Cessna 172 with Wild Fuel Gauge Needle

"C J Campbell" wrote in message
You were taught a very popular myth. No doubt you were also taught the myth
(spread by Rod Machado and others) that your fuel gauge is only required to
be accurate when it reads zero fuel.

The myth is that they have to only be accurate at zero. The truth is that there's
no requirement for accuracy at all. All the misinterpreted rule says is the EMPTY
mark means zero USABLE fuel.

"Ron Natalie" wrote in message
. ..

"C J Campbell" wrote in message
You were taught a very popular myth. No doubt you were also taught the
myth
(spread by Rod Machado and others) that your fuel gauge is only required
to
be accurate when it reads zero fuel.

The myth is that they have to only be accurate at zero. The truth is
that there's
no requirement for accuracy at all. All the misinterpreted rule says is
the EMPTY
mark means zero USABLE fuel.


That is pretty much what I said, except that 91.205 says that you have to
have fuel gauges indicating the quantity of fuel in each tank. However,
91.205 does not say how accurate a gauge has to be to meet this requirement.
I do know from painful personal experience that some FAA inspectors will
write up a plane if they think the gauge is too inaccurate.

Ron Natalie wrote:

no requirement for accuracy at all. All the misinterpreted rule says is the
EMPTY
mark means zero USABLE fuel.

Actually, the rule says that zero USABLE fuel will give an EMPTY indication, not
the other way around as you stated.

An empty indication does NOT necessarily mean zero usable fuel.

That what makes this world such a great place - you trust your gauge and I will
trust a visual check for full tanks, and known fuel burn.

And we can agree to disagree.

"C J Campbell" wrote in message ...
" jls" wrote in message
news
Anybody know the reason for this? The needle on the pilot's side is
stable, but the needle on the co-pilot side swings wildly, especially when
the tank is full. A float moves the needle around the dial. Why doesn't
it stay still and be good like its brother?

It probably is a bad sending unit, especially if it is a late model 172. You
can replace the sending units, but they just go bad again.

The earlier ones do it, too. They have a wirewound potentiometer
that wears out and starts getting intermittent.

Dan

"Dan Thomas" wrote in message
om...
"C J Campbell" wrote in message
...
" jls" wrote in message
news
Anybody know the reason for this? The needle on the pilot's side is
stable, but the needle on the co-pilot side swings wildly, especially
when
the tank is full. A float moves the needle around the dial. Why
doesn't
it stay still and be good like its brother?

It probably is a bad sending unit, especially if it is a late model 172.
You
can replace the sending units, but they just go bad again.

The earlier ones do it, too. They have a wirewound potentiometer
that wears out and starts getting intermittent.


You would think they would have fixed the problem by now, but the new ones
are even worse than the old ones.

Google Groups result:

Your shorter link is: http://makeashorterlink.com/?D23212077

jls wrote:
Anybody know the reason for this? The needle on the pilot's side is
stable, but the needle on the co-pilot side swings wildly, especially when
the tank is full. A float moves the needle around the dial. Why doesn't
it stay still and be good like its brother?


MikeM
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