Accident Overview
A private pilot, receiving dual instruction from a certified flight instructor (CFI) to become familiar with a newly acquired tailwheel-equipped airplane, was practicing full-stop landings and takeoffs at the departure airport. After the CFI demonstrated the first landing, the pilot performed four subsequent landings with the CFI monitoring and assisting as needed. The CFI reported that the first landing was normal; the second required minor directional control assistance; the third required no assistance; and the fourth required some assistance from base leg to final but the landing and rollout were normal.
The Accident Sequence
On the fifth landing, the pilot executed a three-point touchdown and rolled straight ahead. During the rollout, the airplane suddenly swerved to the right. The CFI observed that the pilot had already applied full left corrective rudder. The CFI then applied left brake in an attempt to correct the swerve, but the application seemed ineffective. He subsequently applied right brake to slow the airplane's pending departure from the runway. The aircraft then pitched over onto its nose, then onto its back, coming to rest in a snow bank bordering the runway. The top of the rudder sustained substantial damage.
Brake System Details
The airplane was equipped with a supplemental type certificate (STC) non-standard brake system. According to the CFI, when he had ferried the airplane, he noted that the brake system had extreme sensitivity. The CFI stated that he had advised the pilot early in the instruction to avoid using the brakes in normal operations due to their sensitivity.
CFI's Assessment
The CFI stated that he believes the sensitivity of the brake system was a causal factor in the accident.