Air India replaced throttle module twice on crashed Dreamliner after Boeing directive

Air India replaced the Throttle Control Module (TCM) of its Boeing 787-8 that crashed last month twice in the last six years, following a maintenance directive from Boeing issued in 2019, PTI reported on Sunday, citing people familiar with the matter.

The TCM, which includes fuel control switches, was changed on the aircraft in 2019 and again in 2023, as mentioned in the Aircraft Accident Investigation Bureau’s (AAIB) preliminary report released on Saturday.

The report, however, stated that the replacements were not linked to the fuel control switches, which have come under scrutiny in the ongoing investigation.

Air India flight AI171 to London crashed 32 seconds after takeoff from Ahmedabad on June 12, killing all 241 on board and several others on the ground.

According to the AAIB, fuel supply to both engines was cut off within a second of each other immediately after takeoff.

Fuel switches regulate fuel flow into aircraft engines and have two positions – ‘RUN’ and ‘CUT OFF’.

In this case, the switches were cut off and then turned back on, but the engines failed to regain sufficient thrust before the aircraft crashed into a building.

The report suggests that Boeing’s revised Maintenance Planning Document (MPD) issued in 2019 requires operators to replace the TCM every 24,000 flight hours. Specific details of the MPD were not immediately available.

The AAIB report noted that the US Federal Aviation Administration (FAA) had issued a Special Airworthiness Information Bulletin in December 2018 about the potential disengagement of fuel control switch locking features on Boeing aircraft, but it was advisory and not mandatory.

"As per the information from Air India, the suggested inspections were not carried out as the SAIB was advisory and not mandatory. The scrutiny of maintenance records revealed that the throttle control module was replaced on VT-ANB in 2019 and 2023.

"However, the reason for the replacement was not linked to the fuel control switch. There has been no defect reported pertaining to the fuel control switch since 2023 on VT-ANB," the report said.

At this stage, the agency has not issued any recommended actions for operators or manufacturers of Boeing 787-8 aircraft or GE GEnx-1B engines.