Bravo vibrations

[toomany]

howdy fellow bravo drivers. this isn't a new thing but it does become more concerning at times. Several times on climb out the engine seems to be vibrating a little more than what i feel is within normal parameters. Today leaving BKW was one of those times. On climb out today, and several times previously, the vibration was more than normal. Each time this occurs it seems to smooth out once higher (at 8-10,000 it seems to dampen a bit). Today was no different, once at 10,000 it got a little less pronounced and once in cruise at 11K it was what seems to be normal for this aircraft. While in cruise i went from 29.5/2350 to 30/2200. At 2200 i could feel the vibration deepen through my seat and noticed a pair of sunglasses vibrating pretty good on the windscreen. After several different settings from 27/2200 to 30/2400 i settled back into 29.5/2350 where the frequency seemed to increase and "smooth" compared to previous settings. Has anyone experienced this and if so what'd you do to smooth it out. I'm aware the lycomings vibrate a little more than continentals but the 540 in my comanche never gets as pronounced as the mooney in climb or any other phase of flight. I plan on balancing the prop next week but wanted to get input from the group as well. Any help is greatly appreciated.

 

 

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[LANCECASPER]

4 hours ago, toomany said:

 

howdy fellow bravo drivers. this isn't a new thing but it does become more concerning at times. Several times on climb out the engine seems to be vibrating a little more than what i feel is within normal parameters. Today leaving BKW was one of those times. On climb out today, and several times previously, the vibration was more than normal. Each time this occurs it seems to smooth out once higher (at 8-10,000 it seems to dampen a bit). Today was no different, once at 10,000 it got a little less pronounced and once in cruise at 11K it was what seems to be normal for this aircraft. While in cruise i went from 29.5/2350 to 30/2200. At 2200 i could feel the vibration deepen through my seat and noticed a pair of sunglasses vibrating pretty good on the windscreen. After several different settings from 27/2200 to 30/2400 i settled back into 29.5/2350 where the frequency seemed to increase and "smooth" compared to previous settings. Has anyone experienced this and if so what'd you do to smooth it out. I'm aware the lycomings vibrate a little more than continentals but the 540 in my comanche never gets as pronounced as the mooney in climb or any other phase of flight. I plan on balancing the prop next week but wanted to get input from the group as well. Any help is greatly appreciated.

 

 

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The Bravos don't have the smoothest of engines, but the first thing I would have done is a dynamic balancing of the prop. They will balance it at normal cruise rpm (2400). That helped a lot on the last Bravo I owned. Also these engines run much more smoothly on fine wire spark plugs.

[Boilermonkey]

Some vibration is normal, but not a lot.  If dynamic balancing doesn't work you might look at your engine mounts.   After that things become elusive and expensive.

 

 

[cbarry]

Not a mechanic, but I would confirm your fuel injectors are clean (simple items first).

[toomany]

Thanks for the input guys. I am running fine wires and the lorde mounts were replaced 500hrs. ago w the overhaul. I will check the gami's after the prop balance if things don't smooth out a bit.
thanks again - greatly appreciated.


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[Fritz1]

dynamic balancing will most likely take care of the vibrations, I had mine balanced at 2300 rpm, still runs smoother at 2400 rpm, something about the resonance frequency of the entire system, not an exact science, you may get another result the next day and may need 2 or 3 sessions to get it really smooth, the Lord mounts are installed with a specific torque, re-torquing them probably can't hurt, the engine mount is bolted to the fuselage with four bolts, think 1/4", checking tightness of these bolts probably can't hurt either, engines sound and feel different over open water or mountain ranges when you are out of gliding range of any airport, your A&P can check blade tracking of the prop and feel if the blades have excessive play, if the A&P does not know how to do this, fly the airplane to a prop shop and see what they say, they will typically do a re-seal up to 700h and thereafter recommend an overhaul

[toomany]

Thanks Fritz1 - ill do the dynamic balance this week and check lorde mounts and motor mount torque. everything was installed w torque seal so i should be able to find anything that may have moved over time. i agree engines always seem torun smoother when not over open water or wooded mountains.


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[LANCECASPER]

3 hours ago, toomany said:

Thanks Fritz1 - ill do the dynamic balance this week and check lorde mounts and motor mount torque. everything was installed w torque seal so i should be able to find anything that may have moved over time. i agree engines always seem torun smoother when not over open water or wooded mountains.


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I would do one thing at a time and see if it makes it better or worse.

[Fritz1]

Yes, good point

[PilotX]

On 12/15/2024 at 9:56 AM, toomany said:

Thanks Fritz1 - ill do the dynamic balance this week and check lorde mounts and motor mount torque. everything was installed w torque seal so i should be able to find anything that may have moved over time. i agree engines always seem torun smoother when not over open water or wooded mountains.


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Any luck with the dynamic balance? Reached out to the locals and they told my I was almost due for an overhaul (2019 OH, 300hours). 

[toomany]

From what i can tell the dynamic balance made a big difference. The panel no longer looks like i'm flying in a chopper. We balanced it at 2350 which is the most common cruise rpm for me. on the 15 min flight back to lns i varied pitch from 2200-2400 and all was good. i keep a pair of sunglasses on the glaresheild - before the balance they would bounce all over the place at 2200, after the balance barely a noticeable vibration. I had the guys at Forward Aero at thv do it - i highly recommend them.


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