New Delhi: The preliminary report by the Aircraft Accident Investigation Bureau (AAIB), has said that flight AI 2379 from Phuket to Delhi on August 4 suffered a temporary loss of pressure in all three hydraulic systems, triggering an autopilot disengagement, stall warning and altitude upset.
The report also noted that the Pilot In Charge (PIC), with over 5,000 hours of flying experience, tested non-negative to psyco-active substance, with the AAIB recommending appropriate action by the Directorate General of Civil Aviation (DGCA).
The aircraft, with 137 passengers, was cruising at Flight Level 360 when the incident occurred. The aircraft’s flight-control system first detected a loss of pressure in the green hydraulic system. Within seconds, the blue and yellow hydraulic systems also showed a loss of pressure, the report states.
The autopilot disengaged and a continuous repetitive chime sounded. A stall warning was subsequently triggered for two seconds, it said.
The aircraft experienced a significant altitude upset during the incident. It initially climbed 372 feet before descending 292 feet from its assigned FL360. The hydraulic systems subsequently recovered, allowing the aircraft’s flight-control surfaces to function normally.
The co-pilot, who was the pilot flying at the time, initially responded to the situation before the PIC took over the controls.
The incident also resulted in injuries inside the cabin. With the seat-belt signs off, passengers and cabin crew were thrown around during the altitude upset.
A total of 24 people — 20 passengers and four cabin crew members — received medical treatment after the aircraft landed in Delhi. Twenty people were discharged after treatment for minor injuries, while four people with serious injuries were hospitalised.
The aircraft also sustained damage to several cabin components, including overhead ceiling panels, passenger-service units and overhead-bin doors.
An emergency-exit handle and handrails were broken, while a lavatory fixture was uprooted and parts of crew seats were damaged, the report added.
Despite the incident, the flight crew decided against diverting to the nearest en-route airport and continued towards its scheduled destination, Delhi.
The crew later contacted Delhi Air Traffic Control and requested medical priority. The aircraft landed safely on Runway 11L at Indira Gandhi International Airport at 11 AM IST and taxied to its parking bay under its own power, arriving at 11:07 AM IST.
“Detailed investigation regarding technical and other aspects are underway. In this case, it has been observed that the PIC was found non-negative for psycho-active substance in the confirmatory test. The confirmation of use of psycho-active substance is a serious concern and AAIB recommends appropriate actions by DGCA on priority,” the report stated.