Play in the prop when pushing plane?

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SepticTank

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SepticTank
I was putting my plane (Fixed Pitch PA-28-235) into the hangar today and pushing at the base of the prop to get it in, as it has a slight incline; the plane was full of fuel and was heavy. I noticed when i pushed there was some "give" in the propeller, like the whole thing moved backwards towards the plane like 1/32 of an inch (guess). I don't recall noticing this before nor do I see how it'd be possible given how the prop is structurally attached. Is this normal or did I sniff too much 100LL?
 
From day 1 in flight school, my instructor taught me to push/pull on the prop near the hub and look for that slight prop (crankshaft) axial play. There is a thust bearing there and this check was supposed to ensure it wasn't seized. Every single direct-drive opposed engine I've pre-flighted had that slight play.
 
Lycoming's overhaul manual calls for .009" to .016" of clearance there, with the service limit of .026". That's nearly 1/32". It can sound and feel like a lot more than it is.

AV8R_87 said:
From day 1 in flight school, my instructor taught me to push/pull on the prop near the hub and look for that slight prop (crankshaft) axial play. There is a thust bearing there and this check was supposed to ensure it wasn't seized. Every single direct-drive opposed engine I've pre-flighted had that slight play.
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If the thrust bearing was "seized," the crankshaft would not turn at all. Where do instructors get such stuff?
 
Dan Thomas said:
If the thrust bearing was "seized," the crankshaft would not turn at all. Where do instructors get such stuff?
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We keep talking about shock cooling to this day.
Maybe it started as a "see if everything feels ok before attempting to crank" check? You wouldn't tell a student pilot to turn the prop (just in case a mag is hot), but this felt safer?
 
AV8R_87 said:
We keep talking about shock cooling to this day.
Maybe it started as a "see if everything feels ok before attempting to crank" check? You wouldn't tell a student pilot to turn the prop (just in case a mag is hot), but this felt safer?
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It's a waste of time, and gives baseless assurance. The crankshafts turn in the bearings. On each end of the front bearing are thrust faces. On the crankshaft there are thrust faces on each end of the front main journal, and they run against the bearings' thrust faces. Pushing the prop back and forth is doing nothing but making the crank move back and forth in that bearing. If it would not move, it would be seized in that or the other bearings, not at the thrust faces, and you wouldn't be going anywhere anyhow.
 
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