NEW DELHI: A preliminary report by the Aircraft Accident Investigation Bureau (AAIB) has provided a detailed account of the August 4 incident involving Air India flight AI-2379 from Phuket to Delhi.The report examines the pilots’ post-flight medical tests, a series of hydraulic-system failures, the aircraft’s sudden altitude upset, the response of the flight crew, injuries caused inside the cabin and damage to the aircraft.Here are the key points that are covered in the report.
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- Pilot’s psycho-active substance test: Both pilots underwent post-flight medical checks after the aircraft landed in Delhi. Their breath analyser tests were satisfactory. However, a psycho-active substance detection test found the Pilot-In-Command’s sample to be non-negative. His blood sample was subsequently sent for confirmatory testing, which was also found to be non-negative. The co-pilot tested negative in both tests.
- What triggered the incident: The aircraft was cruising at FL360, or about 36,000 feet, when its flight-control system detected a loss of pressure in the green hydraulic system at 04:02:43 UTC. Four seconds later, it detected the loss of the blue and yellow hydraulic systems too.
- Autopilot disengaged: At 04:02:48 UTC, the aircraft’s autopilot disengaged, and a continuous repetitive chime sounded. Three seconds later, a stall warning was triggered for two seconds.
- Aircraft suddenly moved away from its assigned altitude: The co-pilot, who was the pilot flying, initially responded to the situation. The pilot-in-command then took over the controls. During the altitude upset, the aircraft gained 372 feet and then fell 292 feet from its assigned FL360.
- Hydraulic systems recovered: The blue hydraulic system recovered at around 04:02:52 UTC. The yellow and green systems recovered a few seconds later. The recovery restored the flight-control surfaces, and the aircraft returned to normal operating condition.
- Why passengers were injured: The aircraft was cruising at FL360 when the altitude upset occurred and, crucially, the seat-belt signs were off. The sudden movement resulted in injuries to passengers and cabin crew. The cabin supervisor informed the cockpit about the injuries.
- 24 people needed medical attention: On landing in Delhi, the airport medical team treated 20 passengers and four cabin crew members. Twenty were discharged after initial treatment for minor injuries, while four people with serious injuries were hospitalised for further treatment.
- Crew chose to continue to Delhi: After assessing the cabin situation, the flight crew decided not to divert to the nearest en-route airport and continued towards Delhi. They later requested medical priority from Delhi ATC. The aircraft landed safely at IGI Airport at 05:30 UTC.
- Aircraft suffered cabin damage: The altitude upset also caused damage inside the aircraft. The report records cracked and deformed ceiling panels, dislocated passenger-service-unit panels, broken handrails, damaged emergency-exit hardware and dislodged overhead-bin doors. An overhead-bin divider was cracked, a lavatory commode was uprooted, a crew seat was bent, and panels around the rear crew-door area were severely damaged.
- Hydraulic failure being investigated: The A320 has three hydraulic systems, known as green, blue and yellow. The systems provide hydraulic power to major aircraft systems. AAIB has removed relevant hydraulic components and collected hydraulic samples for further analysis.
- Warnings recorded after the flight: The aircraft’s post flight report recorded a sequence of warnings including “HYD GREEN SYS LO PR”, followed by blue and yellow hydraulic warnings. It also recorded “AUTO FLT AP OFF” and an elevator fault.
- Aircraft had an existing MEL item: Before departing Phuket, maintenance personnel found no discrepancies other than an already invoked minimum equipment list (MEL) item. The aircraft had been dispatched under MEL item 29-23-01A, relating to the power transfer unit (PTU), which had been invoked on July 28. The crew’s walk-around inspection found no discrepancies.
- No adverse weather reported: Despite the incident initially being notified as a turbulence encounter, the report says no adverse weather was reported by either the flight crew or ATC during the altitude upset.
- Experienced pilot-in-command: The 34-year-old PIC held a valid ATPL and had 5,055 hours of total flying experience, all recorded on the aircraft type. He had flown the type on August 3, the day before the incident. His recorded rest period before the flight was 21 hours and 59 minutes.
- Co-pilot was flying when the event began: The 32-year-old co-pilot held a valid CPL and had 1,393 hours of flying experience. The report identifies him as the pilot flying during the incident, while the PIC was the pilot monitoring before taking over the controls.
- AAIB calls finding a serious concern: The report says, “The confirmation of use of psycho-active substance is a serious concern, and AAIB recommends appropriate actions by DGCA on priority.” It separately recommends that the DGCA take appropriate measures to prevent abuse of psycho-active substances.
- Flight recorders are being examined: Both the cockpit voice recorder and flight data recorder were recovered. Their downloaded data is now with the investigation team for analysis.
- Airbus experts examined the aircraft: Technical experts assigned by France’s BEA, including Airbus experts, inspected the aircraft from August 13 to 15. Hydraulic components and samples were subsequently collected for testing.
AAIB says the detailed investigation into the technical and other aspects is still underway. Maintenance and operational records, fuel and oil samples, ATC data and flight-recorder information are among the material being examined.The preliminary report records both the hydraulic-system failures and the PIC’s non-negative confirmatory psycho-active substance test, but it does not establish that the substance finding caused the altitude upset. AAIB says the investigation remains in progress and that a final report will be published later.
