty ... don't know where that would be in the regs (if in fact it
is); maybe part 23?

That's an unfortunate myth. (The usual form of the myth is to say that
the gauges only have to be correct when the tanks are empty.) Pilots
who belive it are likely to underestimate the importance of the fuel-
gauge airworthiness requirement. The myth was just debunked on the
other fuel-gauge thread:

There's an urban legend that the fuel gauge is only required to be
correct for an empty tank. The legend apparently arises from a
bizarre
misreading of 23.1337b1. What 23.1337b1 actually says is just
clarifying that the 'empty' reading must correspond to zero USABLE
fuel, as opposed to zero TOTAL fuel. There is nothing whatsoever to
suggest that non-empty readings needn't be correct--that would be
absurd. (If it were true, a gauge that ALWAYS says 'empty' would be
legal! You could just write 'empty' on a piece of paper and call that
your fuel gauge!)

The requirement for indications of a tank's fuel level (not just on
empty) is stated in 91.205b9, 23.1305a1, and 23.1337b.