What happened
On May 11, 2022, a Mitsubishi CL-600-2B19, registration N965SW, was operating a scheduled domestic flight from Victoria Regional Airport to George Bush Intercontinental Airport (IAH) in Houston, Texas. The flight, operated by SkyWest Airlines, landed on runway 8R at approximately 14:18 local time.
Following a normal touchdown and initial deceleration, the aircraft tracked the runway centerline. After the first officer's 90-knot callout, the captain stowed the thrust reversers. The tower controller instructed the crew to turn right toward high-speed taxiway NK. While attempting to comply with this instruction, the aircraft began a continuous right turn with an increasing magnetic heading.
The captain reported a lack of nosewheel steering and attempted to use the rudder pedals and the nosewheel steering tiller to stop the turn, but was unsuccessful. The aircraft's braking was applied, but the plane continued to veer right. The aircraft eventually departed the paved surface and entered the grass, striking an airport sign. The aircraft sustained minor damage to the right-wing flap skin and fairing. The 16 passengers and crew were not injured.
The investigation
Investigators examined the flight data recorder (FDR) and cockpit voice recorder (CVR). The FDR showed that while thrust reversers were deployed with slight asymmetry, the wind gusts (up to 15 knots) and thrust imbalance were not sufficient to make the aircraft uncontrollable. The FDR recorded a Nose Wheel Steer Status of "Failed/Not Armed" and an EICAS chime, but these events occurred after the aircraft had already left the runway.
Post-incident examinations of the nosewheel steering (NWS) components were conducted. The nosewheel steering electronic control unit (ECU) contained several fault codes, including one for a pilot handwheel rate fault, which can be triggered by rapid tiller movement. While the handwheel control unit (tiller) failed an initial return-to-center test, it passed after being cleaned. Other components, including the electrohydraulic servo valve and the hydraulic manifold, showed only minor discrepancies that would not have prevented normal operation.
A review of maintenance records showed several previous reports of "STEERING INOP" messages and issues with the airplane pulling to the right or left during taxi, which had been addressed by various repairs and component replacements.