Vibration from the prop or maybe the hub.

[jbrandv]

Ok, I've now flown N660RV for 1.6 hours. Initial squaks were taken care of but one persists. We had a vibration at high engine speeds. i.e. > 2400 RPM. We had the prop balanced and that helped. Now it's very smooth at 2400 RPM as long as I use the throttle to set the speed. If I open the throttle and use the prop pitch to get back to 2400 RPM the thing shakes like mad. BTW: This is an angle valve IO-540 with a McCauley three blade prop. Is it possible for the blades not to pitch at the same angle? I would have thought that there would be a geared system so that couldn't happen. Frustrated in NM.

 

[Walt]

Ok, I've now flown N660RV for 1.6 hours. Initial squaks were taken care of but one persists. We had a vibration at high engine speeds. i.e. > 2400 RPM. We had the prop balanced and that helped. Now it's very smooth at 2400 RPM as long as I use the throttle to set the speed. If I open the throttle and use the prop pitch to get back to 2400 RPM the thing shakes like mad. BTW: This is an angle valve IO-540 with a McCauley three blade prop. Is it possible for the blades not to pitch at the same angle? I would have thought that there would be a geared system so that couldn't happen. Frustrated in NM.

I would definately get the prop checked by a good prop shop, that is not normal. And yes if the blades are pitching to different angles you will get a aerodynamic imbalance. You should also check that the prop is clocked correctly.

 

[aerhed]

So, what you're saying is that when the prop is on its low pitch stops it is smooth, but it gets rough when oil-pitched off the stops?

 

[Wayne Gillispie]

If I set prop at 2400 rpm then vary the throttle(MAP)...yes mine also produces more vibration at higher MAP. Mine is not excessive to me or other pilots that have flown with me though. Is your engine new, overhauled, any sudden stoppage history, prop new? Magnetos or electronic ignition? Do you have an engine monitor? Are you leaning below 75% power to ROP or LOP? Like the above poster said, rotate the prop 180* then rebalance may be one option. Also prop protractor can verify blade angles.

 

[pierre smith]

I had a serious vibration problem on my Air Tractor's 3 blade Hartzell. A really good prop shop found one blade 1/2 a degree off pitch and another 1/4" out of track.

After their magic massage, it's silky smooth.

Best,

 

[Wayne Gillispie]

Remove six top plugs to turn prop easier. Set a block of wood on the ground 1/16"-1/8" below blades. Rotate through and mark where each blade passes. Use a prop protractor to check blade angles. Let us know what you find out.