Dudley Henriques wrote:

The problem is that the pilots can brief for the right target and then miss
it if the concentration is broken. In this incident, the visuals were missed
as well. It was a multiple error. It involves broken concentration, and this
is the main issue in these accidents. Everyone involved in low altitude work
knows that there are multiple cues and what they are.

I saw an interesting program on Discovery, or maybe The Learning Channel,
a few days ago. It dealt with visual perception. One experiment/example
they used was showing a group of people (about 15 or 20) a film of people
practicing basketball. The group was told to try to count the number
of balls in use. At the end the group was asked if they had seen anything
unusual in the film. About 1/4 to 1/3 of the group raised their hands.
When they played back the film again it turned out the big majority had
just plain not seen a guy in a gorilla suit walk right through the scene.

Visual perception depends a lot on what we expect to see, so it is easy
to believe that a person could miss the visual cues until it was too late
if he was not expecting a problem.

Bill Ranck
Blacksburg, Va.