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Old 02-19-2020, 12:01 PM
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gmcjetpilot gmcjetpilot is offline
 
Join Date: Jan 2005
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Originally Posted by Northernliving View Post
In the Hartzell application guide on pages 1424-1442 it lists many of the props for Vans aircraft. For engine model it denotes IO-XXX, (I)O-XXX, or O-XXX. Does this imply that the prop would be dependent on the fuel delivery system, injected(I) vs carb(O)?
It's complicated. So here is the deal. The prop is tested with a very specific configuration, including ignition, fuel delivery and even air frame. Hartzell in no way has tested every possible combination, including some of the ones in the application guide. However they have "derived" the application and any limitations by similarity.

Bottom line the type certificate for the prop as a very generic note saying ANY CHANGE can affect the prop operations.

How the prop vibrates (or dampens vibrations) for a specific configuration and causes metal fatigue is the issue. Keep in mind they have lots of safety factors and margins on the prop and blades. Back in the day people took fixed pitch metal props, cut them down, re-pitched the heck out of them. They had lots of fixed pitch metal prop fatigue failures. So it was a thing. Sensenich sells safe metal fixed props for the RV fast kit plane market now.... You'd be crazy to mod a fixed metal prop like that today, especially with so many good composite and wood props which are virtually fatigue free (but are subject to environmental damage).

My opinion is FI vs Carb is not a big driver, except if it makes more HP. We have very free flow intake and exhaust which adds power. Cross Over vs 4-into-1 Pipes, Magneto vs Electronic Ignition, Compression ratio Low vs. High, Non counterweight crank vs counter weighted crank, are all players in how the prop vibrates (due to power pulses and size of that pulse). If you can find something close you are good. The fatigue life on these props is pretty long. Just avoid the yellow band RPM's of the configuration that is close to yours and you will be safe.
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Last edited by gmcjetpilot : 02-19-2020 at 12:04 PM.
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