Rattle Noise

[Txbyker]

I've got a rattle noise that can be heard in cruise although faintly with the Bose, clearly with no headphones. I can't tell if it is near the firewall, in the cockpit or outside. All engine indicators are good. Experimenting I find it is loudest with cowl flaps closed and hardly noticeable with cowl flaps half open. I have tied down and secured everything on the engine. The rattle is high pitched and I am thinking now it could be in the overhead vents. Does anyone know if the velocity of the air flow in the overhead vents increases when the cowl flaps are closed?

[fluffysheap]

It could be the cowl flaps? Mine rattle when they are open, but not when closed, so I don't worry about it.

I don't think the overhead vents are related to the cowl flaps or the engine compartment in any way. I think they take their air from the naca scoop on the empennage (at least in my 231) although I could be wrong about that.

[yvesg]

I do not know if the J is built the same as my C in this area but: Check if the muffler rubs against the cowl flaps. I had this happen due to a broken spring. When cowl flaps are open the noise stops.

Yves

C-FQKM

[mulro767]

With the cowl flaps closed there should still be a small gap. If your cowl flaps are touching metal on metal that could be the source of your noise. It's also an easy adjustment.

[N201MKTurbo]

I would check if the cowl is hitting anything in the engine, it will leave marks on the cowl and the part of the engine it hits. If your cowl flaps are not rigged to close tight they could be rattling in the closed position. The cowl flap actuator is mounted on the engine mount, so essentially on the airframe, when you close them they could be re-positioning the cowl by pulling it up a bit. The cowls get loose on the fasteners after a while. Also the engine mounts start to sag after a while, so the two conspire to make things at the bottom of the engine start to touch the cowl.

Aside from the cowl flap issue, I find most rattles are in the glare shield and overhead interior trim, but that is probably just my plane. I hate rattles, they don't mean anything most of the time but they drive me crazy.

Right now my plane has no rattles (knock on wood)