An Africa Airlines Avions de Transport Regional ATR-72-212A, registration TN-AKA performing AW-102 or AW-104 from Brazzaville to Pointe Noire (Congo), was climbing through about FL140 out of Brazzaville when the fire alarm for the left hand engine (PW127F) sounded. The crew worked the related checklist, shut the engine down and continued to Pointe Noire on one engine for a safe landing.
Congo's BEA rated the occurrence an incident and opened an investigation.
Congo's BEA released their final report in French (editorial note: to serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a French only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe).
The final report concludes the probable causes of the serious incident were:
The shutdown of the left engine resulted from an interruption in the
fuel supply. This situation was linked to a prolonged period of uncorrected
side slip, which caused a lateral roll of approximately 5 degrees, disrupting the transfer of fuel to the associated feeder tank. This asymmetry, combined with a reduced fuel level in that compartment, led to the cessation of engine fuel supply and a loss of power.
Contributing Factors
- Prolonged use of the autopilots Vertical Speed (VS) mode without supervision contributed to a loss of airspeed falling below the minimum speed. This could have led to a loss of control of the aircraft.
- The failure to effectively correct the sideslip observed on the yaw indicator (white ball) maintained an aerodynamic asymmetry, causing an imbalance in fuel transfer and increasing the crews workload.
- Insufficient coordination between the pilot flying and the pilot monitoring, particularly regarding task allocation and the management of alerts, delayed the proper implementation of emergency procedures.
- The presence of two non-essential persons in the cockpit, as well as the fact that the cockpit door remained open during the critical phase, distracted the pilots and impaired internal communication, affecting the quality of the response to the anomaly and decision-making.
- The presence of a yaw damper with internal corrosion and a broken ground wire, which were not detected during maintenance operations, impaired yaw control and contributed to the difficulty in controlling the aircraft.
The BEA summarized the sequence of events:
The captain was pilot flying, the first officer pilot monitoring, a third person was on the flight deck in the center service seat. When the aircraft climbed through 3500 feet for FL160 the autopilot was engaged, 3 seconds later a warning activated on the Advisory Display Unit (ADU) which disappeared when the Touch Control Steering was activated. At that time the aircraft was drifting leftwards with a bank of about 5 degrees to the left, the yaw indicator (white ball) showing a consistent leftward deviation, the heading oscillated between 272 and 276 degrees. Repetitive warning messages appeared on the ADU: "RETRIM ROLL L WING DN" and "AILERON MISTRIM". Inputs via TCS and crew adjustments to the left aileron tab resulting in moderate roll oscillations and heading fluctuations of up to 10 degrees. About 90 seconds later the spring tab controlling the vertical rudder moved from -2.5 degrees to -5.5 degrees before changing to +2.5 degrees. 9 minutes later the autopilot changed from HDG to LNAV mode, the heading stabilized at 267 degrees.
Climbing through FL136 the autopilot was switched from maintaining IAS to vertical speed with varying settings, the airspeed fluctuated between 168 and 179 KIAS.
About 21 minutes into the flight, while climbing through FL149 left hand fuel flow and leeft hand engine torque dropped to zero, the high and low pressure turbine speeds decreased. A brief master warning was issued, the airspeed decreased, bank angle, pitch and angle of attack changed. A brief auto-relight period happened, the left hand engine nearly reached the right hand's torque, then the propeller speed control lever was moved into FTR and the left propeller speed and torque dropped to zero. The airspeed decreased to 141 KIAS, the pitch increased to +9 degrees and the AoA to 9.6 degrees. The aircraft rolled sharpy to the left to 30 degrees, the spring tab controlling the rudder moved from +1.9 to -18.1 degrees with no significiant movement of the rudder. The airspeed decreased further to 121 KIAS, the autopilot was disengaged and the captain applied nose down inputs, the airspeed rcovered to 152 KIAS.
About 22 minutes after departure the yaw damper was disengaged, the rudder made a sharp rightward correction from 3.5 to 13.7 degrees in one seconds and the aircraft rolled right to a maximum of 13.7 degrees right.
Two successive master warnings occurred accompanied by drops in left hand fuel flow and left hand engine rpm to zero.
