What happened
During the landing roll, the pilot of the aircraft reported that after touchdown, the tail wheel began to shimmy, causing the airplane to shake. In an attempt to stabilize the aircraft and stop the shimmy, the pilot applied the rudder from side to side.
As the landing roll neared completion, the aircraft veered to the right. The pilot attempted to correct the directional deviation using left rudder and the brake, but the aircraft continued to veer off the paved surface and into the grass. Upon entering the grass, the left main landing gear collapsed, causing the airplane to come to rest on its left side.
The investigation
The investigation into the mechanical state of the aircraft revealed that the tail springs had become unhooked as a direct result of the tail wheel shimmy experienced during the landing.