Although Sikorsky is developing a new main gearbox to solve the problems that have plagued the S-92 over the course of its service life, the new transmission will not be able to run for 30 minutes after a total loss of lubrication. The Canadian Transportation Safety Board (TSB) has pressured for this capability to be added to the S-92 and is currently assessing the FAA’s assertion that such a retrofit is not necessary on the S-92 and that the safety statistics of other Category A helicopters are good enough.
During the investigation into the 2009 fatal crash of a Cougar-operated S-92 off Newfoundland, the TSB determined that the main gearbox failed after loss of oil. As a result, the Canadian agency called for enforcement of the existing 30-minute “run dry” requirement on all main gearboxes (MGBs) for new helicopters. In July, the TSB asked the FAA to clarify its original response and is now studying the FAA’s September answer. Sikorsky got a pass on the regulation by asserting to the FAA that the chances of total main-gearbox oil loss were extremely remote; events have proved otherwise.
