The Air India flight from Phuket to Delhi lost around 300 feet of altitude after all three of its hydraulic systems were affected in a sequence of failures, according to Airbus’ preliminary technical assessment.
The Airbus A320, carrying 137 passengers, including three infants, and eight crew members, was flying on August 4 when the incident occurred at around 04:02 local time. The aircraft later stabilised and landed safely in Delhi. The Aircraft Accident Investigation Bureau (AAIB) said 20 passengers and four cabin crew members were injured.
Three hydraulic systems affected
Airbus analysed data from the aircraft’s Digital Flight Data Recorder (DFDR) and found that the Green Hydraulic system recorded a failure at around 04:02:44. About a second later, the Blue and Yellow systems were also affected.
The sequence temporarily disrupted the aircraft’s elevator and aileron control systems on both sides for around four seconds. During this period, the right elevator moved to around +0.6 degrees, while the left elevator moved to approximately -1.0 degrees. The ailerons entered damping mode, contributing to an increase in the aircraft’s pitch.
Autopilot disconnected during incident
Airbus said AP2, or Autopilot 2, disconnected at around 04:02:46. The first officer then applied a full nose-down pitch input.
The hydraulic systems started recovering within seconds. The Blue system recovered at approximately 04:02:51, followed by the Yellow and Green systems. As pressure returned, the flight-control surfaces also resumed normal operation.
Airbus has asked Air India to conduct operational tests of all three hydraulic systems and inspect the relevant pressure switches, pressure transducers and leak measurement switches. It has also sought details of maintenance work carried out on the hydraulic systems during the month before the incident.
Aircraft faces further inspections
The aircraft recorded load exceedances during the sudden altitude change and will undergo a detailed structural assessment.
Airbus has also recommended testing and ground scanning of the Automatic Flight System and sought data relating to the Flight Guidance/Flight Control Computer and Flight Augmentation Computer. Pilots have also been asked to provide detailed reports on what they observed during the incident.
Pilot’s drug test also under probe
The developments come days after sources said the pilot-in-command (PIC) tested positive for marijuana in a confirmatory drug test.
The pilot reportedly told investigators that he had been prescribed sleeping pills due to personal problems and claimed that the medication resulted in his positive drug test. His conduct during the flight is also being examined after cabin crew members reportedly raised complaints about his behaviour.
According to The Times of India, the PIC appeared to be under the influence of psychoactive substances during the flight. A person familiar with the matter alleged that the pilot was repeatedly sitting on the cockpit floor and attempting to smoke before cabin crew intervened.