NTSB Examines Deicing Holdover Time in Challenger Crash

A key factor being examined in the January 26 fatal takeoff in Bangor, Maine, of a Bombardier Challenger 650 is that the twin jet exceeded the maximum deicing holdover time by more than 17 minutes when it started its takeoff roll, according to the NTSB's preliminary report.

The pilot, copilot, and four passengers were killed when the aircraft crashed just after liftoff. It was operating as a Part 91 business flight under a night IFR flight plan. Weather was reported as IMC, temperature/dew point: -16°C /-19°C; Wind 6 knots from 40 degrees; lowest ceiling: indefinite 1,200 feet agl; and visibility: 3/4 sm in light snow.

A review of the cockpit voice recorder (CVR) indicated the flight crew discussed holdover times during the taxi to Runway 33. The pilot commented that it was “standard” to have 14-18 minutes and that if the wait was more than 30 minutes, they would return to the ramp to deice again. The copilot concurred with the pilot.

Following deicing and anti-icing applications, the twin jet sat for nearly 5 minutes before taxiing from the deice pad at 7:35 p.m. "At that time, about eight minutes and three seconds had elapsed since the start of the anti-icing application," said the report. At 7:42 p.m., the crew radioed the tower that they were ready for takeoff. After the crew received clearance instructions and read them back correctly to the tower, the aircraft began its takeoff roll at 7:44 p.m. with flaps extended to 20 degrees, the pitch trim set at -4.8 degrees, and the wing and cowl anti-ice systems engaged.

At the start of takeoff, it had been more than 17 minutes since the aircraft had left the deicing pad. The corrected snowfall intensity associated with 3/4 sm visibility at night and an outside temperature at or below -1°C was considered “moderate,” said the NTSB report. A moderate snowfall intensity and a -16°C outside temperature resulted in a "maximum holdover time of 9 minutes from the start of the anti-ice application.”