The Super Puma AS332 and EC225 are built by Eurocopter, which describes them as twin-engine, medium-weight civil helicopters. Their spacious cabins make them a favorite for carrying passengers; however, two incidents in 2009, both involving the AS332L1 model, led to both being grounded for 48 hours in 2009 over concerns regarding the safety of their gearboxes.
The first incident occurred on February 22, 2009, when an AS332 carrying two crew members and two passengers had to make an emergency landing after a gearbox malfunction during a winching demonstration. On April 1, a second AS332 crashed in the North Sea, off Scotland, killing all 16 people onboard. In the report by the Air Accidents Investigation Branch, the crash was attributed to “a catastrophic failure of the main rotor gearbox (MGB).”
Investigations into the February 22 crash found that the “intermediate gear wheel had fractured from the bearing at the centre to the outer edge of the gear.” In the April 1 case, the report recorded that the epicyclic module within the MGB had failed. This led to the detachment of the main rotor head from the helicopter, with the rotors then striking the pylon and tail boom, severing it from the fuselage.
After the April 1 tragedy, both AS332 and EC225 models were grounded for 48 hours in order that their gearboxes could be inspected. The Air Accidents Investigation Branch also recommended in its report that the European Aviation Safety Agency oversee Eurocopter’s program of increased inspections and enhanced monitoring, and also that the gearbox monitoring and warning systems on the helicopters be improved.