Which aircraft record entry best describes the action taken for the replacement of several damaged heli-coils in a casting?

• A. Eight 1/4----20inch standard heli-coils were replaced. The damaged inserts were extracted, the tapped holes gaged, then new inserts installed, and tangs removed.
• B. Eight 1/4---20inch standard heli-coils were installed in place of damaged ones.
• C. Eight 1/4---20 inch standard heli-coil inserts were repaired by replacing the damaged inserts with a lock-type insert, after the tapped holes were checked for corrosion.
• D. Eight 1/4----20inch standard heli-coils were replaced. The damaged inserts were extracted, the tapped holes gaged, then new inserts installed, and tangs removed.

Answer: (A)

When you replace damaged heli-coils, you restore the original, clean thread by removing the damaged inserts first, then checking the hole and restoring it to spec before installing new inserts. Gauging the tapped holes ensures the hole size and thread condition are suitable for a new insert, so the bolt will thread correctly and the load will be carried as intended. After confirming the hole is serviceable, you install new standard heli-coil inserts of the same size and remove the tangs so nothing protrudes into the bolt path.

This sequence—extracting the damaged inserts, gauging the holes, installing new standard inserts, and removing tangs—is the proper replacement procedure for multiple damaged heli-coils in a casting, restoring the thread to its original specification.