Cessna 172 Fuel Flowmeter?

Is the fuel flowmeter in the newer Cessna 172s (and others?) a true flow meter
(as in a small turbine meter generating pulses, etc.), or is it a pressure
gauge or pressure transmitter measuring the fuel pressure in (whatever)?

I got the you-know-what scared out of me while in flight and this *&^#@ thing
read ZERO, though everything else (RPM, EGT) was normal. It was OK before
take-off. It finally came off zero, but read low.

Hmmm?

AFAIK, all "fuel flow" gauges in light aircraft read pressure, although they
are calibrated as flow meters. Good symptom of a clogged injector is high
fuel flow...not exactly intuitive.

Now when you get to Shadin and their equivalents, you are looking at
honest-to-goodness fuel flow. Again, AFAIK.

Bob Gardner

"CVBreard" wrote in message
...


Is the fuel flowmeter in the newer Cessna 172s (and others?) a true flow
meter
(as in a small turbine meter generating pulses, etc.), or is it a pressure
gauge or pressure transmitter measuring the fuel pressure in (whatever)?

I got the you-know-what scared out of me while in flight and this *&^#@
thing
read ZERO, though everything else (RPM, EGT) was normal. It was OK before
take-off. It finally came off zero, but read low.

Hmmm?

CVBreard wrote:
Is the fuel flowmeter in the newer Cessna 172s (and others?) a true flow meter
(as in a small turbine meter generating pulses, etc.), or is it a pressure
gauge or pressure transmitter measuring the fuel pressure in (whatever)?

I got the you-know-what scared out of me while in flight and this *&^#@ thing
read ZERO, though everything else (RPM, EGT) was normal. It was OK before
take-off. It finally came off zero, but read low.

Hmmm?
According to the Cessna factory parts book, the original equipment gauge
is fed by a pressure transducer.

Happy Flying!
Scott Skylane

According to the Cessna factory parts book, the original equipment gauge
is fed by a pressure transducer.

-----------------------------------------------------------

Which is measuring the pressure of ______________?

Probably differential pressure across an orifice. These transducers are now
very inexpensive, except in the aviation market.

Rod
"CVBreard" wrote in message
...
According to the Cessna factory parts book, the original equipment gauge
is fed by a pressure transducer.

-----------------------------------------------------------

Which is measuring the pressure of ______________?

That is a valid and accurate way of measuring flow, almost as accurate
as a turbine meter and has less to go wrong. The same method is used
to meter large water flows from water plants and into large plants.

According to the Cessna factory parts book, the original equipment gauge
is fed by a pressure transducer.
-------------------------------------------------------

Measuring the pressure in ________?

On 25 Jan 2005 13:52:45 GMT, (CVBreard) wrote:

According to the Cessna factory parts book, the original equipment gauge
is fed by a pressure transducer.

-----------------------------------------------------------

Which is measuring the pressure of ______________?

Not familiar with the "new" 170-twice. But in other similiar IO-360
installations, it can be measuring the line pressure between the fuel
servo outlet and the orifices in the individual injector nozzles.

TC

On 25 Jan 2005 22:51:43 GMT, (CVBreard) wrote:

According to the Cessna factory parts book, the original equipment gauge
is fed by a pressure transducer.
-------------------------------------------------------

Measuring the pressure in ________?


psi, sometimes referenced to atmospheric pressure at a remote location
(under the hood, as opposed to under the dash), but gage markings will
be in gph. again, this is generic info relating to other IO-360
installations, sorry I can't be more specific.

TC

CVBreard wrote:

According to the Cessna factory parts book, the original equipment gauge
is fed by a pressure transducer.


-----------------------------------------------------------

Which is measuring the pressure of ______________?

Fuel, at the flow divider on top of the engine. This is called metered
pressure, as it is the fuel pressure downstream of the servo unit, just
before it enters the injector nozzles. As you stated, in this case, a
plugged injector, that results in a loss of total fuel flow into the
engine, will register as a fuel flow(pressure) *increase*.

Happy Flying!
Scott Skylane