Theoretically, There should be no endplay in a flight control system. This is especially true for those systems that have hydraulic servos. On most hydraulic servos the pilot valve must be moved about .012” in order to start fluid flow. If a push-pull rod end bearing has endplay it is a sign of poor maintenance and if one bearing has excessive wear it can be assumed that many if not all bearings have endplay. This accumulative endplay could cause the control system to hit the stops prior to making a full input on the pilot valve. This could effect the flight control input and the flight characteristics of the helicopter. Conversely when the control is moved in the opposite direction the controls will be displaced a significant amount before the pilot valve is displaced. Considering the pilot valve must move .012”, a significant amount could be an accumulated ¼ to 3/8ths of an inch or possibly more. And, that is a lot considering some helicopters are equipped with auto pilots that are controlled by variable differential transformers that require about .001” or less to generate a signal. If you have a SCAS system there might be a mismatch between the mechanical input of the pilot valve and the L/RVDT input to the autopilot.
If there is a mismatch between say the left lateral input and the right lateral input there could be force fighting between the servos.
