MIL-F-9490D and jam nuts on rod end bearings

[rfinch]

MIL-F-9490D(USAF) 3.2.8.3.2.1 Retention of threaded joints. All threaded joints which carry critical loads shall be positively locked in the assembled position so that load reversal at the threads is prevented. The use of jam locknuts alone is not a positive locking means unless lockwired or otherwise restrained.

Installing the rod end bearings for the rudder and elevator, I'm seeing a conflict between Vans plans and the above. For instance, the rudder plans (DWG 7, RV-7,9) note the use of jamnut AN316-6 on the rod end bearing. First, shouldn't I use two jamnuts together? And second, since it is a "threaded joint" which seems to carry a "critical load", is the use of jam locknuts alone sufficient?? And third, in general should jamnuts be torqued, if so, to what value?

[Mhead]

The hinge holds the rod end bearing from turning. I'm not sure about the torque here at work.

[rfinch]

Yes, the hinge bolt will prevent the rod end bearing from turning too much. Maybe Probably I am making way too much over this, I'm just trying to understand nuts and bolts. It seems that with just one jam nut on the REB, the REB could begin to rotate some, the ball potentially hitting its stop.

[az_gila]

Originally Posted by rfinch

Yes, the hinge bolt will prevent the rod end bearing from turning too much. Maybe Probably I am making way too much over this, I'm just trying to understand nuts and bolts. It seems that with just one jam nut on the REB, the REB could begin to rotate some, the ball potentially hitting its stop.

I believe that the RV set-up is not "jam nuts alone"... the rod end bearing is mainly retained by the nut plate... the jam nut is additional security.

It should meet the USAF requirements due to the locking plate nut.

gil A - in the Black Hills of SD