Back when I was growing up on the farm, we used several powered
implements that received their power from the tractor through a power
take-off assembly. Somewhere on the device's power train, between the
PTO take-off and the "business end" of the apparatus, there was always
either a belt-drive or a coupling fitted with a "shear" pin. Both of
these systems were intended to protect that tractor (and the implement)
by failing if the implement bit off more than it could handle.

This morning, while driving past the airport on my way to work, the
thought occured to me that a shear pin could be used to protect airplane
engines (at least partially) from prop strikes. My understanding is that
the props on light singles (at least) are connected directly to the
engine's drive shaft.

Recognizing that this issue is driven as much by regulation as by
anything, I'm wondering if there would be any benefit to using shear
pins in these systems. Would it reduce the need for a complete (or
partial) tear-down after a prop strike? Would there be any benefit for
more complex propeller arrangements?

Any thoughts?

Rich Lemert