Investigators scouring the rubble of a Silicon Valley plane crash that killed an experienced pilot and two other Tesla Motors employees learned Thursday the wreck was captured by a neighborhood sound system that could yield clues to the cause of the accident.
The sound system was designed to help locate gunfire but also picked up the Cessna as it slammed into a set of power lines shortly after taking off in dense fog Wednesday, National Transportation Safety Board investigator Josh Cawthra said.
Cawthra said the recordings could give clues to any mechanical errors, allowing investigators to hear sound levels of the engine and propeller noise. It's the first time he'll use such data in a crash investigation.
The sound analysis is one of several areas investigators will pursue as they look at the cause of the wreck. Investigators said no distress calls were sent as the plane took off.
Authorities have identified the three people believed to have been on board the plane as Doug Bourn, Andrew Ingram and Brian Finn. They are all employees of Tesla, an electric car maker.
The San Mateo County coroner's office said it has been working with the families of those men to obtain medical records but could not yet officially confirm they had died in the accident.
Tesla officials confirmed late Thursday the three were employed by the company. In an email to The Associated Press, Tesla said Bourn, 53, was a senior electrical engineer and a five-year employee.
Ingram, 31, was an electrical engineer for 2 1/2 years, according to Tesla, while Finn, 42, was a senior interactive electronics manager since July 2008.
The plane was registered to Air Unique Inc., a company owned by Bourn of Santa Clara. Tesla has said Bourn is a senior electrical engineer at the company.
Elizabeth Houck, 40, a friend of Bourn, said he took her flying several years ago and conducted a thorough preflight check while keeping detailed log books on the aircraft.
"He did not shortcut on preflight procedures," she said. "He was very comfortable behind the wheel."
She believes Bourn would not have taken off in the fog Wednesday if he had any concerns about the aircraft or the weather.
Vicky Tuite, who worked with Bourn at Tesla before leaving the company in 2008, said he also was a flight instructor and offered a class for aspiring pilots at the company.
Shortly after takeoff Wednesday, the Cessna broke apart and skidded down the street, igniting vegetation and cars while raining debris into backyards.
No one was injured on the ground.
Cawthra said investigators were examining the pilot's experience and background. A toxicology report has been requested from the coroner's office, which is standard procedure, he said.
Investigators will also study the plane's maintenance history to determine if there is a safety issue.