Loose Spinner Screw

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MJR Pilot

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MJR Pilot
During pre-flight on my Piper Arrow, I discovered that one of the screws on the prop spinner was loose. Attached a photo - not sure how clear it is, but I would describe the screw as “moderately” loose. Two questions:

(1) Would tightening this screw be considered preventive maintenance that I can perform myself (I’m not an A&P)? In reviewing Part 43 Appendix A part C, I see part (12) allows for “small simple repairs to fairings, nonstructural cover plates, cowlings…” and part (26) allows for “replacement or adjustment of nonstructural standard fasteners incidental to operations”. This seems like a very simple task so I figured I could do it myself, but since I wasn’t sure, I deferred the flight until my mechanic is able to tighten it. Appreciate thoughts on this.

(2) How common is it for these screws to loosen? I’ve owned the plane for 3+ years and have never seen this issue (and I always check the spinner screws during preflight).

Appreciate any and all views. Thanks all.
 

Attachments

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It was likely missed when the spinner was off last and reinstalled. All the screws go in, loose, then they're snugged up. Or the screw was cross-threaded and is now galled and stuck in there.
 
Lndwarrior said:
Blue locktite.
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I fly an experimental and was thinking the same thing but on his certified aircraft he'll likely need an A&P to access the screw, the threaded hole, inspect the spinner for cracking/damage in that area and order (if not in stock) a replacement screw from Aircraft Spruce and find the appropriate retainer/sealer to be applied (if applicable) before they can sign it off. Prolly cost him about $80.00 or so ... :D
 
On the scale from 1-10, tightening that screw is a .03 for owner approved maintenance.
 
Good catch.
Send that picture to your AP and ask him if you can tighten it? Hopefully it is not stripped.
Dynamic Propeller Balance might be a good idea?
 
Gary Ward said:
Good catch.
Send that picture to your AP and ask him if you can tighten it? Hopefully it is not stripped.
Propeller Balance might be a good idea?
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Thanks. The prop came off in February for an overhaul, and the mechanic did a balancing before it was reinstalled. I have flown a few times since then and the screw wasn’t loose until today. I did send it to AP - will see what he comes back with.
 
Any chance you saw or felt a vibration?
 
Dan Thomas said:
It was likely missed when the spinner was off last and reinstalled. All the screws go in, loose, then they're snugged up. Or the screw was cross-threaded and is now galled and stuck in there.
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I think you may be correct about it being improperly installed. The damage to the screw head is indicative of that. It also appears a crack has formed on the corner of the spinner next to the screw.
 
eman1200 said:
Any chance you saw or felt a vibration?
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I did not. Hopefully AP can check it out tomorrow. Was thinking it was just a screw needing tightening, but based on some of these comments seems like there’s a chance it’s a bit more complicated. I have been thinking about getting a new spinner, just for aesthetic purposes, so may get that done with this repair. Any idea on how much a new spinner costs?
 
MJR Pilot said:
I did not. Hopefully AP can check it out tomorrow. Was thinking it was just a screw needing tightening, but based on some of these comments seems like there’s a chance it’s a bit more complicated. I have been thinking about getting a new spinner, just for aesthetic purposes, so may get that done with this repair. Any idea on how much a new spinner costs?
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dunno, expensive I’m assuming. but also, I doubt one screw would cause a shimmy now that i think about it. would need more than that or maybe a crack as well.
 
Is it actually loose, or is it cross threaded?

I would have a hard time believing anyone not just being a douche would care one whit if you tightened that screw.
 
Salty said:
Is it actually loose, or is it cross threaded?

I would have a hard time believing anyone not just being a douche would care one whit if you tightened that screw.
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I think it was just loose - I did some rough tightening with my fingers and that worked pretty well, so don’t think it’s cross threaded but will see what AP says. And yes, completely agree with on second point.
 
MJR Pilot said:
Would tightening this screw be considered preventive maintenance that I can perform myself (I’m not an A&P)?
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Yes, under the items you posted. Don't forget your write-up.;)
MJR Pilot said:
How common is it for these screws to loosen?
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It's not common, but does happen. Make it a preflight item for a spell. If it loosens up again may need to have the nutplate the screw fastens to replaced as it has lost its self-locking capability.
 
I've had loose screws on the spinner, tightened them up and then they would loosen up again. Issue was the screw bracket riveted to the spinner backplate. The bracket had worked loose and the play in the bracket was causing the screw to loosen. Re-riveting the bracket solved the problem.

Make sure you get to the cause of the issue. Play in these screws could enlongate the screw hole or even crack the spinner making for a more expensive repair.
 
I was taught to check for loose screws on the spinner as part of my pre-flight. I've only found one once, on a rented twin. I don't remember how I handled it, other than bringing it to the attention of the instructor.
 
Ever notice that the other end of most fuel sample tubes have a philips screw driver bit? Just sayin...
 
Also notice how the head is boogered-up. Someone has tried tightening this screw before. It might be a Pittsburgh/HF screwdriver was used or underlying issues with the threads or still some other root cause.

Good on you @MJR Pilot for through pre-flight! My kind of pilot.

