The Airbus A320, carrying 137 passengers, was flying from Phuket to Delhi on August 4 when it experienced a sudden altitude variation of about 300 feet.
Airbus’ preliminary technical assessment of the Air India flight AI2379 that suddenly lost around 300 feet of altitude has revealed that all three of the aircraft’s hydraulic systems were affected in a sequence of failures, temporarily disrupting its elevator and aileron control surfaces for about four seconds.
The Airbus A320, carrying 137 passengers, including three infants, and eight crew members, was flying from Phuket to Delhi on August 4 when it experienced a sudden altitude variation of about 300 feet 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 sustained injuries in the incident.
Airbus conducted its initial assessment after analysing data from the aircraft’s Digital Flight Data Recorder (DFDR).
Triple Hydraulic Failure
According to an Airbus Customer Services technical dossier dated August 10, a failure was first recorded in the Green Hydraulic system at around 04:02:44. About a second later, the Blue and Yellow hydraulic systems were also affected.
The sequence temporarily affected the aircraft’s elevator and aileron control systems on both sides. Airbus estimates that the control surfaces were affected for approximately 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, with their deflection 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.
Following the disconnection, the first officer applied a full nose-down pitch input. The hydraulic systems began recovering within seconds, with the Blue system recovering at approximately 04:02:51, followed by the Yellow and Green systems.
As hydraulic pressure was restored, the aircraft’s flight-control surfaces also returned to normal operation.
Airbus Orders Checks Of All Three Hydraulic Systems
Following its preliminary assessment, Airbus has asked Air India to conduct operational tests of the aircraft’s Green, Blue and Yellow hydraulic systems.
The manufacturer has also sought inspections of the relevant pressure switches, pressure transducers and leak measurement switches. Air India has been asked to provide details of maintenance work carried out on the aircraft’s hydraulic systems during the month preceding the incident.
The Automatic Flight System is also being examined, with Airbus recommending system testing and ground scanning. It has sought specific data relating to the Flight Guidance/Flight Control Computer and the Flight Augmentation Computer.
Aircraft To Undergo Structural Inspection
The sudden change in altitude also resulted in recorded load exceedances, according to Airbus.
As a result, the aircraft will require a detailed structural assessment in addition to inspections of its various systems. Airbus has also asked Air India to provide detailed reports from the pilots describing what they observed and the circumstances surrounding the incident.
