A helicopter on a photography mission for a real estate firm lost power and plunged into the Washington Channel near the 14th Street bridge yesterday morning, killing three passengers while scores of people looked on from the shore.

Only the pilot, identified as Jack C. Turley, 37, of Baltimore, survived the crash, apparently by jumping clear of the aircraft as it hit the water, police said.

He was listed in serious condition with possible back injuries at George Washington University Medical Center, according to a spokeswoman.

Among those killed was free-lance photographer William S. Weems, whose work has appeared in National Geographic magazine and who has published several pictorial books.

He was taking pictures for a promotional brochure for Sumner Realty Co., 2000 Pennsylvania Ave. NW, according to the Baltimore advertising firm that hired him.

Authorities said the five-passenger Bell Jet Ranger was hovering 200 feet above the water around 7:30 a.m. when it apparently lost power, then plunged into the channel about 100 yards from a busy waterfront area of seafood wholesalers and yacht slips off Maine Avenue SW.

"I heard the noise of the motor stop and then I heard them hit the water," said Norman Matthews, who sells fish from a boat belonging to Capt. Red's Seafood. "It just dropped into the water."

Although D.C. harbor police and Fire Department boats arrived within five minutes, rescuers were hampered in their attempts to go after the three passengers because they did not carry diving equipment on board, authorities said.

Harbor police had to return to their marina at 550 Water St. SW to retrieve air tanks, causing a delay of about 10 minutes, police said. Police said the first passenger was brought to the surface at 7:50 a.m., about 20 minutes after the crash, but several witnesses said that 26 minutes had elapsed.

Witnesses described dramatic rescue attempts as several small boats and at least one swimmer set off in the direction of the spreading oil slick and debris.

Tom Whitford, a free-lance writer who lives aboard a houseboat, said he dived into the water when he saw the pilot clinging to an inflatable pontoon, which police said may have detached from the upended helicopter.

"I was afraid he would slip back," said Whitford, 46, who swam about 70 yards before another man in a dinghy reached the pilot.

Two of the victims, identified as Robert Joy, 45, of Potomac Avenue NW, and Victoria Hinckley, 24, of 2409 Ridge Road Dr. in Alexandria, were taken to George Washington Medical Center with massive chest injuries, according to a hospital spokeswoman.

Joy died at 9:11 a.m. and Hinckley died at 11:39 a.m., the spokeswoman said.

Weems, 44, of 2030 Pierce Mill Rd. NW, was taken to Washington Hospital Center, where he was pronounced dead at 8:45 a.m.

Gerry Willse, senior vice president of the Baltimore advertising firm Barton Gillet, said Weems had been working on the brochure for about three weeks and had been waiting for yesterday's clear weather to complete his last series of photos.

Joy, owner of the Red Balloon toy store in Georgetown, was a neighbor and friend of Weems' who had been invited along for the ride, according to friends. Hinckley worked for Sumner Realty.

Federal safety officials began an investigation into the cause of the crash of the jet-powered Bell 206B Jet Ranger, the most widely used civilian helicopter in the country.

Pilot Turley spoke with investigators in his hospital room yesterday and told them that the craft's engine failed, according to Michael Benson, a spokesman for the National Transportation Safety Board.

Benson said the pilot was hovering at an altitude of about 200 feet about 50 feet off Hains Point when the helicopter rotated slightly to one side, then an alarm sounded to warn of engine failure. Turley told investigators that he thought he would be able to maneuver the helicopter over land but was unable to do so.

"His first thought was to get to Hains Point," Benson said. "He thought it would be pretty routine and didn't understand why he couldn't land."

The flight began about 7 a.m. at National Airport, home of the charter firm, Stuart Aviation, which supplied the aircraft, authorities said.

Turley told investigators that he made several passes in the vicinity of Arlington National Cemetery before heading to the area above the Washington Channel.

Once in the area, the helicopter hovered in different positions for at least 15 minutes, according to several witnesses who live in boats along the channel and who said they were awakened by its loud clatter. "It woke everybody up," said James Hamill, a houseboat owner at the Capital Yacht Club.

Scores of marina residents, among them Robert W. Jones, were watching as the Ranger flew south down the channel, then turned back north. The aircraft hovered in one position above the water as a photographer, his feet hanging out, sat in the doorway and took pictures.

