P/N: PTL-KT-44

To improve the fit and function, a few of the standard hardware parts in the McFarlane torque link hardware kit differ from what the IPC calls out.

The kit contains UNJF threaded self-locking castellated nuts:

• Qty 1 MS17825-4, and
• Qty 2 MS17825-5

These are, respectively, provided in the place of the following UNF threaded plain castellated nuts (as called out in the IPC):

• Qty 1 AN310-4, and
• Qty 2 AN310-5.

AC43.13-1B Section 4 paragraph 7.64b explicitly allows this substitution. "Self-locking castellated nuts with cotter pins or lock wire may be used in any system."
The current Piper IPCs that cover this kit's eligibility require NAS6604 and NAS6605 bolts in combination with AN310 nuts for main gear torque link assemblies. The AN310 nuts have UNF threads, while the NAS bolts have UNJF threads, which is a fit issue. UNJF threads have a larger root radius than UNF threads, which causes interference when a UNJF external thread is used with a UNF internal thread. When assembled in this combination, the peaks of the UNF nut threads gouge out the valleys of the UNJF bolt threads. To fix this fit issue, the McFarlane torque link hardware kits contain standard hardware nuts that do not match the IPC. This fit issue appears to have been caused by an update to the Piper IPCs where the bolts for these aircraft were changed from AN174 and AN175 bolts of UNF thread type to NAS6604 and NAS6605 bolts of UNJF thread type, but the nuts were not also changed.