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Every month in Model Aviation,
the AMA's monthly publication, there is a "Safety" column that reports on model-related
accidents and issues like not charging Li−Po batteries in appropriate containers,
not smoking around glow fuel and gasoline, not flipping your propeller with a bare
finger, etc. Many moons ago the big safety concern was not flying control line models
too near to high voltage power lines. This photo from the April 1957 edition of
American Modeler shows some guy attempting to retrieve a radio control
model from its landing spot atop a set of telegraph wires. He is standing on a barbed
wire fence using a wooden pole to prod it off the lines. The captions asks, "Who
knows line voltage?"
I looked it up. Typical telegraph line voltages ran from 500 to 1,200 volts according
to the 1922
Railway Signaling and Communications manual. Power line voltage on
overhead lines in a typical neighborhood runs from 2 kilovolts to about 35 kilovolts.
It only takes about 100 milliamps (1/10 amp) passing through your heart to
kill you. A typical hand to
hand resistance with a pathway through the heart is 1,000 to 2,000 ohms
(for dry hands). Ohm's Law states that V (voltage) = I (current) * R (resistance),
so the voltage required to force 100 mA through your heart would be V = 0.1
* 2,000 = 200 V. If you happen to have sweaty palms, the resistance could be
much lower and accordingly a lower voltage would do you in. A high enough voltage
could force enough current through a seemingly dry wooden pole to kill you as well.
How NOT to Retrieve a Model
What NOT to do to retrieve a model. Who knows line voltage? Never stand
on metal wire!
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