What happened
On 1 June 2013, a DHC-8-402 Dash 8, registration G-FLBD, was performing a commercial passenger flight from the Isle of Man to Liverpool Airport. The weather conditions were favorable, and the flight was initially following a standard arrival procedure for Runway 27 under radar vectors provided by Air Traffic Control.
During the approach, the co-pilot requested to transition to a visual approach. The commander approved this request, and permission was granted by ATC. As the aircraft moved toward the runway, the co-lag began configuring the aircraft for landing. During this phase, the aircraft's descent rate increased, and the flight path fell below the recommended glide slope. This deviation triggered an EGPWS "CAUTION OBSTACLE" alert.
To avoid a potential conflict with terrain or an obstacle, such as the Runcorn Bridge, the crew disengaged the autopilot and executed a right turn. The crew maintained the aircraft on a base leg to stabilize the descent and eventually continued to a safe landing. There were no injuries and no damage to the aircraft.
The investigation
The AAIB examined the flight crew's actions and analyzed flight data provided by the operator. The investigation established that while the aircraft was on the base leg, the rate of descent reached approximately 2,000 ft/min. The EGPWS alert was triggered when the aircraft was at a radio height of 894 ft. The investigation also noted that the co-pilot, acting as the handling pilot, had become distracted by the landing configuration tasks, which led to a loss of focus on monitoring the vertical flight profile.