Prop gov pad O-ring fitting jam nut torque?

roee · #1 02-03-2013, 03:00 PM

I need to re-clock the 45deg elbow fitting on the prop governor pad. This fitting is of the type that has straight threads, an O-ring seal, and a jam nut (the fitting is Lycoming p/n 74070).

My question is, what is the specified torque for the jam nut?

Thanks!
-Roee

rzbill · #2 02-03-2013, 06:13 PM

Roee,

The torque for this style O-ring fitting has been questioned multiple times here on VAF for the fuel pump. I can't remember an instance of a torque value being reported from an aviation source.

I believe the fitting is essentially an SAE J514 ORB (O-ring boss) but I don't have documentation to that effect so I am not comfortable suggesting a value from the industrial tables.

roee · #3 02-04-2013, 05:45 PM

From Aerosport:

23-24 ft-lb.

From an old overhaul manual published by Superior:

110 in-lb.

So it seems that there is no consensus on this, even among the pros. But from that I would conclude that either torque setting should be fine, or anything inbetween.

az_gila · #4 02-05-2013, 09:16 AM

I believe that Lycomings answer is in Table VI here -

Not sure of the thread size so I can't quote the exact number...

If it's a 9/16-18 thread it matches the Aerosport number quoted earlier.

rzbill · #5 02-05-2013, 04:10 PM

Well, how do you like that.....my printed 1776 doc that I keep with my engine stuff is incomplete and does not include that page.

That's awesome Gil. The ORB numbers do follow the industrial charts I have for the SAE ORB fittings.

They are comparatively tight, so I was concerned about being held accountable for an aluminum engine casting.

az_gila · #6 02-05-2013, 04:32 PM

Quote:

Originally Posted by rzbill

Well, how do you like that.....my printed 1776 doc that I keep with my engine stuff is incomplete and does not include that page.

That's awesome Gil. The ORB numbers do follow the industrial charts I have for the SAE ORB fittings.

They are comparatively tight, so I was concerned about being held accountable for an aluminum engine casting.

Yes, I bet you had this page... apparently now obsolete...

It was the one I used too...

roee · #7 02-05-2013, 05:53 PM

Thanks, Gil! Lycoming SSP-1776, doesn't get any more authoritative than that. I too had an older version of SSP-1776 that didn't have that table.

And yes, it's a -06 fitting, so that corroborates the numbers from Aerosport.

Is the newer version of SSP-1776 available in PDF somewhere? Don't really want to spend $75 to buy a new paper copy from Lycoming...