Weight and balance is probably one of the most neglected topics outside the
qualifying exams. One rarely sees scales lying around at club airfields or
pilots asking for weights of passengers and their baggage. Experience tends
to be relied upon to avoid awkward parts of the envelope. How nice it would
be if there was an instrument read-out or display on the panel.
However load cells in our AUW range do not come cheaply (=A3100's) and they are
needed on all the wheels. The mono Europa offers a unique opportunity to do
something though, as the outrigger load can be neglected, leaving two wheels
only. Furthermore as the arms of the loads are usually limited to the three
fixed values for crew, fuel and baggage, these can be preset at loading time
( or if not a variable adjusted). This enables the tailwheel load to be
deduced from the change in mainwheel load *
So all we need is one sensor on the mainwheel. Again the Europa provides us
with an almost made-to-measure (sic) solution, the damper block. A
measurement of the change in spacing of the plates with load gives a
proportional (or at least calibrateable) reading of the load change.
My question to the Europa borg collective is therefore what is the most cost
effective way rugged way of measuring a distance of around half an inch (with
over-run to allow us our bounces) ? A linear pot. or capacitor comes to mind
(whether rotational or physically linear) but I have a feeling there must be
out there somewhere some neat devices with digital output which would save us
the trouble of re-inventing strain gauges and their circuitry.
Graham C. G-EMIN
*=09=09wt/wm=09=09=09=09(d-M)/(T-d)
where
M =09distance of mainwheel from datum
T =09distance of tailwheel from datum
d distance of added load, wt+wm
---From which some interesting figures can be derived e.g. one fifth of your
baggage weight goes on the tail.
P.S a much more challenging (impossible ?) task would be to do it in the air !
-though as only fuel can change signficantly in flight it would be simple to
input the gauge reading or flow rate to make the appropriate change. The
passengers can't move about in our machines, and the coffee and sandwiches
don't weigh much.
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