"I was looking at it through binoculars," said Jones, a houseboat owner. "All of a sudden, he {the pilot} backed the helicopter up, put the nose down in a 10-degree angle as if leaving the scene. Then he banked to the left . . . and the engine failed."

Marilyn Sharkey was watching from the railing of her houseboat, Corsair II, just before leaving for work. "They were taking pictures . . . The engine quit and there was dead silence. It went right down," she said.

"It hit more-or-less flat, just like a huge belly-whopper," said Hamill. "The fact that he got it into a fairly flat position would indicate that he was trying to fly it . . . . The plane was under some sort of control {during the plunge}," said Hamill, who flies glider aircraft.

Several witnesses said the water in the channel splashed as high as 25 feet when the helicopter hit. The pilot apparently triggered inflatable emergency pontoons, but they were not enough to keep the helicopter from rolling upside down, trapping the passengers underwater.

By chance, the helicopter came down within 100 yards of a group of Washington residents who were unusually well equipped to join in a rescue.

Hamill had a portable short-wave radio in his hand when the helicopter went down and made an immediate call to the harbor police. Several boat owners reached the pilot within moments.

Ken Feil, a Washington Post photo editor who was in the cabin of his boat making coffee when the crash occurred, jumped into a dinghy with a neighbor and set out across the channel.

"There were bits and pieces of plastic and insulation floating in the water and there was fuel all around," he said. "By that time there were six to eight boats out there, so I went back to the dock."

D.C. Police Chief Maurice T. Turner Jr., who called the response time of the harbor police and Fire Department "very admirable," said all the passengers were removed from the water by 8:05 a.m.

Several witnesses, however, disputed the official chronology and said rescue efforts were painfully slow, noting the frustration of watching a police boat arrive, then depart to pick up divers and equipment.

"It took 26 minutes for the divers to get dressed and into the water," said Ellie Truman, a resident of the marina. "For a city that has an airport located on the river, they have to be better prepared than that . . . . The president flies over there, heads of state fly over there -- that's just ridiculous.

"I wanted to go in {the water}; the pilot was saying there were three other people, and I felt so helpless and frustrated. I kept screaming, 'Where're the divers?' and they kept saying, 'They're coming, they're coming.' But when you're talking about people's lives, every second helps," Truman said.

Whitford is an experienced scuba diver who said he was ready to go down to look for the victims had there been any diving equipment aboard the first police and fire boats to reach the scene.

"If we'd been able to get ahold of a {diving} tank, we could have done something more," Whitford said.

One victim was taken from the scene by helicopter. Witnesses saw two of the victims being taken away with resuscitation gear over their mouths and noses.

Weems had been trying to get a photograph of the Rosslyn skyline from behind the Tidal Basin, according to Willse, the Baltimore advertising executive.

Salvage crews used a crane to lift the generally intact wreckage of the helicopter from the channel yesterday afternoon.

Benson, the NTSB spokesman, said the helicopter would be taken to an Army Corps of Engineers warehouse at 12th and Water streets SW.

Benson said the helicopter would be examined closely for mechanical defects, but declined to speculate on the cause of the crash.

Other areas of inquiry, he said, include the pilot's history, weather at the time of the accident and the maintenance history of the aircraft.

If the engine did fail, that in itself would not explain the seriousness of the accident, helicopter experts said yesterday. Helicopters are supposed to be able to glide to a safe landing without power, a technique known as auto-rotation.

Even so, losing power while hovering at low altitude -- which apparently happened -- is an extremely difficult situation for a pilot to handle. Without any forward motion to initiate a glide, experts said, the aircraft has nowhere to go but down, and it does that quickly.

Turley, who had 6,000 flying hours in turbine-powered helicopters, told investigators that he had practiced auto-rotation countless times and was baffled by the helicopter's performance, according to Benson.

At the marina on the Washington Channel, residents spoke of feeling grief for the helicopter passengers and anger that it had come so close to the crowded marina, where 75 to 100 boats and houseboats are docked, with fuel tanks full of gasoline or diesel fuel.

"You can imagine what would have taken place if it had come down in the marina," said Hamill, a vice commodore of the yacht club. "It would have been a holocaust."

"We've complained on a number of occasions about {helicopters} flying much too close to the sailboats . . . especially the military choppers. We've complained to the FAA. It changes for a while, then it drifts back. It's bloody dangerous business. It's just too dangerous." Staff writers Victoria Churchville and Eric Charles May contributed to this report.