EdL;n1134377 said:
I’m still a relative novice in these contraptions. Trying to understand how a spinner coming off would hit the rotor, since it’s at the back of the prop/engine and well below the rotor and how it’s loss, given its relatively small diameter, could cause such vibration even if only one of the retaining bolts was kept in place. I’m not disagreeing this is what happened, just seeking some insights on these points.
/Ed
My speculation is (because this is experimental aviation, w/ out deep pockets like certified aviation) we really don't know exactly how much airflow is going UP through the entire rotor blade disc. I'm guessing extensive wind tunnel testing would shed some light as to how much air. But, the expense & availability of such testing equipment are big factors.
1. As in all aircraft with wings, some air is being deflected downward to provide lift.
2. In a gyroplane, since the rotor blade disc is tilted slightly aft to the incoming airflow, some air is also going up through the rotor blade disc between gaps between the passing of each rotor blade.
I assume there is some airflow upward that'd easily carry a lightweight prop spinner into the rotor blades. Especially if the spinner was above the prop blast, or skips, or bounces upwards off that prop blast as it departed the prop hub.
Anyone who has stood in proximity of the backside of a running prop on the the ground has felt the rush of incoming air surround & try to pull them into it. I like to think there is a similar effect underneath the rotor blades in flight. Maybe not as strong as the backside of an engine-driven airfoil such as a prop, or a set of helicopter rotor blades, but a distinct movement of air up into them.
It also may have been flung upward by being hit by a prop blade. We have heard of pieces of props hitting the rotor blades as they have disintegrated either by failing in their structure or being struck by foreign objects that aid in that disintegration.
We also don't know the airspeed and direction of movement of the gyroplane at the time of the prop spinner coming off. It may have been in a vertical descent. It may have been in a normal flight mode. It may have just executed a hard turn.
We do know that Britta is a careful & cautious gyroplane pilot & instructor. We also know Mark is a careful & cautious aircraft maintenance fellow, as well as also being a careful & cautious gyroplane pilot.
I have viewed a video of another gyroplane's prop spinner departing the prop hub, so is is not unheard of, but is a rarity.