The Weekly Reflektion Week 13 / 2020

In last week’s Reflektion we talked about the importance of listening to what people say and trying to understand the message that they are trying to convey. This week we will also talk about communication and the importance of giving people the information they need to make their decisions.

When you are asked for information that is to be used in assessing a risk and/or making a decision, do you make sure you communicate the information that is required? Do you make sure you understand the significance of the information?

Continental Airlines Flight 1404 was a flight from Denver International Airport in Denver, Colorado, United States to Houston, Texas. On the evening of December 20, 2008, the flight crashed while taking off resulting in two critical injuries, 36 non-critical injuries and the loss of the Boeing 737-524 aircraft. Luckily there were no fatalities.

41 seconds into the take-off, the flight crew felt a bump and heard a rattling sound and subsequently aborted the take-off. The aircraft then started to move away from the runway centre line and made a sudden left turn. The aircraft eventually crashed, and the starboard engine caught fire. The passengers and crew escaped through the port emergency escape chutes.

The National Transportation Safety Board (NTSB) investigation into the crash could find no mechanical faults with the aircraft and no obvious problems with the runway. Denver airport is exposed to significant wind gusts from the Rocky Mountains and the investigators considered whether a cross wind gust had caused the aircraft deviation. The weather reports however indicated that there were cross wind gusts that may have been greater than the limits for take-off for this model of the Boeing 737. Simulation of the aircrafts’ movements during take-off indicated that a cross wind of 45 knots (83 km/hr) could have caused the crash. Further investigation into the weather information indicated gusts of 45 knots were measured by the airport anemometers. The 737 has a crosswind limitation for take-off of 33 knots (61 km/h) on a dry runway.

Information on wind speeds are communicated to the flight crew before take-off and the winds reported were between 24 and 27 knots (44 and 50 km/h), within the limitation. The flight crew had reacted to the wind speed when they observed the speed of clouds passing over the airport just prior to take-off. However, they used the controller’s information in their decision to start take-off.

The airport anemometers measured the wind speed continuously and values were sent to the monitoring station every second. These values were averaged over a 10 second period and this information was displayed on the controller’s screen. The ‘standard operating procedure’ for communication of wind speed information was that the anemometer at the start of the runway was used to as the basis for the information to the flight crew. There were however other anemometers that were measuring the wind speed along the runway. When the controller reported wind speeds of 24 to 27 knops from the anemometer at the start of the runway another anemometer displayed a cross wind of 40 knots (74 km/hr).

When providing information that may be critical to a decision being made, it is important that the information is correct. It is also important that any other information relevant to the decision is also communicated. This requires that the people providing the information understand how the information is being used and how the information is compiled and calculated. It also requires the people providing the information to assess what other information they have that could be critical to the decision. Communication is seldom only one way.