What was found
A PRE-FLIGHT REVEALED ELEVATOR WAS NOT HITTING DOWN STOP. FURTHER INSPECTION REVEALED DOWN STOP BOLT WAS PUSHED IN. DISASSEMBLY REVEALED MS21078-3 NUTPLATE IS A TWO-PIECE PRESSED NUTPLATE THAT CAN BE DISLODGED WITH REPEATED HITTING. OTHER AIRCRAFT OF 172R THAT HAVE BEEN INSPECTED USE THIS NUTPLATE. THE PROBLEM OF ORDERING NUTPLATES IS THAT MS21078-3 NUTPLATES ORDERED FROM CESSNA ARE PRESSED IN TYPE. ANOTHER MS21078-3 NUTPLATE ORDER FROM AIRCRAFT VENDOR IS NOT PRESSED IN TYPE. THE SOLID MS21078-3 WAS INSTALLED AS REPLACEMENT.