The International Cessna^® 170 Association

Fairly new to me 52’ 170b with the o300. In the last two or so flights I’ve noticed the propeller gives out what sounds like grinding or scraping noise at low rpms, basically idle. Doesn’t do it at higher RPMS at all. Can even feel the vibration of it through the yoke. Wondering if this is somewhat normal or what I should say to the mechanic. I’m not super mechanically inclined but I like to act like I know what I’m talking about so I don’t get swindled haha.

You might check for interference between the prop/spinner and the cowl. The interference could be so slight that increased slipstream pushes the cowl back out of the way.

Mine used to whistle at idle, and sounded like an alternator bearing failure, but was actually the propeller slipstream interacting with a venturi (incorrectly mounted on the left side of the airplane).

Also, if you have an original starter, check for proper adjustment of the pull cable and actuator arm on the starter.

One of my first flight students as a young CFI was our friend and former Member Bob Edmondson who was taking his pvt pilot check ride in a different C150 than he usually trained in. As they taxied out the examiner asked him “what is that whistling noise?” ...and Bob had no answer, so he was told to return to the tie down area and find out.
I was sitting inside the office when he came in with the question and I informed him it was the propeller-wash passing thru the venturi. I never knew if the examiner really didn’t know or if he was testing Bob. Anyway, they resumed the check ride.

I once flew a King Air E90 out of maintenance and on climbout there was a sound like a grinding which caused me to return for an immediate landing. It turned out to be some kind of harmonic interference between the new engine reinstallations and the cowling. Removing the cowlings searching for the problem (nothing found) and reinstalling them and on another test flight... the problem no longer existed.

Without hearing the sound you are describing triguy, it’s difficult to know what you are experiencing. But you are wise to get it looked at. There is no “normal” grinding sound that a 170 emanates.

Except the grinding of teeth of a 170 passenger on landing

Well, found the problem is the propeller shaft has begun to rub the cowling fairly bad. Seems to be getting worse. Either the engine is falling down, or the cowling is riding up. Should be interesting to see what mechanic says. Haha

There’s a possibility your engine mount (rubber donuts or Lord mounts) are shot.