Shaking during flight?!

[myda40]

Hello all, I have been having some shaking during flight, especially during climb and descent that makes it uncomfortable. It is usually just felt in the front seats and you can see it on the instrument panel with the G1000 shaking a bunch, generally calms down during cruise flight but still a little here and there. Mechanic went through it, passed the annual, still shook so we sent mags to get overhauled, $1,600 later after the overhaul that mechanic though would solve it, we still have the shake. Engine instruments are all green and she sounds amazing, any idea what may cause that bit of shaking?

[Rich]

Is this new behavior? I'd for sure check engine mounts, including where the engine truss structure attaches to the firewall. And dynamic prop balancing. Excessive vibration is hard on everything in the airplane, but especially instruments. It can also shake wiring connectors loose.

[Chris B]

...any idea what may cause that bit of shaking?

First thing I would check is propeller balance.

Chris

[myda40]

Yes this is a new problem, it has been on and off since beginning of May and I keep sending it back and it's draining my wallet because no one seems to catch it and when I take them up, it decides to not shake and rattle as much so they keep telling me it is normal, but when I and doing cross countries especially the climb out gets really shaky and I have owned her since 2016 and fly 3-5 times a week so I could tell it isn't normal. I am just trying to see what I can tell a different mechanic to see if they can catch it that way, thanks guys!

[Rich]

When was the last time your prop was overhauled?

[Chris B]

Yes this is a new problem, it has been on and off since beginning of May and I keep sending it back and it's draining my wallet because no one seems to catch it and when I take them up, it decides to not shake and rattle as much so they keep telling me it is normal, but when I and doing cross countries especially the climb out gets really shaky and I have owned her since 2016 and fly 3-5 times a week so I could tell it isn't normal. I am just trying to see what I can tell a different mechanic to see if they can catch it that way, thanks guys!

Propeller vibration is apparently sensitive to relatively small variations in RPM.

How many hours on the engine?

What mixture setting (ROP or LOP)?

Can you post the engine logs from a flight with the problem?

Rich has a good point about the mounts, but that gets expensive. A 2005 should not be old enough for calendar time to be a factor.

Chris

[myda40]

When was the last time your prop was overhauled?

Haven't had one yet, only 640 hrs on the engine, they feel really tight though and adjusting the prop rpm doesn't settle the shake enough to be noticeable so I kind of kicked the prop being the problem to the curb

[myda40]

Yes this is a new problem, it has been on and off since beginning of May and I keep sending it back and it's draining my wallet because no one seems to catch it and when I take them up, it decides to not shake and rattle as much so they keep telling me it is normal, but when I and doing cross countries especially the climb out gets really shaky and I have owned her since 2016 and fly 3-5 times a week so I could tell it isn't normal. I am just trying to see what I can tell a different mechanic to see if they can catch it that way, thanks guys!

Propeller vibration is apparently sensitive to relatively small variations in RPM.

How many hours on the engine?

What mixture setting (ROP or LOP)?

Rich has a good point about the mounts, but that gets expensive. A 2005 should not be old enough for calendar time to be a factor.

Chris

I have 640 hours on the engine total and usually run it LOP

[Chris B]

I have 640 hours on the engine total and usually run it LOP

Next time try running rich when this happens. That will eliminate a bunch of possible factors for troubleshooting.

Also, I added this after you started your reply (sorry):

Can you post the engine logs from a flight with the problem?

Chris

[Rich]

The reason I mentioned the prop was I had half the ball bearings broken and races get completely shot in my MT after a very few years. No obvious looseness or anything. My symptoms were different in that basically the broken parts wind bind and the prop acted basically like a fixed-pitch prop. The bad news is it would take a chunk of change to open up the hub and check it out. Prop overhaul recommended intervals run 6-7 years.

I mentioned the points where the engine mount frame mounts to the firewall is twofold: They are supposed to be checked periodically AND I had what was then an 8-year-old Cherokee 140 that I found with those bolts to be loose enough to turn with one's finger. All turned out to be loose. This isn't particularly expensive to check. The dynafocal mounts you can make a quick check by simply making sure that the gap between the spinner and cowling is the same all around If they're giving up the ghost the engine will sag. But there are also torque settings for these which could be easily checked.

Given it's intermittent a prop balance might not be recommended at this time.