Wind Shear Analysis

     Our perceptions of reality are often influenced by what we expect to see. Knowledge can be missing, inaccurate, or incomplete. Time pressures, workload, and reliance on past experience encourage acceptance of what appears to be complete information. Systems where information is fragmented are at risk of missing a piece of the puzzle. When information is stored in more than one location and can be changed in one place and not others there is an increased risk of error. Sometimes we don’t know what we don’t know or make assumptions without realizing the limits of our understanding. Knowledge may exist in a vacuum and be only partially correct. Without sharing information it is difficult to understand with clarity.

In the Charlotte Windshear crash, knowledge was missing, incomplete and existing in a vacuum in the following ways:

• Crew was tuned to air traffic control channel that did not have information about the weather conditions broadcast on other channels which warned of a windshear alert.
• Captain incorrectly thought the plane was at 450 rather than 200 feet resulting in rapid descent into extremely hazardous conditions.
• The flight originated in Columbia, where the weather information provided to the crew indicated that conditions at Charlotte were similar to those encountered an hour earlier.
• The captain asked for a report from the last pilot to land, whom the controller said reported a “smooth ride all the way down the final.”
• An on-board windshear alert system did not detect the severe windshear conditions during the go-around because it was programmed not to work while the flaps retract in order to reduce nuisance alarms.
• Cues of possible windshear include turbulence. This cue did not occur and the lack of turbulence masked the hazardous condition.