AOPA Pilot Magazine - July 2021 - 98

P&E SAVVY MAINTENANCE
drum provided by the fueling company
(which had agreed to deal with the
costly disposal of the nasty stuff). We
disconnected the fuel line going to the
engine-driven fuel pump and drained all
the fuel from that as well.
Next, five gallons of 100LL (donated
by the fueling company) was poured into
the main tank, pumped through the system
using the electric boost pump, and drained
from the disconnected fuel line into a fivegallon
bucket. We tested the fuel in the
bucket for Jet A contamination by means
of " the paper-towel test. " A few drops
were placed on a paper towel and allowed
to evaporate completely. Pure 100LL will
not leave an oily ring on the paper towel,
but even small amounts of Jet A contamination
will leave an obvious ring. The stuff
in the bucket flunked the test.
Another five gallons of 100LL were
98 |
poured into the tank, and the process
repeated. Once again, it flunked. We had
to repeat the procedure three more times
before we were satisfied that the system
was essentially kerosene-free. We reconnected
the fuel line and cowled up the
engine. The fueling company topped off
the airplane (at no charge). Finally, six
hours after the misfueling incident, I was
good to go.
TAKEAWAYS
I learned some important lessons that day.
Perhaps the most important is that it's
impossible to distinguish pure avgas and a
mixture of avgas and Jet A by color alone.
My main tanks had been about half full of
avgas, so after the misfueling they contained
roughly a 50-50 mix. If you take a jar
full of pure 100LL and another jar with a
50/50 mix of 100LL and Jet A, I guarantee
you will not be able to see any difference in
color or clarity between the two.
I had not realized that before. I was
always taught that you sump the tanks and
observe the color-100LL is blue and Jet A
is straw colored. What I was not taught is
that a mixture of 100LL and Jet A is also
blue and that you simply can't tell the difference
visually.
I was also taught that since Jet A is
significantly heavier than avgas (6.7 versus
5.85 pounds per gallon), the Jet A and
100LL will separate just like oil and water
with the Jet A at the bottom (where the
sump drain is) and the 100LL at the top.
That's true, but only if the contaminated
fuel is allowed to sit for hours. It turns out
that 100LL and Jet A mix quite well, and
the mixture takes a surprisingly long time
to separate.
I still shudder to think what might
have happened had I not spotted that Jet
A truck in front of my airplane.
There are at least two good ways to
distinguish pure 100LL from kerosenecontaminated
100LL. One is by odor: Jet
A has a distinctive odor that is detectable
even in small concentrations. The other
(and probably best) is by using the papertowel
test: Pour a sample on a white paper
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AOPA Pilot Magazine - July 2021

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