The serious incident involving Air India flight AI2379, an Airbus A320 operating from Phuket to Delhi on 4 August 2026, has been widely described as a “triple hydraulic failure.” However, Airbus’s preliminary DFDR analysis suggests a more complex and technically significant event: a rapid, sequential loss of indicated hydraulic availability across the Green, Blue, and Yellow systems; a temporary loss of elevator and aileron control; and recovery of all three systems within seconds.
According to the publicly reported Airbus analysis, the Green hydraulic system was the first to register a loss of pressure, shortly before 09:32:44. About a second later, the Blue and Yellow systems also lost pressure. Elevator and aileron control then became unavailable for approximately four seconds. During this interval, the aircraft pitched up, and the First Officer applied a full nose-down sidestick input, but the flight-control surfaces initially showed no corresponding response. At about 09:32:51, the Blue system recovered first, followed shortly thereafter by the Yellow and Green systems. Flight-control response returned, the aircraft was stabilised, and the crew subsequently continued the flight to Delhi and landed safely.
This sequence is important because it does not resemble a conventional, sustained triple hydraulic failure involving major fluid loss or permanent loss of pressure generation. A serious leak sufficient to depressurise all three independent hydraulic systems would not normally disappear spontaneously within seconds. Nor would an aircraft suffering continuing total hydraulic loss be expected to regain normal flight-control authority and proceed to destination. The rapid restoration of all three systems therefore points more strongly to a transient common-mode disturbance, a hydraulic-pressure sensing anomaly, an electrical or wiring problem, or temporary removal of hydraulic actuators from service by the flight-control system. Airbus has reportedly requested checks of pressure switches, sensors, associated wiring, hydraulic-system condition, and recent maintenance history to establish whether the recorded pressure losses were genuine or the result of erroneous system indications.
The distinction is fundamental. A major technical difference exists between all three systems registering low or unavailable pressure and all three systems physically failing. Airbus’s preliminary analysis establishes the former, but the root cause remains unresolved.
The pitch-up during the approximately four-second interval also requires careful interpretation. It should not be automatically attributed to “aileron float-up.” Although a control surface deprived of hydraulic actuation may move under aerodynamic loads, the ailerons are primarily roll-control surfaces. Their contribution to pitch would depend on whether both surfaces moved symmetrically, their actual positions, aircraft speed and aerodynamic loading. The elevators and trimmable horizontal stabiliser are therefore equally, if not more, important in explaining the longitudinal response. If elevator servo-control capability was temporarily lost while the stabiliser remained at its cruise trim setting, the aircraft could experience a transient pitch change until hydraulic control was restored.
The A320 is fly-by-wire, but its primary flight controls are hydraulically actuated. The First Officer’s nose-down sidestick input could therefore be recorded electrically even when the elevators were temporarily unresponsive. The reported DFDR sequence—hydraulic indications deteriorating, loss of control-surface response, the aircraft pitching up, a full nose-down sidestick input producing no immediate effect, followed by the restoration of hydraulic capability and control response—matches that architecture.
The investigation will need to correlate Green, Blue and Yellow pressure and pressure-switch states with reservoir quantities, pump status, electrical-bus condition, flight-control computer status, elevator and aileron positions, THS position, sidestick inputs, pitch attitude, pitch rate and normal acceleration. Of particular importance is determining whether hydraulic pressure actually disappeared and, if so, why three independent systems were affected within roughly one second and recovered just as rapidly.
The fact that the aircraft subsequently stabilised, remained fully controllable, and continued to Delhi is one of the strongest indications that this was not a sustained loss of all three hydraulic systems involving major fluid depletion. A genuine fault in one system cannot yet be ruled out, but the available evidence is more consistent with a short-duration, common-mode hydraulic or hydraulic-sensing disturbance that temporarily deprived the aircraft of normal elevator and aileron authority.
At this stage, it is more accurate to describe AI2379 as a transient triple-system hydraulic-availability event rather than a confirmed physical failure of all three hydraulic systems. Airbus’s DFDR analysis has established the sequence and seriousness of the event; identifying the mechanism that caused it remains the investigation's central task.
Author: GR Mohan
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