LAS VEGAS (AP) -- Federal investigators are focusing on unexplained turns and a sudden climb that a sightseeing helicopter made moments before it crashed in a remote canyon east of Las Vegas last week, killing the pilot and four passengers on a twilight tour marking marriage milestones.
A preliminary National Transportation Safety Board report issued Tuesday summarizes details already made public by a board member after he viewed the charred wreckage of the Dec. 7 crash near Lake Mead.
"The left turn and climb are not part of the normal route," said the report, which makes no conclusions or recommendations. NTSB officials said a final report on the crash could take a year.
Radar records show that about a minute before the crash, the aircraft operated by Sundance Helicopters of Las Vegas climbed 600 feet and turned sharply left, fell 800 feet, turned left again and plunged into a ravine, the report said.
The pilot, Landon Nield, 31, of Las Vegas, died in the crash, along with Kansas tourists Delwin and Tamara Chapman, both 49, and India visitors Lovish Bhanot, 28, and Anupama Bhola, 26.
The Chapmans were celebrating their 25th wedding anniversary. Bhanot and Bhola were honeymooning after their marriage last month in a suburb of New Delhi, India.
Nield, a devout Mormon who grew up in Wyoming and Utah, was also a newlywed - he married in Las Vegas in June. He had no history of accidents or violations, according to the Federal Aviation Administration.
Sundance officials did not immediately respond to messages seeking comment.
Company chief executive Larry Pietropaolo has said there was no distress call before the helicopter GPS signal stopped during what typically would have been a 40-minute twilight tour over Hoover Dam and the neon-lit Las Vegas Strip.
Chief NTSB Investigator Bill English was due to leave Las Vegas on Tuesday, a day after large pieces of the AS350-B2 wreckage were airlifted out of the canyon for transport to Phoenix and testing at an NTSB lab. The French accident investigation agency BEA is also taking part because the aircraft was built in France.
Transportation board member Mark Rosekind told reporters last week that the ill-fated helicopter, built in 1989, underwent routine maintenance the day before the crash. The engine was replaced, along with mechanical devices called servo-actuators in the tail and main rotor.
The chopper made one test flight and two passenger tours before the fatal last flight. Rosekind said evidence showed the engine was producing power when the aircraft crashed.
The helicopter was not required to have a "black box" data recorder, and was not equipped with one.
Rosekind said a data record from the ill-fated aircraft could have helped investigators determine what caused the aircraft to go off course.
NTSB officials interviewed several witnesses on the ground who reported hearing or seeing the helicopter in its last minute of flight, as well as passengers from one of the earlier tours and Sundance mechanics and employees. The results of those interviews weren't made public.
The crash renewed questions about air tour safety and focused scrutiny on a company that had at least five accidents since 1994 and was the subject of 10 federal enforcement actions, mostly for minor infractions.
In September 2003, a pilot and six passengers were killed when a Sundance helicopter slammed into a canyon wall east of the Grand Canyon West Airport. The pilot was blamed for violating federal aviation regulations. The company was not punished.
Pietropaolo has headed the company for 3 1/2 years. He said he believes Sundance has an excellent safety record compared with the air tour industry and general aviation.
The Federal Aviation Administration last year proposed new rules for helicopter operators, including tour companies, requiring onboard technology and equipment to avoid terrain and obstacles.
(Copyright 2011 by The Associated Press. All Rights Reserved.)