The left engine power lever was reduced to idle, the right hand power lever to RAMP, and the crew initiated the engine fire procedure.
The aircraft landed in Pointe Noire without further incident about 77 minutes after departure.
Congo's BEA rated the occurrence an incident and opened an investigation.
Congo's BEA released their final report in French (editorial note: to serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a French only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe).
The final report concludes the probable causes of the serious incident were:
The shutdown of the left engine resulted from an interruption in the
fuel supply. This situation was linked to a prolonged period of uncorrected
side slip, which caused a lateral roll of approximately 5 degrees, disrupting the transfer of fuel to the associated feeder tank. This asymmetry, combined with a reduced fuel level in that compartment, led to the cessation of engine fuel supply and a loss of power.
Contributing Factors
- Prolonged use of the autopilots Vertical Speed (VS) mode without supervision contributed to a loss of airspeed falling below the minimum speed. This could have led to a loss of control of the aircraft.
- The failure to effectively correct the sideslip observed on the yaw indicator (white ball) maintained an aerodynamic asymmetry, causing an imbalance in fuel transfer and increasing the crews workload.
- Insufficient coordination between the pilot flying and the pilot monitoring, particularly regarding task allocation and the management of alerts, delayed the proper implementation of emergency procedures.
- The presence of two non-essential persons in the cockpit, as well as the fact that the cockpit door remained open during the critical phase, distracted the pilots and impaired internal communication, affecting the quality of the response to the anomaly and decision-making.
- The presence of a yaw damper with internal corrosion and a broken ground wire, which were not detected during maintenance operations, impaired yaw control and contributed to the difficulty in controlling the aircraft.
The BEA summarized the sequence of events:
The captain was pilot flying, the first officer pilot monitoring, a third person was on the flight deck in the center service seat. When the aircraft climbed through 3500 feet for FL160 the autopilot was engaged, 3 seconds later a warning activated on the Advisory Display Unit (ADU) which disappeared when the Touch Control Steering was activated. At that time the aircraft was drifting leftwards with a bank of about 5 degrees to the left, the yaw indicator (white ball) showing a consistent leftward deviation, the heading oscillated between 272 and 276 degrees. Repetitive warning messages appeared on the ADU: "RETRIM ROLL L WING DN" and "AILERON MISTRIM". Inputs via TCS and crew adjustments to the left aileron tab resulting in moderate roll oscillations and heading fluctuations of up to 10 degrees. About 90 seconds later the spring tab controlling the vertical rudder moved from -2.5 degrees to -5.5 degrees before changing to +2.5 degrees. 9 minutes later the autopilot changed from HDG to LNAV mode, the heading stabilized at 267 degrees.
Climbing through FL136 the autopilot was switched from maintaining IAS to vertical speed with varying settings, the airspeed fluctuated between 168 and 179 KIAS.
About 21 minutes into the flight, while climbing through FL149 left hand fuel flow and leeft hand engine torque dropped to zero, the high and low pressure turbine speeds decreased. A brief master warning was issued, the airspeed decreased, bank angle, pitch and angle of attack changed. A brief auto-relight period happened, the left hand engine nearly reached the right hand's torque, then the propeller speed control lever was moved into FTR and the left propeller speed and torque dropped to zero. The airspeed decreased to 141 KIAS, the pitch increased to +9 degrees and the AoA to 9.6 degrees. The aircraft rolled sharpy to the left to 30 degrees, the spring tab controlling the rudder moved from +1.9 to -18.1 degrees with no significiant movement of the rudder. The airspeed decreased further to 121 KIAS, the autopilot was disengaged and the captain applied nose down inputs, the airspeed rcovered to 152 KIAS.
About 22 minutes after departure the yaw damper was disengaged, the rudder made a sharp rightward correction from 3.5 to 13.7 degrees in one seconds and the aircraft rolled right to a maximum of 13.7 degrees right.
Two successive master warnings occurred accompanied by drops in left hand fuel flow and left hand engine rpm to zero.
The left engine power lever was reduced to idle, the right hand power lever to RAMP, and the crew initiated the engine fire procedure.
The aircraft landed in Pointe Noire without further incident about 77 minutes after departure.
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