Incident Overview
A Beech 1900D airplane was landing on a dry, paved runway measuring 6,398 feet long by 150 feet wide. The approach required a correction for a left crosswind. During the landing roll, after the crew activated the Decoto power steering system, the airplane suddenly veered to the right. The aircraft continued off the right side of the runway into soft terrain, where the nose landing gear collapsed.
Captain's Statement
In a written statement to the NTSB, the captain reported that due to strong winds, it was necessary to engage the power steering to assist with a left turn, which he described as a normal procedure. Upon engaging the system (which had been armed by the first officer at his request), the aircraft executed an immediate right turn of approximately 45 degrees. Both pilots attempted to counteract the event with full left rudder and maximum left braking, but all attempts were unsuccessful. The aircraft exited the runway, resulting in collapse of the nose gear and shearing of the propeller blades.
Investigation Findings
Investigators from the NTSB and FAA conducted extensive tests on the Decoto power steering system and associated components in the presence of the parties. No preaccident mechanical anomalies were noted with the system. The Flight Data Recorder revealed that the crew activated the power steering system at a derived ground speed of about 40 to 50 knots. The Decoto Power Steering System flight manual supplement states: "Use of power steering is limited to taxi operations only."
Conclusion
The accident occurred when the power steering system was activated during the landing roll at a ground speed above taxiing limits, contrary to the flight manual supplement's restriction. The system then caused an uncommanded right turn, which the pilots could not overcome with available controls.