What happened
The incident occurred while the airplane was taxiing along a parallel taxiway. The failure of the right wheel brake took place near the end of that taxiway, precisely as the pilot was preparing to turn the aircraft onto the runway. Unable to rely on the braking system for the maneuver, the pilot attempted to execute the turn using differential power between the engines.
This method proved insufficient to keep the aircraft on the paved surface. The airplane crossed over the runway and continued forward, eventually running into trees located on the opposite side of the pavement. Just before the aircraft ran off the runway entirely, the pilot pulled the mixture controls to idle cutoff in an effort to stop the engines.
The investigation
A post-accident examination of the aircraft revealed significant mechanical issues with the braking system. Specifically, the inspection found that the brake pads on the right wheel were completely worn away. This total loss of friction material explains why the brake failed during the taxiing phase. It was noted that the airplane had reportedly undergone an annual inspection approximately one month prior to the accident.