Most casual discussions of hand-propping begin and end with the admonition "Don't." That's not bad advice, except when there's no other way to start the engine. In fact, hand-propping is a time-honored practice, dating to the beginning of heavier-than-air flight. That it's still employed says as much about the legacy of aviation as it does our ability to manage risk.
This is a companion discussion topic for the original entry at https://www.avweb.com/flight-safety/technique/hand-propping-demystified