Daijiworld Media Network – New Delhi
New Delhi, Aug 14: Airbus’ preliminary technical assessment of Air India flight AI2379 has revealed that all three hydraulic systems of the aircraft were affected in a sequence of failures, temporarily disrupting the elevator and aileron control surfaces for around 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 suddenly lost around 300 feet in altitude at about 4.02 am 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 preliminary assessment after analysing data from the aircraft’s Digital Flight Data Recorder (DFDR).
According to the Airbus technical assessment, a failure was first recorded in the Green Hydraulic system at around 4.02.44 am. About a second later, the Blue and Yellow hydraulic systems were also affected.
The sequence temporarily disrupted the aircraft’s elevator and aileron control systems on both sides. Airbus estimated that the control surfaces were affected for approximately four seconds.
During the incident, 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.
Airbus said AP2, or Autopilot 2, disconnected at around 4.02.46 am.
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 4.02.51 am, followed by the Yellow and Green systems.
As hydraulic pressure was restored, the aircraft’s flight-control surfaces also returned to normal operation.
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.
The sudden altitude change also resulted in recorded load exceedances, according to Airbus. The aircraft will therefore 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.
The developments come days after the pilot-in-command of the Phuket-Delhi flight tested positive for marijuana in a confirmatory drug test, according to reports. The pilot has been taken off flying duties as the investigation continues.
The pilot reportedly told investigators that he had been prescribed sleeping pills because of personal problems and claimed that the medication resulted in his positive drug test. His conduct during the flight is also being examined following complaints reportedly raised by cabin crew members.
However, investigators have not established any link between the pilot’s drug-test result and the aircraft’s technical problems. The AAIB probe into the incident is continuing, with Airbus and other specialists assisting the investigation.
The preliminary technical findings do not by themselves establish the final cause of the aircraft’s sudden altitude loss.