13 февраля  CL-600

     Investigation team of the Interstate Aviation Committee consisting of official representatives of Rostransnadzor and flight safety inspection of Vnukovo airport has completed the investigation of the fatal accident with Canadair Regional Jet SE CRJ100-SE (CL-600-2B19) N168CK (USA) aircraft occurred in Vnukovo Airport (Moscow) on February 13, 2007. 
      Official representatives of Canada (state of the aircraft design and manufacture), USA (state of aircraft registry and also state of engines design and manufacture), Switzerland (state providing information on aircraft maintenance), France (state providing assistance in flight recorders decoding) participated in the Investigation team work.
      In course of the investigation full range of activities assessment of flight and maintenance documentation on aircraft operation and crew training, decoding and analysis of onboard and ground recorders data was held. Evaluation of weather conditions in Vnukovo Airport and procedure of aircraft deicing was carried out. Mathematic simulation of aircraft takeoff was performed and similar aircraft accidents in the world with CL-600-2B19 and CL-600-2B16type of aircraft were studied.
      In course of investigation activities of three last accidents with this type of aircraft the perspective on need of priorities in development of flight safety level of CL-600-2B19 and CL-600-2B16 type of aircraft in conditions of possible icing was provided jointly with aircraft designer. As a result, on March 7, 2008 two Airworthiness Directives № CF-2008-15 and CF-2008-16 issued by Transport Canada and which introduce additional limitations on crew actions during preparation for takeoff in conditions of possible icing have emerged.
      According to the results of all carried out activities the Investigation team made the following conclusion:
      Accident with CRJ100-SE aircraft registration number N168CK was caused by wing lifting properties loss at takeoff phase that resulted in aircraft stall immediately after RWY lift off, starboard wing collision with unpaved RWY followed by destruction and fire outbreak.
      Wing lifting properties loss under actual meteorological conditions (snow shower with intensity rate from moderate to heavy, temperature minus 60С, dew point temperature minus 70С) was xaused by ground icing despite deicing procedure which could be combination of the following factors¹:
      – irregularities of guidelines determining the procedure of aircraft deicing during two stage procedure that resulted in possibility of difference of requirements for 3-minutes interval reference between first and second processing stages;
      – non-receipt of full meteorological documentation by the crew during preparation for flight and, as a result, inability of correct determination of de-icing fluid holdover time and failure of aircraft reprocessing;
      – violation of aircraft de-icing route recommended by FOM, non-compliance with recommended 3-minutes interval between first and second processing stages;
      – lack of proper supervision from crew members and/or airlines representatives over efficiency and quality of deicing;
      – failure to engage wing deicing system prior to takeoff that is compulsory requirement of aircraft FOM for actual meteorological conditions.
      Jointing compound protrusion on wing upper and lower surface for value significantly exceeding limitations of valid specifications and aircraft nose wheel lift at the speed of 12 knots below recommended one reduced stall angle-of-attack margin.
      Existing procedural technique of aircraft airfoil monitoring before departure together with inefficiency of existing stall protection system at the takeoff phase due to increased wing sensitivity even to insignificant leading edge contamination can not fully guarantee prevention of similar accidents in the future.
     Text of final report with conclusion about accident causes and recommendations on flight safety development is agreed with official representatives of all states involved in investigation.
      Two members of the Investigation team and representatives of Rostransnadzor and Vnulovo Airport signed Final report with dissenting opinions. Its substance points out that aircraft accident was caused by "unprofessional, inadequate crew actions during aircraft piloting at takeoff phase resulted in ... aircraft stalling in 5 seconds after lift off' from the RWY, while ground icing is denied.
      The Investigation team emphasized that dissenting opinions disregard all materials collected by the Investigation team in course of the investigation, in particular - results of mathematic modeling which indicate that uncontrolled aircraft rolling (stalling) started immediately after aircraft liftoff from the RWY, at angles of attack which are significantly less than aircraft stall angles of attack with "clean wing", under significant dissymetrical lift deficiency which can only be explained by ground icing effect.   
    
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¹Factors are listed in chronological order. It was not possible to determine "quantitive" impact of each of them.