What was found
(AU) IN CRUISE, THE NR 1 ENGINE MADE A SOFT BANG AND BEGAN TO RUN ROUGH. THE AIRCRAFT MADE AN UNSCHEDULED LANDING. POST- FLIGHT INSPECTION FOUND THE NR 9 CYLINDER PUSH ROD CRACKED. BROKEN AND BANGED UP WITH THE BALL END, AT THE ROCKER ARM, FULLY DETACHED FROM THE ROD WITH THE ROD END COLLAR CRACKED AND STARTING TO SPREAD. THE PUSH ROD WAS REPLACED AND THE ENGINE WAS GROUND RUN SERVICEABLE.