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 flight, the helicopter performed several tasks across various locations in Scotland before attempting to return to the heliport.
During the final stages of the flight, the aircraft experienced a double engine flameout, with the right engine failing first, followed shortly by the left engine. The helicopter descended at a high rate of descent and struck the building in an upright position. The impact caused the roof to collapse, and the helicopter became embedded in the structure. The accident resulted in 3 fatalities from the aircraft occupants and 7 fatalities from individuals in or near the bar, totaling 10 deaths. Additionally, 11 people suffered serious injuries, with one person later succumbing to their wounds.
The investigation
AAIB investigators examined the wreckage and the aircraft's systems in detail. Engineering analysis of the fuel system 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 found no evidence of fuel leaks prior to the impact or structural failures in the fuel delivery lines. Both engines were found to be mechanically sound, with no evidence of foreign object damage or internal component failure.
Data recovered from the aircraft's non-volatile memory indicated that the aircraft's warning unit had recorded several low fuel warnings for both supply tanks prior to the loss of power. The investigation also noted that the aircraft's rotor and transmission systems were not rotating at the moment of impact. Furthermore, the SHED BUS switch was found in the NORM position, meaning the radio altimeter and steerable landing light were unavailable to the pilot during the descent.
Findings
- The right engine flamed out, followed shortly by the left engine.
- The aircraft's fuel supply tanks were significantly depleted, with the right supply tank empty and the left supply tank nearly empty.
- The aircraft's warning system had triggered intermittent and permanent low fuel warnings prior to the engine failures.
- The SHED BUS switch was not set to the emergency position, which would have provided access to the radio altimeter and landing light.