What happened
Between 29 December 2006 and 3 January 2007, a series of serious incidents occurred at Runway 27 of Bristol International Airport. On 29 December 2006, three separate aircraft experienced difficulties during landing operations. First, a Boeing 737-800, registration G-XLAC, experienced issues during its arrival. Shortly after, an ATR-72-202, registration G-BWDA, veered off the runway. Later that same day, two Embraer aircraft, including G-EMBO, also experienced runway excursions. The sequence of events concluded on 3 January 2007, when the Boeing 737-800, registration G-XLAC, was involved in another incident at the same airfield.
The investigation
The AAIB investigation examined the runway surface conditions, the aircraft involved, and the communication protocols used by air traffic control. The investigation focused on recent runway resurfacing works at the airport, specifically the application of a Marshall Asphalt base course. Investigators analyzed flight data recorder information, including deceleration and lateral effects, and reviewed the use of Continuous Friction Measuring Equipment (CFME) to assess the runway state. The inquiry also looked into how braking action reports were communicated to flight crews and whether the information provided by air traffic control accurately reflected the available friction.
Findings
- The primary cause of the incidents was reduced friction on ungrooved sections of the runway base course, which led to insufficient braking action and poor lateral control during landings in wet and windy conditions.
- Air traffic control reports, based on Mu-meter friction assessments, provided flight crews with a false sense of security regarding the available braking action on the wet surface.
- Safety information regarding 'slippery when wet' conditions, published via CAA communications, was not effectively passed from operators to the flight crews.
- In one instance, the ATR-72-202, registration G-BWDA, landed in a crosswind that exceeded the operator's published limits, and the use of reverse thrust was inconsistent with the company's manual.