[chris]

A small helicopter on a low-altitude photo assignment spun out of control and dropped into a field behind Indian Fields Elementary School in South Brunswick on the morning of July 20, 2011, seriously injuring the two people aboard, authorities said.

The two-seat Robinson R22 Beta, registered to Nassau Helicopters Inc. and based at Princeton Airport, had been circling slowly at about 150 feet over the school and nearby commercial property while aerial photographs were taken, according to accounts given to investigators. Witnesses said the aircraft completed roughly a circuit and a half before its tail swung around and it came down in a slow rotation, settling on its belly on a dirt road about 100 feet from the building. School was not in session.

The pilot, Edmund Eilbacher, 27, of Hillsborough, and his passenger, Julia Armstrong-Robertson, 44, of Newark, Delaware, were pulled from the wreckage by roofers working on the school while fuel leaked from the aircraft, police said. Armstrong-Robertson, a freelance aerial photographer who owned Aero-Imaging Inc., had hired the flight for a shoot in the Dayton section of the township.

Both were taken to Robert Wood Johnson University Hospital in New Brunswick and admitted to surgical intensive care in critical condition with chest and back injuries, hospital and police officials said. Neither was killed.

South Brunswick police fielded a series of 911 calls as the helicopter went down, and recordings of those calls were later released. One caller can be heard walking toward the crumpled aircraft to check on the occupants while still on the line with a dispatcher.

Federal investigators pointed to a loss of tail rotor effectiveness, an aerodynamic condition that can produce an uncommanded spin at low speed and low altitude. The National Transportation Safety Board, which examined the wreckage in Clayton, Delaware, in late August 2011, noted that a low rotor rpm warning tone sounded and continued through impact after the pilot cut the throttle in an attempt to halt the spin, and that the engine had been running normally up to that point.