CEN09IA618

The helicopter pilot observed a caution light for the number one hydraulic system and a corresponding complete loss of hydraulic system pressure for that system. The pilot declared an emergency and performed a run-on landing. A postincident examination of the system's hydraulic pump revealed that two of its cover attachment bolts had separated. The bolt heads fractured in tension from their shanks via intergranular cracks which initiated at the filet radius between the bead and the shank. The bolt fractures exhibited intergranular fracture features over 90 percent of the surface. The operator’s incident report safety recommendation stated that the pump's cover bolts should be replaced at overhaul; however, it is not required. The helicopter had accumulated 269 hours since overhaul.

On July 1, 2009, at 1815 central daylight time, a Bell 230 helicopter, N880SF, sustained no damage during a forced landing at the General Downing - Peoria International Airport (PIA), near Peoria, Illinois, after it lost fluid in its number one hydraulic system during cruise flight. The commercial helicopter pilot, two emergency medical services (EMS) crewmembers, and the patient were not injured. Visual meteorological conditions prevailed and no flight plan was filed. The local non-scheduled domestic 14 Code of Federal Regulations Part 135 EMS transport flight departed PIA at time unknown. According to the operator’s incident report, the pilot observed a caution light for the number one hydraulic system and a corresponding complete loss of hydraulic system pressure for that system. The pilot declared an emergency and performed a run-on landing. Examination of the system's hydraulic pump revealed that two of its cover attachment bolts had separated. The separated bolt heads were retained by safety wire. This hydraulic pump manufacturer’s part number was 65132-1. The Bell Helicopter part number is 222-380-009-105, which is also usable on the Bell 222 series and 430 model helicopters. The bolts that sustained the separation were part number MS24678-17. According to the helicopter manufacturer, these hydraulic pumps do not have a scheduled overhaul cycle and the pumps are replaced on-condition. The manufacturer does not track the service times of these pumps. Reportedly, this was the first failure of the hydraulic pump cover attachment bolts. The pump manufacturer had the failed bolts examined. The bolt heads fractured in tension from their shanks via intergranular cracks initiating at the filet radius between the bead and the shank. The bolt fractures exhibited intergranular fracture features over 90 percent of the surface. According to the operator, the incident pump accumulated 269 hours of time prior to the bolt failures. The operator’s incident report safety recommendation indicated, “Recommend pump cover bolts be replaced at overhaul.”