Crash of B.C. Ferries vessel linked to propulsion system
Jan 08 2012
The Coastal Inspiration at Esquimalt Graving Dock for repairs last month.Photograph by: Darren Stone, timescolonist.com
The Coastal Inspiration's hard landing at the Duke Point ferry terminal last month has been linked to its propulsion system - but questions remain about why backup systems did not prevent the crash.
The vessel uses a controlled-pitch constantpropulsion system, similar to 17 others in the B.C. Ferries fleet. The propeller rotates at a constant speed, even when the vessel is stationary, because its pitch - or angle - can be set near zero.
The system, used on vessels around the world for about 70 years, is popular because it offers reduced maintenance and fuel costs, although concerns have been raised about the danger of losing control of the pitch.
But Mark Collins, B.C. Ferries' engineering vicepresident, said the Coastal Inspiration has three backup systems in case there is a pitch control failure. One of the backups is independently connected to the control room, which increases the odds of at least one of the systems working in an emergency.
Collins said it would take a "catastrophic explosion in the engine room" to take out all the systems at once.
B.C. Ferries is still investigating the Coastal Inspiration accident, which has closed the Duke Point terminal for several weeks until repairs can be made. Ferry traffic has been rerouted to Departure Bay. The ferry is expected to be back in service on Jan. 20.
Collins said the Coastal Inspiration's hard landing was nothing like the Queen of Oak Bay's crash into a marina in Horseshoe Bay in 2005. The propeller on the Queen of Oak Bay stopped turning, causing a loss of control, while the propeller on the Coastal Inspiration continued to turn, driving the vessel forward.
A missing cotter pin was found to be the cause of the Queen of Oak Bay incident, which caused $3 million damage to property.
B.C. Ferries has control-pitch systems on 18 vessels, about half its fleet. Nine of those have fixed propeller speeds with control-pitch systems, including the three Coastal Class vessels, the two Spirit Class vessels, the Northern Expedition and Adventure, and the Queens of Capilano and Cumberland. Nine other ships have control of both propeller pitch and propeller speed, including the Queen of Oak Bay.
A due-diligence report conducted before the three Coastal vessels arrived in 2008 warned the propulsion system could pose safety problems when docking.
The motors "simplify the overall system and eliminate high maintenance," but they pose risks if the control of the propellers is lost, according to the report by Glosten Associates, a Seattle-based marine engineer consulting group.
"When the nearly feathered propeller is rotating at full RPM, any failure in pitch control could have severe consequences," the authors said.
Glosten Associates did not suggest changes, but recommended B.C. Ferries "consider including this topic in [its] vessel training program."
Marc McAllister, of McAllister Marine Survey and Design Ltd., which does consulting work with B.C.
Ferries, said constant propulsion is efficient and typically dependable.
"To say that losing control of the pitch would be dangerous, that's true, but the same thing can be said about a [variable-speed] engine that is running at full throttle and couldn't slow down when you wanted to," he said.