What happened
On the night of 29 November 2013, a Eurocopter EC1SB helicopter, operating in support of police operations, crashed into the roof of The Clutha Vaults bar in central Glasgow. The aircraft had departed Glasgow City Heliport earlier that evening to assist with a search operation. During the final stages of the flight, the right engine experienced a flameout, followed shortly by a failure of the left engine.
The helicopter descended at a high rate of speed and struck the building in an upright position. The impact caused the roof to collapse, and the aircraft became embedded within the structure. The accident resulted in 9 fatalities, including the three occupants of the helicopter and six individuals in or near the bar. Additionally, 32 people sustained injuries, 12 of which were classified as serious.
The investigation
AAIB investigators conducted a detailed engineering examination of the aircraft and its systems. The investigation focused on the fuel system, the engines, and the transmission components.
Analysis of the fuel tank group revealed that while the main tank held 76 kg of fuel, the right supply tank was empty and the left supply tank contained only 0.4 kg. The investigation confirmed that the fuel system had not leaked prior to the impact and that the fuel pumps and valves were functional.
Regarding the engines, both Turbomeca Arrius 2B2 engines were examined. While the engines suffered external damage from the impact, there was no evidence of foreign object damage, lubrication failure, or intake blockage. Data from the Full-Authority-Digital-Engine-Controls (FADECs) confirmed that the right engine flamed out first, followed by the left engine.
Examination of the transmission, main rotor, and Fenestron tail rotor indicated that these components were not rotating at the moment of impact. Furthermore, there was no evidence of any failure in the hydraulic, electrical, or flight control systems prior to the crash.
Findings
- The right engine flamed out, followed shortly by the left engine.
- The aircraft struck the building at a high rate of descent.
- The fuel quantity transmitters had triggered low fuel warnings, specifically indicating that the right supply tank was empty and the left supply tank was critically low.
- The SHED BUS switch was found in the NORM position, meaning the radio altimeter and steerable landing light were not available to the pilot during the descent.
- There was no evidence of structural failure, birdstrike, or in-flight fire prior to the impact.