A Final Investigation Report BFU18-1626-FX by the concerned Authority in Germany has found that a South Arfrican Airways (SAA) Airbus A340-642 flight crew were not properly trained for a scenario, which occured resulting a temporary loss of control of the aircraft , that was operating a commercial flight from Johannesburg to Frankfurt with 259 people on board in 2018.
The German Federal Bureau of Aircraft Accident Investigation’s findings highlighted a rare and unpredictable wind conditions at high altitude — due to which the aircraft exceeded the maximum operating speed at Flight Level (FL) 380 in Swiss airspace.
The Report -BFU18-1626-FX read as ,
The aircraft was in cruise flight at Flight Level (FL) 380 in Swiss airspace, when a change of wind conditions at high altitude caused the exceedance of the maximum operating Mach. The Pilot in Command (PIC) deactivated the autopilot and steered the aircraft manually into climb.
While reaching FL 400, the maximum angle of attack was reached several times and the stall warning activated. The PIC initiated the descent stabilizing the flight path again at FL 340
• A rapidly turning wind direction during cruise flight, unpredictable for the flight crew. This caused an overspeed condition.
• The flight crew did not respond to this overspeed condition with the procedure Abnormal and Emergency Procedures / Misc / Overspeed Recovery.
• The PIC had deactivated the autopilot and in the course of the incorrect application of the OEB No. 49, he had two Air Data Reference (ADR) of the three Air Data Inertial Reference Units (ADIRU) switched off. Subsequently, the Autothrust (A/THR) was deactivated and flight idle thrust initially maintained.
• Temporarily, the aircraft was controlled in Alternate Law.
• Due to the dynamic pitch-up control inputs of the PIC, the subsequent climb and the low engine thrust in flight idle, rapid deceleration of airspeed and triggering of the stall warning occurred.
• Due to the erroneous application of the OEB No. 49, the aircraft was close to a stall at high altitude. • The PIC’s control inputs during the active stall warning were insufficient and not energetic enough to stabilise the flight attitude in time.
• Crew cooperation during the overspeed condition and the stall recovery was erroneous in regard to the analysis of the situation and the implementation of procedures.
Though, the German investigation found the pilots to be experienced , report said, the cockpit crew applied the recovery procedures erroneously , leaving the plane close to stalling.
Further investigation revealed that the Airbus A340 simulator they trained on was technically not able to correctly produce the type of conditions they experienced for the first time during the sudden wind change on the flight. The simulator training of the pilots was limited to explanations by the simulator trainers.
“The operator neglected to update the simulator software even though in 2006 the aircraft manufacturer had published an update. The training department should have noticed and remedied this deficit,” the report found.
On 8 December 2014, the aircraft manufacturer, as type certificate holder, published a Red OEB, which described how pilots could deactivate the high angle of attack protection, if they suspect a malfunction.
The OEB described that in continuous straight and level flight without g-factor caused for example by a turn, the indication of the Vprot increases with increasing Mach. Subsequently, two of the three ADRs should be deactivated.
The operator confirmed that the used Airbus A340 simulator was technically not able to reproduce the OEB No. 49 entry conditions and the overspeed condition. The pilots’ training in regard to the OEB No. 49 during the simulator training was limited to the explanations of the simulator trainer.
At the time of the occurrence, the simulator’s FCPC had the Standard W6.3. This standard was implemented in September 2002. In June 2006, the aircraft manufacturer had implemented the new autopilot disconnect logic with the FCPC Version W10.
The pilots also did not have any training material available to explain how to deal with such an incident. There were no injuries and no damage in the 2018 incident that occurred as the aircraft flew over Clariden, Switzerland.
The report labelled the incident as “serious” and that there had been a high probability of an accident. The probe found that the pilot in charge deactivated the autopilot and steered the aircraft manually into climb.
The maximum angle was reached several times and the aircraft system’s stall warning was activated several times for a few seconds. The Airbus 340 is equipped with a high speed protection to prevent in-flight speeds which could cause structural overload or loss of control.
The flight crew reported to have temporarily lost control of the aircraft caused by a rare but unpredictable weather phenomenon so that there was a high probability of an accident.
