Tunisair Airbus A320 Longitudinal Runway Excursion at Paris-Orly (TS-IMC)

Incident Overview and Aircraft Details On 12 March 2013, at 10:15 UTC, a Tunisair Airbus A320 with registration TS-IMC experienced a longitudinal runway excursion during taxiing after landing at Paris-Orly Airport (94). The aircraft was operating a public transport flight from Djerba, Tunisia, and was carrying 140 passengers, 4 cabin crew members, and 2 pilots. The incident resulted in slight damage to the nose gear. ## Flight Progression and Approach The aircraft departed Djerba at 07:12 UTC, with the co-pilot acting as pilot flying. During the flight, the crew received ATIS information indicating that only runway 08 was in service, covered in dry snow, and that the runway exit could be via runway 02/20 or taxiway W31. The crew was informed of the braking condition as 'medium' at 09:32, which later changed to 'medium to poor' at 09:51. The crew recalculated landing distances accordingly and noted the presence of wet snow on the runway. ## Landing and Runway Excursion The aircraft landed at 10:13:30 UTC at a conventional speed of 136 kt. Thrust reversers were deployed at 10:13:31, and deceleration was stable at approximately 0.3 g. The captain took control during the landing roll, intending to exit via runway 02/20. At 10:13:46, the autobrake was disengaged, and deceleration dropped to 0.12 g. Thrust reversers were retracted at 10:13:56. At 10:13:58, while taxiing at 42 kt and approaching the intersection with runway 02/20, the controller requested the crew to exit via the end of runway 08. The crew continued taxiing toward the runway end, located approximately 1,700 meters away. A slight increase in N1 was recorded between 10:14:03 and 10:14:40, with ground speed stabilizing around 60 kt. At 10:14:45, the crew began braking approximately 480 meters from the runway end. Deceleration was 0.12 g, and increased brake pressure did not slow the aircraft. The captain applied the parking brake and attempted to control the trajectory using the rudder. At 10:15:12, the aircraft left the runway at a ground speed of 17 kt and came to a stop four seconds later. The captain informed air traffic control that braking was poor, and emergency services responded quickly with no fire risk detected. ## Meteorological and Runway Conditions On 12 March 2013, continuous and variable snowfall occurred at Orly between 07:00 and 23:45 UTC. Surface winds were from the north to north-northeast at approximately 10 kt, with snow depth reaching 8 cm during the day. Between 10:00 and 10:20, precipitation was light continuous snow, with surface winds from 020° at 6 kt. The investigation could not determine if the crew was aware of the 09:31 SNOWTAM, but the crew knew wet snow was present on the runway. ## Runway Treatment and Braking Performance Aéroports de Paris (ADP) managed the Orly platform. Precipitation began around 04:30 as freezing rain, followed by continuous snow. Runway 08/26 was treated and reopened at 06:45. From 07:30, treatment of runway 06/24 led to single-runway operations on 08/26 for takeoffs and landings. Friction measurements between 09:14 and 09:23 were communicated to relevant parties, including the control tower, and integrated into the 09:31 SNOWTAM and 10:00 METAR. The transmitted values corresponded to 'medium' braking action. Following the incident, Airbus estimated braking effectiveness based on recorded parameters during the last third of the runway, classifying it as 'Medium to Poor'. In case of braking loss, the QRH 'Loss of Braking' procedure requires full thrust reverser deployment and maximum brake pressure of 1,000 PSI. If the aircraft still does not brake, the procedure requires using the parking brake in successive actions. ## Crew Testimony and Findings The captain and co-pilot stated they regularly considered meteorological information during the approach. The landing was normal on a less contaminated part of the runway. As they prepared to exit via W4, the controller requested they extend to W31. They observed that the last third of the runway was not clean and had snow on the surface, unlike the touchdown zone. The captain was surprised and helpless during braking, while the co-pilot noted the last third appeared icy. The aircraft left the runway while the captain was using the parking brake as a last resort. ## Lessons and Conclusion Established facts include that crews landing before the Tunisair flight estimated braking quality between 'medium' and 'medium to poor', which were indicative observations not prejudging the runway end condition. The crew correctly managed the landing roll to exit at mid-runway and was not concerned by the controller's request to extend to W31, relying on observed braking performance. Frequent takeoffs and landings on the same runway limit contaminant accumulation on the taxiing part, while less-used runway ends contaminate faster and can become very slippery. This situation could be reminded to air traffic control to assist in runway exit management. The use of measurement means is operationally very penalizing as it requires runway closure for about 20 minutes. No real-time and remote means exists currently. The fact that the last third of the runway was not properly snow-cleared represented a potential risk of longitudinal excursion, especially in case of acceleration-stop. The aircraft only partially left the runway, and application of the 'Loss of Braking' procedure might have avoided the incident. The inability to measure runway friction in real time did not allow detection of the inhomogeneous runway contamination. This led to a degraded perception of braking conditions at the runway end by the crew and controllers, causing the runway excursion. The non-application of the 'Loss of Braking' procedure may have contributed to the incident.