What happened
On 29 December 2006, an Embraer EMB-145EU, registration G-EMBT, was performing a passenger flight from Edinburgh to Bristol Airport. During the approach, the commander encountered strong crosswind conditions, with the wind estimated at approximately 15 degrees of drift angle. Due to the wind intensity, the pilot initiated a go-around. On the subsequent approach, despite a reported crosswind of 31 kt, the pilot continued the landing.
Upon touchdown on Runway 27, the aircraft was subjected to heavy braking and significant crosswind forces. During the ground roll, the pilot experienced a sudden loss of hydraulic assistance to the rudder, accompanied by a Master Caution and a 'rudder sys 1-2 inop' EICAS message. To maintain directional control, the pilot utilized asymmetric braking and significant rudder pedal input. Eventually, the aircraft slowed to a speed where the pilot could use the tiller to steer the plane to a normal exit from the runway. There were no injuries and no fatalities among the 4 crew and 15 passengers on board.
The investigation
The AAIB examined the flight data recorder (FDR) and the aircraft's rudder control systems. The investigation focused on the Rudder Hardover Protection System (RHPS), which is designed to shut off hydraulic power to the rudder Power Control Unit in the event of a detected runaway. The investigation analyzed the timing of the Master Caution relative to the FDR data, noting that the deceleration of the aircraft decreased during the period the hydraulic systems were shut off. The investigation also looked into the runway surface conditions, which were noted as wet and ungrooved in a recently resurfaced section.
Findings
- The loss of hydraulic power to the rudder was caused by the activation of the RHPS.
- The activation was likely triggered by heavy rudder pedal forces applied by the pilot while attempting to maintain directional control during a strong crosswind landing on a slippery runway.
- Two of the three necessary conditions for RHPS activation were met: engine N2 speeds were above 56%, and rudder deflection exceeded 5 degrees.
- The third condition, pedal force exceeding 130 lbf, was likely met due to the pilot's efforts to counteract the crosswind and braking forces.
- The investigation could not definitively confirm the exact pedal force due to limitations in the FDR's recording parameters, but the timing of the system shutoff aligns with the pilot's reported sensation of losing assistance.