The Cessna 310R that crashed in pieces into an East Palo Alto neighborhood flew in a level or slight climb at low altitude until it struck high-tension power lines and a transmission tower, according to a preliminary report released Wednesday night by the National Transportation Safety Board (NTSB).
Multiple witnesses living near the accident site reported observing portions of the accident sequence.
One witness, who was walking on a levee near the crash site, said she saw an airplane "suddenly appear from the fog" to her left. She said she continued to watch the airplane fly from her left to her right at a low altitude until it impacted the power lines, according to the report.
Parts of the twin-engine Cessna, piloted by Doug Bourn, a senior Tesla engineer, impacted several residential structures and the ground following the collision with the power lines and tower, the report noted.
Bourn, a licensed commercial pilot, and his two passengers, Andrew Ingram and Brian Finn, also Tesla employees, were flying to Hawthorne, Calif., for a meeting. All three men were killed. The airplane was registered to Air Unique, Inc., of Santa Clara, and piloted by Bourn as a personal flight.
"Instrument meteorological conditions prevailed and an instrument flight plan was filed for the cross-country flight," the NTSB report said.
"Examination of the accident site revealed that the airplane struck power lines and a power line tower about 50 feet above ground level. Various portions of wreckage debris, power lines, and power-line tower structure were scattered throughout the wreckage debris path," according to the report.
The wreckage debris path was measured on a southwesterly heading for approximately 900 feet from the tower and wires to the main fuselage, which came to rest in front of a residence on Beech Street. A post-crash fire and wreckage debris damaged four residential structures and at least five vehicles along the debris path.
All major structural parts of the airplane were located within the wreckage debris path and are being studied by NTSB investigators. A fuel-laden wing, believed to have been severed by hitting the power lines and tower, crashed into a home housing a day care center and burst into flames, but all of the seven persons there escaped unhurt.
The plane's engine, landing gear and part of the fuselage destroyed a carport and the car in it, and the engine continued on, smashing the side of a garage and winding up inside the garage.
Joshua Cawthra, the NTSB lead aviation accident investigator, said a final report to determine the exact cause of the crash would take six months to a year.
"The process is very time consuming. It depends on where the investigation leads us. If it's mechanical failure we have to dig deeper as to why there was a failure," he said.
Cawthra said whether the plane impacted with the tower or wires first isn't known at this point.
"We may never know. It was pretty instantaneous," he said.