Overview
• Operator: One Air
• Aircraft Model: Boeing 747-400 Freighter
• Registration: G-ONEE
• Flight Number: HC-211
• Route: London Heathrow (UK) → Hong Kong (China)
• Date: 8 February 2024
• Occupants: Crew unspecified
• Nature of Incident: Dual generator failure, loss of lateral navigation, unreliable airspeed indications
Incident Summary
One Air flight HC-211, a Boeing 747-400 Freighter (G-ONEE), was climbing out of London Heathrow (UK) when two of its four electrical generators failed at FL250 over the North Sea. The failure resulted in the loss of lateral navigation and all pitot probe heating, leading to unreliable flight instrument indications.
The crew initially turned back towards England but, due to marginal weather conditions at Heathrow, opted to divert to Amsterdam Schiphol (Netherlands). The aircraft landed safely on runway 06 approximately 85 minutes after departure.
An interim report from the UK AAIB (Air Accidents Investigation Branch) later confirmed that water leakage into the avionics bay caused the electrical failures, affecting navigation systems, pitot heating, and cabin pressurization. The investigation remains ongoing.
Sequence of Events
Departure & Initial Climb
• The aircraft departed Heathrow’s runway 09R into adverse weather conditions, including rain, thick cloud, and icing.
• At FL250, two electrical generators failed, leading to:
• Loss of two electrical buses
• Complete failure of all pitot probe heaters
• Loss of lateral navigation capabilities
Emergency Response & Diversion Decision
• The crew declared an emergency and initially turned back towards England.
• Unreliable airspeed indications emerged due to the pitot probe heater failure.
• Heathrow’s weather conditions were marginal, leading the crew to divert to Amsterdam Schiphol, which had clear weather.
Approach & Safe Landing
• The aircraft did not require a fuel dump before landing.
• The crew safely landed on runway 06 at Amsterdam Schiphol 85 minutes after departure.
Investigation Findings & Interim Report
AAIB Preliminary Findings (May 2024)
• The aircraft experienced failures on two electrical buses, leading to:
• Loss of pitot heating → Resulting in unreliable airspeed indications
• Cabin altitude increase → Potential impact on crew workload
• Navigation system failures → Loss of lateral navigation
AAIB Interim Report (February 2025)
• The failures were traced back to water leakage into the avionics bay, which caused:
• Electrical short circuits leading to generator failure
• Inoperative pitot probe heaters, a critical flight safety concern
• Unreliable airspeed readings, requiring immediate diversion
• The crew’s decision to divert to Amsterdam was appropriate, as Heathrow’s conditions were unfavorable.
• The final report is still pending further analysis.
Safety Concerns & Industry Implications
This incident highlights critical safety concerns related to water ingress in aircraft avionics and its potential impact on electrical and navigation systems. The loss of pitot heating is particularly dangerous, as it can lead to unreliable airspeed readings—a factor in several past aviation accidents.
Recommendations for Operators
• Enhanced avionics bay sealing: Regular checks for potential water leakage points in aircraft electronics compartments.
• Redundant electrical system monitoring: Improved diagnostics to detect and isolate failures before they escalate.
• Pitot heating reliability improvements: Evaluating backup heating mechanisms to prevent airspeed data loss.
• Updated flight crew training: Emphasizing procedures for handling simultaneous electrical and instrument failures.
Disclaimer
This report is based on available information as of 10 February 2025. While every effort has been made to ensure accuracy, the completeness of the details cannot be guaranteed. If you are the rightful owner of any referenced materials and wish them removed, please email takedown@cockpitking.com.
