EASA OKs Redesigned Airbus Helicopters EC225 Shaft
The EASA has certified the redesigned vertical bevel gear shaft for the Airbus Helicopters EC225, which has suffered in-flight failures and a nine-month grounding in 2012 and 2013. Manufacturing of the redesigned gear shaft is under way for production aircraft and for retrofits, and installations for both applications are slated to begin in the second half of this year.
Airbus Helicopters says that the new design eliminates all three factors that, combined, caused two unexpected vertical shaft failures (see poster). It provides corrosion resistance, compensates for residual stress and eliminates stress hot spots. To protect against corrosion, a smoother shape inside the shaft will prevent “mud” retention areas. Reinforcement in the welding area compensates for residual stress. Improved internal geometry removes hot spots such as small-radius angles that concentrate stress.
Airbus Helicopters chief technology officer Jean-Brice Dumont described the module-level exchange procedure as “not very complicated” for the operator’s maintenance technicians and promised that Airbus Helicopters’ production capacity will not impede the process of retrofitting the fleet. Downtime will be six days.