Danish authorities say a failed pitch change structure on a Hartzell propeller not due for overhaul for another year and a half was a contributing factor in the crash a Socata that killed four people earlier this month. The plane crashed along the coast on Aug. 6 and investigators discovered one of the propeller blades was turned 180 degrees from the proper position because of the broken hardware. The Danish Civil Aviation Administration report says that with one blade reversed, severe vibrations would have occurred. The Danish agency said Hartzell had earlier issued a service letter (HC-SL-61-226) regarding a modification of the "pitch change knob" on that type of propeller (HC-C3YK-1BF) at the next overhaul. The prop on the crash plane was due for overhaul in 2006. AVweb wasn't able to find an FAA Airworthiness Directive on the problem.