Accident to the McDonnell Douglas DC-9-83 registered EC-LTV on 07/21/2014 near Gossi (Mali)

Diffusée avec l'accord du Président de la Commission d'enquête sur les accidents et incidents d'aviation civile du Mali :

À la suite de l'accident survenu au McDonnell Douglas MD 83 dans la région de Gossi (Mali) le 24 juillet 2014, les autorités de l'aviation civile maliennes ont ouvert une enquête de sécurité et ont sollicité l'assistance technique du BEA.

L'avion, qui assurait la liaison Ouagadougou (Burkina Faso) - Alger (Algérie), avait à son bord 112 passagers, dont 54 Français, et six membres d'équipage.

EC-LTV

Publications

Press release

  • Published with the agreement of the President of the Commission of Inquiry into civil aviation accidents and incidents of the Republic of Mali.

    Following the accident that occurred to the McDonnell Douglas MD 83 in the region of Gossi (Mali) on 24 July 2014, Malian civil aviation authorities initiated a Safety Investigation and requested technical assistance from the BEA. Two investigators from the BEA travelled to the accident site on 25 July.

    The two flight recorders, the Flight Data Recorder (FDR) and the Cockpit Voice Recorder (CVR), which were recovered on 25 July, were transported by Malian civil aviation authorities, accompanied by the French Gendarmerie, and handed over officially this morning to the Director of the BEA. Work on opening them began immediately.

    BEA investigators were quickly able to read out the data from the FDR. Work on decoding and analysing the data in detail will now start, with members of the Malian Commission of Inquiry.

    The CVR was damaged in the impact. Work is continuing on this recorder in order to extract data from it.

    The BEA reminds you that only the President of the Commission of Inquiry of the Republic of Mali is authorised to communicate on the results of the ongoing work and the next stages of the investigation.

    The aeroplane, which was flying the Ouagadougou (Burkina Faso) to Algiers (Algeria) route, had 110 passengers on board, including 54 French citizens, as well as six crew members.

  •  With the agreement of the President of the Commission of Inquiry, who will be present, a progress report on the initial validated information on the circumstances of the accident to the McDonnell Douglas MD 83, which occurred on 24 July 2014, will be presented during a media event that will take place at the BEA, Le Bourget on Thursday 7 August from 14h to 14h45 Accreditation: due to limited capacity at the BEA headquarters, it is essential that journalists who wish to attend this media event confirm their presence by email by the evening of Wednesday 6 August at the latest to ang[at]bea-fr.org or sfu[at]bea-fr.org

  • Published with the agreement of the President of the Mali Commission of Inquiry

    The Commission of Inquiry set up by the Republic of Mali brought together representatives of the following States at the BEA:

    • Algeria, Burkina Faso, France, Mali, Spain, United States.

    Working sessions involving around twenty aviation Safety Investigators took place at the BEA in the presence of the President of the Mali Commission of Inquiry and the Director of the BEA. These sessions made it possible to determine how the investigation will be organised, to review progress on the information available and to decide on the work to be launched as a priority.

    The investigation is organised around three working groups:

    • The Aircraft Group is initially tasked with producing a graphic representation of the accident site wreckage and deducing from this a probable final trajectory (angle and attitude on impact).
    • The Systems Group is prioritising a reconstitution of the history of the flight, based on the recorded flight data, radio communications data and information on meteorological conditions.
    • The Operations Group will initially collect Air Traffic Control information (radar and radio communications), meteorological information and the flight dossier on departure from Ouagadougou.

    These three groups started work immediately.

    In the context of the Systems Group, work on the flight recorders has continued.

    The readout of some flight parameters from the Flight Data Recorder (FDR) made it possible to recreate a first image of the aeroplane’s flight path. Other parameters have yet to be validated. Finally, additional calculations must be performed using a behaviour and performance model of the aeroplane and its engines, in order to further define the scenario of the event, in particular the end of the flight.

    The magnetic tape in the Cockpit Voice Recorder (CVR), which was damaged, was repaired and read out. Unfortunately, the recordings that it contains are unusable, due apparently to a recorder malfunction, with no link to the damage that resulted from the accident. Analysis continues to try to find a means of extracting some information, but is it not possible to predict the outcome of this approach.

    The absence of usable data from the CVR at present underlines the need to collect all data on communications that the crew may have made with organisations on the ground or with other aircraft.

    The aeroplane’s flight path as it was reconstituted from the FDR data, superimposed over a satellite image of the cloud mass present on the day of the accident, shows a normal climb and start of cruise, with some moderate route changes that are typical of a strategy to avoid any stormy developments.

