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A321, Sandefjord Norway, 2006
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Revision as of 09:48, 5 July 2010 by Integrator1
On 26 March 2006, an Airbus A321-200 being operated by Danish Airline My Travel Airways Scandinavia (since renamed Thomas Cook Airlines Scandinavia) on a passenger flight from Tenerife to Sandefjord Airport Torp experienced minimal braking action during the daylight landing roll in wet snow conditions and normal visibility at destination and an overrun occurred. The aircraft came to a stop positioned sideways in relation to the runway centreline with the right hand main landing gear 2 metres beyond the limit of the paved surface. After the engines had been shut down, passenger evacuation was accomplished using the forward left hand cabin door only. The aircraft suffered minor damage to the skin and nose landing gear and there were no injuries to the occupants.
An Investigation was carried out by AIBN (the Norwegian AIB). It was established that the First Officer had been designated PF for the landing and that the touchdown, in the presence of a slight tailwind component had been both later than normal and ‘soft’. Reverse thrust was selected but no braking deceleration was detected with autobrake selected so manual braking was attempted with a similar result. As the runway end neared, the aircraft commander took control and attempted to steer the aircraft to the left towards more favourable overrun terrain.
The Investigation considered the deterioration in the runway surface state which had occurred whilst the accident aircraft had been approaching destination and judged it likely that the runway had started out as a bare and moist runway to which moisture was gradually added by snow fall. They concluded that this, combined with a fall in air temperature meant that the lower layer of moisture had probably frozen to ice at the same time as moist new snowfall was added on top. “Hence, it is deducted that when OY-VKA landed the runway was covered by a thin layer of ice with fresh snow fall on top.”
It was concluded that an over-estimation by the flight crew of likely braking effectiveness on a contaminated runway in deteriorating conditions, which had only been notified to them at a late stage in the approach, was the primary reason for the failure to decelerate normally.
It was also considered that the accident "illustrates the problems of trusting measured friction figures in all types of conditions" and that a contributory circumstance was the considerable disagreement among airframe manufacturers and Regulatory Authorities on defining contamination.
The AIBN noted that the accident was “similar to several other runway excursions on slippery runways in Norway (in recent years, which) have many similar causal factors”. It is of the view that there are no safety benefits in individually investigating all these occurrences and advises that it is therefore working on a general report on ‘Winter Operations and Friction Measurements’. That report will highlight the common cause factors found in this type of event and will specifically highlight safety areas of general nature which are outside of the aircraft operators’ direct area of responsibility.
Since some specific matters disclosed by the Investigation were deemed to require action ahead of the issue of the general report, 5 Safety Recommendations were made:
Safety Recommendation SL no. 2010/04T
Upon touchdown on runway contaminated by 8 mm new snow, with an air temperature of -2° C and dew point temperature of -3° C, the crew experienced very POOR Braking Action, whereas the reported was MEDIUM. AIBN recommends that My Travel Airways Scandinavia / Thomas Cook Airlines Scandinavia evaluate if the procedures for use of the Airbus concept of “fluid contamination” allow the required safety margins when calculating landing distances on contaminated runways.
Safety Recommendation SL no. 2010/05T
AIBN’s investigations show that there is poor (POOR) Braking Action on runways covered with moist contamination (loose, dry snow and new snow, slush) and a dewpoint spread of less than 3 K. AIBN recommends that My Travel Airways Scandinavia / Thomas Cook Airlines Scandinavia evaluate if the procedures for use of FC values for moist contamination allow the required safety margins.
Safety Recommendation SL no. 2010/06T
During landing on contaminated / slippery runway OY-VKA was landed longer in on the runway due to a deviation from optimal procedures for such conditions. Further, there were indications on crew uncertainties regarding correct functioning of the Auto Brake system. AIBN recommends that My Travel Airways Scandinavia / Thomas Cook Airlines Scandinavia uses this incident in their training of their pilots in winter operations.
Safety Recommendation SL no. 2010/07T
AIBN has found that Sandfjord Airport Torp had well prepared winter maintenance procedures but that there were uncertainties regarding the correct application of the procedures. AIBN recommends that Sandfjord Airport Torp uses this incident as an example in their training of their personnel in winter operations
Safety Recommendation SL no. 2010/08T
During the landing on a slippery runway OY-KVA collided with a Localiser Monitoring Antennae basement which protruded above the runway surface. AIBN recommends that Sandfjord Airport Torp perform a risk assessment regarding the safety zones adjacent to the runway.
The AIBN Final Report was published on 9 March 2010 and may be seen in full at SKYbrary bookshelf:AIBN Report SL 2010/05