Date: 15th November 2024
Location: Enroute near Ketchikan, Alaska, USA
Aircraft: Boeing 777-300, registration VT-ALO
Operator: Air India
Flight Number: AI-185
Route: Delhi, India, to Vancouver, Canada
Occupants: Unknown
Injuries: None reported
Summary of Events
On 15th November 2024, Air India flight AI-185, a Boeing 777-300 operating from Delhi to Vancouver, experienced a “FIRE CARGO AFT” warning while cruising at FL330 near Ketchikan, Alaska. The crew declared a Mayday and initiated a direct diversion to Vancouver, the nearest suitable airport. Shortly thereafter, the fire warning ceased, prompting the crew to downgrade the emergency to PAN PAN. The flight landed safely on Vancouver’s runway 26L approximately one hour later.
Emergency services inspected the aircraft upon landing and found no evidence of fire, heat, or smoke in the cargo hold. Passengers disembarked safely, and the aircraft was cleared to return to service after an 8-hour inspection.
Aircraft Information
The Boeing 777-300 is a long-haul, wide-body aircraft equipped with advanced safety systems, including fire detection and suppression systems in the cargo holds. The cargo compartments are equipped with multiple smoke detectors and fire suppression bottles to detect and mitigate fire risks.
Sequence of Events
1. Cruise Phase:
• The aircraft was cruising at FL330 approximately 425 nautical miles north-northwest of Vancouver when the crew received a “FIRE CARGO AFT” warning on the flight deck.
2. Emergency Declaration:
• The crew declared Mayday, assessed the situation, and determined Vancouver as the nearest suitable airport. The aircraft set a direct course to Vancouver.
3. Warning Ceases:
• Shortly after initiating the diversion, the fire warning ceased, leading the crew to downgrade the emergency to PAN PAN.
4. Safe Landing:
• The aircraft landed safely on Vancouver’s runway 26L. Emergency services were on standby and conducted an immediate external inspection.
5. Cargo Hold Inspection:
• After all passengers disembarked, emergency services opened the cargo holds. No evidence of fire, smoke, or heat was found.
6. Post-Incident:
• The aircraft underwent a detailed inspection before being cleared to operate the return flight.
Initial Findings
Potential Causes of Fire Warning
1. Sensor Fault or Malfunction:
• A malfunctioning smoke detector or sensor may have triggered a false warning.
2. Cargo Content:
• Certain cargo materials can emit substances that might trigger sensitive smoke detectors, even in the absence of fire.
3. Electrical Anomaly:
• Wiring or connectivity issues in the cargo fire detection system could result in spurious warnings.
4. Transient Smoke Event:
• A brief occurrence of smoke or particulates in the cargo hold might have triggered the warning, dissipating before landing.
Maintenance Actions
• Inspection of Cargo Holds:
• A thorough check of the aft cargo hold was conducted, revealing no signs of fire or damage.
• Fire Detection System Check:
• The sensors and wiring for the cargo fire detection system were inspected and tested for anomalies.
• Verification of Cargo Contents:
• The airline reviewed the cargo manifest to identify any items that might have contributed to the warning.
Safety Risks
1. False Warnings:
• False fire warnings can cause significant operational disruptions and increase crew workload during critical flight phases.
2. Undetected Hazards:
• A false negative in fire detection could lead to delayed response in actual emergencies.
3. Diversion Impacts:
• Diversions to handle fire warnings can impose significant operational and logistical challenges, including passenger inconvenience and potential airspace congestion.
Recommendations
1. Enhanced Maintenance Protocols:
• Regular calibration and testing of fire detection systems to minimize false warnings.
2. Cargo Content Assessment:
• Implement stricter monitoring of cargo contents, especially materials that may emit particulates or vapours.
3. Crew Training:
• Reinforce procedures for managing fire warnings, including prioritizing safe diversion and coordination with emergency services.
4. Data Review:
• Analyse fleet-wide data to identify trends or recurring issues in fire detection systems.
Safety Lessons and Industry Impact
This incident highlights the critical role of robust fire detection systems and the importance of prompt crew response to fire warnings. While no fire was found, the event underscores the need for ongoing maintenance and monitoring of aircraft systems to ensure passenger and crew safety.
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Our investigation reports are based on all the evidence and facts we have at the time of writing and posting. We apologise if any details are missed or are not fully accurate.