Tempting to just make the symptoms go away by retightening.

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Those screws look like they might be AN526 non-structural screws. That screw is made of a cheaper, soft steel. If that spinner backplate has the all-metal nutplates, that soft screw galls in them and will get stuck like that. Should be using structural screws if that's the case. The soft screws work ok with nylock nuts and nutplates.

It would be smart to check the parts catalog for that airplane and see what's called out for that location.
 
They look like commercial stainless steel screws. Are there stainless versions of the structural screws? I recall structural screws have a shorter thread and a full diameter next to the head, which commercial truss or pan head screws don't have. And get a good quality phillips driver/bit. Degrease it w gasoline so it won't cam out.
 
Dan Thomas said:
Those screws look like they might be AN526 non-structural screws.
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nrpetersen said:
They look like commercial stainless steel screws.
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FYI: Some use NAS221 or AN526 or whatever panheads with some requiring a plastic washer under the head. Depends on the OEM, but the 221/526 are common. The screws look okay from the picture but as noted a quick check in the IPC will confirm. I always kept a supply of the previous numbers in stock when balancing props as most were worn or previously installed with a cordless.
 
nrpetersen said:
They look like commercial stainless steel screws. Are there stainless versions of the structural screws? I recall structural screws have a shorter thread and a full diameter next to the head, which commercial truss or pan head screws don't have. And get a good quality phillips driver/bit. Degrease it w gasoline so it won't cam out.
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The stainless doesn't have that little radial mark between the socket and rim of the head. Stainless also galls real easily. I've never seen a stainless structural screw, but it might exist. There are stainless bolts available.

A bit of valve grinding compound on the phillips bit will get good grip on that screw. The fine grade of compound works best.
 
Just as an aside, I have been advised to never tighten spinner screws sequentially around the spinner as it can lead to cracking. Always tighten in a criss-cross pattern to distribute any clamping force.

End of PSA. Carry on.
 
Could call, Chip.

And lug nuts. And prop bolts. And in general, any other radial spaced fasteners.
 
My practice is to use tape to index the Spinner to the Bulkheads.

There may be small differences in attachments that could be “ flexed” by

varying positions that could result in cracking.
 
Back the screw out and check the threads. If OK just screw back in and if it feels normal and goes all the way your OK. If a new screw does not solve the problem then you will need to pull the spinner and fix. However, a missing spinner screw will not result in wings falling off, the engine to fall off the mounts, etc.

Try common sense.
 
Dan Thomas said:
One of the comments there says that it seems like carbide dust. Valve grinding compound is just carbide grit in either water or oil, available both ways, and available in coarse or fine grits. The grit used in sparkplug cleaning blasters is also carbide grit.
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I don't know what it is. It works.

I know the guy who is Solder-It. I have seen the demo where he cross threads a screw, totally buggers up the head, then adds a drop of Screw Grab and hads it to you to easily turn the screw out.
 
Why do people use $5 Harbor Freight screwdrivers on $6500 props?

Spend the coin and get a screwdriver that will never bugger-up a screw again. Few air planes cost less than $85K-$150K these days. The Snappy guy had this set on sale in December.

Screen Shot 2023-03-08 at 8.57.53 PM.png

Yes it is expensive, but our planes are worth having a few basic professional tools available.

https://shop.snapon.com/product/SGDX6040BR
 
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Removing & tightening screws isn't rocket surgery. Any fairly decent tool will do nicely. But get a correct size screwdriver (or bit) to properly fit the screw head. One that is slightly too large or too small will slip and once the slipping begins damage to the screw head has occurred.

A good mechanic can tell when a screw is going to move and how much force it will take. Most can tell before a driver slips long before it does.

Some have mentioned good ways & tools to address stubborn screws that are hard to remove. If a screw is difficult to put in then stop and find out what the problem is. Forcing a screw in will only mean that you have more work to do later ...
 
NordicDave said:
Why do people use $5 Harbor Freight screwdrivers on $6500 props?

Spend the coin and get a screwdriver that will never bugger-up a screw again. Few air planes cost less than $85K-$150K these days. The Snappy guy had this set on sale in December.

View attachment 115627

Yes it is expensive, but our planes are worth having a few basic professional tools available.

https://shop.snapon.com/product/SGDX6040BR
Click to expand...

I agree, discovered Snap On screwdriver quality a long time ago. Even the old craftsman screwdrivers don't come close to a snap on screwdriver.

I like using long shank screw drivers as much as possible even when you don't need a long shank. And I buy a new one every few years, even snap on screwdrivers don't last forever. Not all of my tools are snap on and I have mix of tools I gathered for the hangar but I try to use only that long shank snap on screwdriver for most everything on the plane.
IMG_0224(1).JPG
 
Wagondriver said:
30 something posts about 1 loose screw on a spinner, wow.
That’s got to be a record.
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It's not about just one spinner screw. Airplanes are full of Phillips-head screws that can suffer galling or seizure or corrosion that cause troubles with installation or removal and consequent socket failure. Bad and good practices have been discussed here and some silent lurkers are learning things.
 
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