New Delhi: The investigation into the Air India Phuket-Delhi flight that suffered a sudden altitude upset last month has taken another turn after the pilot-in-command was found non-negative for a psychoactive substance in a confirmatory test.
The Aircraft Accident Investigation Bureau (AAIB) has now put the finding on record in its preliminary report into flight AI2379, which was flying from Phuket to Delhi on August 4. The Airbus A320 was carrying 145 people, including 137 passengers and eight crew members.
The aircraft was cruising at 36,000 feet when the trouble began.
According to the AAIB report, the aircraft detected a loss of pressure in its green hydraulic system at about 4:02:43 UTC. Four seconds later, the blue and yellow hydraulic systems also showed a loss of pressure. The autopilot then disconnected and a stall warning was triggered.
The aircraft briefly climbed 372 feet and then dropped 292 feet from its assigned altitude during the upset.
The hydraulic systems recovered within seconds and flight controls returned to normal. The crew decided to continue towards Delhi rather than divert to another airport. Later, the pilots requested medical priority from air traffic control before the aircraft landed safely at Delhi airport at 5:30 UTC.
The sudden movement inside the cabin left passengers and crew injured. Twenty-four people received medical assistance after landing, including 20 passengers and four cabin crew members. Twenty of them were discharged after treatment for minor injuries, while four people with more serious injuries were hospitalised.
The cabin itself also suffered damage. The AAIB found cracked ceiling panels, damaged overhead bins, broken handrails and other fittings inside the aircraft.
But the technical investigation is not the only issue now under scrutiny.
After the flight reached Delhi, both pilots underwent post-flight medical checks. Their breathalyser tests were satisfactory. They were also tested for psychoactive substances.
The initial screening of the pilot-in-command was non-negative. Blood samples from both pilots were then sent to a laboratory for confirmation. The confirmatory test for the pilot-in-command was again non-negative, while the co-pilot tested negative in both tests.
The AAIB has described the finding as a serious concern and has recommended that the Directorate General of Civil Aviation take appropriate action to prevent the abuse of psychoactive substances among aviation personnel.
Importantly, the preliminary report does not say that the substance found in the pilot’s test caused the hydraulic failure or the altitude upset. The investigation into the technical cause is still continuing.
The A320 has three separate hydraulic systems green, blue and yellow which provide power to important flight-control systems and other aircraft functions. Investigators are now examining how all three systems showed pressure loss within seconds of one another.
The aircraft had also been operating with a Minimum Equipment List item concerning its Power Transfer Unit, which had been invoked on July 28. The AAIB has removed relevant hydraulic components and collected hydraulic fluid samples for further examination.
Investigators have also recovered the cockpit voice recorder and flight data recorder. Their downloaded data is being examined along with maintenance and operational records.
Technical experts from Airbus, working through France’s Bureau of Enquiry and Analysis for Civil Aviation Safety, inspected the aircraft in Delhi between August 13 and 15. The investigation team has collected additional evidence from the aircraft and from other agencies involved in the flight.
The AAIB has stressed that its report is preliminary and subject to change. Its main purpose is to determine what happened and identify measures that could prevent a similar incident in the future, rather than assign blame.
For now, two separate questions remain on the table. One concerns why an aircraft at cruising altitude suddenly lost pressure in all three hydraulic systems and suffered an altitude upset. The other concerns the confirmed non-negative psychoactive-substance test involving the pilot-in-command.
Both are serious matters, but the preliminary report has not established a connection between them.
The final investigation will have to bring those pieces together the aircraft’s technical condition, the actions of the crew, the medical findings and the data recorded during those few critical seconds in the sky.
Until then, the AAIB’s findings remain preliminary, and the investigation continues.
