On October 2, 2005 the passenger vessel ETHAN ALLEN
capsized while touring Lake George with 47
passengers and one crewmember on board. After
remaining inverted on the surface for a short
period, the vessel subsequently sank. The master and
27 passengers survived. Twenty passengers died.
According to numerous eyewitnesses on and near the
vessel during the time of the accident, no obvious
adverse weather, sea conditions, equipment failures
or operator errors appeared to cause the capsize.
Since the vessel operated only on Lake George, it
was not required to be inspected by the U.S. Coast
Guard.
The National Transportation Safety Board selected
JMS Naval Architects & Salvage Engineers to perform
a detailed intact stability analysis on the design,
configuration and passenger loading of the ETHAN
ALLEN to aid their investigation into the probable
cause.
ETHAN ALLEN is a Dyer 40 fiberglass mono-hull design
built in 1964. The design has been in production
since 1960 in a variety of configurations including
tour boats similar to the ETHAN ALLEN. JMS validated
available engineering drawings, lines plans and
previous stability calculations performed on the
vessel. Many of those plans and calculations were
discovered to be inconsistent, inaccurate and
therefore unreliable. In order to develop an
accurate hull form for the vessel, a detailed laser
survey was completed to produce a three dimensional
computer model of the hull to be used for the
analysis.
During her 41 years of operation, the ETHAN ALLEN
was modified several times with protective canopies
over the passenger area without any reassessment of
its stability. JMS calculated the maximum allowable
passenger loading for the each of the configurations
and determined that the vessel would have been
permitted to carry only 14 passengers based on U.S.
Coast Guard stability criteria. A dynamic analysis
was also conducted to study the effects of a passing
wave and shifting passenger weight.
Using the results of JMS’ analysis, the NTSB
determined that the probable cause of the capsizing
was the vessel’s insufficient stability to resist
the combined forces of a passing wave or waves, a
sharp turn, and the resulting involuntary movement
of passengers. The study underscored inadequacies in
the existing stability standards for small passenger
vessels and inconsistencies in how these vessels are
regulated when they are not under U.S. Coast Guard
jurisdiction. As a result of this and other recent
small passenger vessel incidents, the Coast Guard is
reassessing the potential consequences of revising
stability regulations for all domestic passenger
vessels to account for increased passenger and
vessel weight.
JMS also developed a computer animation recreating
the accident event and to help explain the technical
aspects of this accident. The animation is based on
the technical results of the JMS report as well as
survivor and eyewitness accounts.
Links to the NTSB final report, presentations and
web cast from the public hearing on 25 July 2006 can
be found here:
http://www.ntsb.gov/Events/Boardmeeting.htm#
JMS performed similar work for the NTSB in 1999 on
the Arkansas DUKW Tour Boat MISS MAJESTIC accident.
More information can be found here:
www.jmsnet.com/dukw.htm
