Hi all, I fly a 1979 PA 34–200 T. Purchased the plane about a year ago and I’ve been doing some heavy maintenance to it, upgrading, etc. Ever since I bought it, there was a slight vibration during flight which I attributed to typical Twin behavior, but over the last 20 hours that has become more and more pronounced.
It is a constant vibration at cruise speed and I can feel it in the glare shield and the Rudder pedals. Nothing to declare an emergency about but definitely gets your attention and not normal. The control wheel has no noticeable vibration.
The vibration does seem to change based on direction of flight (winds?)
Right engine was sagging so I Replaced all motor mounts on the right engine and had it dynamically balanced. Initial balance was .56 IPS which was rather rough and final was .07 ips at 2400 RPM. I have yet to do the right engine, but the balancing and motor mounts did pretty much nothing for the vibration.
I’ve tried various tests, including gear down cruise power, and the vibration persists. Had gear doors re-rigged and replaced right door due to warping. The fit is not perfect but I figure gear down would eliminate or reduce door to wing skin vibration if that was the culprit. No change gear up or down.
Although the cowl flaps have free play (all bushings /hardware ordered ) Cowl Flaps up or down does not make a difference either. what I do notice is if I pull one engine to idle the vibration cuts approx in half. It is the same on either engine so I don’t think it is a propeller or engine issue.
I think everything is pointing to an airframe vibration from the tests performed.
Any ideas of what to check / similar experience insights would be greatly appreciated.
Engines are 800/550 smoh. Props 250/150 spoh.
It is a constant vibration at cruise speed and I can feel it in the glare shield and the Rudder pedals. Nothing to declare an emergency about but definitely gets your attention and not normal. The control wheel has no noticeable vibration.
The vibration does seem to change based on direction of flight (winds?)
Right engine was sagging so I Replaced all motor mounts on the right engine and had it dynamically balanced. Initial balance was .56 IPS which was rather rough and final was .07 ips at 2400 RPM. I have yet to do the right engine, but the balancing and motor mounts did pretty much nothing for the vibration.
I’ve tried various tests, including gear down cruise power, and the vibration persists. Had gear doors re-rigged and replaced right door due to warping. The fit is not perfect but I figure gear down would eliminate or reduce door to wing skin vibration if that was the culprit. No change gear up or down.
Although the cowl flaps have free play (all bushings /hardware ordered ) Cowl Flaps up or down does not make a difference either. what I do notice is if I pull one engine to idle the vibration cuts approx in half. It is the same on either engine so I don’t think it is a propeller or engine issue.
I think everything is pointing to an airframe vibration from the tests performed.
Any ideas of what to check / similar experience insights would be greatly appreciated.
Engines are 800/550 smoh. Props 250/150 spoh.