Source : German Federal Bureau of Aircraft Accident Investigation / BFU18-1626-FX
The pilot then initiated a descent and stabilised the flight path again. The Swiss Transportation Safety Investigation Board delegated the investigation to the German Federal Bureau of Aircraft Accident Investigation in November 2018. The German investigation found the rapidly turning wind direction was unpredictable for the flight crew and caused an overspeed condition.
The flight crew did not respond to this overspeed condition with the relevant “abnormal and emergency” and overspeed recovery procedures. “The control inputs by the pilot in charge during the active stall warning were insufficient and not energetic enough to stabilise the flight attitude in time,” states the report.
“Crew co-operation during the overspeed condition and the stall recovery was erroneous in regard to the analysis of the situation and the implementation of procedures.”
The report concludes that high-altitude overspeed training with drastic wind speeds would have better prepared the pilots for such an event and minimised the surprise.
• PIC and co-pilot 2 had the required ratings in their licences to control the aircraft. Co-pilot 1 did not hold the licence required by the company - ATPL(A).
• The PIC’s type experience was relatively low due to the recent re-training to A340.
• The PIC’s experience on long-haul flights was very low.
• Due to their flight hours on type and on long-haul flights, co-pilot 1 and co-pilot 2 were experienced.
• The manual deactivation of the autopilot did not correspond with the overspeed recovery procedure. This action aided the later temporary loss of control.
• The flight crew did not know the airspeed at which high speed protection becomes active and the autopilot is automatically deactivated. The filtered Mach system logic was not known to them. • The dynamic pitch up control inputs were too abrupt which caused a higher gload which resulted in Vprot increase.
• The decision to apply OEB No. 49 was not correct since the entry conditions were not given.
• Both pilots misinterpreted the Vprot increase as entry condition for the OEB No. 49. The PIC followed his interpretation and instructed to switch off two ADRs.
• The A/THR was deactivated because of the shut-down of the two ADRs whereby flight idle thrust was continued.
• The completion of the OEB No. 49 checklist under consideration of the entry conditions the aircraft manufacturer had stipulated was not observed.
• For about four years, OEB No. 49 had been in the QRH. Prior to each flight, the flight crew had to brief the OEB procedure.
• The recovery of the flight attitude, after the stall warning had been active, was late, insufficient and not forceful enough.
• The pilots’ situational awareness that protection systems of the aircraft had been deactivated was limited. Prior to the stall warning activation, they were not aware that speed was reducing and engine thrust was in flight idle.
• Insufficient monitoring of cockpit instruments, because the pilots neither reacted to the change in engine values nor to the airspeed and therefore did not apply the respective procedures. This resulted in a critical flight attitude.
• Insufficient cooperation and cockpit communication due to non-action (e. g. Stall Recovery Procedure) in critical flight attitudes
The Report also highlighted that the Co-pilot 1 did not perform his task as pilot monitoring during the stall recovery and During the Stall Warning, the flight crew lost situational awareness and temporarily control of the aircraft.
The wrong application of the OEB No. 49 and the inconsistent implementation of the later necessary recovery procedures, including Standard Operating Procedures, e.g. respective call-outs, and abnormal procedures, show that they were not correctly applied.
As per the report , SAA has implemented new processes to check pilots’ licences and the checklists of the training department and flight operations were adapted to ensure that the simulator software version and that of the real aircraft concur. The flight operations and training department now monitor pilots’ training.
Meanwhile, SAA responded to the report, saying: “SAA is aware that the report in question was published on the German regulatory website of the German Federal Bureau of Aircraft and Accident Investigation. SAA has not officially received the report from the SACAA nor the German regulator.
“It must be noted that this safety report relates to an incident which occurred in November 2018, both SAA and the SACAA had previously completed and provided inputs to the German Investigative Authority prior to business rescue and subsequent restructuring of the airline.
“The company has been reorganised and relaunched under new management, and according to current management procedures and SAA’s Safety Management System, as soon as this report is officially received and confirmed, SAA will study the report judicially. A response on the findings and any possible remedial actions required will be communicated to all stakeholders and implemented internally.”
The involved Airbus A340-642 is a four-engine transport aircraft with a MTOM of 347,630 kg. It is powered by four Rolls-Royce Trent 556-61 jet engines. As part of the Air Operator Certificate, the aircraft was certified for commercial passenger transport. In accordance with SACAA regulations, it had a certificate of registration.
Display Picture Credit : Bougainvillea / Picture For representation Only.
