FGD135: According to Mahon's report (p128) the radar had an IFF mode (Identification Friend or Foe) with a range of 150 miles and an ASR mode (Aircraft Surveillance) with a range of 40 miles.
Most of the ground/air communications were between the aircraft and Mac Station on HF radio. The radar was not located at Mac Station. Instead, it was at the Ice Tower, by the runway. The Tower only had VHF radio. So Mac Station was in contact with the aircraft on HF, and Mac Station and the Tower were relaying messages to eachother on VHF.
The F/O was handling communications, but at one point, Capt Collins took over and attempted to contact the Tower on VHF. He had no success. Shortly thereafter, he saw the ground and went down VMC.
The probable explanation for the captain's decision to abandon the radar assist is that he suspected that he wouldn't be actually getting it. If he wasn't getting VHF radio at a range of 50 miles out then the same would probably apply to the radar within 40 miles. So if he maintained MSA to the waypoint, he would end up stuck above the cloud layer with no way of getting through it, given that he had been told that the NDB wasn't working.
Last edited by ampan; 30th Dec 2011 at 20:38.