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vibration

jwilbur

Well Known Member
Trying to figure out what's normal and what's a problem in my RV10.

After cleaning injector nozzles at the advice of someone to help find a different problem (an EGT dropping with reduced power), I made flight #3 this morning and noticed a pretty bad vibration that was not there on flight #1 or #2. I could feel it in the floor through my feet and in the stick. High frequency - like I was holding a small electric detail sander. Had to let go of the stick a few times just to get a rest from it. Was planning to fly two hours, but called it after only about 40 minutes partially because of this vibration and partially because of rain.

I was running 2300, 23"-26" (varying between 65% and 75% power). Vibration much worse at 75% power, still there but much diminished at 65%. Not there at all when I reduced power to descend and land.

Standard Van's FWF:
IO540-D4A5, 2 blade Hartzel CS prop, dual mags.

Any comments or ideas?
 
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Have you had your propellor balanced?

Not yet. But I had no vibration on first two flights. Could it come on so suddenly? Also, I never changed the RPM but can make the vibration come and go with power (i.e. prop changing pitch. finer pitch, less vibration). Not sure I can simulate on the ground. I'll look into that. Thanks.
 
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This was addressed in the Superior guide mentioned elsewhere.

The author discussed vibration and mentioned sudden onset vibration. One of the areas he looked at first was mounting and interference with structure. He quotes an instance where a guy had vibration through the airframe etc, it was diagnosed to a clamp making hard contact with the engine.

I know this is a simplistic approach, but it can be checked with a good torch and a 15 minute look around with the cowls off. Have a good look, shake the motor good and hard and listen.

If that cures it, I like Merlot - New World please and it can be delivered to Florida :D:D

Offer still stands if you can't download the guide, drop me a line, I have an emailable copy.
 
Hard to tell BUT

Hard to tell where your vibrations originate but I doubt it is an out of balance prop.
More than likely something is loose and starts vibrating at certain propeller settings and or air speeds.
It maybe as minor as a couple of loose screws holding a bracket or something more serious.
Having to let go of the stick to get a rest from vibrations is way too much to ignore and you must find out where it originates.
Good luck and hope you find the source.
 
This was addressed in the Superior guide mentioned elsewhere. ... Offer still stands if you can't download the guide, drop me a line, I have an emailable copy.

Not familiar with "the Superior guide". ... We'll just have to wait and see about the wine. No promises. But if this is my answer, it'll sure make me happy.

Having to let go of the stick to get a rest from vibrations is way too much to ignore and you must find out where it originates.

Completely agree. I ended this flight early and am reluctant to takeoff again without finding a plausible explanation.
 
Had similar happen - exhaust pipe

the bracket had slipped and allowed the exhaust pipe rub against the lower cowl.
 
Have you checked the side skin on the passenger side by their calves? This is a common area that others have mentioned for a resonant vibration. It is on mine. Just touch the skin while in cruise. It needs an extra stiffener or something to dampen. I prosealed a z channel on mine.
 
Have you checked the side skin on the passenger side by their calves? This is a common area that others have mentioned for a resonant vibration. It is on mine. Just touch the skin while in cruise. It needs an extra stiffener or something to dampen. I prosealed a z channel on mine.

I have not. But I will. I ran across a thread discussing this and it seemed like a different symptom. If memory serves that was a vibration at low speeds that dampened out with an increase in power, which is opposite in my case.
 
While your looking things over under the cowling, don't forget to take the prop spinner off and check things over real good under there.
 
I had a similar issue when I started balancing my injectors.

The engine would start to prematurely run rough as I started going LOP. I would feel it first through my feet. I didn't notice it at first, because it was always there. Other RV-10 pilots picked up on it right away.

It turned out to be bad mag timing. One of the mags had drifted. Once I timed the mags and they were back in sync, the problem went away.

I don't know if that is your issue, but it sounds like similar symptoms.
 
carbon brush SB on Slick Mags

Bob's post reminds me, did you check for the carbon brush SB on your mags? That would cause them to fail after a couple of hours.
Upload your engine logs to Savvy and take a look at the data. It might tell you if the vibration was ignition or fuel related.
 
Bob's post reminds me, did you check for the carbon brush SB on your mags? That would cause them to fail after a couple of hours.
Upload your engine logs to Savvy and take a look at the data. It might tell you if the vibration was ignition or fuel related.

