those that are interested: the 3 blade Aero Products were the first Props used on C-130's
when the "B" model and on to the "H" model used Hamilton Standard.
One of the engine builders
on this site talked about 'Harmonics".. that was an understatement.
when you have more than one prop, a vibration develops..Prop sync comes into play. and Aero Products
just could not get it together.
I have been told the C-133 was worse, you could stand in the cargo compt. and you will vibrate off the plane of rotation.
the c-133 also began to fall out of the sky due to internal failure in the wings and wing box.