What happened
The incident occurred immediately following the completion of an agricultural spray operation. The pilot returned to the home airport with the intention of landing the aircraft. During the landing roll, the pilot realized that braking capability was completely absent on the left wheel.
Faced with a critical loss of directional control and stopping power, the pilot made the decision to intentionally ground loop the aircraft. This maneuver was executed specifically in an effort to reduce the extent of structural damage to the airframe upon stopping.
The investigation
Post-accident examination revealed a mechanical failure within the braking system. According to the pilot's account, there was a significant loss of fluid from the left brake master cylinder. The leak originated at the O-ring seal, identified by part number 800-001-6.
Findings
The primary contributing factor was loss of left brake pressure due to the failed O-ring seal in the master cylinder. This mechanical failure necessitated the emergency ground loop maneuver during the landing roll.