If you take just about any airplane apart at the joints between control surfaces, you will find movable bearings connected to rods. These bearings, called rod ends, allow our control surfaces to move smoothly when we apply pressure to our yoke or stick. The typical construction is a chrome steel ball with a hole in the center for a bolt to pass through, housed in a bronze or brass bearing stock, which is pressed into a carbon steel component that connects the whole assembly to the controls.
When you check your rod ends on preflight, carefully rock your control surfaces back and forth, and as you do, listen for clicking noises. If you can hear a good click every time you change the direction of the deflection, chances are that the rod end at that location needs to be replaced.
If you can see the ball moving loosely in the retainer, the plane should be grounded until the damaged rod end can be replaced.
Why: The control surface will be out of rig, and the plane will not fly as well or as fast at best. Worse yet, a damaged rod end can cause jammed controls when controls are moved under aerodynamic loads. If the wear is bad enough, the control surface may even be free to shift or vibrate at the joint – and introduce the possibility of flutter. Although unlikely at speeds below 160mph, flutter is a problem many people don’t walk away from.
Rod ends do need some tender loving care, in the way of lubrication. Taking a look at the Beech Maintenance Manual for example, many rod ends have a 25 flight-hour lubrication frequency. When you consider that most rod ends get attacked by moisture, high speeds, bugs, dirt and rain, its no wonder the lubrication frequency isn’t daily.
If you are going to lube your rod ends, it is important to use the right lubricant. Some pilots have made the mistake of using a light oil, such as WD-40 or LPS-1 to lube their rod ends. This is the wrong oil for the job, since the high wind velocity that most wings see can drive this lubricant right out of the bearings. In reality, you need something that gets a bit stiffer in order to provide the best protection for rod ends. A good lubricant for the job is LPS-3.
SIMPLE SAFETY: There is no rocket science to rod ends. If you take care of them with regular lubrication and exercise, they will provide you with years of trouble-free operation. Conversely, if you neglect them and ignore them, they can do something to grab your attention in a most spectacular way that you won’t soon forget. Do the right thing, and keep your rod ends cleaned and lubricated.