What happened
On the night of 13 November 2002, a British Aerospace ATP, registration SE-LGX, was performing a freight flight in the airspace northeast of Stockholm/Arlanda Airport. During the approach for landing, the aircraft experienced a sudden power loss within its left electrical system. This failure resulted in the loss of all flight and navigational instruments (EFIS2) on the pilot's side. The electrical disruption triggered the Master Caution horn and caused the main emergency lamp to flash.
Faced with the loss of critical displays, the crew determined that no specific items in the existing emergency checklist appeared to match the current fault. To avoid the risks associated with troubleshooting the electrical system while in flight, the pilots elected to declare an emergency. Air traffic control provided radar vectors for the most direct route to runway 19 R, and the crew successfully completed the landing without further incident or damage to the aircraft.
The investigation
The Swedish Accident Investigation Board (SHK) examined the simultaneous failure of the aircraft's electrical components. The investigation established that the power loss was the result of two independent faults occurring at the same time. One of these faults originated in a component from an older version of the system that had known deficiencies.
Investigators also reviewed the crew's response and the utility of the onboard emergency procedures. While the crew could have potentially restored electrical functions by cross-connecting the right-hand electrical system, the investigation focused heavily on the usability of the documentation provided to the pilots.
Findings
- The primary cause of the electrical failure was two independent faults occurring simultaneously within the aircraft's electrical system.
- The emergency checklist was found to be difficult to use, characterized by a non-intuitive logic, small typeface, and a lack of clear headings that corresponded to warning panel alerts.
- The crew's decision to land immediately was a safety-conscious choice to avoid complicating the electrical situation through manual fault-finding.
Safety action
Following the investigation, the SHK issued recommendations to the Swedish Civil Aviation Administration regarding the oversight of Air Operator Certificates (AOCs). The recommendations emphasize the need to evaluate emergency checklists for comprehensibility and user-friendliness. Furthermore, the SHK advocated for the establishment of an international standard for the logic, arrangement, and layout of emergency checklists used in professional aviation to ensure they serve as effective aids during critical flight phases.