PA-30 B vibration

[DBpa30b]

I currently have a 66 PA-30B. during the run up there is no vibration. But after I rotate there begins a slight vibration, after I reach cruise alt and lean to 50 to 75 degrees ROP it is still there.

Any suggestions would be much appreciated.

Thanks, and happy flying

[N3322G]

Hi Dean,

Well, this could be a lot of things. Since I don't know you or what level of experience you have, I'll start as if you know little and pardon if that is not the case. More than one Twin owner has had a challenge keeping the props synced, un-synced props cause vibration. Once you get the props synced, do you use the control lock to keep them there?

Next, has the vibration been there since you got the Twin? If yes, where do you see the vibration? visor, instruments? Do you feel it in the floor board?

If the vibration is new. Has any maintenance been performed? If so, would any of the maintenance potentially left something loose on the airframe? cowl flaps, gear doors? stab? ailerons etc.

Have the props been overhauled per Hartzell spec? Have they been dynamically balanced?

Does the twin have an engine monitor that shows the health of each cylinder?

How much time is there before engine overhaul?

Has the aircraft sat for any length of time?

The ultimate help in my opinion is to get another Twin owner to fly with you and see if they feel the vibration also. Are you registered for any of the upcoming CPPP courses?

[DBpa30b]

Thanks for the input, I'll start with this every day is a day to learn so any input is much appreciated, I am a CFI, II and MEI and I have owned the AC for approx 4 yrs now and have put 500 hrs on it. I will answer the questions you pose, yes I do keep the props synced as close as possible. I have the electronic tachs. One thing I don't do is set the control lock.

No, the vibration started about 1 yr ago after I had some work done on the landing gear doors but it wasn't a huge deal. I haven't noticed anything loose on the control surfaces. The vibration is noticed in the control yoke and the compass on top of the dash. a little on the visors.

There is approx 300 hrs on the right and 50 on the left, yes I had them dynamically balanced when I nstalled the overhauled prop.

No engine monitor to view each cylinder, there are 1700 hrs on both engines and the compression is in the mid to upper 70's on all cylinders

It sat for approx 6 months and was only run during that time not flown.

I was going to start with having the props balanced again to start with.

I just had the annual completed in December and the mechanic flew it back to the home base he owns a 64 - PA-30 and he said he didn't noticed anything out of the ordinary.

Anymore thoughts?

[Kristin Winter]

Does the vibration change with changes in the RPM of the engines? The engines could be vibrating themselves or they are setting up a resonances somewhere else.

When you extend the landing gear, does the vibration change?

You might try having you mechanic put the aircraft up on jacks. First see that the landing gear is being retracted all the so that the strut is hitting the bumper. Then, check whether the gear doors are closing tight enough. You might also check to see if the main gear door hinges are loose. If they are sloppy, replacing the hinge, or putting in a large hinge pin might solve that problem.

Have you been running the heater or the blower. I have seen the fans on these loose some of the blades which cause them not to be balanced and will create a vibration.

Those are my thoughts.

[N3322G]

Dean

Kristin covered what I would have asked about the gear.

There's a nice section in the maintenance manual about adjusting the gear doors. The hinges do wear after awhile and they do require picky adjustment. The maintenance manual is on this website under Tech Pubs. While I'm not a mechanic and Kristin is, after 40 years I have 'learned-by-check-book'. If there has been a problem with the twin and it gets fixed, I try to learn from it and prevent it from happening again, if that is under my control.

It sounds like the vibration started about the time the gear door work was done, so I'd have a tendency to focus there - however since everything gets taken apart at annual and put back together, there are now a lot of places to look.

One of the vibration problems I've had fixed in the past was the rubber bumpers located on the gear doors themselves were incorrect in one case and on inside out in another. Mechanics are people too and they will make mistakes. IMHO , good ones use your philosophy of there is something new to learn every day and when they do make a mistake, they do everything in their power to set it right as soon as possible.

wrt the mechanic flying it not noticing any vibration - I don't either as often when I'm left seat or when there's light chop. When I have fewer things demanding my attention or I'm right seat, then I pick up on more nuances of the plane and will notice things like vibration.

Hope this helps. BTW, even with your experience, I'd recommend the CPPP course. We have 40 years with this twin and have taken it twice (1993 and 2010) and learned a bunch both times.

[DBpa30b]

Thanks to you both for the input. Funny you should say that about the bumpers, that is about the same time they were changed out. I will have that looked at and report on it.

Once again thank you.

[N8632Y]

Pat,
You mentioned about ,
"Once you get the props synced, do you use the control lock to keep them there?"
I have to admit,,,i've never heard of a control lock to keep them there,,,
could you please expand?
Maybe I have one, and don't know, or have never seen one to know one?
thanks,,,,
steve
PA30C

[Zach Grant L1011jock]

Steve,
I think he means the friction lock on the throttle quadrant, but I'll let him answer for sure.
Zach

[N8632Y]

Zach,
thanks, i'm familiar w/ friction lock...
never a dumb question , right?
I would think, why lock in props, where's the fun of constantly resynching them w/ each changing condition, wind, power, climb/descent?
I like always trying to synch those things...
Regards to horizon digital tachs?
I don't sync them by the numbers, i try and listen, should the numbers being equal be correct sync,,,i'm always close, but i can never get exact,
nor do i try to...i listen and feel them, and call it "good enough"...
steve

[N3322G]

Steve and Zach,

Yes, I/she did mean the friction lock.

[steen]

Hi, Dean,
Is the vibration rpm related....is it smoother at 2400 than at 2300? Does the vibration occur after leaning or is it all the time? Is it there at high cruise power settings and low cruise, or only at 70% or higher?
The first thing I would check, other than old engine mount pads, is dirty fuel injectors. Can you lean to lean-of-peak and still stay smooth....sort of....and if you cannot you have a dirty fuel injector. Stock injectors are not Gammi's but they are fairly smooth lean unless dirty....then they buck and jump when leaned to the "cool side".
Fouled plugs also come to mind...do you run fine element plugs? I've found they really improve the smoothness of my engine ops over the long haul.
For a stiff four-banger these engines try to run smooth but a small item disrupts the smooth pretty quick. Did a plug get dropped at annual? It doesn't take much.
Steen

[DBpa30b]

Steen,

I spoke with the A&P that performed the annual inspection this last weekend. The vibration happens at all RPM ranges even when leaned. The only thing I haven't tried is lowering the gear and see what happens. I never really noticed while landing. The injectors were cleaned and they are gammi's.

I will post what happens.

Thanks for the imput.

Dean

[Andreas Riedel]

Hi Dean, a few years ago i had the same problems with slight vibration in cruise. Did not notice while climbing but was noticable in cruise. Aftere a lot of hours under the cowling and with the help of the Gammi engine monitor my mechanic could trace it back to a broken magneto on the left engine. The inner housing was broken off which gave one cylinder the wrong info. This only happened at certain revs so could not be detected on the ground. Got a new magneto, problem solved.
Good luck
andreas