Mixing Lever to Scissors Lever Control Tube
I find this all the time on aircraft, another standard aircraft hardware installation, again not a standard, Huey installation, in the hardware installation of the long control tube from the stabilizer bar mixing lever to the scissors lever.
As depicted in the enclosed Page out of the manual there should be two washers under the head of the bolt and one under the nut.
This is done on both top and bottom of the control tube.
This is also in the text of the installation.
The reason is to allow clearance between bolt with key installed and the scissors levers on the bottom to move past each other.
The reason is the tube can be installed with either end up or down.
When removing components, mechanics will generally reinstall hardware in the removed part as it came off.
With the hardware installed in the same way on both ends the tube it can be installed either end up or down and still have clearance. Be sure that there is clearance between the key and the scissors lever.