SA-227 AC Metro III
Flight Crew Multiengine; Flight Crew Commercial; Flight Crew Instrument
Flight Crew Last 90 Days 75; Flight Crew Total 861; Flight Crew Type 300
Aircraft Equipment Problem Critical; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
General Maintenance Action
Aircraft
During normal landing; and on landing roll at a speed of 25-30 KTS; the steering was engaged and the aircraft abruptly veered to the right and off into the grass stopping about 20 feet off the runway. No lights were hit; no injuries; and the aircraft did not sustain any damage. After the plane was towed back to the ramp a mechanic inspected the aircraft for damage; and none was reported. He did find that that a Nose Steering Coupler (sensor) had failed to be safety wired and thus had fallen off. This caused the steering to fail because it had no sensing functions as to what was straight in relation to the rudder pedals or to the nose gear itself.
SA-227 flight crew experience an unintentional excursion from runway during landing roll-out when steering was engaged. Nose Steering Coupler reportedly failed and fell off.