History of Flight
On May 11, 2022, at about 1419 central daylight time, SkyWest flight 5069, a Mitsubishi CL-600-2B19 (registration N965SW), struck an airport sign during a runway excursion after landing on runway 8R at George Bush Intercontinental Airport (IAH), Houston, Texas. The 16 passengers and crew were not injured. The flight was a scheduled domestic passenger service from Victoria Regional Airport (VCT) to IAH.
The cockpit voice recorder (CVR) captured the touchdown sound at 1418:59. The captain, the pilot flying, reported a normal touchdown and initial rollout. Shortly after the first officer's 90-knot callout at 1419:09, the captain stowed the reversers. The tower instructed the flight to turn right toward high-speed taxiway NK. The captain complied, but the airplane continued turning right with increasing magnetic heading. At 1419:14, the captain commented about a lack of nosewheel steering.
The captain attempted to stop the turn using rudder pedals and the nosewheel steering tiller but was unsuccessful. A "STEERING INOP" caution message appeared on the EICAS display. The CVR recorded an EICAS chime, and the flight data recorder (FDR) registered a steering fault after the airplane departed the runway. At 1419:18, sounds consistent with leaving paved surface were recorded. About 4 seconds later, the Nose Wheel Steer Status became Failed/Not Armed. The captain continued braking until the airplane stopped in grass alongside the taxiway.
Aircraft Information
The Mitsubishi Heavy Industries Regional Jet Flight Crew Operating Manual notes that the nosewheel can be steered up to 70° via the tiller handwheel and up to 7° via rudder pedals. If the nosewheel steering (NWS) electronic control unit (ECU) detects a failure or hydraulic system No. 3 fails, NWS reverts to shimmy-damping mode, allowing free-castering; pilots can maintain directional control using rudder, differential braking, and differential thrust. The ECU stores fault codes in nonvolatile memory in reverse chronological order without timestamps.
According to the Fault Isolation Manual, NWS is deactivated when weight-on-wheels (WOW) indicates "air." The mechanical cam inside the nose landing gear (NLG) strut keeps the NLG straight when fully extended. FDR data showed normal WOW switch and hydraulic system No. 3 pressure operation. If the tiller handwheel is not centered during touchdown with a steering angle less than 7°, the ECU would not detect a fault and would combine tiller and rudder pedal commands.
The "STEERING INOP" caution message appears when the ECU detects a fault, including system component failures, improper voltages, degraded performance, or unexpected conditions such as handwheel angles greater than 7° during touchdown or movement rates exceeding 500° per second.
Meteorological Information
Wind data from IAH's automated surface observing system showed that between 1419 and 1420, the 2-minute average wind was 12–14 knots from 125°–133°, and gusts were 16–20 knots from 134°–137°. Runway 8L magnetic heading was 087°. The right crosswind component for steady wind ranged 7–10 knots; for gusts, 12–15 knots. The most recent report at 1353 indicated wind from 120° at 9 knots. Visual meteorological conditions prevailed, and the runway was dry.
Damage to Aircraft
The airplane sustained minor damage to the right wing trailing edge flap skin and fairing.
Flight Recorder Data
FDR data indicated touchdown at 1418:59 at 133 knots with magnetic heading 92°, both engines near idle. About 4 seconds later, thrust reversers deployed, and engine thrust increased asymmetrically (right engine N1 about 12% higher). The captain applied brakes as reverse thrust reached 50% N1. At about 71 knots, the airplane began a right turn. Left wheel brake pressure reached about 750 psi, right about 500 psi. Two left rudder inputs (20° and 15°) occurred. Brakes were released at 58 knots, then full left rudder (25°) was applied and held. The rate of turn reduced slightly. About 4 seconds after full rudder, the CVR recorded a rumbling sound and increased noise consistent with departing the runway into grass at 50 knots. About 4–5 seconds later, Nose Wheel Steer Status changed to Failed/Not Armed, and an EICAS chime was heard. The FDR did not record nosewheel steering angle or tiller position.
Post-Incident Examinations
SkyWest maintenance downloaded the ECU's nonvolatile memory, which contained fault codes (including codes for handwheel rate fault, warm boot, air-to-ground mode command fault, etc.). No dates or timestamps were associated with the codes, so direct correlation to the incident was not possible. Maintenance could not determine why the "STEERING INOP" message occurred using the Fault Isolation Manual. A timing check of the handwheel return-to-center was within limits.
SkyWest replaced the handwheel control unit and ECU; voltage checks of feedback RVDTs and rudder pedal RVDT were within limits, and the NWS system operated normally. Components sent to manufacturers included the ECU, handwheel control unit, electrohydraulic servo valve, steering selector valve, rudder RVDT, wiring harness, hydraulic manifold, and compensator. The handwheel control unit failed the return-to-center test at Safran (exceeded 4 seconds) but passed after cleaning. The electrohydraulic servo valve had a minor null bias shift. The steering selector valve passed functional tests but failed insulation resistance. The NLG wire harness failed a dielectric strength test due to broken shield wires (health monitoring only). The hydraulic manifold had slightly high flow (1.41 GPM vs 1.40 max). None of these discrepancies would have prevented normal NWS operation.
Maintenance Records
Review of maintenance records over the 12 months before the incident showed seven pilot-reported NWS discrepancies, including one tiller not centered with airplane pulling right and a "STEERING INOP" message, and six reports of the EICAS message. Most were cleared by resets or operational checks with no anomalies found; one was cleared after replacing a right feedback RVDT. Six months after the incident, two additional discrepancies occurred: one involved excessive pull to the left and was resolved by replacing the left feedback RVDT; another involved a "STEERING INOP" message and hard left pull, resolved by replacing the right feedback RVDT.