My brother is a CFII.  One summer he was practicing touch-and-go's in a
C172.  After one memorable landing, a prop blade separated while he was
throttling up for another take-off.  Although he quickly shut-down the
engine and rolled to a stop, the resultant vibration caused the engine to
slump as the engine mount failed.  The engine was about to depart from the
airframe!  Talk about a serious weight and balance problem!  He shudders to
this date when thinking about what the outcome would have been if the prop
would have failed moments later ... I think a guardian angel was riding
co-pilot that day.  Lesson learned: "Don't mess with props", or you can't be
too safe when it comes to props.

Dana Westphal
L2K-165
"Building over Geologic Time"
or "I'm glad that I'm building a plastic airplane, lest it be a rust heap by
now".