The tour helicopter that went down just west of Lake Mead had its engine and other parts replaced the day before it crashed, killing five people, investigators revealed Friday.
The aircraft operated by Sundance Helicopters was on a routine flight Wednesday until a minute before impact when the chopper took an unplanned sharp left turn and then steeply declined into a ravine, National Transportation Safety Board member Mark Rosekind said. Whether the maintenance or other factors caused the sudden descent are details still being considered in the investigation.
A preliminary report is expected to be available within 10 business days. The full report will not be released for at least nine months.
"The last minute are where things changed," Rosekind said. "Why? That part we don't know that yet."
Clark County Coroner Michael Murphy said the victims are not easily recognizable. Staff confirmed that the coroner's office is working with family members in New Delhi, India, to match medical records for two unnamed passengers.
Three other victims, the pilot, Landon Nield of Las Vegas, and passengers Delwin and Tamara Chapman, a Utica, Kan., couple celebrating their 25th wedding anniversary, had been identified by relatives.
Nield, 31, who had been a pilot for seven years, was hired by Sundance nearly three years ago and had no history of accidents or violations, according to the Federal Aviation Administration. He was a devout Mormon who became the father of two stepchildren when he married in June.
Delwin Chapman, 49, served on the Utica City Council and ran a construction company. His wife, known as Tammy, also 49, operated a hair salon before recently closing shop. She was diagnosed with multiple sclerosis a few years ago. The couple had four daughters.
Funeral services for the known victims have not yet been scheduled, family members said.
On Friday -- the NTSB's first full day at the 2.7-square-mile crash site -- crews removed the helicopter's engine, took photos and began reviewing the aircraft's maintenance records, interviewing witnesses and collecting the pilot's 72-hour history leading up to the crash.
The remote location of the site delayed the investigation Thursday and was difficult for investigators to reach, Rosekind said. It takes a trip of nearly a mile on an all-terrain vehicle, about a 100-yard hike and a climb up a 10-foot ladder to reach the wreckage.
Records show the helicopter underwent routine 100-hour flight maintenance Tuesday, a check that resulted in the engine and two mechanical control devices called actuators being replaced because of lifetime limits on the parts, Rosekind said.
The aircraft then completed a maintenance flight and two tours before the crash during Wednesday's 40-minute "twilight tour" scheduled to loop from McCarran International Airport, over the Strip to Hoover Dam and back.
When investigators separated the engine from the wreckage Friday, an initial examination indicated it was producing power at the time of impact, Rosekind said. But the engine is still under review with the actuators, which also were removed from the site.
Sundance Helicopters through a statement said it is fully cooperating with the investigation. The company has had its share of trials, including at least five accidents and 10 federal enforcement actions since 1994. Tours resumed Friday, but the company said it will give refunds as requested.
The Associated Press contributed to this report.