LOS ANGELES, CA — A recording from NewsChopper4 captured sounds consistent with rotor-speed alerts during the final 29 seconds before the helicopter crashed in Chatsworth last month, killing three people, according to a preliminary federal report released Tuesday.
The National Transportation Safety Board's report describes that video, most of which captures events prior to the fatal Sept. 15 crash.
"During most of the recording, the ambient helicopter noise remained consistent with normal operations. During the last 29 seconds of the flight, the recording captured the helicopter noise as it changed frequency, along with intermittent and continuous horns, consistent with the helicopter's main rotor high rpm, low rotor rpm and other aural advisories," the report reads.
The agency has not yet identified what caused the crash and cautioned that the information released Tuesday is preliminary and subject to change.
Reporter Eliana Moreno and pilot George Marciniw were killed aboard the helicopter, along with 29-year-old Edy Gutierrez Mejia on the ground, authorities previously said.
The helicopter went down at about 6:55 p.m. while covering a fatal collision involving an SUV and a Metro bus near Nordhoff Street and De Soto Avenue.
The NTSB report lists one person on the ground with minor injuries. Fire officials initially reported that two people on the ground were injured.
A 4-minute, 21-second video taken by the reporter captured footage of the traffic crash as well as sounds from the helicopter's engine and main rotor. For most of the recording, the helicopter noise was consistent with normal operations, investigators wrote.
During the final 29 seconds, the noise changed frequency. The recording also captured intermittent and continuous horns consistent with alerts for high and low main rotor speeds and other audible advisories, according to the report.
Flight-tracking data cited in the report showed the helicopter departed Whiteman Airport at about 5:24 p.m. and flew roughly nine miles west. It spent about an hour and 24 minutes maneuvering near the traffic crash.
During the last minute of flight, the helicopter was about 800 feet above the ground and slowed to a ground speed of about 6 knots.
It then began descending rapidly while turning right. The last tracking point placed the helicopter directly above the crash site, still descending rapidly and traveling at a ground speed of about 38 knots.
Security cameras at nearby buildings recorded the helicopter descending and striking a metal storage container. A fire broke out shortly after impact, investigators said.
Investigators found extensive fire damage to the helicopter's body and debris extending about 30 feet around the main wreckage. All major components were either still attached to the body or within that debris field.
The report identifies the aircraft as a Eurocopter AS 350 B2 operated by Angel City Air. Its wreckage was moved to a secure facility for additional examination.
At a Sept. 16 briefing, NTSB investigator in charge Fabian Salazar called the onboard recording "probably the most important evidence that we have discovered so far" and said investigators planned to send it to the agency's laboratory for sound analysis.
Salazar said at that briefing that a final report identifying a probable cause could take about 18 months, depending on the circumstances of the investigation.
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