The Hazards of Hand-propping
April 2010
I don't know about you, but hand-propping an airplane tends to conjure up visions of a dashing, leather-clad pilot swinging the prop wildly after someone yells Contact! from the cockpit. And, of course, the engine always starts on the first try.
The reason hand-propping works at all is because most aircraft engines have magnetos. When the engine spins it turns the magnetos, creating sparks in the cylinders. If fuel and air are present in the proper ratio, the engine starts. But if the engine has high-compression cylinders, a ring-gear starter, or a geared or belt-reduction propeller, then hand-propping typically doesn't work.
The real issue with hand-propping, however, is safety. Grabbing the equivalent of a giant saw blade and sending it whirring at 1000 RPM poses an obvious hazard. Spinning propellers have many times proven dangerous–even deadly–to hand-proppers.
To increase safety, most airplanes designed for hand-propping have tailwheels, which puts the prop disc an at angle that's easy for the "propper" to avoid once the engine fires. However, the angle of the lower-mounted propeller on nosewheel airplanes is much harder to avoid.
The other danger is that airplanes sometimes get away from hand-proppers, colliding with hangars or other airplanes. Passengers on board these planes have been injured and killed in these collisions. In a few freak cases, the airplane has actually taken off unpiloted, which I'm sure quickly piqued the interest of passengers who got a ride worth telling their grandkids about.
From an insurance perspective, Avemco's policy does not exclude hand-propping, but a careless hand-propping claim does call into question the judgment of the person responsible. It's best to leave this to the folks with birds that don't have electric starters and who know how to safely hand prop their aircraft.
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