Final Report: ATC warning system faulted in MU-2 crash

 - January 24, 2007, 10:16 AM

Mitsubishi MU-2B-60, Parker, Colo., Aug. 4, 2005–The NTSB blamed the accident on the commercial pilot’s failure to fly a stabilized instrument approach at night. Contributing factors were the dark night and low clouds, the inadequate design and function of the airport facility’s minimum safe altitude warning system (MSAW), and the FAA’s inadequate procedure for updating information to air traffic controllers.

The tower controller heard a low-altitude alert from the MSAW system when the MU-2 was five miles out from the airport. He immediately notified the pilot but it was too late. Within seconds, the airplane had crashed about four miles from the airport on an instrument approach. The pilot was killed in the accident.

The way the MSAW was set up, tower would receive an aural alarm only for aircraft within five nm of the airport. In this case, approach handed the airplane over to tower when the MU-2 was about 10.7 miles out, leaving a 5.7-mile segment in which both controllers could receive visual alerts but only approach received an aural alarm. In 2004, the FAA eliminated approach’s responsibility to inform the tower controller of a low-altitude alert if the tower had MSAW capability. In this case, approach thought the MSAW alarm parameter was set for 10 miles from the airport, not five.

Because the FAA had improperly informed controllers about the alarm parameters, the approach controller concluded that the airplane was no longer her responsibility after she handed it over to the tower.