In an effort to reduce serious injuries, the U.S. Navy is retrofitting its
special warfare high-speed boats with new shock-absorbing seats.
The high-speed crafts, called Mark Vs, have been in operation since the mid-1990s,
but it took several years for the U.S. Special Operations Command to determine,
through medical surveys, that the crews were suffering an unusual high rate
of injuries, ranging from sprained ankles to broken backs and whiplash.
“When guys ride these boats at 45-50 knots, in significant sea states,
they were getting injured,” said Cmdr. Robert Womer, former chief of maritime
programs at the Naval Special Warfare Command.
The 57-ton Mark V typically carries special operations forces, primarily SEAL
combat swimmers. Both the craft operators and passengers get hurt during rides,
but the crews experience a higher level of injury because they spend more time
on the boat.
In response to unofficial injury reports, the NSWC in 1998 kicked off a number
of studies to try to pinpoint the cause of the injuries, which many already
suspected resulted from the intense pounding that craft operators were taking
during high-speed rides.
“They found the dynamic forces they were experiencing when riding the
craft were sufficient to cause significant injuries,” Womer told National
Defense. Gravity forces at 45-50 knots, and the momentum created with rapid
accelerations and decelerations, can put tremendous stress on the human body,
no matter how physically fit, he noted. “If the seas are calm, we would
not experience many injuries. Turbulent seas are a major factor.”
After completing several shock-mitigation studies, the Naval Special Warfare
Command concluded that the Mark V seats needed to be replaced. Two civilian
government employees came up with a novel concept for a shock-absorbing seat,
Womer explained. To make the new seats, the original seat manufacturer, a company
called Stidd Systems Inc., of Greenport, N.Y., partnered with Taylor Devices
Inc., of North Tonawanda, N.Y., which produces shock absorbers like those used
in cars.
The companies created a shock-absorbing seat that looks like the original,
but is mounted into a rigid frame, so it allows about seven inches of vertical
movement, up and down.
The Navy purchased 400 seats, enough to equip all 20 Mark V boats now in operation.
Each boat has 21 seats, but only 20 will be swapped. All 400 will be installed
by the end of the year, said Womer.
“It takes a long time to produce 400 seats,” he said. “We
are replacing the front couple of rows first, because that is where the crewmen
sit. Back rows are for passengers, and they are not exposed to the same degree
of dynamic force as the crewmen.”
But even after the new seats are in place, the injury problem may not go away,
Womer added. “We are not certain that all these injuries are from boat
rides. We think we know, but did not institute a really robust medical surveillance
program until fairly recently. ... We don’t have any really good figures
on the true injury rates.”
Also complicating attempts to study injury patterns is the lifestyle of special
operators, noted naval special warfare spokesperson Patricia O’Connor.
“These are hard-charging warriors,” she said. “They don’t
want to complain that they have a sore back. If they do, inevitably they may
be asked by their boss to sit out a mission.” They also tend to practice
strenuous sports, she added. “On their off hours, they are mountain biking,
skiing, doing all kinds of activities that could possibly impact their body.
We need to try to capture that data as well, and get a better picture of what
these guys are doing.”
Another ergonomic upgrade planned for the Mark V is to move the throttle control
from the engineering panel—which is located 3.5 feet away from the driver—to
the armrest mount. The driver has to lean over frequently, or even get out of
his seat, to slow the boat down or speed up. Moving the throttle position from
the engineering panel up to the armrest allows the operator to control from
his seat both the speed and the direction of the boat.
The U.S. Special Operations Command recently approved funding for the throttle-control
modifications.