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ChangingMinds Blog! > Blog Archive > 29-Jun-14

Sunday 29-June-14

Deadly language

On July 6th 2013, Asiana flight B772 from Seoul, South Korea, crashed at San Francisco as it came in to land. Coming in at a high pitch angle, it touched down short of the runway, the landing gear and tail section broke off, sending the Boeing 777 skidded along the runway. The left wing hit ground equipment, spinning the aircraft around and breaking off the engines as the plane burst into flames.

Some were lucky. Others were not. Remarkably, only 2 occupants were killed, though 10 were left in a critical condition, 38 had serious injuries, 82 had minor injuries and 175 escaped uninjured. The two killed were Chinese 16 year old girls on a school outing.

So what happened?

Amongst other errors, when they realized they were too low on the approach, they decided to do a 'go around', flying around in a circle to get more height for a better approach. The pilots pulled back on the controls to go upwards. Doing this actually reduces lift and the plane will drop unless it is accompanied by a boost to the engines. This normally happens automatically, but this time it did not, and the plane dropped to a point where the go-around could not happen and they were forced to an emergency landing with the results as described above.

A key part of the problem was poorly written documentation. Even Boeing admitted in its subsequent report that 'the complexities of the autothrottle and autopilot flight director systems that were inadequately described in Boeing?s documentation and Asiana?s pilot training, which increased the likelihood of mode error.' The autothrottle is a system that normally cuts in to keep up the speed of the aircraft and stop it dropping when the pitch angle is changed. However, there are situations when it is automatically turned off. Pilots are told about this through a statement tucked away in the 1600-page operation manual, which states:

When the pitch mode is FLCH or TOGA, or the airplane is below 400 feet above the airport on takeoff, or below 100 feet radio altitude on approach, the autothrottle will not automatically activate.

Just look at the linguistic complexity of this. It is of the form 'When X or Y or Z then Q'. This needs care in reading. It also includes a negative ('not automatically activate') which the brain does not easily activate. A better phrasing that might have saved lives and injuries would be to warn early about non-activation of the autothrottle.

For example:

Warning: The autothrottle system will NOT automatically activate in ANY of the following conditions:

• The pitch mode is FLCH or TOGA

• The airplane is below 400 feet above the airport on takeoff

• The airplane  below 100 feet radio altitude on approach

When you write anything, do consider how people will read it. Consider also the impact of their misunderstanding and make appropriate effort to ensure they are alerted to factors that could lead to significant risks. In this, consider:

• Clarity that avoids ambiguity
• Accuracy so everything is correct
• Simplicity for ease of understanding
• Emphasis of critical points

Oh look. That spells 'CASE'.