Conversations recorded in the moments before a commuter plane and a smaller plane collided, killing 10 people, indicate the pilot of the larger aircraft did not see the other one until impact.
The recordings also reveal that SkyWest Metroliner Flight 834 was warned by the Salt Lake International Airport control tower just before the Jan. 15 collision to be on the lookout not for the single-engine plane but for a Western Airlines Boeing 727.
The tapes are certified rerecordings authorized for release Saturday by the Federal Aviation Administration.
The crash, which rained debris on a residential neighborhood, remains under investigation by the FAA, and the National Transportation Safety Board will hold a public hearing into the cause of the accident, although no date has been set.
60 Seconds of Conversation
The tape includes 60 seconds of cockpit conversation before the collision. At that point, the tape, while full of static and nearly unintelligible, records an expletive.
During the last 20 seconds of the tape, the controller, apparently unsure a collision had occurred, calmly continues asking the Metroliner pilot to respond.
"SkyWest 834 is cleared visual approach runway 34 left . . . SkyWest 834 is cleared visual approach runway 34 left . . . Sky-West 834, Salt Lake," the controller repeated.
"The interesting thing about this tape is that it shows that the controllers were giving the Sky-West traffic advisories for a Western 612, which was ahead of the Metroliner and off to his left," said Ron Nelson, general manager of Debron Air at Salt Lake Airport No. 2, the point of origin for the private Mooney M-20C aircraft involved in the crash.
"The impact occurred off to the right of the Metroliner. The controllers were having the pilot look away from where the Mooney was coming to watch out for the Western plane," he said.
Nelson, who listened to the tape several times, said the controllers also told the Metroliner to turn north. This required the pilot to raise one wing, further hindering the pilot's ability to see to the right.
That's where the Mooney approached, authorities said.
"The SkyWest pilots were following directions, looking for traffic, but that took them away from looking in the other direction where the Mooney was flying," Nelson said.
Nelson, who has flown for nine years and taught aviation for several years at Salt Lake International Airport, said that when the Metroliner was turning, the Mooney was climbing and its nose would have been up. Because that restricts forward visibility, it also could have been difficult for the Mooney pilot to see the Metroliner.
As to the flight controllers, Nelson said, their "top priority is to separate Instrument Flight Traffic (the Western plane and Metroliner) from other IFT traffic working in the airspace. Their No. 2 priority is to separate IFT traffic from other Visual Flight Rule traffic (the Mooney) in the area."
An NTSB official has said the Mooney showed up on radar, but none of the air traffic controllers interviewed at the Salt Lake International Airport reported seeing the planes close together.