Jet temporarily lost pressure in all three hydraulic systems, investigators say.
The captain of an Air India flight that experienced a dramatic altitude drop while flying from Phuket to Delhi tested “non-negative” for a psychoactive substance in a confirmatory test, according to a preliminary investigation into the incident.
The Aircraft Accident Investigation Bureau (AAIB) described the result as a “serious concern” and recommended that the Directorate General of Civil Aviation (DGCA) take appropriate action as a priority.
The co-pilot tested negative in both the initial screening and confirmatory tests.
The finding comes as investigators revealed that flight AI2379 temporarily lost pressure in all three hydraulic systems during the August 4 incident, affecting the Airbus A320’s flight controls.
The AAIB has not established any link between the captain’s test result and the technical failure or the aircraft’s sudden change in altitude. The investigation is ongoing.
What happened at 36,000 feet
According to the AAIB’s preliminary findings, the aircraft was cruising at 36,000 feet when its flight-control system detected a loss of pressure in the Green hydraulic system.
Four seconds later, pressure was also lost in the Blue and Yellow hydraulic systems. The autopilot then disengaged, triggering a warning in the cockpit, while a stall warning sounded briefly.
The co-pilot, who was flying the aircraft at the time, initially attempted to regain control before the pilot-in-command took over.
During the upset, the aircraft first climbed 372 feet above its assigned altitude before descending 292 feet below it.
The Blue hydraulic system recovered first, followed seconds later by the Yellow and Green systems, restoring operation of the aircraft’s flight-control surfaces.
Reuters reported last month, citing an initial Airbus analysis, that the aircraft’s elevators and ailerons were unavailable for about four seconds following the loss of hydraulic pressure. The assessment did not determine what caused the pressure loss.
24 injured
The aircraft, registered as VT-EXO, was carrying 137 passengers, including three infants, along with eight crew members.
Twenty passengers and four cabin crew members were injured during the incident.
The preliminary investigation found damage to several parts of the aircraft’s cabin, including ceiling panels and overhead storage compartments.
The aircraft stabilised after the hydraulic systems recovered and subsequently landed safely in Delhi.
The incident was initially reported as a turbulence encounter. However, the AAIB investigation has since focused on the loss of hydraulic pressure and the resulting altitude upset.
Captain’s test
Because the flight originated outside India, both pilots underwent post-flight breathalyser tests after arriving in Delhi. According to the preliminary report, both tests produced satisfactory results.
Both pilots were also screened for psychoactive substances.
The pilot-in-command’s sample returned a “non-negative” result in the initial screening, after which blood samples were sent to a laboratory for confirmatory testing.
The pilot-in-command’s confirmatory test also returned a “non-negative” result, while the co-pilot tested negative in both tests, according to the AAIB.
“The confirmation of use of psycho-active substances is a serious concern and AAIB recommends appropriate actions by DGCA on priority,” the preliminary report said.
Both pilots were removed from flying duties following the incident, pending the investigation and completion of the testing process.
Hydraulic systems under scrutiny
Investigators are examining why the Airbus A320’s three independent hydraulic systems registered pressure losses within seconds of one another.
An initial Airbus assessment reviewed by Reuters last month found that the Green, Blue and Yellow hydraulic systems lost pressure in quick succession, briefly leaving the pilots unable to operate the aircraft’s elevators and ailerons.
The assessment did not establish what caused the loss of hydraulic pressure.
Airbus asked Air India to carry out checks on the aircraft’s hydraulic systems, pressure sensors and switches, as well as inspections of certain components and wiring.
The AAIB’s investigation remains ongoing, and the bureau has stressed that the preliminary findings do not establish the probable cause of the incident.
The AAIB said a final investigation report will be published in due course.
