Source: 2013 Q3 Beartracks, Russ Erb
Recently I visited Three Sigma to adjust the autopilot and noted the tail dragging a few inches lower than normal, mostly because the tail wheel was suddenly flat.
When I pulled the tail wheel off, I noticed something unusual. The tail wheel assembly was loose on the tail spring, even though the cotter pin showed that the nut had not moved on the attaching bolt. Additionally, the tail spring was loose at the front where it bolts into the fuselage. In both cases the problem was that the paint that was on the tail spring between it and other parts was eroded by the movements under load, and when that paint film was removed it left a gap between parts that made things loose. In the photos you can see where the paint was rubbed off under the washer and between the spring and tail wheel bracket.
However, the key point is that neither of these now loose bolts were apparent as long as they were under load (tail sitting on tail wheel). For those of you who have been flying awhile, I recommend you jack up the back of the airplane so there is no load on the tail wheel and check to see that everything attached to the tail spring is still secure. I mentioned this on the Bearhawk group and three other people confirmed that they fly on rough strips and they have to tighten up the bolts on the tail wheel spring on a regular basis.
Eric Newton stated that Bob Barrows recommends using a locking nut instead of a castle nut on the tail spring just so you can torque it properly without needing to line anything up. He said this is important to prevent shimmy. Hmmm…I’ve had an occasional issue with tail wheel shimmy in the last year that I didn’t have before. Maybe I’ve just solved that problem too.