In addition to the points made by others, let me throw this out:

Suppose the prop strike occurs when the engine is set to high power (maybe not the most likely scenario but quite possible).
The prop makes contact with something and the pin shears. At that very instant, the engine is set to high power but now has
no load on it. With no load, the engine will speed up a lot - way past redline. A likely outcome would be pistons,
connecting rods, and parts of cylinders/heads flying out in all directions, possibly followed by fire - considerably more
damage than from a normal prop strike!

Eric Law

"Rich Lemert" wrote in message link.net...
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