More vibration information... need advice

[glenadavis]

My new to me 12 has a viration that starts around 100 kts causing stick shake and vibration I can feel in the panel and pedals. Its slight, but definately there. Below 100 knots it's perfectly smooth. I will have the prop re-balanced (done previously in 2018) and the carbs balanced soon. I will try to determine the next time I fly if it's RPM related. I'll climb at full power but keeping the speed below 100 kts and see if the vibrations exist. Hopefully that will tell me if its airspeed related or RPM related. Any other thoughts?

 

[seagull]

I just worked on a -12 that a friend bought. I personally flew it home and it had a noticeable vibration above 100kts. I re-pitched the prop, it was a little coarse. Balanced the carbs, they were not far off. Also balanced the prop to .01ips. It was .40ips when I started. The plane was smooth afterwards and I suspect the prop was the issue. This plane had 700 hours on the airframe but less than 50 on the prop and gearbox which were both replaced due to a minor prop strike.

 

[CTCole]

I'm a fan of prop balancing, but first I'd want to know if the vibration came from the engine & prop or from the airframe. You mentioned that it occurs above 100 kts -- is that true both in a dive, with the engine power & rpms reduced, and in a climb, with more engine power? Can you identify a rpm where the vibration appears?

Good hunting.

 

[glenadavis]

I'm a fan of prop balancing, but first I'd want to know if the vibration came from the engine & prop or from the airframe. You mentioned that it occurs above 100 kts -- is that true both in a dive, with the engine power & rpms reduced, and in a climb, with more engine power? Can you identify a rpm where the vibration appears?

Good hunting.

As soon as the bad weather passes, I’ll do that testing and report the findings.

 

[Walt]

Always better to troubleshoot on the ground, not much you can do in the air, flying it more probably won’t fix it and may not be safe.

 

[PCHunt]

As soon as the bad weather passes, I’ll do that testing and report the findings.

On rare occasions, a wheel may spin up when airborne and cause vibration. Apply the brakes when the vibe is present, and see if it stops. Not very likely, but easy to find out. If it's the nose wheel, this trick won't work.

 

[Dvalcik]

On rare occasions, a wheel may spin up when airborne and cause vibration. Apply the brakes when the vibe is present, and see if it stops. Not very likely, but easy to find out. If it's the nose wheel, this trick won't work.

It could also be the breakout force on the castering nose wheel. Others can chime in.

 

[sansoneservices]

My new to me 12 has a viration that starts around 100 kts causing stick shake and vibration I can feel in the panel and pedals. Its slight, but definately there. Below 100 knots it's perfectly smooth. I will have the prop re-balanced (done previously in 2018) and the carbs balanced soon. I will try to determine the next time I fly if it's RPM related. I'll climb at full power but keeping the speed below 100 kts and see if the vibrations exist. Hopefully that will tell me if its airspeed related or RPM related. Any other thoughts?

+1 for dynamic prop balance. Also agree with another post regarding you determine if it's engine or airframe