Excessive vibration

[JoefromGeorgia]

I have been enduring excessive vibration in my 76 Piper Lance for a few years. It seems to be getting slightly worse over time and I feel I need to try and address it again. It occurs primarily in cruise. It appears to be from the engine or prop because it can be dramatically reduced above 2500 rpm and below 2200 rpm. I have had the prop dynamically balanced and replaced the engine mounts. No change. I have performed all the checks in the Hartzell manual (blade track, lubrication, etc...). I do not feel it is from the airframe, but there are no loose control surfaces, etc. There are no obvious problems (leaking grease...)

The engine and blade are both high time since new/overhaul. 13 years and 1600 hours on both. The prop is a Hartzell 3 blade, overhaul reccomendation is 6 yrs/2400 hrs. The engine is a Lycoming IO540K1A5D.

With few avenues left, would a prop overhaul be as good a place to start as any? Funds are limited so trying to make best use of $. Other needs also. Thanks for the input!

[WLIU]

So what did the tech who did the prop balance have to say. The display on the balancer shows all the vibration that originates in the engine and you can see the mags vs the crank, etc. If the tech did not see anything in the engine or prop, then the question is what else in the front of the airplane can be vibrating in response to the engine.

If I recall correctly, the Lance and its siblings have the nose gear hanging from engine mount tubing. Could there be worn bushings or a cracked tube that is allowing motion? Are the landing gear up hooks that could be loose. Gear door loose?

Best of luck,

Wes
N78PS

[JoefromGeorgia]

good thought on nose gear Wes, will check. The tech said the balance looked good. I am looking at the graph and can not interpret it. The graph has some curious spikes in it, but not in the range I have the problem, I will have further discussion with the tech.


thanks
Joe
N7698C

[Bill Berson]

You could ask the prop shop about an internal prop inspection, rather than a full overhaul.