"It circled over, then it turned sideways and just came straight down," he said.

The fact that the blades were still intact after impact with the Yacht Club Building indicates that transmission failure is a distinct possibility, Yarman said.

"The blades were damaged, but not damaged like I would expect at high RPMS [revolutions per minute]," Yurman said. "In this, we show no signs of autorotation."

A clue to the puzzle may lie in the helicopter's transmission indicator, which lights up if pieces of transmission gears begin to clog the aircraft's motor.

"If that light comes on, you better land the aircraft right then," Retta said. "That's something all kids learn in flight school."

The transmission equipment was recovered near the crash site and is presently being analyzed, Yurman said.

Yurman said yesterday that his investigation is only in the preliminary stages. It may be weeks before investigators can finally locate the problem with the chopper.

After every thirty flight-hours, state police maintenance crews inspect the plane, and pilots check the unit daily, Bennett said Wednesday. The helicopter's engine had been serviced last year, he said.

The crash was the first in the 26-year history of the state police helicopter unit, according to Dean R. Bennett, chief pilot for the state police. "We pray it will not happen to us again."

According to NTSB records, the A350B AStar helicopter has been involved in 63 accidents in the United States, killing 57 on-board passengers. It averages 3.5 accidents per 100,000 hours of flight.

"The helicopter has an average failure rate for popular vehicles of the same size," Breiling said.

The remaining State Police helicopters have been grounded and will fly only in emergencies, Col. Charles Henderson, Superintendent of the State Police, told The Associated Press yesterday.

Caring for the Families

The two state troopers aboard the helicopter were James Mattaliano, 33, of Sandwich and Paul A. Perry, 39, of Salem. They were 12 and 14-year veterans of the State Police, respectively. Both had extensive flying experience, Bennett said.

Also killed were longtime AT&T technicians Arthur T. Howell, 47, of Malden and Michael McCarthy, 46, of Weymouth. Both men were just shy of completing 29 years of service with the firm. They would have been eligible for retirement next year, said S. Kay Gibbs, a spokesperson for AT&T.