RV-6 Vibrations during cruise

Hi,

This community has been so great. Every time I post a problem I get a lot of great answers. Anyway, here is my latest question.

I am a new owner of an RV6. I didn't build it and I have very little maintenance skills. Anyway, my RV6 has 600 hrs on the O 320 engine. I have logged about 50 hours in it. When I'm in cruise under almost all power settings, the aircraft/engine has a moderate constant vibration. It is not outrageous, but it is moderate enough that you can see my hand vibrating while holding the stick constantly. My feet really feel the vibrations when placed on the rudder pedals. As far as I know, these vibrations have always been there but since I am just getting to learn the aircraft, I'm not sure if it is a common thing with RVs or if it's something out of the ordinary. Please advise.

Steve

triguyinla said:

Hi,

This community has been so great. Every time I post a problem I get a lot of great answers. Anyway, here is my latest question.

I am a new owner of an RV6. I didn't build it and I have very little maintenance skills. Anyway, my RV6 has 600 hrs on the O 320 engine. I have logged about 50 hours in it. When I'm in cruise under almost all power settings, the aircraft/engine has a moderate constant vibration. It is not outrageous, but it is moderate enough that you can see my hand vibrating while holding the stick constantly. My feet really feel the vibrations when placed on the rudder pedals. As far as I know, these vibrations have always been there but since I am just getting to learn the aircraft, I'm not sure if it is a common thing with RVs or if it's something out of the ordinary. Please advise.

Steve

Click to expand...

Kind of hard to say without flying the plane, but I'd bet it could be improved.

What kind of aircraft are you used to? The four cylinder Lycomings are not as smooth as six cylinder Continentals as a rule. If you're used to a well maintained Bonanza, the vibration may be normal.

The very first thing I'd do is get someone who's familiar with RVs to ride and offer an opinion. Lot's of RVs around Long Beach and SoCal, so that shouldn't be much of a problem.

Second thing I'd do is have the prop balanced. This should be done periodically anyway and can have a major difference in perceived vibration.

There are a ton of things that can cause increased vibration, but someone experienced can point you in the right direction.

Balance the prop. Check runout on the crank. Check prop tracking.

triguyinla said:

Hi,

This community has been so great. Every time I post a problem I get a lot of great answers. Anyway, here is my latest question.

I am a new owner of an RV6. I didn't build it and I have very little maintenance skills. Anyway, my RV6 has 600 hrs on the O 320 engine. I have logged about 50 hours in it. When I'm in cruise under almost all power settings, the aircraft/engine has a moderate constant vibration. It is not outrageous, but it is moderate enough that you can see my hand vibrating while holding the stick constantly. My feet really feel the vibrations when placed on the rudder pedals. As far as I know, these vibrations have always been there but since I am just getting to learn the aircraft, I'm not sure if it is a common thing with RVs or if it's something out of the ordinary. Please advise.

Steve

Click to expand...

Spent a lot of time chasing "vibrations" in our 6. ...

A couple of quick items.

Take a look at your exhaust pipes. Are they loose? Do they hit the bottom of the fuselage?

Others have mentioned the prop balancing. What type of prop do you have?

Do you have a conical or dynafocal engine mount?

Does it vibrate the same if you switch from one "mag" to the other and run on just one? (might want to check this first on the ground).

Another thing to check that I've seen on several planes including mine. The FAB airbox rides really close to the cowl and can rub which will certainly cause a rough feeling airplane. Is there any evidence of rubbing?

I don't feel any in my RV-6A

The only time I feel any difference from the steady beat of the engine is when I don't start leaning soon enough in the climb (at 4,000 ft it gets aggravated with me and tells me that I am choking it to death with all the fuel) or when I run a tank dry. If the stick is vibrating your hand and the rudder peddles are vibrating your feet it might not be a bad idea to look your tail over. I assume you can tell if it is engine vibration but one can be fooled. If you have a Vetterman exhaust system the hangers are notorious for breaking at the crimp end where the tube is flattened to accept a mounting bolt. The unsupported pipe is subtle but it will get your attention to the extent that you know something isn't right. I remade all of mine with stainless steel tube from Aircraft Spruce as they broke. Note: radius the end of the crimp so it transitions smoothly from the flat to the tube - squashing it in the steel jaws of a bench vice is not the answer. It's been a while but I think I worked mine with a mallet on a wood block. I found the left side of my filter air box did occasionally contact the cowl on the left side and I glued some rubber sheet to the FAB on that side.

Bob Axsom