Either the prop or spinner could fail from contact-vibration damage-- with interesting results for anyone nearby.


Prop charts are very general guidelines & not to be taken as absolute. There is a gigantic range of engine HP & performance characteristics, plus substantial airframe effects that complicate prop selection.

For example, in the 40-size engines, there exists nearly 100% difference in output between the weakest and strongest 40-size sport engines currently on the market. That makes for an enormous difference in prop selection for one engine size -- & the charts don't cover it.

Similarly, the airframe & its intended use powerfully influences prop selection. Is it a small clean speedster, a blunt-nosed biplane, a trainer, a 3D type? All of these factors can make a prop chart only vaguely usefull. Use the chart, but expect to do a lot of experimentation to get a good match.