The analysis has found flight records showing all the three hydraulic systems losing pressure at once, which is not possible. Because they are by design set up as independent units with separate power sources. Indications are that false signals interfered with the aircraft's controls leadng to autopilot getting cut off. Any external signal manipulation is ruled out although it is a rising dangerous global issue—If at least one proved right, many past accidents will have to be re-examined! Then what caused the Airbus incident?

NEW DELHI, Aug 14: A preliminary Airbus analysis of Air India Phuket-Delhi flight AI2379 mishap on August 4 has revealed a rapid triple hydraulic pressure drop that left key flight controls unresponsive for four seconds, causing a 300-foot altitude drop, injuring 13 passengers and and four crew.

Airbus has not established a definitive root cause or assigned fault, and investigations by the Aircraft Accident Investigation Bureau (AAIB) are ongoing alongside other factors like the pilot testing positive for drugs.

The Airbus A320neo aircraft was carrying 137 passengers and eight crew. The cause of the mishap reported as Clear Air Turbulence (CAT) was later interpreted as pilot's drug use. Now the manufacturer has come to the conclusion after primary inspection that the cause is neither of the two but what looked like a glitch in the hydraulic system of the aircraft.

Now further analysis is likely to point a finger at poor maintenance as the main cause of the malfunctioning or simply hardware fatigue? But all the three hydraulic systems losing pressure at once is not possible. And the cause of the mishap lies elsewhere.

The following is an expert analysis:-

The Airbus A320 lost flight controls for four seconds apparently after multiple hydraulic systems failures. The manufacturer's analysis showed that the aircraft suffered failure of three hydraulic systems within two seconds and the systems were recovered in seven seconds.

Just before 9:32:44 IST (4:02:44 UTC), there was loss of one hydraulic system, and at 9:32:45 IST (4:02:45 UTC), the two other hydraulic systems were also lost, as per the report. Then at 9:32:51, all three systems were recovered. Pressure switches showed loss of hydraulic pressure that led to the loss of actuators.

Flight data showed green, blue and yellow hydraulic systems registered pressure drops within one second of each other, triggering nine fault messages in one minute.

The aircraft briefly lacked normal elevator and aileron response for about four seconds, during which the co-pilot applied a nose-down input before hydraulic pressure recovered.

Air India initially blamed turbulence before shifting focus, while separate reports noted the pilot-in-command subsequently tested positive for a psychoactive substance (marijuana), keeping multiple lines of inquiry open.

Is Airbus at fault?

The preliminary Airbus data identifies a technical anomaly and pressure switch/component issues, but it does not prove a manufacturing or design defect.

Airbus has asked Air India to inspect and perform deeper maintenance checks on all three hydraulic systems, pressure switches, and transmitters to determine if it was a physical failure or a faulty sensor signal.

Then is it poor maintenance?

Pinpointing a sensor glitch doesn't immediately default to poor maintenance. Components can experience unpredictable hardware fatigue, internal wear, or localized electrical spikes between routine service intervals.

Airbus has ordered Air India to conduct fluid and pressure tests.

An Airbus A320 has three separate, independent hydraulic networks (Green, Blue, and Yellow) specifically so that a single failure cannot cause a disaster. For all three to log low-pressure warnings within one second is extremely rare.

The technical tests requested by Airbus will isolate what actually happened.

Differentiating a physical leak from a false reading:

Technicians will run operational pressure tests on all three lines and physically check the fluid levels in the Yellow and Blue reservoirs.

If the physical fluid levels are full and lines hold pressure, it proves the hydraulics never actually failed. Instead, a false electrical signal tricked the flight computer into triggering an emergency state, forcing the autopilot to disconnect.

Airbus specifically ordered the removal and bench-testing of the pressure switch on the Green system.

A pressure switch detects if the fluid pressure drops below a safe threshold. If this physical hardware piece is faulty, it can send an erroneous "zero pressure" alert to the cockpit even if the system is fully pressurized.

Air India must inspect the pressure transducers (which convert physical pressure into electrical data) and examine the aircraft's internal wire routing.

A localized wiring short circuit, wire chafing, or bad grounding could send a simultaneous electrical surge through multiple sensors. Finding broken insulation or moisture in the wire harnesses would explain the simultaneous multi-system warnings.

