What was found
NR 1 ENGINE BEEP SWITCH ON THE LT COLLECTIVE BECAME INTERMITTENTLY UNRESPONSIVE IN FLIGHT, RESULTING IN PILOTS INITIATING ENGINE BEEP FAILURE/FREEZE EMERGENCY PROCEDURES AND RETURNING TO BASE FOR AN UNSCHEDULED LANDING. SUBSEQUENT INSPECTION DETERMINED THE LT COLLECTIVE BEEP SWITCH WAS INTERMITTENTLY FAILING TO PROVIDE INPUT TO ENGINE CONTROL SYSTEM DUE TO A FAULTY SWITCH. THE LT COLLECTIVE THRUST STICK ASSEMBLY WAS REMOVED AS UNSERVICEABLE AND REPLACED WITH SERVICEABLE ASSEMBLY. AIRCRAFT WAS RETURNED TO SERVICE.