What happened
On the morning of January 21, 2012, an ATR-72-212A, registration EC-HCG, operated by Air Nostrum, was preparing for a scheduled domestic flight from San Sebastian Airport to Madrid. During the engine start sequence, the crew successfully started the number 2 engine using the propeller brake. Following this, the captain initiated the start for the left engine.
As the ground handling crew worked to remove the chocks, the aircraft began to move forward unexpectedly. A ground operator noticed the movement and attempted to warn the crew, but the aircraft's right propeller struck a ground power unit (GPU). The impact caused all six propeller blades to break, with fragments striking the aircraft's fuselage and causing a crack that penetrated into the passenger cabin. The aircraft eventually came to a halt when the right main landing gear door impacted the GPU. There were no injuries among the 24 passengers or the crew, and the passengers were safely disembarked.
The investigation
The CIAIAC investigation examined the sequence of ground operations, the cockpit environment, and the technical status of the aircraft. Investigators reviewed cockpit voice recorder (CVR) data, which revealed that the crew was distracted by an alignment issue with the attitude and heading reference system (AHRS) and other external factors. The investigation also looked into the communication methods used between the flight crew and the ground handling personnel, noting that visual signals were used instead of the aircraft's interphone system.
Findings
- The primary cause of the incident was the failure of the crew to adhere to procedures, specifically regarding the release of the parking brake without conscious awareness of the aircraft's movement.
- The captain's attention was divided due to an AHRS technical issue and external distractions, leading to the parking brake being released in haste to maintain the flight schedule.
- Low visibility caused by darkness and rain hampered the crew's ability to monitor external references.
- Ground personnel used visual signals rather than headphones to communicate with the cockpit, which limited the effectiveness of warnings.
- The handling operator's manuals lacked specific instructions for reporting ground incidents to the airport authorities.
- A technical fault was discovered in the flight data recorder (FDR), which had not been recording data for two days; the cockpit warning light for this fault failed to illuminate due to an issue in the monitoring system.