Fuel switches cut off before Air India crash, preliminary report says | BBC News

Key Concepts

• Air accident investigation
• Preliminary report
• Boeing 787 Dreamliner
• Fuel control switches (run/cutoff)
• Loss of thrust
• Flight data recorder (FDR)
• Cockpit voice recorder (CVR)
• Pilot error vs. mechanical/electrical failure
• Engine reignition
• Survivability analysis
• Psychological assessment of pilots
• Software corruption
• Mandatory inspections
• Recommendations to industry

Air India Flight Crash: Preliminary Report Findings

Initial Report Overview

The preliminary report from India's air accident investigation bureau concerns the Air India Boeing 787 Dreamliner crash a month prior, shortly after takeoff from Ahmedabad en route to London. The crash resulted in 260 fatalities. The report is a compilation of facts discovered so far in the investigation.

Data Analysis and Potential Cause

• Mechanical Issues: The initial data suggests no apparent mechanical issues with the 787 Dreamliner.
• Fuel Control Switches: The flight data recorder indicates that both fuel control switches were moved from the "run" to the "cutoff" position shortly after takeoff. These switches are typically activated before takeoff and deactivated upon landing. This action could have caused the loss of thrust.
• Engine Restart Attempt: The report notes that both engines subsequently returned to the "run" position, indicating a restart attempt. However, one engine failed to reignite completely, potentially contributing to the crash.
• Cockpit Voice Recorder: The cockpit voice recorder captured a conversation between the pilots regarding the switches, with one pilot questioning why the other switched them off, and the other denying doing so.

Important Considerations and Caveats

• Preliminary Findings: The report emphasizes that these are preliminary findings based on initial data analysis.
• Pilot Error: While the fuel switch incident is highlighted, the report refrains from definitively attributing the crash to pilot error. It only presents the recorded data.
• Complexity of Investigation: The investigation is complicated by the fact that this is one of the first crashes involving a Boeing 787 Dreamliner, considered a highly advanced and safe aircraft.
• Wreckage Condition: The full fuel tank at the time of the crash resulted in a severe explosion, charring the wreckage and complicating data retrieval.

Expert Analysis: David Gleeve, Aviation Safety Investigator

Fuel Switch Incident

• Possible Causes: David Gleeve suggests several possibilities for the fuel switch incident:
  • Software issue
  • Electrical arcing problem
  • Human intervention (deliberate or accidental)
• Timing: The 1-second time gap between the switch transitions could be due to the sampling frequency of the switch positions.
• Pilot Communication: The cockpit voice recording, where pilots deny switching off the fuel switches, suggests that it might not have been a deliberate human action.

Criticality of Fuel Switches

• Engine Control: The fuel switches are analogous to the key switch in a car, directly controlling engine operation.
• Engine Failure Procedures: Recycling the switches (off to on) is part of the procedure for double engine failure.
• Switch Position Detection: It is critical that the sensors detect the switch remaining in the "on" position during flight.

Aircraft Recovery

• Limited Recovery Potential: Gleeve believes that recovery was unlikely once the engines began to wind down.
• Engine Restart Lag: Similar to a turbocharged car, there is a lag in power delivery during engine restart.
• Single-Engine Flight Capability: The aircraft should have been capable of flying with one engine at full power.
• Eliminated Causes: The investigation has ruled out or found strong indications against bird strikes or water in the fuel.

Future Investigation Focus

• Survivability: Analyzing why one person survived while others did not.
• Psychological Assessment: Investigating potential pilot error or deliberate malicious acts.
• Engineering Analysis: Examining how the switches could have moved themselves, considering their design requires lifting and moving.
• Electronics Analysis: Investigating potential software corruption that could have sent false signals to shut down the engines.

Boeing's Involvement

• Information Flow: Boeing will receive information through the National Transportation Safety Board's accredited representative.
• No Immediate Action: As of the report's release, aviation authorities have not issued mandatory inspections or grounding orders for the 787 fleet.

Public Safety

• No Cause for Concern: Gleeve states that he would be comfortable flying on a 787, emphasizing the aircraft's safety systems and the thoroughness of the investigation.

Investigation Timeline

• Traditional Timeline: Traditionally, accident reports are completed within a year.
• Modern Complexities: Due to complexities, modern investigations can take two to two and a half years.
• Recommendations vs. Full Report: Recommendations to the industry are released as soon as possible for immediate action, separate from the full report.
• Immediate Industry Response: The industry will respond immediately to any recommendations issued by the investigators.

Synthesis/Conclusion

The preliminary report on the Air India Boeing 787 Dreamliner crash highlights the potential role of fuel control switches being moved to the "cutoff" position shortly after takeoff, leading to a loss of thrust. While the report stops short of attributing the crash to pilot error, the cockpit voice recording and the unusual switch behavior raise significant questions. The investigation is ongoing, focusing on various factors, including human factors, mechanical/electrical systems, and software. Despite the crash, experts emphasize that the 787 is a safe aircraft, and the industry will learn from the investigation to prevent future incidents. Recommendations for safety improvements will be implemented immediately as they are identified, even before the final report is completed.