    • The aeroplane took off from Ouagadougou at 1h151. It climbed and reached flight level 310 at 1h37.
    • At flight level 310, the aeroplane stabilised in cruise at a speed of about 280 kt.
    • Around two minutes after the start of cruise, while remaining at flight level 310, the speed dropped progressively.
    • The aeroplane began descending progressively and the speed continued to drop down to about 160 kt.
    • The aeroplane then turned left and quickly lost altitude, with large changes in pitch and bank. The rotation to the left continued until the end of the recording. The last recorded point, 1h47mn15s, corresponds to an altitude of 1,600ft, a speed of about 380 kt and an extremely high descent speed.

    An interim report will be published in mid-September by the President of the Mali Commission of Inquiry.

  • Press release from the BEA and the Commission d'Enquêtes Accidents et Incidents de l’Aviation civile (Mali) Following the publication of the Interim Report on 20 September 2014 in Bamako (Mali), investigative work has continued, based on the analysis of the accident flight parameters. Progress made in this work has led the Republic of Mali Commission of Inquiry and the BEA to communicate jointly the following information.

    On 24 July 2014, the MD-83 registered EC-LTV was performing scheduled night flight AH 5017 from Ouagadougou (Burkina Faso) to Algiers (Algeria). Takeoff occurred at 01h15, the climb towards the cruise altitude took place without any significant events, and the crew made several heading changes in order to fly around a storm cell. The autopilot and the autothrottle were engaged. The aeroplane reached the cruise altitude of 31,000 ft, that’s to say about 9,500 m. The autopilot then switched to the mode that maintains the altitude and the autothrottle to the mode that maintains the speed (Mach).

    About two minutes after levelling off at an altitude of 31,000 ft, calculations performed by the manufacturer and validated by the investigation team indicate that the recorded EPR, the main parameter for engine power management, became erroneous on the right engine and then about 55 seconds later on the left engine.

    This was likely due to icing of the pressure sensors located on the engine nose cones. If the engine anti-ice protection system is activated, these pressure sensors are heated by hot air.

    Analysis of the available data indicates that the crew likely did not activate the system during climb and cruise.

    As a result of the icing of the pressure sensors, the erroneous information transmitted to the autothrottle meant that the latter limited the thrust delivered by the engines. Under these conditions, the thrust was insufficient to maintain cruise speed and the aeroplane slowed down. The autopilot then commanded an increase in the aeroplane’s pitch attitude in order to maintain the altitude in spite of this loss of speed.

    This explains how, from the beginning of the error in measuring the EPR values, the aeroplane’s speed dropped from 290 kt to 200 kt in about 5 minutes and 35 seconds and the angle of attack increased until the aeroplane stalled.

    About 20 seconds after the beginning of the aeroplane stall, the autopilot was disengaged. The aeroplane rolled suddenly to the left until it reached a bank angle of 140°, and a nose-down pitch of 80°  

    The recorded parameters indicate that there were no stall recovery manœuvres by the crew.

    However, in the moments following the aeroplane stall, the flight control surfaces remained deflected nose-up and in a right roll.

    CORRECTIVE ACTIONS

    At least two similar events occurred, in June 2002 and in June 2014, with no serious consequences.

    The event in June 2002 was the subject of an NTSB investigation report. On 4 June 2002, the McDonnell Douglas MD-82, registered N823NK performing Spirit Airlines flight 970, suffered a loss of thrust on both engines, in cruise at an altitude of 33,000 ft, that is about 10,000m. The two pressure sensors, located on the engine nose bullets, were blocked by ice crystals, leading to incorrect indications and over-estimation of the EPR. The crew noticed the drop in speed and the precursor indications of a stall just before disengagement of the autopilot and putting the aeroplane into a descent. They had not activated the engine anti-ice systems. This event occurred during the day, outside the clouds.

    On 8 June 2014, the MD83 registered EC-JUG belonging to Swiftair, which was performing a passenger transport flight at flight level FL 330, suffered a drop in speed while it was flying during the daytime above the cloud layer. The crew detected the problem, put the aeroplane into a descent and activated the engine anti-ice systems without reaching a stall situation, then continued the flight.

    This background, as well as the data on the accident to flight AH5017, was shared with the European Aviation Safety Agency (EASA) and through EASA with the American authorities (FAA); they should serve as the basis for future publication of corrective measures aimed at assisting crews in identifying and responding to similar situations to those encountered at the time of this accident.

    NEXT STEPS

    The investigative work is continuing, in particular on the analysis of:

    • the flight parameters to complete the scenario described above,
    • possible crew reactions, despite the absence of Cockpit Voice Recorder data from the accident flight, which remain unusable to this day,
    • the training and follow-up of Swiftair crews,
    • previous events and the follow-up undertaken.

    The publication of the final report is planned before the end of December 2015.