Thanks Jay for the maintenance tips on the Bonner sticks. I’m sure that after cleaning and lubrication with the correct grease will make them feel like new. I didn’t know about the push to set as a design feature of the trims, but had already determined that pushing them helped for some reason. Now I know why.

As you know, the trims on Bonner sticks were purely mechanical, and this was also done on later stick designs as well for cost and complexity reasons. However, the Bonner trims actually moved the stick’s centering point instead of the pot. So the end points of servo travel never changed for a control. This means that if you give up trim, the stick moves that amount, and the remaining travel of the stick is reduced in the up direction.

On both the F&M and PCS systems that I have with the Bonner sticks, the throttle trim levers on the right side of the throttle stick look nice, but are not connected in any way to the stick assembly. This is because Bonner stick trims do not change the endpoints of servo travel, so even if they were connected the net result would be nothing. On the F&M system, the right auxiliary panel lever is a throttle trim that is wired electrically to the throttle pot. The left auxiliary panel lever is the fifth control channel. This feature was briefly mentioned in a RCM review in the March 1966 issue. This allowed a low trim setting for engine kill. I guess if you flew an early PCS, you just threw a rag into the engine or pulled the fuel line.

F&M made two digital systems, the Digital 5 and later a three channel system. I don’t believe they ever made a six channel set.