Prop click when manually turned.

P

PilotPaul

Filing Flight Plan
Joined
Dec 5, 2012
Messages
7
Display Name
Display name:
PilotPaul
A friend and I were preflighting my Cessna 150 when we found the following. When I manually turn the prop on my Cessna 150,there is a distinct "click" feel to the prop, similar to what you would notice when turning a watch. Plus there is a clicking sound in the cowling.

My friend also owns a 150. When we turned his prop we did not notice any such clicking.

My mechanic feels it is no big deal, but it still make me nervous.

What do you think?
 
impulse coupler in mag.
 
I agree, I'm not convinced that what the OP is trying to describe to us is the impulse coupler. For one thing he says it is absent from his buddies 150 and he also seems to be describing two distinct sources of this "clicking".

Could be alternator or even vacuum pump. Might also be spinner rubbing on cowl or something like that.
 
Agree this doesn't sound like the impulse coupler.
 
Thanks everyone for the replies!

The sound occurs about once a degree of rotation. So a full rotation of the prop may generate around 300 or so clicks. I took a video (to capture the sound) and uploaded it to YouTube: SOUND.

This video was captured by placing my cell phone in the cowling while turning the prop.

So what do you think?
 
PilotPaul said:
Thanks everyone for the replies!

The sound occurs about once a degree of rotation. So a full rotation of the prop may generate around 300 or so clicks. I took a video (to capture the sound) and uploaded it to YouTube: SOUND.

This video was captured by placing my cell phone in the cowling while turning the prop.

So what do you think?
Click to expand...

Sounds like a bad alternator bearing.

Oh, by the way, turning the prop in a direction that makes the impulse click is asking to get hurt or dead if that engine fires. You would be the latest of many who have found that out the hard way. Never assume the mags are dead. Ever.


Dan
 
Last edited:
Dan Thomas said:
Sounds like a bad alternator bearing.

Oh, by the way, turning the prop in a direction that makes the impulse click is asking to get hurt or dead if that engine fires. You would be the latest of many who have found that out the hard way. Never assume the mags are dead. Ever.
Dan
Click to expand...
or the spinner scraping the cowl.
 
PilotPaul said:
The sound occurs about once a degree of rotation. So a full rotation of the prop may generate around 300 or so clicks.
Click to expand...

Ah, that is a very important clue. That is not the usual click every 1/2 revolution (on a 4-cylinder engine).

It sounds more like creaking which, as already pointed out, could be a bearing.

Have a good mechanic look at it. Don't take our (PoA) word for it.
 
If it seems to not be normal, have someone else look at it for sure. I had quite a few things that 1 mechanic said was normal and ended up being pretty serious after looked into by another mechanic. I have learned my lesson about flying with things that others said were normal and I was not comfortable with. Ended up costing me a lot of money. Could have been worse though..
 
Tom-D said:
or the spinner scraping the cowl.
Click to expand...

Don't think so. A cowling rub would have a scratchy sound rather than the muffled rumble. The mag clicks every half revolution, and there are a lot of little rumbles between those clicks. From the sound, it seems to me that the alternator's front bearing (a ball bearing) has a split or pitted inner race. The series of interrupted rumbles match that sort of thing. The alternator turns at about that many times in a half-rev.

Dan
 
Dan Thomas said:
Don't think so. A cowling rub would have a scratchy sound rather than the muffled rumble. The mag clicks every half revolution, and there are a lot of little rumbles between those clicks. From the sound, it seems to me that the alternator's front bearing (a ball bearing) has a split or pitted inner race. The series of interrupted rumbles match that sort of thing. The alternator turns at about that many times in a half-rev.

Dan
Click to expand...

This is not a belt driven alternator. that would emit the sound you are hearing.

This is a gear driven alternator mounted directly to the accessory case, the front bearing is a massive ball bearing that I have never seen fail. but the cooling fan is mounted on the rotating shaft and is plastic, it does wear and touch the housing, and makes a tic tic tic as each blade comes by the support leg of the alternator.
 
BigBadLou said:
Have a good mechanic look at it.
Click to expand...

You bet, and have them inspect the cowl and spinner area. the engine mounts get old and the engine sags allowing the spinner to touch the cowl.
 
Tom-D said:
This is not a belt driven alternator. that would emit the sound you are hearing.

This is a gear driven alternator mounted directly to the accessory case, the front bearing is a massive ball bearing that I have never seen fail.
Click to expand...

I know that, that's why it's muffled the way it is.

Dan
 
PilotPaul said:
When I manually turn the prop on my Cessna 150,there is a distinct "click" feel to the prop, similar to what you would notice when turning a watch. Plus there is a clicking sound in the cowling.

What do you think?
Click to expand...

It's the rubber band after turning too many times, starts to "double knot":lol: Just kidding ...
 
Grab the prop in both hands and yank it forward and shove it back. How far does the crankshaft move in the case?
 
Henning said:
Grab the prop in both hands and yank it forward and shove it back. How far does the crankshaft move in the case?
Click to expand...

What difference does that make?
 
Tom-D said:
What difference does that make?
Click to expand...

Just an indicator, the sound is actually more telling than the motion. If it doesn't move is more my concern than if it does. Nothing really to go on, but pretty much the worst thing that it could be is a damaged thrust face chattering.
 
Henning said:
Just an indicator, the sound is actually more telling than the motion. If it doesn't move is more my concern than if it does. Nothing really to go on, but pretty much the worst thing that it could be is a damaged thrust face chattering.
Click to expand...

Understand you've never had a 0-200 apart, but as long as the rotation is free, the crankshaft end play can be zero.

I've never seen one that way, but it is allowed.

This is an 0-300 thrust bearing, same as the 0-200 just thrust washers front and back of front main bearing.
 

Attachments

  • Thrust bearing.jpg
    Thrust bearing.jpg
    69.2 KB · Views: 30
Last edited:
Am I imagining this - I seem to recall the Warriors I flew used to do that. It's kind of a ratchety pawl type sound, but with more strike and less echo. Then there would be a loud clunk when the mag fired.

I might be imagining it, it's been a while.
 
bflynn said:
Am I imagining this - I seem to recall the Warriors I flew used to do that. It's kind of a ratchety pawl type sound, but with more strike and less echo. Then there would be a loud clunk when the mag fired.

I might be imagining it, it's been a while.
Click to expand...

Piper equals a Lycoming
Early Cessna equals a TCM 0-200/ 150,,, 0-300, 170/172 thru 67
 
You must log in or register to reply here.
Back
Top