The investigation shifts to checking why fluid was lost or how independent lines crossed. This points toward localized maintenance wear or a rare mechanical breakage.

The flight controls did not actually freeze due to a lack of pressure. Instead, the sudden drop occurred because the flight computer reacted to bad data, prompting a stall warning and forcing the co-pilot to manually nose-down the aircraft to recover.

How a false signal tricks the system?

Modern commercial airplanes rely on Fly-by-Wire (FBW) technology. The pilots do not pull on physical cables to move the flaps or tail; instead, their cockpit controls send electronic requests to flight computers, which then command hydraulic actuators to move the flight surfaces.

A false electrical signal tricks this system in two main ways:

The Sensor Glitch: A pressure sensor relies on a steady electrical current to report system health. If a sensor suffers an internal short circuit, moisture ingress, or component breakdown, its electrical voltage drops to zero.

The Computer's Interpretation: The flight computer cannot "see" the physical hydraulic fluid. It only sees the voltage drop. The computer interprets this zero-voltage signal as a total loss of hydraulic pressure, even if the pipes are completely full of fluid.

Because all three independent hydraulic systems registered these "zero" readings within one second, the computers concluded that the aircraft had suffered a total, catastrophic hydraulic failure.

What happens when the autopilot disconnects?

When the computers detect conflicting data or a critical multi-system failure, they are programmed to instantly disconnect the autopilot. This is a deliberate safety design. The computer essentially tells the crew: "I can no longer guarantee safe flight using automated logic. Humans must take over immediately."

When the autopilot disconnected on Flight AI2379, the following chain reaction occurred:

1. Instant Degraded Flight Mode (Alternate Law) To protect the plane, the flight computers automatically dropped from "Normal Law" (where the computer prevents the pilot from over-stressing the aircraft) to "Alternate Law". In this mode, some automatic safety protections are stripped away, and the aircraft handles much more sensitively.
2. Cockpit Warnings and Confusion: An instantaneous barrage of loud master warning chimes and bright red alerts flashed on the electronic displays. The crew had to instantly diagnose a complex, multi-system emergency while the plane began to react dynamically to the environment.
3. Unintended Nose-Down Input The sudden lack of normal control response, combined with a momentary activation of a stall warning (likely triggered by the bad sensor data), led the co-pilot to manually apply a nose-down input using the side-stick. This manual correction, coupled with the brief loss of automated pitch control, caused the aircraft to plunge 300 feet in a matter of seconds.
4. The Recovery Fortunately, the false signals cleared after roughly four seconds. The computers recognized that pressure was normal, the flight controls responded properly to the manual inputs, and the crew stabilized the aircraft before making an emergency landing.

Why the pilot's nose-down input did not cause the initial plunge?

The aircraft controls were completely unresponsive when he pushed the stick. According to the preliminary Airbus flight data recorder analysis, the 300-foot drop was caused by a highly complex mechanical and computer timeline, rather than pilot panic.

The real timeline of the plunge

1. Total Hydraulic Loss: The aircraft's Green, Blue, and Yellow hydraulic systems dropped pressure simultaneously. This starved the mechanical actuators of physical power
2. Control Surfaces Drift: Because there was no hydraulic pressure holding them in place, the aircraft’s main flight controls—the elevators (which control pitch) and ailerons (which control roll)—physically drifted on their own without any pilot command. This mechanical drifting caused the aircraft to pitch down and begin its sudden plunge.
3. The Autopilot Disconnects & Stall Warnings Sound: Realizing it could no longer fly the plane, the autopilot disconnected. Simultaneously, the aircraft's computers generated an aerodynamic stall warning in the cockpit..
4. The Pilot Reacts Legally: Hearing a stall warning, the co-pilot followed standard international aviation training: he pushed his side-stick fully forward (nose-down) to lower the nose, gain airspeed, and break the supposed stall.
5. A 4-Second Freeze: For four agonizing seconds, the co-pilot held the stick forward, but the plane did not react to him because the hydraulic failure left the controls entirely unresponsive.
6. The Sudden Grip: After four seconds, the hydraulic pressure suddenly flooded back into the system. The flight control computers reconnected instantly. Because the co-pilot was still holding the stick forward, the plane immediately executed his full nose-down command violently.

