ORIGINAL: Laurence-RCU
Guess I was asleep in logic and physics class 65 years ago so I have to ask;
When using a prop meter to determine RPM does it matter where on the prop the meter is aimed.
We find that there is a difference in RPM if the meter is at the tip than if midway from tip to center of prop.
Laurence
Your tachometer is probably a photocell with some signal conditioning. I'll bet your tach's signal conditioning is having trouble with reading the tips, and showing a lower reading than at midway between tip and hub.
With the engine holding constant RPM, stay behind the prop, with the sun somewhere in front of the prop. Take readings with the tach behind the tip, and several other locations closer to the hub. I'll wager your readings will be consistent, at all locations closer to the hub.
Best wishes,
Dave Olson