Piper PA-18-135 N9952Q accident near Del Norte, Colorado

Probable cause

The pilot's loss of directional control during the landing roll, which resulted in a runway excursion. Contributing to the accident were the sensitivity of the brake system and the certified flight instructor pilot's delayed remedial action.

NTSB analysis

The pilot, who held a private pilot certificate, was receiving dual instruction from a certified flight instructor (CFI) to become familiar with his newly acquired tailwheel-equipped airplane. After practicing some standard flight maneuvers at altitude, the pilot returned to the departure airport to practice full stop landings and takeoffs. The CFI demonstrated the first landing, and then the pilot performed the next four landings and takeoffs with the CFI monitoring the controls and providing assistance when necessary. The CFI stated that the pilot's first landing was normal, the second landing required minor directional control assistance, the third landing required no assistance, and the fourth landing required some assistance from the base leg to final approach but the landing and roll were normal. On the fifth landing, the pilot made a nice three-point touchdown and rolled straight ahead. During the landing roll, the airplane suddenly swerved to the right and the CFI noticed that the pilot had already applied full left corrective rudder. The CFI then applied the left brake, but the application was ineffective. He then applied right brake to slow the airplane's pending departure off the runway. The airplane nosed over and came to rest in a snow bank that was bordering the runway. The top of the rudder sustained substantial damage.

The airplane was equipped with a supplemental type certificate non-standard brake system. The CFI stated that, when he had ferried the airplane, he noted that the brake system was extremely sensitive. The CFI stated that he told the pilot early in his instruction that the use of the brakes should be avoided in normal operations due to their sensitivity. The CFI stated that he believes that the sensitivity of the brake system was a causal factor in the accident.

Text from the NTSB. Open the NTSB docket for CEN12CA132 for the full record.