NTSB Debunks Ice-bridging Hypothesis

The NTSB’s debunking of the ice-bridging hypothesis in the conclusions of its investigation of the Feb. 16, 2005, fatal crash of a Circuit City Citation 560 and determining that the pilots did not activate the de-icing boots on the approach will take some pilots back seven years. In February 2000 the long-time policy of waiting for ice to build before activating boots got the boot. At that time the FAA adopted a series of ADs that required operators of 14 selected regional turboprop and business jet models with pneumatic de-icing boots to activate the boots immediately upon the first sign of ice accumulation, reversing a long-time procedure of waiting for ice to build before activation. The FAA dropped the Citation 500 series from the requirement because it said Cessna flight-test data “determined that the airplane had an acceptable stall warning margin with ice shapes present.” The NTSB said the Circuit City pilots did not activate the de-ice boots on the approach, “which was contrary to company procedures and manufacturer guidance.”