cowl screw identification help

[sleeper-319]

Hi all, I recently lost a cowl screw. When looking it up in the parts manual, it shows this screw as a AN526-1032R10. However when I look that item up at Spruce, the screw looks different than the one I removed (see pic). The one I removed has a washer and a countersunk screw head, whereas the one in the manual is a flat, button head screw. Am I reading the manual wrong, or is it likely a previous owner or shop replaced these with a different kind of screw?    

Any help is appreciated. :-)

Plane is an 87 M20J, 201 LM

 

 

Edited April 14, 2022 by sleeper-319

[Hank]

Those are what hold on my one-piece belly. To buy spares, I flew to Aircraft Spruce, laid a set on the counter [along with samples of other screws I wanted] and they brought them out to me. I'll probably go by the hangar this weekend and can take a picture of the bag & label if you need.

[kortopates]

both types of screws are used in your cowling. The pictured screw and washer is the on the outside of the cowling in front; the first fastener. The flat button head screws are used behind the spinner inside the air inlets.


Sent from my iPhone using Tapatalk

[sleeper-319]

@kortopates, on mine, the 4 screws behind the spinner are the same style as the one pictured, but a few mm shorter. The parts manual shows all 6 screws at the front of the cowl being the button head type (AN526-1032R10). Or maybe I’m reading it wrong. It’s at the hangar, so I can’t double check right now. I’ll post a pic of the page later today. 

[jaylw314]

All six screws on mine are AN507 flat head screws with countersunk washers as well.  IIRC, I ordered R10's (5/8") screws to replace them and they're a little on the long side.

Nowadays, it's MS24693-S273

https://www.aircraftspruce.com/catalog/hapages/ms24693.php?clickkey=8057

I have no idea why the IPC says truss head screw, I can't imagine that would have worked without a washer either?

[Guest]

The parts manuals have small errors in parts call-outs, and after several decades of maintenance wrong screws are often found in many areas.  

Clarence

[sleeper-319]

Thanks for the help everyone! Measure the screws and washers and got a replacement (and a few spares) ordered.

[carusoam]

The magic of MS in action!

-a-