The helicopter damage was consistent with "powered rotation" – from the engine moving the rotors – when the flight crashed, according to a preliminary report by the National Transportation Safety Board.

The finding is significant because investigators determined immediately after the accident that the copter was in a fast descent at the time of impact, after having climbed to try to get out of thick clouds. That gave rise to the notion that perhaps the engines had failed.

The preliminary reportdoesn't pinpoint the likely cause of the crash on a fog-shrouded slope. That is expected to come when the final investigative report issued is in about a year.

Investigators did detail the extensive damage to the Sikorsky S-76B helicopter, which hit the side of a mountain in Calabasas, California, with great force.

"The entire fuselage/cabin and both engines were subjected to a postcrash fire. The cockpit was highly fragmented. The instrument panel was destroyed and most instruments were displaced from their panel mounts. Flight controls were fragmented and fire damaged," the report said.

A witness a mountain bike trail saw the copter just before it crashed close by.

"He said he began to hear the sound of a helicopter, which he described as appropriate for a helicopter flying while in a powered condition. He perceived the sound getting louder and saw a blue and white helicopter emerge from the clouds," the report said.

"He judged it to be moving fast, travelling on a forward and descending trajectory. It started to roll to the left such that he caught a glimpse of its belly. He observed it for seconds 1 to 2 seconds, before it impacted terrain about 50 feet below his position."

The helicopter took off Sunday, Jan. 26, in Orange County to fly Bryant, his 13-year-old daughter and their friends about 90 miles to a youth basketball tournament in Thousand Oaks, California. Their S-76B was a big helicopter outfitted for executive transport and a model with a generally good safety record.

It was piloted by Ara Zobayan of Huntington Beach, California, who was qualified to fly both visually and on instruments, Federal Aviation Administration records show. He received his commercial pilot's license in 2007.

The helicopter was being flown by sight, not instruments, following Southern California's freeways as it worked its way northwest. But as it got closer to its destination, the helicopter ventured from the flatlands into more rugged terrain and encountered a thick layer of fog.

Though it was outfitted with many luxury appointments, the NTSB said it lacked the helicopter version of a terrain awareness and warning system, or TAWS, which tells pilots if they are headed toward a hill or mountain obscured by clouds. Though the NTSB has recommended TAWS be required equipment aboard large passenger-carrying elements, it is still considered optional.

The helicopter carrying the retired NBA superstar and his party was flown up a canyon in Calabasas. Zobayan radioed air traffic controllers, having already received permission to transit controlled airspace with less than normal visibility, saying he was going to try to rise above the clouds. Investigators said he climbed to 2,300 feet above sea level, made a left turn and then crashed at high speed into the mountainside at 1,085 feet. The craft hit with such force that debris was scattered over a 600-foot area.

There were no survivors. A thin trail of smoke rose from the wreckage for hours after the crash.

Though Zabayan missed hitting the top of the hill by about 30 feet, investigators said there were even higher slopes in the area with which he would have had to contend.

A full investigation is expected to determine whether the cause of the accident was pilot error or mechanical failure. But it won't be easy. Unlike commercial aircraft, the helicopter didn't have cockpit voice or flight data recorders aboard. The NTSB hauled away wreckage in large white bags to analyze it for clues.