The federal investigation into the sinking of the Alaska Ranger has prompted the Coast Guard to issue an unusual nationwide warning to ship owners about the risks of controllable-pitch propellers that can go into reverse when electric power is lost.

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The federal investigation into the sinking of the Alaska Ranger has prompted the Coast Guard to issue an unusual safety warning to ship owners about the risks of controllable-pitch propellers that can go into reverse when electric power is lost.

The Coast Guard decided to issue the notice to ship owners and operators because “sitting on this for six months is against the interest of marine safety,” said Capt. Mike Rand, chairman of the Marine Board of Investigation. “That’s why we got it out right away.”

The Coast Guard and the National Transportation Safety Board are investigating why the Ranger sank, triggering one of the largest open-water rescues in Coast Guard history. A final report is expected within six months.

Five of the 47 crewmen perished in the frigid Bering Sea after the ship lost power on Easter Sunday and then went into reverse, severely hampering the crew’s ability to safely abandon ship. The reverse course also may have played a role in the final stages of flooding that sank the vessel, Coast Guard investigators say.

Nationwide, hundreds of seagoing ships have controllable-pitch propulsion systems, which allow the angle of the propeller blades to be adjusted to improve efficiency and directional control.

“The Coast Guard strongly recommends that owners, operators and masters of vessels with controllable-pitch propellers understand the design and operation of the system,” the Coast Guard safety notice states.

Rand said he struggled with how to word the warning, which was issued earlier this month, because it is not clear that all controllable-pitch systems will send a vessel into reverse if electric power is lost. Also unclear is at what point that might happen.

The Coast Guard alert also noted that on the cruise ship MS Explorer, the controllable-pitch propeller flipped into reverse after the ship lost electrical power Nov. 23 while off Antarctica. The 154 tourists, guides and crew were safely evacuated. But after they were in their life boats, the ship began traveling backward. The Explorer sank the next day.

Difficult decision

The Ranger’s troubles on March 23 began after it suffered a leak in its stern while cruising to a mackerel-fishing ground in the Bering Sea. The ship was part of a trawl fleet that catches and processes fish at sea, and was operated by the Seattle-based Fishing Company of Alaska.

As the water kept rising, the Ranger’s lights began to flicker and electric power was lost, according to a survivor’s testimony. The vessel then went into reverse and soon listed sharply, according to testimony from survivors.

The ship’s officers in the wheelhouse, Capt. Eric Peter Jacobsen of Lynnwood and First Mate David Silveira of San Diego, faced a dismal choice. They could keep the main engine running, which would propel the boat backward. Or, they could use battery-operated controls to shut down the engine, which would leave the vessel adrift.

The engines kept running and the vessel kept going in reverse as the crew prepared to evacuate. Coast Guard officials are still trying to understand the decisions made that day in the wheelhouse. Both Jacobsen and Silveira perished.

The Coast Guard safety alert noted the hazards of trying to evacuate a ship that’s moving in reverse.

Typically, life rafts — attached to the vessel by lines — are supposed to be drawn tight against the vessel’s side, so that crew can board them. But the Alaska Ranger was moving backward, so two of three life rafts shot to a position forward of the bow.

Stranded aboard a sinking ship, most of the 47 crew members were then forced to jump into the 34-degree water.

“Ultimately, only 22 members of the vessel’s crew made it into the life rafts. Of the other 25 members who never made it into a life raft, four died and one remains missing,” the Coast Guard notice stated.

“Going down pretty fast”

It’s unclear what caused the initial leak in the ship’s stern. But even after water flooded rear compartments, the vessel initially appeared to ride steady in the water, without listing unduly from side to side, according to crew testimony. Some survivors said they had hoped the vessel would stay afloat until a sister ship could come to the crew’s rescue.

After the electrical system failed, the propeller lapsed into reverse. The vessel listed sharply and appeared to be in a much more precarious position, according to survivors.

“That’s when things started getting supercritical,” said Gwen Rains, a federal fishery observer who survived the sinking. “We started going down pretty fast after that.”

Those eyewitness accounts appear to match what some experts note about the Alaska Ranger’s design. Even with water rushing in the stern compartments, the vessel was designed to be able to float, said Herbert Roeser, chairman of Trans Marine Propulsion Systems, a Seattle-based company that helped maintain the Alaska Ranger.

But once the vessel started going into reverse, the stern would have been driven down into the sea. Water then would have flowed on deck, then down into the fish-factory area below deck, which could have had a disastrous effect on stability, Roeser said.

“When we got water into the factory area, then we were in trouble with her,” said Roeser, who wasn’t on the boat but analyzed the events of that day. He also testified in a June Coast Guard hearing in Boston.

Coast Guard investigators are developing a model to simulate the effects that the reverse motion had on the vessel’s stability, Rand said.

“We hope the model will be able to explain this,” Rand said.

Hal Bernton: 206-464-2581 or hbernton@seattletimes.com