The violent pitch-down trajectory when the controls finally responded caused a severe negative-G event. The pilot monitoring (the Captain, who was standing at the time) and any unbuckled passengers were instantly launched upward, hitting the ceiling of the jet. While the pilot's input didn't start the plunge, the extreme severity of the final drop was aggravated when the unresponsive controls suddenly "woke up" and registered his full stall-recovery maneuver all at once.

Something to do with electric supply? Is the power supply common?

The three hydraulic systems on the Airbus A320 do not share a common electrical power supply. In fact, their power architecture is intentionally separated to ensure that an electrical failure in one system cannot disable the others. Because the systems are fundamentally isolated, investigators are highly focused on an electrical power glitch, but they are looking at a shared data or sensing network rather than a shared power source.

How the hydraulic systems power architecture works

The Airbus A320 uses three independent hydraulic circuits—Green, Blue, and Yellow—specifically engineered to prevent a single point of failure from knocking out all three: Green, Yellow, Blue.

Additionally, a mechanical device called the Power Transfer Unit (PTU) can physically transfer pressure between the Green and Yellow systems without mixing their fluids. Because the plane's engines and core electrical generators were functioning normally during Flight AI2379, a total physical power loss to all three systems simultaneously is mechanically impossible.

If power isn't common, why did all three log a failure same time?

While the hydraulic pumps have different power sources, the electronic pressure switches and transducers that monitor them feed their data back to the cockpit through centralized warning computers. A localized electrical short circuit, a bad grounding wire, or a glitch in the Bus Power Control Unit (BPCU) can cause a momentary voltage drop across the sensor monitoring network. This would trick the computer into recording a triple pressure drop, even though the physical systems still had pressure.

Any foreign electronic interference?

No, a "faulty sensor signal" in an aircraft's internal hydraulic system does not imply ground-based hacking or foreign electronic interference. However, external signal manipulation is a rising dangerous fglobal issue, but internal mechanical systems operate differently from external communication systems.

The pressure switches, sensors, and transmitters in the hydraulic loops are physically hardwired inside the aircraft’s fuselage. They do not receive radio frequencies or external data feeds from the ground.

In this context, a faulty signal refers to an internal hardware breakdown, such as a short circuit in the wiring, a cracked physical pressure switch, or fluid contamination causing a sensor to glitch.

Concern about instruments being falsified from the ground is highly valid, but it is restricted to systems relying on external radio and satellite signals.

How signals are disrupted from the ground?

GPS Spoofing: Ground-based transmitters send fake, high-power satellite signals. This tricks the flight computer into displaying wrong coordinates or drifting off course, an issue that has spiked near conflict zones and major airports.

Spurious Warnings: Because TAWS relies on GPS data, ground-spoofed coordinates can trick the cockpit into screaming false terrain or collision alerts

Signal Jamming: Malicious radio frequency interference (RFI) from the ground can block or degrade landing signals during low-visibility approaches.

The investigators are dealing strictly with internal plumbing, wiring, and pressure sensors—not external electronic warfare.

Comprehensive system breakdown

Green System: This circuit is driven purely by a mechanical Engine-Driven Pump (EDP) mounted directly onto Engine 1. It operates without any backup electrical pumps, completely isolating it from the aircraft's electrical grids during normal operations.

Blue System: This network is entirely electrical under normal conditions, powered by a dedicated AC Electric Pump. If the aircraft suffers a total electrical failure, an emergency wind turbine called a Ram Air Turbine (RAT) automatically drops out of the belly of the plane to mechanically pump pressure using passing airflow.

Yellow System This circuit relies primarily on Engine 2's mechanical pump. However, it features extensive redundancy options, including an alternative electric pump (primarily used on the ground to operate the cargo doors without running the engines) and a manual hand pump.

Conclusion: There is no shared plumbing or fluid between these three systems. A physical failure across all three at once would require separate major leaks occurring at the exact same second. Not possible. No electric failure either. Because the power supplies are completely separated. So the focus shifts to the shared sensor monitoring wiring paths and the central Elevator Aileron Computers (ELAC) that gather information from all three lines simultaneously to trigger automated protection modes.