A US federal investigation into the helicopter crash that killed basketball legend Kobe Bryant is looking into whether a dangerous amount of fog may have been the cause of the tragic incident.
The aircraft which was carrying Bryant and eight others, including his 13-year-old daughter Gianna, crashed into a hillside outside Los Angeles while flying in fog considered dangerous enough that local police agencies grounded their choppers.
The helicopter plunged into a steep hillside at about 9.45am (local time) on Sunday with an impact that scattered debris over an area the size of a football field and killed all aboard.
The helicopter was operating under “special visual flight rules” (SVFR), according to an air traffic control conversation with the pilot, captured by website LiveATC.net.
An SVFR clearance allows a pilot to fly in weather conditions worse than those allowed for regular visual flight rules (VFR).
Pilots can request SVFR clearance before takeoff or mid-flight, especially if conditions suddenly change, CNN transportation analyst Peter Goelz said.
While SVFR clearance is “pretty normal,” he said, “it’s not something that’s often recommended.”
“If you’re a pilot, and you’re in marginal conditions, or changing conditions that become marginal, you might call air traffic control” to request SVFR, Mr Goelz said.
If granted SVFR clearance, the pilot will typically keep tighter communication with air traffic control.
The Burbank Airport control tower allowed the helicopter to proceed using the special clearance, the audio reveals.
“Maintain special VFR at or below 2500,” the pilot confirmed to the controller.
Later in the flight, the pilot apparently asked for “flight following,” a service in which controllers are in regular contract with an aircraft.
The controller told the pilot “you’re still too low level for flight following at this time.” That could mean the helicopter was too low to be seen on air traffic control radar.
The 41-year-old Bryant was one of the game’s most popular players and the face of the 16-time NBA champion Lakers.
The exact cause of the crash is still unknown, but conditions at the time were such that the Los Angeles Police Department and the county sheriff’s department grounded their helicopters.
The Los Angeles County medical examiner, Dr Jonathan Lucas, said the rugged terrain complicated efforts to recover the remains. He estimated it would take at least a couple of days to complete that task before identifications can be made.
Bryant’s helicopter left Santa Ana in Orange County, south of Los Angeles, shortly after 9am and circled for a time just east of Interstate 5, near Glendale.
Air traffic controllers noted poor visibility around Burbank, just to the north, and Van Nuys, to the northwest.
After holding up the helicopter for other aircraft, they cleared the Sikorsky S-76 to proceed north along Interstate 5 through Burbank before turning west to follow US Route 101, the Ventura Highway.
Shortly after 9.40am the helicopter turned again, toward the southeast, and climbed to more than 600 metres.
It then descended and crashed into the hillside at about 426 metres, according to data from Flightradar24.
When it struck the ground, the helicopter was flying at about 160 knots and descending at a rate of more than 1220 metres per minute, the data showed.
The chopper went down in Calabasas, about 48km northwest of downtown Los Angeles.
Federal transportation safety investigators were on their way to the scene.
Among other things, they will look at the pilot’s history, the chopper’s maintenance records and the records of its owner and operator, said NTSB board member Jennifer Homendy at a news conference.
Kurt Deetz, a pilot who used to fly Bryant in the chopper, said the crash was more likely caused by bad weather than engine or mechanical issues.
“The likelihood of a catastrophic twin engine failure on that aircraft – it just doesn’t happen,” he told the Los Angeles Times.
Justin Green, an aviation lawyer in New York who flew helicopters in the Marine Corps, said pilots can become disoriented in low visibility, losing track of which direction is up.
Green said a pilot flying an S-76 would be instrument-rated, meaning that person could fly the helicopter without relying on visual cues from outside.
Among those also killed in the crash were John Altobelli, 56, longtime head coach of Southern California’s Orange Coast College baseball team; his wife, Keri; and daughter, Alyssa, who played on the same basketball team as Bryant’s daughter, said Altobelli’s brother, Tony, sports information director at the school.
Costa Mesa Mayor Katrina Foley tweeted that the dead also included Christina Mauser, a girls basketball coach at a nearby elementary school.
Her husband, Matt Mauser, said in a Facebook post: “My kids and I are devastated. We lost our beautiful wife and mom today in a helicopter crash.”
The National Transportation Safety Board typically issues a preliminary report within about 10 days that will give a rough summary of what investigators have learned. A ruling on the cause can take a year or more.