Nose wheel steering inspection
have no professional or expert qualifications of any kind.
Checking all items of the nose wheel steering on an Ercoupe is very important. It is even more so if the previous pilot has experienced any nose wheel shimmy.
The nose wheel does not have any shimmy dampener, so start by checking the nose tire inflation. It should be approximately 20 psi.
Then check the scissors for play. If they move, and the nose wheel does not, look closely to see where the play is located.
The early Coupe's had a steel scissors, which used phenolic bushings. These bushings had steel inserts with teeth on them to grip the scissors. Those bolts must be tight, so that the steel insert turns inside the phenolic bushing. The bolt does not turn inside the bushing.
Later aluminum scissors had brass bushings in the scissors which allowed the bolt to turn in the bushing. These bolts must be snug, but not so tight that the bolt cannot turn inside the bushing. Side play in either type can cause nose wheel shimmy.
Further checks should be made with the nose wheel off the ground. Use about 200 lbs of weight carefully placed on the horizontal stabilizer on the area where the two front bolts hold the stabilizer to the fuselage (sand bags work well). Do not use the tail tie down to pull the tail down as the tie down nut is only held on with two 3/32 rivets.
Once the tail is down and safely blocked, as well as wheel chocks on the main wheels, check for further play in the nose wheel steering. Look closely at the steering collars. If they move up and down or tip in any direction, you most likely will have to remove the nose strut to repair. Only .003 clearance is allowed in the up and down direction, so if you can see movement, it most likely exceeds this.
Check for play in the steering rod, there should be none, if there is any, it is most likely in the rod end bearings.
Now check in the cockpit, check for play in the control wheel, universal joints, control chain, and especially in the control column. A little play in the control wheel, universal joints or control chain will generally not cause nose wheel shimmy. However, play in the control column in any direction (up/down or back and forth, or between the shaft and the quadrant) can/will cause nose wheel shimmy.
While in the cockpit you can also check for play in the pitch control, and aileron control. There should not be any, however, a little bit can be tolerated.