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 1967 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!
Posted December 28, 2013