Small Aircraft; High Wing; 1 Eng; Fixed Gear
Flight Crew Private
Flight Crew Last 90 Days 11; Flight Crew Total 776; Flight Crew Type 584
Distraction; Confusion
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Aircraft Aircraft Damaged; Flight Crew Diverted
Aircraft
I was level at 3000 ft in cruise configuration when an enormous vibration started. I closed the throttle to minimize the vibration and [advised ATC]. Even at idle; the vibration was so bad that I worried that the engine was going to be ripped off of the airframe. I didn't know the cause of the vibration. I supposed that something in the engine had failed. ATC was helping me find a private grass strip. But I never did see [it] and ended up selecting a soybean field. Once I was sure I had the field made; I switched the mags off. The prop came to a stop and I could see the damage to the tip of the prop. The landing was smooth with no damage to the airplane or anything on the ground. After I got out of the airplane; I could see that the spinner and its mounting bracket had been ripped off also (the mounting lugs of the bracket were still under the prop bolts).
GA pilot reported an off field landing after the propeller spinner and backing plate failed in flight.