The Cessna 152 was cleared to take off from ûpoint A, and eight seconds later a 172 at ûpoint B was cleared to taxi into position and ûhold. The impact was at point C.

Posted on the wall of my organic chemistry lab at the University of Wisconsin was a sign that read, “Expectations cloud observations.” It’s a postulate that’s as true in aviation as it is in science.

In a chem lab, if you expect the solution to have a bluish tint, your eyes may fool you and spot blue when there’s really none to be found. In doing an aircraft preflight, a fuel tester may look like blue avgas rather than water simply because you have an eyeful of sky. …