What happened
On the night of 31 January 2014, a Bae Jetstream 3200, registration ES-PJR, was performing a commercial flight at Torsby airport in Värmland, Sweden. The aircraft, operated by AS Avies, was arriving during darkness under winter weather conditions characterized by snow and low visibility. During the landing phase, the aircraft experienced a serious incident on the runway surface, which was contaminated with snow.
The investigation
The Swedish Accident Investigation Authority (SHK) examined the operational procedures and technical capabilities of the aircraft and the operator. The investigation focused on the methods used by the crew to determine landing distances on slippery surfaces. Investigators reviewed the operator's manuals, including the Operations Manual (OM-A), the Aircraft Flight Manual (AFM), and various performance manuals. The inquiry also scrutinized the technical state of the aircraft's de-icing systems and the accuracy of the performance calculations provided to the crew for use in winter conditions.
Findings
- The operator lacked a standardized and reliable system for calculating aircraft performance on contaminated runways.
- There was significant ambiguity regarding which documentation the crew should use for calculations, as different manuals (OM-A, OM-B, AFM, and Performance Manual) provided conflicting or inconsistent information.
- The operator's performance calculation system failed to adequately account for critical variables, such as runway acceleration distance on contaminated surfaces, the impact of the measured friction coefficient on landing/take-off capabilities, and the necessity for obstacle clearance adjustments.
- The crew could not consistently present or utilize verified performance data that addressed the specific challenges of slippery or snowy runway conditions.
Safety action
Following the investigation, the Estonian Civil Aviation Administration (the operator's regulatory authority) issued a cockpit bulletin and a pilot information leaflet to clarify procedures for operating on slippery or contaminated runways. The operator also distributed revised performance calculations to crews operating in Sweden to mitigate the risk of future incidents.