Wednesday, January 24, 2007

NTSB: 2005 crash of Cessna Citation 560 in Pueblo, Colorado

The National Transportation Safety Board (NTSB) has issued a report on the February 2005 crash of a Cessna Citation 560 (similar to the one in the photo) in Pueblo, Colorado. The twin engine business jet was operated by Martinair, Inc. for Circuit City Stores, Inc.

At the time of the accident, the aircraft was operating under 14 CFR Part 91 on an IFR flight plan. The aircraft crashed about 4 nautical miles east of Pueblo Memorial Airport on February 16, 2005, while on an ILS approach to runway 26R. The two pilots and six passengers aboard were killed and the aircraft was destroyed by impact forces and post-crash fire.

In a press release that accompanied the report, the NTSB summarizes the cause of the accident as "the flight crew's failure to effectively monitor and maintain airspeed and comply with procedures for deice boot activation on their approach to Pueblo, Colorado, which led to an aerodynamic stall. Contributing to the accident was the FAA's failure to establish adequate certification requirements for flight into icing conditions, which led to the inadequate stall warning margin provided by the airplane's stall warning system."
The Board's investigation determined that the aircraft encountered icing conditions during the flight resulting in an accumulation of thin, rough ice on the wing leading edges that degraded the aircraft's performance. According to the Cessna 560 airplane flight manual (AFM), pilots are trained to increase the landing reference airspeed whenever any residual ice is present or can be expected during approach and landing. An examination of the cockpit voice recorder (CVR) did not record either pilot mention increasing the airspeed during the approach.

Additionally, company and AFM procedures for approach and landing in icing conditions required pilots to activate the deice system when any ice accumulation, regardless of thickness, was visible and to continue to monitor the wing leading edges for ice. Despite this guidance, there is no evidence that the accident flight crew activated the deice boots during the approach. The flight crew of the trailing Circuit City "sister ship" did cycle the deice boots numerous times and maintained increased airspeed during the approach and subsequently landed safely.

As a result, the Board recommended that the Federal Aviation Administration require that operational training for the Cessna 560 (Citation) aircraft emphasize the AFM requirements to increase airspeed and operate the deice boots during approaches when ice is present on the wings. The Board also recommended that the FAA require that all airplanes equipped with pneumatic deice boots have a mode that will automatically continue to cycle the deice boots once the system has been activated.

The investigation also determined that the airplane's stall warning system did not activate until after the aerodynamic stall occurred. The warning system is intended to provide flight crews with adequate warning of an impending stall in time to take preventative action. Because of the higher stall speeds that occur in icing conditions, the margin between the warning and the stall occurrence can be diminished. The Board recommended that the FAA require modification of the Cessna 560's stall warning system to provide an adequate warning margin in icing conditions that existed on this approach.

The Board further concluded that ice bridging does not occur on modern airplanes; therefore, there is no reason for flight crews to delay activation of the deice boots. The Board recommended that the FAA require that guidance for aircraft with pneumatic deice boots be revised to indicate that the leading edge deice boots should be activated as soon as the aircraft enters icing conditions.

The Board also called on the FAA to develop pilot training programs to emphasize monitoring skills and workload management.

Additionally, the Board reiterated two recommendations issued in 1996 and 1998 to the FAA calling for revised certification standards for aircraft operating in icing conditions. The Board has classified the FAA's response to these recommendations as unacceptable.
Here is the link to the synopsis of the NTSB report: NTSB Synopsis AAR-07/02

The press release notes that the NTSB's full report will be available in several weeks.