Air India flight AI2379 travelled from Phuket to Delhi on August 4. However, the incident involved more than ordinary turbulence, according to Airbus’s initial engineering report. The document says all three hydraulic systems failed one after another. Consequently, major control surfaces stopped responding for nearly four seconds. During that period, the aircraft suddenly dropped around 300 feet. Several people onboard suffered injuries.
Air India had asked Airbus technical questions after the incident. Airbus’s engineering team then sent this preliminary response. The document says engineers decoded data from the Flight Data Recorder. They prepared the initial assessment using that information. However, Airbus has not presented this report as a final conclusion.
The document identifies the aircraft as an Airbus A320neo. It also records the route from Phuket’s VTSP airport to Delhi’s Indira Gandhi International Airport.
Airbus mapped the entire sequence second by second. The critical event lasted only seven seconds. During that window, all three hydraulic systems failed. The aircraft’s nose rose unexpectedly. Autopilot disconnected, while pilot commands produced no response. Surprisingly, the systems later recovered automatically.
Green Failed First, Then Blue and Yellow Followed
Aircraft wings and tails contain movable surfaces that control climbing, descending, and turning. Hydraulic pressure powers these components, much like fluid pressure operates vehicle brakes.
The A320 carries three separate hydraulic systems called Green, Blue, and Yellow. Designers use three systems so remaining units can support control after one failure. However, AI2379 allegedly lost all three within roughly one second.
The Green system failed first. That failure disabled Green control for the left elevator and both ailerons. Two spoilers also stopped working. However, aircraft systems automatically switched to backup channels. Until that moment, behaviour matched the intended design.
During the following second, Blue and Yellow also failed. At that point, no backup remained. Elevators controlling nose movement stopped working. Ailerons responsible for banking also became ineffective. Remaining spoilers also shut down.
Airbus says these surfaces remained unavailable for around four seconds. Without hydraulic pressure, airflow began moving them freely. The ailerons reportedly shifted by nearly 13.5 degrees. Consequently, the aircraft’s nose moved upward.
Autopilot then disconnected. According to the report, pilots commanded the nose downward fully. However, control surfaces did not respond because they remained inactive. In simple terms, pilots issued commands while the aircraft failed to follow them.
Control Returned, but the Cause Remains Unclear
Around seven seconds later, the Blue system returned first. Yellow recovered several seconds afterwards, followed by Green. Once pressure returned, control surfaces began working again. Pilots then regained command of the aircraft.
The automatic recovery itself raises another investigation question. If any physical component had completely broken, spontaneous restoration would appear unusual.
Airbus says the flight-control behaviour resulted from lost hydraulic pressure. The report records low-pressure indications from at least two pressure switches. Engineers also detected an issue involving one Green-system pressure switch.
However, the document does not claim hydraulic fluid leaked. It also does not state that any pump failed. Instead, it only says sensors showed low pressure.
Therefore, investigators still must determine what actually happened. Genuine pressure loss remains one possibility. Incorrect signals from sensors or wiring represent another. Airbus has consequently requested a broader technical investigation.
The company asked Air India to conduct operational tests on all three hydraulic systems. Airbus also specified separate checks for pressure switches, transducers, and related indication systems.
Additionally, engineers requested removal and identification of pressure transducers plus leak-measuring switches on a designated panel. Airbus said wiring checks may also become necessary. The company plans to provide further instructions later.
Airbus also requested complete maintenance records for hydraulic work performed during the previous month.
Automatic Flight Systems, Airframe and Pilot Reports Also Face Review
Airbus also requested data from computers linked with the automatic flight system. Engineers want information covering the exact date and time of the incident. Moreover, they asked for ground scanning plus prescribed testing of that entire system.
Therefore, investigators are not limiting their work to hydraulics. They are also examining the aircraft’s automatic control architecture.
The report further says the sudden altitude change may have placed excessive stress on the aircraft structure. Therefore, Airbus requested a specific structural inspection and corresponding results.
The company also warned that the jolt could have affected the airframe. Depending on inspection findings, engineers may add further checks.
Airbus acknowledged that the case remains complicated. Therefore, reaching a final technical conclusion may take longer than usual cases.
The company has also requested detailed reports from the pilots. Investigators need those accounts to understand what crews saw and experienced inside the cockpit.
When Airbus prepared this assessment, it had not yet received the complete crew account.
Importantly, this document represents only Airbus’s preliminary assessment. The company itself describes it as an initial analysis and seeks additional information.
India’s Aircraft Accident Investigation Bureau retains authority to determine the actual cause. AAIB continues investigating the incident.
For now, Air India and DGCA have issued no public statement regarding this technical assessment.
