An A320 Lost All Three Hydraulic Systems in Four Seconds

India’s Aircraft Accident Investigation Bureau has published findings on Air India flight AI 2379 that aviation engineers are struggling to explain. On 4 August the Airbus A320neo, registered VT-EXO, was cruising at 36,000 feet from Phuket to Delhi when the flight control system recorded a loss of pressure in the green hydraulic system at 04:02:43 UTC. Four seconds later it registered the loss of the blue and yellow systems as well. The aircraft climbed 372 feet, then dropped 292 feet, triggering a stall warning. Twenty-four people aboard were injured. The investigation remains open, with the focus still on the hydraulic systems.

What makes the finding unusual is the architecture of the aircraft. An A320’s three hydraulic systems are deliberately independent: separate reservoirs, separate pumps, no transfer of fluid between them. The design exists precisely so that a single failure, a leak or a contaminated fluid batch cannot take out more than one circuit. Losing all three within four seconds is not a scenario the redundancy was built to produce, and investigators have not yet identified a mechanism that would explain it. Earlier in the inquiry the AAIB sought detailed hydraulic maintenance records from the airline, suggesting servicing history is among the lines being examined.

A second finding sits alongside the technical one. The AAIB reported that the pilot in command tested non-negative for psychoactive substances following the flight, a result the bureau described as a matter of serious concern for aviation safety. A non-negative screening result is not a conviction and requires confirmatory testing to establish what was present and at what level, but it triggers immediate regulatory attention in India, where the Directorate General of Civil Aviation runs a mandatory random testing programme. The report does not link the test result to the cause of the upset.

For passengers, nothing about this changes how to book or fly. The A320neo family remains among the most heavily used and closely monitored airliners in service, and a preliminary report is a snapshot of an unfinished investigation rather than a verdict. What it does provide is an unusually clear window into how modern safety inquiries work: two separate concerns, one mechanical and one human, surfaced in the same document, neither yet established as causal, both published because investigators would rather share an incomplete picture than a delayed one.

Sources: FlightGlobal, Euronews