Correct me if I'm wrong, but I thought that SB affected specific SN ranges manufactured between 2004 & 2006. Are brand new mags, which is what Joe has, subject to this SB?
 
Correct me if I'm wrong, but I thought that SB affected specific SN ranges manufactured between 2004 & 2006. Are brand new mags, which is what Joe has, subject to this SB?

Nah, you are correct. Didn't know which engine he has. Could still be a mag issue though.
 
Maybe

If you cleaned the injector nozzles and then get a vibration, could it be the injector nozzles are not reassembled properly? If the vibration is tranfering to the stick and goes away with lower power setting, I suspect it has a lot of energy, like a bad nozzle.
 
If you cleaned the injector nozzles and then get a vibration, could it be the injector nozzles are not reassembled properly? If the vibration is tranfering to the stick and goes away with lower power setting, I suspect it has a lot of energy, like a bad nozzle.

I think a bad nozzle would present itself in the engine data with a high (or very low) EGT on one cylinder. My EGT behavior is the same after the cleaning as before.
 
Is it possible that an unsecured injector fuel tube or other component could be vibrating and causing a pulsation in fuel flow to one or more cylinders?
 
Is it possible that an unsecured injector fuel tube or other component could be vibrating and causing a pulsation in fuel flow to one or more cylinders?

I suppose anything is possible. I intend to do a very thorough inspection for this kind of thing when I get back to the hangar.
 
Joe says the vibration is like holding a small electric sander. An engine miss at 2300 rpm is a low frequency. Half crank speed or 19hz. Sounds similar to a problem I had in my RV6 that could be described the same way. I had a section of baffle seal on top rear push backwards in flight that caused a vibration I felt strong in the floor and through the whole plane 150 kts and above. The frequency stayed the same but was more intense at higher speeds. Would also come and go related to power as the engine torques the clearance changes seal to cowl... I caught it looking through the oil door on the opposite side with a light before pulling the cowl. When I pulled the cowl the seal flipped forward to it's proper position.
 
The frequency stayed the same but was more intense at higher speeds. Would also come and go related to power as the engine torques the clearance changes seal to cowl...


This brings up a good question: was the vibration experienced a constant frequency with amplitude varying with engine or airspeed, or was the frequency varying at relatively constant amplitude?

Or did both vary with airspeed and engine rotational speed?
 
This brings up a good question: was the vibration experienced a constant frequency with amplitude varying with engine or airspeed, or was the frequency varying at relatively constant amplitude?

Or did both vary with airspeed and engine rotational speed?

It felt to me like a constant frequency. Amplitude would change with power.
 
Solved

Sounds similar to a problem I had in my RV6 that could be described the same way. I had a section of baffle seal on top rear push backwards in flight that caused a vibration I felt strong in the floor and through the whole plane 150 kts and above. The frequency stayed the same but was more intense at higher speeds. Would also come and go related to power as the engine torques the clearance changes seal to cowl... I caught it looking through the oil door on the opposite side with a light before pulling the cowl. When I pulled the cowl the seal flipped forward to it's proper position.

Finally had a chance to inspect. No interference with anything. No loose brackets, etc. My top cowl was already off but upon inspection, I noticed a black spot and looked at the baffling. Lo and behold, the baffling material corresponding to the black spot was laying the wrong way. This was rear right side (not back) - right over cylinder #5. Checked a bunch of other things, buttoned it all back up, and went for a nice 90 minute ride. No vibration at all. Nice and smooth just like previous flights. Comparing CHTs between the two flights, #5 10-15 degrees cooler with the baffle correct, but this could just be coincidence as I'm breaking in the engine and expect some cooling.

Special thanks to leadnut for chiming in. It is very unlikely I would have considered this.
 
Finally had a chance to inspect. No interference with anything. No loose brackets, etc. My top cowl was already off but upon inspection, I noticed a black spot and looked at the baffling. Lo and behold, the baffling material corresponding to the black spot was laying the wrong way. This was rear right side (not back) - right over cylinder #5. Checked a bunch of other things, buttoned it all back up, and went for a nice 90 minute ride. No vibration at all. Nice and smooth just like previous flights. Comparing CHTs between the two flights, #5 10-15 degrees cooler with the baffle correct, but this could just be coincidence as I'm breaking in the engine and expect some cooling.

Special thanks to leadnut for chiming in. It is very unlikely I would have considered this.

I'm glad you got that figured out. Chasing this kind of stuff down can be such a PITA.
 
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