To: (Separate email addresses with commas)
From: (Your email address)
Message: (Optional)
Send
Cancel

Thanks!

Close

The Logic Behind Class E Airspace

Skyline-Photo

If you were like most pilots during training, you were told to memorize Class E airspace on the map, as well as its requirements. No one explained why Class E has so many variations, and it's pretty complicated if you don't understand the logic behind it.

Class E is the most common type of airspace in the United States, but it's often the least understood.

Class E Is Controlled - But How?

One big confusion point for students is that Class E airspace IS controlled airspace. But why is it controlled?

In Class E, IFR aircraft are controlled by ATC. This might be a center facility (Air Route Traffic Control Center) or approach/departure facility. As a VFR aircraft, you're on your own, but IFR aircraft must operate on an ATC clearance. That means the airspace is controlled.

Weather Requirements

Have you ever wondered why we have weather minimums? Imagine you're flying IFR and pop out of a cloud layer. Suddenly, you spot a VFR aircraft below. The VFR weather minimums give both of you enough time to see and avoid each other.

Here's what you need to fly VFR through Class E below 10,000 feet MSL:

Class E Weather Minimums - Below 10,000 Feet

If you fly 10,000 feet MSL and above in Class E airspace, the weather minimums are raised:

Class E Weather Minimums - 10,000 Feet And Above

So, why do the requirements change at 10,000' MSL? Think about aircraft speed restrictions.

FAR 91.117 states that below 10,000 feet MSL, you cannot exceed 250 knots without a clearance. This helps separate slow flying traffic from larger, faster traffic by giving them more time to see and avoid each other.

Once you go above 10,000', speeds increase. So, to provide enough time to see and avoid aircraft, your weather minimums increase, too.

Class E Altitudes

The toughest part about Class E airspace may be recognizing where it starts. It seems to start at random altitudes all over the map, but there's logic to it.

Class E Enroute Airspace

You may have heard that Class E airspace starts at 14,500 feet, but if you look at the sectional, this isn't really the case. In the vast majority of areas, there are enough airports and victor airways to have Class E begin at 1,200 feet AGL. This is known as enroute Class E airspace.

On a sectional, it appears inside fuzzy blue borders:

Class E at 1,200 feet

Class E Transition Areas

In a Class E transition area, the Class E floor drops down to 700 feet AGL. On a sectional map, you can find these transition areas by looking for a broad, magenta line that is fuzzy on the inner side. It often surrounds individual airports or groups of airports.

Class E to 700 feet

So why does the Class E airspace suddenly drop from 1,200 feet AGL to 700 feet AGL in these areas? Think of it like Class B or C airspace, it drops down to protect aircraft on approach or departure from an airport.

Class B vs. Class E to 700 feet

You might ask, why would an IFR pilot be down at 700 feet miles away from the airport? Well, they wouldn't. In MVFR weather, you could have a VFR aircraft just a few hundred feet below an IFR aircraft in the clouds. These transition areas drop down low enough to separate IFR aircraft from VFR aircraft below.

Transition Area Shapes

OK, so Class E transition areas are just those magenta circles, right? Nope. You're going to find out there's a whole lot more to Class E than that.

In cases like the airspace image below, the airspace designer is taking into account the terrain elevation, as well as the amount and the types of aircraft using that airspace.

Class E to 700 feet - large area

For larger, and faster planes, you need larger, more protective Class E transition areas. When you have rising terrain, the transition area must be larger to allow them to climb up to a safe en-route altitude.

Different Shapes

Some Class E airspace isn't circular, and many Class E transition areas have rectangular areas jutting off of the airspace. Why are they there? These extensions protect approaches and departures to and from airport runways. They also extend Class E airspace to protect aircraft transitioning into or out of airport areas from enroute waypoints such as VORs.

For instance, at Summersville Airport (KSXL) below, you can see the Class E extensions protect runway approach and departure procedures:

Class E to 700 feet with approach

At this airport, to comply with proper terrain avoidance, the protective Class E airspace has been extended in either direction. It's longer to the northeast due to rising terrain.

Getting easier yet? While confusing at first, once you know the logic behind the placement, it's easy to understand why it's there.

Class E Surface Areas

Just when you thought you were finally getting the hang of Class E, you see this on your sectional map - a Class E surface area. It looks a lot like Class D airspace, but with a magenta border instead of blue:

Class E to the surface

This is Class E airspace that extends down to the surface for and airport. It's nearly always surrounded by a Class E transition area, so the airspace mimics the wedding-cake shelves of Class C and B airspace. It's just a much less-controlled version of those types of airspace.

Class B vs. Class E to the surface

Class E surface areas are often in place to protect precision instrument approaches. You'll also commonly find Class E surface areas with rectangular extensions for approach and departure procedures.

All airports with Class E surface areas are required to have a weather station and the ability for aircraft to contact ATC from the ground. In this case, ATC may include Flight Service, a center facility, or an approach/departure facility.

Now It Makes Sense, Right?

I remember when I was in flight training, no one explained WHY there were so many variations in Class E airspace, and that really confused me. I never thought about why it was there, or the logic behind placement.

IFR traffic in Class E airspace is controlled by ATC, and the weather and speed restrictions make sure that IFR and VFR can see and avoid each other. While many of it's characteristics may seem arbitrary, it makes a lot of sense when you think how aircraft use the airspace.

Now that you're a Class E expert, you'll always have some cool ideas to toss around at parties.

On second thought, don't do that...keep that for the pilot's lounge.

Want to learn more about airspace? Check out our online course.

Swayne Martin

Swayne is an editor at Boldmethod, commercially licensed pilot with multi-engine and instrument ratings, and a commercial aviation student at the University of North Dakota. He's the author of the articles, quizzes and lists you love to read every week. Swayne's experience ranges from international flights in a King Air F90 to ferrying a 1943 Grumman Widgeon across the country. You can reach Swayne at swayne@boldmethod.com, and follow his flying adventures at http://www.swaynemartin.com.

Images Courtesy:

Recommended Stories

Latest Stories

    Load More
    Share on Facebook Share on Twitter Share via Email