What happened
On 28 January 1999, a Fokker F27 Mark 500, registration G-JEAD, was involved in a ground incident at Liverpool Airport during a scheduled freight operation. The crew had arrived at the airport following two previous sectors and were preparing to transport cargo to Edinburgh. At the time of the occurrence, weather conditions were poor, characterized by rain, a cloudbase of 800 feet, and visibility of approximately 6,000 metres.
After receiving taxi clearance for Runway 27, the crew was instructed to follow a 'Follow Me' vehicle. During the taxi, the pilot noted that the vehicle was moving too quickly for the prevailing conditions, causing the gap between the aircraft and the vehicle to widen to roughly 50 metres. As the aircraft approached the runway, the vehicle briefly stopped before turning east. While the pilot attempted to maintain the vehicle's precise wheel tracks, the left main landing gear subsequently sank into very soft ground. The crew immediately notified Air Traffic Control and shut down the engines. It was noted that the 'Follow Me' vehicle did not return to assist the crew following the incident.
The investigation
The investigation examined the surface conditions at the edge of the paved manoeuvring area. It was established that the area of soft ground had been covered with a thin layer of asphalt, intended to prevent debris from entering the taxiway. However, there were no lights or edge markings present to signal the boundary between the paved surface and the unpaved area.
Analysis of photographic evidence revealed that the 'Follow Me' vehicle had previously driven across this thin asphalt layer, which had been sufficient to support the vehicle's weight but not that of the Fokker F27 Mark 500.
Findings
- The incident was caused by the pilot's inability to distinguish the taxiway surface from the asphalt-covered soft ground under the prevailing low-light and rainy conditions.
- The 'Follow Me' vehicle had utilized an inappropriate route that did not accurately represent the weight-bearing capacity of the surface for a larger aircraft.