What happened
On 12 September 2015, an Embraer EMB-145MP, registration A6-RRA, was operating a scheduled flight from Abu Dhabi International Airport to Salalah International Airport. The aircraft was carrying 11 passengers and three crewmembers. While climbing through flight level 360, the primary flight display, multi-function flight display, and the engine indicating and crew alerting system suddenly went blank, replaced by red crosses.
Following the display failure, the crew detected an electrical odor. Due to the potential for an electrical fire, the commander initiated emergency procedures, and the crew donned oxygen masks. The autopilot disengaged as a result of the computer failure, requiring the copilot to fly the aircraft manually. Although the crew initially intended to divert to Muscat, the loss of the ground proximity warning system led them to change their destination to Al Ain International Airport to avoid high terrain.
The investigation
An investigation by the GCAA AAIS focused on the failure of the No.1 integrated computer (IC-600). Investigators examined the aircraft's technical systems, including the data acquisition units and the symbol generator. The investigation also reviewed the crew's response, the effectiveness of their crew resource management, and the consistency of the aircraft's emergency checklists.
Findings
- The primary cause of the incident was the overheating of the power supply printed board assembly within the No.1 IC-600.
- This overheating was likely triggered by a short circuit resulting from an internal breakdown of a transformer (T1).
- The failure caused the cockpit displays to blank out and led to the automatic disengagement of the autopilot.
- The crew demonstrated effective crew resource management and correctly identified the need to divert to Al Ain due to the loss of the GPWS.
- Discrepancies were noted between the Airplane Operations Manual (AOM) and the Quick Reference Handbook (QRH), specifically regarding inconsistent instructions for electrical smoke and autopilot failure procedures.
Safety action
- The GCAA AAIS recommended that Embraer review and revise the checklists and procedures in both the AOM and QRH to ensure consistency, specifically regarding the Electrical System Fire or Smoke, IC Failure/IC Bus Failure, and Autopilot Failure procedures.