What happened
On 27 April 2008, an Airbus A340-313, registration G-VAIR, was conducting a commercial passenger flight from London Heathrow to Nairobi. During the approach to Runway 06 at Nairobi Airport, the crew received information from air traffic control that an aircraft ahead had reported low landing visibility.
The first officer, acting as pilot flying, continued the approach using autopilot and autothroblle. While the crew initially had good visual contact with the runway lights, the aircraft entered a patch of fog at a low altitude. This caused the pilot flying to lose sight of the right side of the runway and the runway lights, while the commander lost sight of the right edge of the runway.
Upon realizing the loss of visual cues, the commander initiated a go-around. The crew advanced the thrust levers to full power, and the aircraft became airborne again after being on the ground for less than five seconds. During the event, the main landing gear left a set of marks that began 800 m from the runway threshold. These marks tracked 160 m along the runway before the left gear departed the paved surface, traveling 180 m parallel to the runway before stopping. The right gear remained on the paved shoulder.
The investigation
The investigation was conducted by the UK AAIB with assistance from the Kenyan Ministry of Transport and the French BEA. Investigators examined the aircraft for damage and inspected the runway condition.
Physical inspections of G-VAIR revealed minor scratches to the left aft lower fuselage and mud spray on the fuselage and left horizontal stabilizer. One runway edge light was destroyed during the incident. The investigation also reviewed data from the aircraft's flight recorders and the airport's Automated Weather Observation System (AWOS), which had recorded a minimum RVR of 550 m at the time of arrival.
Findings
- The touchdown zone of Runway 06 was heavily contaminated with rubber deposits, which may have obscured the centerline markings.
- The left set of main gear marks left the paved surface, while the right set remained on the paved shoulder.
- The loss of visual references due to fog at a critical phase of flight led to the commander'0s decision to initiate a go-around after the aircraft had already drifted off the paved surface.
- The runway edge lighting was positioned 7.5 m from the edge of the paved strip, which deviates from ICAO standards requiring a maximum distance of 3 m.
- There was a discrepancy between the RVR recorded by the AWSS and the information provided to the crew, which investigators are looking into regarding the effect of light luminescence from edge lights on visibility.