CFI Topics

The “WHY” of Airspace Classes

Lesson 4

What do you teach as the reason for having airspace classes, i.e. A, B, C, D, and E? Everything above 18,000 feet MSL must be on an instrument flight plan, with an instrument pilot, in an instrument equipped airplane. Operations in Class B airspace must have an operating Mode C transponder with prior permission to enter and have 3 miles visibility and remain clear of clouds. These rules and all of the other regulations that apply to the various classes of controlled airspace are there for one reason and one reason only; to separate instrument flights from other instrument flights and from participating VFR flights as controller work load allows. If everyone flew in visual meteorological conditions (VMC) and followed “see and avoid, and see and be seen” there would be no need to regulate airspace. There would be a whole lot less color and complexity to the chart.

In the early days of flying in the clouds, there was little traffic and the chance of a collision was remote. Today however, with more and more air traffic, there is an increasing need for noise abatement. (Have you ever heard the sound that two airplanes make when they collide?) This can only be accomplished by having established regulations that describe what is required for pilots to operate in a given class of airspace.

Filing an Instrument Flight Plan effectively “erases” the airspace because these flights are under positive control with radar and constant communication. VFR flights must fly with the minimum visibility and cloud separations as determined by the particular class of airspace that is transitioned.

Early in the student’s training we teach the five classes of controlled and one class of uncontrolled airspace and how to recognize the different classes by their chart symbol and color, what communication is required to enter and transition, what weather minimums are necessary, what equipment an aircraft must have and what pilot qualifications are needed. It is rarely, if ever, taught how to use the information to “visualize” where IFR traffic may be concentrated. Useful IFR traffic information is in the chart symbols and fully understanding these symbols will reveal their secrets and can add to the safety of flight by allowing the pilot to use the hidden information to his or her advantage.

As mentioned earlier and to summarize, the faded magenta band and magenta dashed line define where Class E begins; 700 ft. AGL and on the surface respectively - and is used to define where an instrument approach is available whether the airport has a tower or is non-towered.

The magenta dashed line is sometimes used at towered airports as an extension of Class D and protects an IFR approach down to the surface. (See Figure 2).

Here is a brief explanation of how these symbols work. An IFR flight receives “separation” services only in controlled airspace; A, B, C, D, & E. What does “separation” mean in this context? When a pilot files and receives a clearance for an instrument flight, that flight is handled under positive control and separation is provided either by radar contact and communication or by communication alone with constant updates of position as reported by the pilot. When an instrument flight is conducted in visual meteorological conditions (VMC) the pilot is responsible to “see and avoid” other traffic. Flights conducted in (VMC) and not on an IFR flight plan must follow visual flight rules (VFR) even if the flight receives radar services. Since Class E airspace is one of the “controlled” airspaces utilized by both VFR and IFR flights, the VFR pilot must have the proper visibility and cloud separation criteria to be legal in that airspace. Therefore, a VFR flight can not fly in Class E airspace in conditions less than 3 miles visibility and/or less than the standard cloud separation of 500 ft. below, 1,000 ft. above, and 2,000 ft. of horizontal distance from clouds, (Special VFR is the exception). The VFR chart then is the tool to determine where those areas of Class E exist. Remember to teach the importance of understanding the faded magenta band and magenta dashed line – to protect an IFR flight as it descends on an approach to an airport.

Study the VFR chart and see how you can determine and teach where IFR traffic is likely to be, based on all of those crazy colors and lines. You will even get skilled at knowing what type of approach is likely to be available at an airport based on the now familiar symbols. Challenge your fellow CFI’s with this new knowledge and encourage them to share it with their students. Maybe you can win lunch.

Here are a couple of clues to what type of approach is probably at the airport based on the VFR chart symbology. When there is a magenta dashed area connected to Class Delta airspace, (see Figure 2), that airport has either an ILS, PAR, or one of the new GPS approaches such as an LPV. If there is a magenta tint band in the vicinity of either a non-towered or towered airport there is – most likely – a VOR, LOC, or GPS such as an L/NAV or other non-precision approach. Check the terrain and availability of VORs near the airport for additional clues as to the type of approach. No Class E surface area or VOR? Then the approach is probably GPS. Test yourself by trying to guess the approach type and then look up the airport in the IFR approach publications and see if you are correct.

Figure 2

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