Departure and Initial Event
The aircraft departed the right side of runway 22R and struck a taxiway sign during the initial phase of the event.
Rollout and Loss of Control
During the rollout, the nose of the airplane began to move to the left and then to the right. The instructor took control of the airplane, straightened the nose, and continued the rollout. As the airplane slowed, it started to move to the right again. The instructor attempted to correct by pumping the left rudder, but the airplane continued its rightward movement. He then applied and held full left rudder, but determined that the airplane would depart the runway.
Collision with Runway Sign
After releasing the left rudder pedal, the instructor intended to stop in the dirt. However, he did not see a runway sign, which collided with the lower right wing. The collision spun the airplane around, resulting in substantial damage to the lower wing spar.
Summary
The aircraft sustained substantial damage to the lower wing spar after striking a taxiway sign and subsequently colliding with a runway sign during the rollout phase of a training flight.