Phuket-Delhi flight: Probe finds hydraulic failure; pilot sacked

Mumbai: A preliminary investigation by the Aircraft Accident Investigation Bureau (AAIB) found that an Air India Airbus A320 briefly lost pressure in all three hydraulic systems at 36,000 feet during an August 4 flight. The incident caused the aircraft to gain and then lose altitude, triggering an autopilot disconnect and a stall warning and injuring 24 people.

The pilot-in-command on the Phuket-Delhi flight, later found positive for a psychoactive substance, was sacked by the carrier, Air India said Friday.

The AAIB did not have any direction for Airbus or engine maker CFM International.


Experts said the simultaneous loss of all three hydraulic systems was uncommon and raised questions about a possible common cause.

Air India flight AI2379, an Airbus A320-251N, was carrying 145 people.

"The confirmation of use of psycho-active substance is a serious concern," the bureau said, recommending that the Directorate General of Civil Aviation (DGCA) take "appropriate actions" on priority to prevent the abuse of psychoactive substances.

Air India said Friday it had terminated the pilot's employment with immediate effect and was cooperating with investigators by providing access to relevant "operational, maintenance and technical records."

Eyes on Power Transfer Unit

The airline has also started voluntary testing of all its pilots and said it has "zero tolerance" for any breach of safety, fitness or regulatory requirements.

The three hydraulic systems, which operate independently, lost pressure within seconds while the aircraft was in cruise. Aviation safety expert Captain John Cox, president and CEO of Safety Operating Systems LLC and a former A320 captain, said the simultaneous failure was highly unusual.

"The remote idea that three hydraulic systems are going to fail simultaneously goes against everything I know about how airliners are designed and built," he said.

The aircraft detected a loss of the green hydraulic system at 04:02:43 UTC (9:32 am IST), followed four seconds later by that of the blue and yellow systems. The autopilot disengaged, a continuous repetitive chime sounded and a stall warning followed for two seconds.

The co-pilot, who was flying the aircraft, initially responded before the pilot-in-command took control. The aircraft climbed 372 feet above its assigned altitude and then fell 292 feet.

The blue hydraulic system recovered first, followed within seconds by the yellow and green systems, after which the flight-control surfaces recovered and normal operation resumed.

David Soucie, a former US Federal Aviation Administration (FAA) safety inspector, said investigators need to establish what could have affected three normally independent systems within seconds and then allowed all three to recover. "I would want to determine whether we experienced three genuine pressure losses or whether there was a common electrical, sensing, control or indication event," he said.

The aircraft had been dispatched from Phuket with a Minimum Equipment List item relating to its Power Transfer Unit, which had been invoked on July 28. The investigation has not established whether the PTU issue was connected to the hydraulic failure. Soucie said investigators should also examine the aircraft's maintenance history and the deferred PTU.

The aircraft sustained damage to overhead bins, ceiling panels, handrails and other cabin components.

Both pilots passed their post-flight, breath-analyser tests. The pilot-in-command's psychoactive-substance screening test was non-negative, as was the confirmatory blood test. The co-pilot tested negative for both.

The crew chose to continue to Delhi rather than divert to the nearest airport en route and later requested medical priority from air traffic control. The aircraft landed safely at Indira Gandhi International Airport at 05:30 UTC (11 am IST).

Captain Amit Singh, founder and director of Safety Matters Foundation, said the occurrence had correctly been classified as an accident but questioned the level of new technical information in the report.

"There is no new information that has been provided in this report than what was available in the first week. The leaked Airbus report contained much more details on the investigation," he said. "If there was a hydraulic failure then the report must provide details of what failed and what component tests have revealed so far. No analysis but only information."

That report had said a temporary loss of hydraulic systems led to the loss of key control surfaces for about four seconds based on an initial assessment of digital flight data recorder (DFDR) data by Airbus.

ET had earlier reported Airbus had also asked Air India to establish whether the hydraulic loss was a genuine failure or a spurious signal from a faulty component.