NTSB Identification: NYC06IA176.
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Incident occurred Monday, July 17, 2006 in Philadelphia, PA
Probable Cause Approval Date: 07/25/2007
Aircraft: Eurocopter AS-350 BA, registration: N606TV
Injuries: 2 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

While en route to the destination airport, the helicopter's hydraulic system caution light momentarily illuminated and the associated aural warning sounded. The pilot elected to continue to the intended destination, and nearing the runway, the helicopter lost hydraulic boost. The pilot subsequently performed a run-on landing to a runway. Following the incident, a company mechanic removed the hydraulic pump and pulley, and found that the hydraulic pump drive shaft splines and the coupling sleeve exhibited "excessive wear." A new hydraulic pump was installed, the helicopter was test flown, and was then returned to service. About 3 weeks later, while flying the same helicopter, the pilot experienced a similar series of events, resulting in another run-on landing and no damage to the helicopter. Following that incident, the hydraulic system test switch was identified as faulty, and was subsequently replaced. After a check by a mechanic and another company pilot, the helicopter was test flown with no discrepancies noted and returned to service. Examination of the hydraulic pump drive shaft and coupling sleeve revealed that while the mating splines of both components were severely worn, there was enough spline material remaining to enable the coupling sleeve to drive the hydraulic pump. Examination and functional testing of the hydraulic switch removed from the helicopter revealed no anomalies.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

A loss of hydraulic boost for undetermined reasons.

Full narrative available

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