Vibration

[1911Tex]

Normal liftoff; pull back lightly on the stick or let the airplane climb and gain airspeed at its own pace, no problem. However, immediately after liftoff, if I push the nose down to gain quick airspeed, there is an immediate very noticeable vibration throughout the fuselage. Not felt in the rudder pedals, nor the stick (ailerons). Only in the fuselage. Of course using half (takeoff flaps). No vibration at any time, climb or cruise. Thinking maybe the prop bolts need tightening? Sensenich composit prop. Any ideas?

[Pascal]

I am very interested in the answer. I have the same propeller, and I believe the same problem. The vibration appears at specific RPMs. Also, it has been raining cats and dogs here for the last four months, and I even though I have some propeller covers, I suspect the propeller has absorbed a lot of moisture and is has become noticeably unbalanced.

I will be replacing that propeller with an MT on the next annual.

[Derek]

I've never experienced this problem with my mt prop. The mt prop is possibly the best money I've ever spent. All around performance is so much better. Makes me wonder why the factory doesn't use them.

[Don]

Geez...if you really think the prop bolts are loose I would not fly the plane again until it was checked out by an A&P.
With that said, immediately after rotation, I do get some slight vibration in the fuselage. In my case, it is the gear tires still spinning from the take off run. Once they quit rotating the vibration stops.

[Colin]

I was going to say exactly what Don said, on both counts.

My only day in a DA20 was in one with the wooden prop and a few times I got a funny vibration on descent. I did not enjoy it.

[mdieter]

Geez...if you really think the prop bolts are loose I would not fly the plane again until it was checked out by an A&P.
With that said, immediately after rotation, I do get some slight vibration in the fuselage. In my case, it is the gear tires still spinning from the take off run. Once they quit rotating the vibration stops.

I had this vibration problem for a while. Drove me crazy trying to figure it out. A GoPro cam watching the gear was the final diagnostic. Replaced the tire and all good now.

[1911Tex]

If the prop bolts prove they were torqued correctly....next step will be the tire. Will report back. Thanks.

[1911Tex]

Prop nuts 20-28 in.lbs. under recommended 370-380 in.lbs. torque. A/P recommended checking torque not less than every quarter due to plane being hangered and not tied down outdoors, instead of at my normal 6 month oil/filter change. Simple 5 minute job; remove top cowl, torque nuts. He also stated, even though hangered, in an extended wet spell check more often. Vibration down to almost imperceptible level; gear tire rotation may be the remaining factor as mentioned above. Thanks for all above comments!

[Pascal]

Flew yesterday before having a mechanic retorquing the propeller bolts. The unbalanced propeller problem had mostly disappeared.

Presumably the propeller's wood has dried, thus eliminating the unbalanced weight in the propeller brought by several weeks in a row with copious rainfall. The instrument panel does not vibrate like a Harley Davidson motorcycle anymore.

Today a mechanic retorqued the propeller bolts. Then I flew it for an hour. The engine felt smoother, objectively.

The a&p mechanic told me it was time to clean up the propeller. For those with a Sensenich propeller, which cleaning product/technique do you use?

[1911Tex]

Pascal: Contact Sensenich factory (813.752.3711). I don't know what "cleanup" means per your A/P (IRAN/Overhaul/etc?). I would rely on no ones opinion, only the advice of the manufacturer to answer your question. On their website homepage www.sensenich.com you can lookup the date of manufacture of your prop as well as a lot of great info.