Factual Information
On 15 July 2002, a Sikorsky S-61N helicopter, registration G-BBHM, was involved in an accident at Poole, Dorset. The commander was a 41-year-old male and the co-pilot a 43-year-old male.
Flight data recordings from the crash-protected flight data recorder and the Health and Usage Monitoring System (HUMS) were analyzed. The recordings covered the flight prior to the onset of the event, the onset of the event, and low engine oil pressure parameters. Time correlation of recordings and CVFDR noise analysis were also performed. Previous investigations and analysis of HUMS data were reviewed.
Examination of the wreckage included a strip examination of the engines, No 5 bearing, oil jet assemblies, main drive shaft assemblies, T bolts, Thomas coupling, engine mounting rear support assembly, other bearings, and the main gear box.
Tests and research conducted included metallurgical tests, electron microscopy, examination of illumination of flight deck captions, oil jet flow testing, oil jet resonance testing, and analysis of IHUMS data.
Additional information considered included previous events, AAIB Safety Recommendations arising from previous events, safety actions, a comparison with Sea King/Gnome experience, and studies on shaft misalignment and dynamic behaviour of the main drive shaft.
Investigation
The investigation was carried out by the Air Accidents Investigation Branch in accordance with the Civil Aviation (Investigation of Air Accidents and Incidents) Regulations 1996. The report includes analysis of operational and engineering aspects related to the accident.