NTSB recommends adding reserve buoyancy to amphibious craft

The National Transportation Safety Board has recommended that operators of amphibious passenger vehicles provide their craft with enough reserve buoyancy — from watertight spaces or built-in floatation — so that they remain afloat when flooded.

The NTSB report came in response to the sinking of Miss Majestic in Lake Hamilton, Ark., on May 1, 1999 (PM #42). Thirteen of the 20 passengers, including three children, died when the amphibious craft sank in 51 feet of water. The lack of adequate reserve buoyancy and an inoperative bilge pump were factors in the accident.

The NTSB concluded that water entered Miss Majestic’s hull through a gap between the vehicle’s drive shaft and its housing. A critical clamp that held a watertight rubber boot in place on the through-hull aft shaft had been improperly secured during routine maintenance and was not checked before the vehicle went back into service.

It is estimated that water entered the hull at the rate of 220 gallons per minute. The fact that the vehicle lacked an operative bilge pump and alarms, watertight bulkheads, and reserve buoyancy exacerbated the situation. The NTSB report also noted that the vehicle’s canopy might have trapped some of the victims as the vehicle sank.

On Dec. 11, 2001, another amphibious tour boat sank in Seattle’s Lake Union (PM #63) when a hull-access plug failed to be replaced during routine maintenance. No one was injured in that accident.

These incidents have forced the U.S. Coast Guard to take a closer look at the operation and maintenance of the World War II-era amphibious craft, popularly known as ducks because of their military designation as DUKWs.

Following the Miss Majestic accident, the Coast Guard issued new inspection guidelines for the boats. In that document, the Coast Guard noted: “The vehicles were built with a life expectancy of only a few months. Although mechanically rugged, hull construction was simplified for the sake of the accelerated production schedule and the vehicle’s anticipated short life expectancy.”

But the Coast Guard questioned the practicality of using floatation foam to increase reserve buoyancy: “Although foam floatation can augment subdivision, foam installation generally tends to aggravate maintenance problems by restricting access. A vessel designed without foam floatation is much easier for the owner to maintain and the Coast Guard to inspect.”

The Coast Guard has not instituted any requirements for reserve buoyancy in response to the NTSB’s recommendations.

Phil Young, director of operations for Boston Duck Tours Inc., said his company has added reserve buoyancy to one of its 17 vehicles, but that the modifications were difficult and costly because of the small amount of void space within the hull.

But Boston Duck Tours has taken a number of other measures to make the boats safer. The company has installed redundant, alarmed bilge pumps, modified the shaft through-hull fitting to minimize potential flooding, and installed canopy curtains with emergency ripcords. They have even refitted their windshields with air shocks so that they can be opened quickly in the event of an emergency.

Until owners are able to provide sufficient buoyancy, the NTSB recommends:

  • Installation of high-volume, alarmed bilge pumps,
  • In-water inspection following any service involving hull penetrations,
  • Verification of watertight condition prior to each water operation.

    Miss Majestic was built in 1944 and is one of approximately 250 former DUKWs that operate as tour boats throughout the United States.

    Land and Lake Tours, the parent company of White and Yellow Duck Tours, owned and operated Miss Majestic. The company, which owned 12 DUKWs, had been operating tours since 1963 without an accident.

    All assets of the company, including the salvaged Miss Majestic have been sold at auction with the proceeds being distributed among the survivors who filed lawsuits.

  • By Professional Mariner Staff