A: On an old-fashioned clock or watch, with hour and minute hands, those are the times of day when the minute hand sits directly above and covers the hour hand, so it appears that there is but one hand on the clock.
Thus was his introduction to airspace for student pilots.
We live and fly in a three-dimensional world, yet our airspace is depicted on two-dimensional sectional charts. I ask my students to imagine they were in a rocket launched vertically from a specific place on a sectional chart, and to identify each type of airspace they would travel through, including the lower and upper altitudes of that airspace. Some were easy and others, not so much, but all were a fun learning experience.
Let’s try one: Place your rocket at Chicago Midway Airport (MDW). Use a sectional and name the airspace and altitudes of each as you ascend to space. Complete your answer before looking at the next line.
Class C from 620 feet msl up to but not including 3,000; Class B from 3,000 to 10,000; Class E from 10,000 to but not including 18,000; Class A from 18,000 to FL600; and Class E above FL600.
As you just discovered, a little creativity can go a long way in helping pilots visualize 3-D airspace from a 2-D chart in our 3-D world.
Craig Brown is a senior aviation technical specialist in the AOPA Pilot Information Center.