Inside the fuel flow transducer, is a miniature neutrally buoyant rotor finely balanced on jewelled bearings.

1. A typicalfuel flow transducer or any flow transducer for that matter, is
used to measure flow of a liquid through a pipeline. You’ve seen them
used at gas stations, vehicles with digital fuel meters, gas pipe lines,
industries and so forth.
Different modelsof Fuel Flow Transducer are available dependingon
the density and viscosity of the liquid to be measure.
Here’s how it worksin an aircraft;
liquid enters through one side and
entersthe flow chamber. It follows
a helical flow path, and exits
vertically, thereby venting vapor
bubbles that might form during the
fuel flow. Asthe liquid flows, it has
a velocity that can be measured
and this velocity is directly
proportional to flow rate.

2. Inside the fuel flow transducer, is a miniature neutrally buoyant rotor
finely balanced on jewelled bearings. As the fuel flows past the arms of
the rotor, it pushesagainst the armsof the rotor and so, the rotor begins
to spin.
Now, on one side of the spinning rotor is an infrared light emitter while
on the other side, is an infrared light detector. As the arms of the rotor
spin, it interruptsaninfrared light and thisconstant on-off is calculated
to arrive at the spin rate and therefore, the fuel flow rate. Ingenious,
simple and fool proof.
Aircrafts use a more sensitive but rugged version of a typical fuel flow
transducer. Rugged because a fuel flow transducer in aircraft needs to
withstand aircraft engine vibrations, varying temperatures (-55°C to
70°C ) and varying pressures (up to 2,000 psi fuel pressure). It also has
to meet FAA regulation regarding blocked rotor pressure drops.
Installation of fuel flow transducer 231 in the Aircraft Engine.
The fuel flow transducer 231 is to be mounted in a horizontal position
with the wires facing upwards; this ensures that the rotor is in proper
orientationvis-a-vizthe internalfuelflow channel. Thisisvitalotherwise
the rotor will fail. Also, there should be no bend in the fuel pipe for up to
6 inches on either side of the fuel flow transducer.
If the aircraft uses a carburetted engine, place the fuel flow transducer
before the carburettor. Ifthe transducer isgoing tobe placedhigher than
the carburettor, insert an anti-siphon loop in the line that peaks higher
than the transducer.
If the aircraft uses an injected engine, place the fuel flow transducer
betweenthe engine fuelpump and the servoregulator. If the aircraft has
as an fuel injected engine with vapor return lines, the fuel flow

3. transducer needs to be placed between the servo regulator and the flow
divider.
Ideally, avoid mounting the transducer betweenthe electric boost pump
and the mechanicalpump. Also, donot hard mount the transducer tothe
engine as violent vibrations may damage the internal parts of the
transducer.
For more information, please visit :
https://www.jpinstruments.com/shop/fuel-flow-transducer-
231/
JPI Sales:
1-800-345-4574
714-557-3805
FAX: 714-557-9840
sales@jpinstruments.com
JPI Technical Support:
1-800-345-4574
714-557-3805
support@jpinstruments.com
J.P. Instruments Inc:
3185-B Airway Ave
Costa Mesa, CA 92626