on june 30, i had an apc 21x10 fail in flight. this prop had never been damaged in any way, but was about 15 yrs old. airplane is an aeroworks edge with a dle 55 engine.failure occured in level flight at 3/4 throttle. blades departed the hub about 1 1/2 inches from the center line. have not found the blades, but do have the hub. this prop was carfully balanced by scraping some material from the top surface near the tip. didn' require much. the throttle pushrod retained the the engine, so was able to glide in without much damage.