What happened
The aircraft executed a normal approach before touching down on a 4001-foot runway. Initial braking appeared standard, but approximately 1000 feet into the rollout, the aircraft began drifting to the right. The pilot attempted to correct this drift using full left rudder and asymmetrical brake application. Despite these efforts, the aircraft departed the paved surface and encountered down-sloping terrain. This terrain caused the nose gear to collapse and buckled the right wing. The aircraft was not equipped with thrust reversers.
The investigation
A mechanical examination revealed that the brake lines on the left main landing gear had been reversed. This installation error caused errant command signals to be transmitted to the anti-skid control unit during heavy brake application, effectively negating the anti-skid function. It was determined that these lines had been mis-installed during a previous brake overhaul. The investigation noted that the maintenance manual did not adequately address the criticality of proper hose installation, as it allowed either hose to be installed in the inboard or outboard brake housing ports.
Findings
The primary contributing factor was the reversed brake lines on the left main landing gear. This error disabled the anti-skid function, leading to a loss of directional control during the critical rollout phase. The lack of clear guidance in the maintenance manual regarding hose orientation likely facilitated this installation error.