ORIGINAL: Tired Old Man
RTK and I talked about this on the phone last night. It was a wood prop in excellent condition. The BME 115/116 uses a center nut to retain the prop, along with the option of using outer prop scres for indexing purposes. The outer screws do not provide propeller clamping force so are a personal option, not a requirement.
There was no evidence of any propeller damage or defect prior to the engine run. I often fly with RTK and know he takes very good care of his equipment and is more than a little fussy with anything concerning the engine.
That his propeller self destructed is a big wake up call for me. I often stand off to the side during a run up but I think that is something I will do no more.
I wonder if the practice of using only the center nut on a 115cc engine is a good idea. The outer screws at least can spread the load.
On high-torque YS engines, the use of a lock prop nut is a must.
Regardless, standing in front of or close to a spinning prop is a bad idea. Sometimes, fellow club members or speculators fall in the danger zone of a spinning prop, without knowing it. The pilot should never point the airplane to people without have it constrained.