IFR Fix: Controlled airspace, sort of

Want to get a pilot off his high horse? Ask him to tell you about Class E airspace. Not just to change the mood during a hangar session. Nowadays the topic is fair game for instrument proficiency work when you consider that Class E airspace may become anchored to substantially more real estate if the announced closure of 149 contract control towers moves forward on June 15.

But that’s not the only reason. Ubiquitous and a bit weird to contemplate, Class E airspace has caused more than a few primary student pilots to pose this logical question: Why do they call it controlled airspace if you don’t have to ask anyone’s permission to be there, and no one throws you out for misbehaving?

The practiced response is that it’s about weather rules, not access rules. Don’t go in there when weather is below prescribed minimums because—this is where the answer gets tricky—there could be an aircraft on an instrument approach (“A what?”) operating under the highly desirable assumption that the airspace is traffic-free.

This idea remains obscure to many among the non-IFR-initiated, so use caution, instrument pilot!

E for eccentric

Excluding altitudinous Class A airspace, Class E airspace is the only controlled airspace that may originate at some level higher than an airport’s surface. Yes, classes B and C usually have “shelves” of airspace with floors above ground level, but always attached to a surface-based stem, not free-floating.

If an airport is situated in Class G (uncontrolled) airspace but has an instrument approach procedure, the familiar keyhole-shaped outlines found on sectional charts show, by form and color of boundaries, where and how low Class E airspace extends around the airport.

At some locations, a Class E swath may adjoin a conventional Class D layout—again, a way of instructing interlopers to keep instrument approach lanes open in less-than-VFR weather.

Sequester or not, some Class C airspace reverts—defaults, if you prefer—to Class E when the tower staff goes go home for the evening.

If there were a gizmo aboard the aircraft to keep track of how much time is flown in various classes of airspace, Class E would run away with it for piston pilots who leave the traffic pattern.

Doubtless, there is an app for that.