Air India 171 crash probe zeroes in on electrical failure

Six months after the catastrophic crash of Air India’s AI-171 Ahmedabad–Gatwick flight, investigators say their inquiry is now centred on a series of electrical and power-distribution failures — not pilot error — as the possible trigger of the disaster that killed 260 people, including 19 on the ground.

The Ministry of Civil Aviation has told Parliament that “all probable causes” remain under active scrutiny. But officials involved in the probe say no “incriminating evidence” has emerged so far to suggest that Captain Sumeet Sabharwal or First Officer Clive Kunder acted deliberately or made a mistake that led to the crash.

Technical ‘snag under the scanner’

The Aircraft Accident Investigation Bureau (AAIB), which released its 15-page preliminary report on July 12, detailed the final moments of the flight. According to the report, the aircraft’s engine fuel control switches moved from ‘RUN’ to ‘CUTOFF’ within a second of each other moments after take-off.

While the cockpit exchange referenced in the report — one pilot asking the other why he cut off the switch, and the latter denying it — has fuelled speculation of pilot action, investigators say the sequence is more likely linked to a critical electrical malfunction.

Officials said that flight-data analysis and wreckage examination point to a “specific electrical snag” originating in the aircraft’s aft electrical system — a high-stakes zone that powers hydraulic pumps, the Auxiliary Power Unit (APU), engine controls, fuel pumps and nitrogen-generation components.

The malfunction is believed to have triggered a cascading failure across power-distribution and flight-critical systems, including cockpit instrumentation, seconds after the Dreamliner lifted off.

Seconds without instruments

According to officials, instrumentation in the cockpit went dark until the Ram Air Turbine (RAT) deployed and began supplying hydraulic power. The preliminary report notes that RAT power kicked in eight seconds after take-off — just 13 seconds before the pilots made the chilling Mayday call.

“Until RAT power came on, a dual-engine relight was impossible as the battery backup cannot support it,” said an official. Investigators believe the pilots were steering the aircraft and attempting to regain thrust while manually cycling the fuel switches in the mandated sequence once RAT support became available. But with minimal altitude and time, recovery proved impossible.

A survivor’s account of “flickering cabin lights” — describing systems repeatedly switching between main power, backup generators and attempted relight — also reinforces the electrical-failure hypothesis, investigators say.

Prior snags, critical clues

The AAIB report highlights that the APU was recovered intact and notes a key entry in the previous flight’s technical log: crew of AI-423 had reported a “STAB POS XDCR” status message, which maintenance in Ahmedabad subsequently cleared before releasing the aircraft for AI-171.

Investigators have been examining whether a history of technical snags or a system malfunction could have affected the FADEC (Full Authority Digital Engine Control) — the aircraft’s “brain” — causing uncommanded actions.

Compounding the mystery, the preliminary report states that even the Emergency Locator Transmitter (ELT), which should activate automatically in a crash, remained silent.

Probe enters final lap

Officials say the investigation, which involves specialists in human factors, forensics, aero-engineering, Boeing pilots, and Dreamliner maintenance experts — is expected to be completed within six months.

The AAIB has not yet released its final report.