What happened
On 19 March 2009, a BAe 146-200 operated by South African Airlink experienced two separate engine-related incidents during a single day of scheduled domestic operations. The first event occurred after landing at George Aerodrome (FAGG), where the number 1 engine flamed out and the number 3 engine entered a hung state. Following line maintenance to rectify the issue, the aircraft departed George for Cape Town International Aerodrome (FACT).
During the return flight to Cape Town, the flight crew noted that the number 2 engine was not performing correctly en route. Upon landing on runway 19 at FACT, the aircraft suffered a four-engine flame out. As the throttles were moved to the ground idle position, the engines spontaneously spooled down to sub-idle levels and flamed out. The aircraft managed to roll forward using its remaining momentum to vacate the runway onto taxiway Charlie, where the crew eventually restarted the engines after consulting maintenance personnel.
The investigation
SACAA AIID investigators examined the maintenance history and the mechanical state of the Thrust Modulation System (TMS). The investigation established that the aircraft's TMS had been deactivated during base maintenance to address a known fault. While the manufacturer's manual required the removal of three primary circuit breakers to depower the system, the Aircraft Maintenance Organisation (AMO) had instead pulled seven circuit breakers, including four actuator centering breakers.
Crucially, the maintenance documentation failed to record that the four centering circuit breakers had been removed. This omission meant that line stations were unaware of the improper configuration. The investigation confirmed that because these specific breakers were pulled, the actuators failed to center. Consequently, when the crew retarded the throttles to ground idle during landing, the retracted actuators caused the power levers to move below the required idle position, triggering the uncommanded engine shutdowns.
Findings
- The primary cause of the four-engine flameout was the improper deactivation of the TMS by the maintenance organization.
- The AMO failed to adhere to the manufacturer's maintenance manual and the Minimum Equipment List (MEL) procedures.
- The removal of the four actuator centering circuit breakers prevented the actuators from returning to their proper position.
- There was a lack of communication and documentation regarding the specific circuit breakers pulled during maintenance.
- The maintenance organization's training did not sufficiently emphasize the necessity of duplicate inspections for engine control system maintenance.