What happened
On 25 November 2010, a Boeing 737-8K5, registration G-FDZR, was performing a scheduled passenger flight from Lanzarote to Newcastle Airport. During the approach, the crew monitored rapidly changing weather conditions. Based on recent reports, the pilots used a landing performance calculator and determined that the aircraft could safely land on a wet runway with a slight tailwind.
However, shortly before arrival, air traffic control reported that a previous landing had encountered significant contamination, with the runway surface described as having 3 to 4 mm of snow. Despite this, the crew proceeded with the approach, intending to use full reverse thrust and autobrake settings. The aircraft touched down approximately 150 m beyond the ideal touchdown point.
During the landing roll, the co-pilot reduced the reverse thrust to idle at 67 kt groundspeed. Following this, the crew transitioned to manual braking. The aircraft failed to decelerate as expected and eventually came to a stop on the paved surface, with the nosewheel positioned 10 ft beyond the marked runway end. There were no injuries to the 189 passengers or 8 crew members, and no damage was sustained by the aircraft.
The investigation
The AAIB investigation examined flight data recorder information, which revealed that the aircraft's deceleration decreased significantly after the reverse thrust was retarded to idle. The investigation also reviewed the cockpit voice recorder and airport maintenance logs.
Investigators found that the runway had been inspected visually by an airport official from a moving vehicle, rather than using a Standard Depth Gauge at regular intervals. This visual assessment suggested the snow was patchy, but the actual depth of the contaminant may have been greater than reported. Furthermore, the investigation noted that the pilot applied asymmetric manual braking, with significantly higher pressure applied to the right main landing gear than the left.
Findings
- The aircraft touched down beyond the optimum touchdown zone, increasing the required landing distance.
- The reduction of reverse thrust to idle before the aircraft reached taxi speed contributed to the increased landing distance.
- The runway surface condition was assessed visually rather than through precise depth measurements, which may have led to an inaccurate assessment of the contamination.
- The application of asymmetric manual braking occurred during the landing roll.
Safety action
Two Safety Recommendations were issued:
- It is recommended that the CAA publishes a single, unified definition of Contaminated Runways to prevent confusion caused by conflicting documentation.
- It is recommended that the CAA develops a system for measuring runway contamination depth that provides accurate and timely information to pilots.