NTSB photo shows the wreckage of the Bell 407 which crashed after being hit by a Sikorsky S-64E Skycrane helitanker during a 2023 wildfire near Cabazon, California. (Photo Credit: NTSB via CNN Newsource)

Washington (CNN) — A firefighting helicopter crew’s decision to fly an altitude higher than they were cleared for and the subsequent rapid descent led to the deaths of three people in a midair collision in 2023, according to a final report from the National Transportation Safety Board.

Thursday’s report concludes the investigation into the collision between a Bell 407, on a helicopter coordinator training flight, and a Sikorsky S-64E Skycrane helitanker during a 2023 wildfire near Cabazon, California.

The report concludes the cause of the collision was the Skycrane crew’s decision to enter the airspace around the fire at “an altitude significantly above their maximum cleared altitude, which resulted in their need for an aggressive descent into congested airspace and subsequent failure to see and avoid the Bell 407.”

Both helicopters departed from Hemet-Ryan Airport, east of Los Angeles, and about 18 miles from the fire on August 6, 2023. The Bell helicopter, with three people onboard, traveled north and about three minutes later the Skycrane helicopter headed northeast, with two people inside.

“Likely due to the mountainous terrain,” the report read, “neither helicopter was able to receive a clear radio signal” from its air tactical group supervisor, who the helicopters are supposed to communicate with.

The helicopters both maneuvered to establish radio contact, but the Skycrane helicopter continued into the airspace around the fire at 4,000 feet altitude before they were given clearance to enter at a maximum altitude of 2,500 feet.

The Skycrane initiated a “rapid descent” reaching their cleared altitude, but the right wheel and tire assembly slammed into the other helicopter’s main rotor three seconds later.

An explosion separated the Bell’s tail boom, main rotor, mast and transmission and sent the fuselage crashing into the ground. The three people onboard the Bell were killed. All on-board communication and video recordings in the helicopter were destroyed by the post-crash fire.

NTSB photos show the wreckage of the Bell 407 which crashed in 2023 after being hit by a Sikorsky S-64E Skycrane helitanker during a 2023 wildfire near Cabazon, California. (Photo Credit: NTSB via CNN Newsource)

The Skycrane made an emergency landing in a field. The aircraft only sustained minor damage and the two people inside were not injured.

“The Skycrane pilot should have advised (the Air Tactical Group Supervisor) that the aircraft could not comply with the altitude clearance and should have informed ATGS of their aggressive descent,” the report notes.

The helicopters were among six aircraft responding to the Broadway Fire, which began after a building fire spread to nearby vegetation in Cabazon, a community in Riverside County 90 miles east of Los Angeles.

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