First Incident
While en route to its destination, the helicopter's hydraulic system caution light briefly illuminated and an aural warning sounded. The pilot chose to continue to the intended destination. Approaching the runway, the helicopter experienced a loss of hydraulic boost. The pilot then performed a run-on landing to the runway without damage. After the incident, a company mechanic removed the hydraulic pump and pulley. Inspection revealed that the hydraulic pump drive shaft splines and the coupling sleeve showed excessive wear. A new hydraulic pump was fitted, the helicopter underwent a test flight, and it was placed back into service.
Second Incident
Approximately three weeks later, while flying the same helicopter, the pilot encountered a similar sequence of events, leading to another run-on landing. The helicopter sustained no damage. Following this incident, the hydraulic system test switch was determined to be faulty and was subsequently replaced. After inspection by a mechanic and a second company pilot, the helicopter was test flown without any discrepancies observed and returned to service.
Examination Findings
Inspection of the hydraulic pump drive shaft and coupling sleeve from the first incident revealed that, although the mating splines of both components were heavily worn, sufficient spline material remained to allow the coupling sleeve to drive the hydraulic pump. The hydraulic switch removed from the helicopter after the second incident underwent examination and functional testing, which found no anomalies.