Frequency error before mid-air tragedy

An US air traffic controller listening to three conversations at once - including a personal phone call - may not have heard a critical pilot error before a deadly collision over New York's Hudson River in which a New Zealand pilot was killed last year.

Evidence gathered by the National Transportation Safety Board shows the controller at Teterboro Airport in New Jersey who handled the small plane that collided with a tour helicopter was talking with a friend on his headset while monitoring radio transmissions by the plane's pilot and another controller over speakers.

The controller, Carlyle Turner, directed pilot Steven Altman to contact nearby Newark Liberty International Airport on radio frequency 127.85, according to transcripts and other evidence released yesterday.

At the same second, a Newark controller was telling Turner there was another aircraft in the path of the plane and asking that he alert Altman. One second later, Altman read back a slightly different frequency: 127.871.

"The simultaneous transmissions ... interfered with each other," a summary report said.

During both radio messages, Turner was on a phone call to a friend. When Turner tried to contact Altman in response to the Newark request, he received no reply. Other attempts by controllers to reach Altman moments before the crash also failed.

If Altman was using the wrong frequency, he would not have been able to hear controllers trying to warn him.

Transcripts show Turner assumed he could not reach Altman because of radio problems, saying the pilot was "lost in the hertz".

Moments later, Altman's plane collided with the helicopter. Altman, his two passengers, helicopter pilot Jeremy Clark, who grew up in Auckland, and five Italian tourists on board the helicopter were killed.

- AP