Hey folks. I have come to a fork in the road. I fly a 65' PA30 with 9500hrs on it. It has a beautiful panel and we fly it all the time. Where I would like some input is weather or not we put money into it to keep it nice or sell and upgrade. Here is my issue:
- It has had various vibration issues for awhile, both in motor and airframe. Above 180mph the aircraft shakes, you can feel it in the yoke. On a scale of 1-10 I would call it a 4. We did replace the trim cable last annual and the tail was rebuilt three years ago. I'm not sure what it could be, I feel though that it is in the elevator..... you can see it vibrate very slightly.... but that is too much for me.
- It also needs motors..... I am willing to put new motors on it this annual but if the airframe is tired, I don't want to waste the money.

Thanks for your input in advance.

Jonathan
Chattanooga, TN
N7828Y

Jonathan,

I suggest not giving up yet - especially if it has a nice panel. In 45 years, have had vibrations and have always been able to find a cause. Below are questions that have yielded solutions in the past for me.

1. Did it always vibrate? If not, when did it start? If you can identify the starting point then you may have a causal factor. Does a Comanche-experienced mechanic do the maintenance? Before I'd give up - suggest Heritage or other Comanche-hot shop.

2. When was the last time the lord mounts were changed - it is recommended every 4 years AND they need to be torqued to 450-500 in-lbs ... ask me how I know

3. Have the props been O/H'd in recent memory?

4. Are the gear doors tucked up to spec?

5. are all inspection panels re-secured?

6. are flap tracks worn and need replacing? If the track is not a consistent width near the top, they are wallowed out - be sure the service manual procedure for replacement is followed.

7. It the tail rivet AD complied with in all four areas?

Of course, it could be the engines themselves - what were the last compressions?

Hope something in here helps solve the problem.

You are nowhere near the end of the fatigue life on the airframe if that is what you are asking. I know that some of these airplanes have done thousands of hours of cloud seeding and if there was anything that would prematurely fatigue a non-pressurized aircraft, that would be it. Some of those are well over 10K hours TT.

I don't suppose you are out on the west coast. I would be curious to help you sort that one out. It seems an interesting problem.

A little history; This airplane has been in the same family for 35 years. It was owner maintained for 32 of it. Once the next generation took ownership, the next two annuals were 35k and 25k respectively. Needless to say it suffered from "under-maintenance". It does need new mounts and those will be changed with the new engine install. The Tail Ad has been done and the shop that now works on it is very thorough, but not Comanche experts. As long as the airframe still has life, we will keep investing in its survival. Thanks for the reply. fyi, we are in Chattanooga,TN and our shop is in Cincinnati, OH.

Jonathan

There was a PA30 in Toronto which was used for a traffic spotter. When retired and sold it had somewhere around 18,000TT and was still going strong.

Clarence

Engine isolation mounts are probably your biggest issue as something is knocking against the airframe and causing the vibration. There is a big difference between vibration, and flutter, and much vibration can be resonant throughout the airframe causing different parts to move. Loose or worn trim drum/bushings in the stab trim system can cause flutter. Also gear doors and improperly installed antennas can also cause other vibration issues.
-Zach

We had airframe vibration in our PA-30 that was driving me bonkers trying to figure out. We checked horizontal stabilator balance, balanced the props, etc. It was the engine mounts. Replaced them and all traces of the vibration were gone.

Tim

forgot to mention exhaust stacks banging on cowl flaps