Have A Slice Of Airspace

Since the Airspace series began, many of you have written about your hometown airpace and its unique characteristics — the best way to get to know your own local airspace is to ‘slice‘ it and take a good look.

Figure 1 is the Sectional Chart area around Greenville and Spartanburg in South Carolina. This airspace is typical of many areas around the country where different airspace types cluster together. To help understand the different types of airspace and how they might affect a VFR flight, I planned a trip from the Pickens County airport (LQK). The airport is on the west side of the chart and across from the Spartanburg Downtown Memorial airport (SPA) located on the east side of the chart. Look carefully at the diagram and you will see that I have drawn a line between these two airports to represent my proposed flight path.

Pilots usually spend a good deal of time planning their ‘horizontal‘ navigation, such as calculating how long it will take to get from LQK to SPA, and how much fuel will be required — but this exercise is a look at ‘vertical‘ navigation.

When you look at a chart you are actually looking down through three-dimensional airspace to the surface. What if we took a paper cutter and cut along the course line between LQK and SPA? What types of airspace would the paper cutter cut through as it went? In other words: Let’s visualize the airspace from the side. Figure 2 is an illustration of the airspace slice represented by our route of flight.

For the purpose of discussion, this VFR flight is made with very good weather during the daytime when all the control towers are open and the weather observers are on duty. I selected an altitude of 3,000 feet for the cruise portion of the trip.

    : I am planning a direct flight, but in actual operations a flight around congested areas may be necessary.

Look back and forth between Figures 1 and 2. You see that Pickens Country airport is an uncontrolled airport located in Class G (uncontrolled airspace), but we would enter Class E airspace during our initial climbout. Along the way, we would cross three Victor Airways and (possibly) one military training route. At the Greenville Downtown airport (GMU) we encounter Class D airspace. We would contact the tower controller and let them know we wanted to transition through their area. While flying through the Class D airspace at 3,000 feet, we would be flying under the Class C airspace from the Greenville Spartanburg airport (GSP). The Class D airspace at GMU butts up against the Class C airspace of GSP.


    • : We would need to coordinate with both GMU and GSP so that we enter the Class C airspace only after communications with GSP have been established. Plus, the Class C airspace requires a Mode C (altitude reporting) transponder, so our aircraft must have one — and it must be on and working.

Mode C transponders are needed inside a Class C as well as anywhere over the top of a Class C and above 10,000 feet MSL (they are also normally required anywhere within 30 nm of the primary airport in Class B)


Starting our descent into the Spartanburg Downtown airport (SPA) we see that Class E airspace extends all the way to the surface. We land at SPA — an non-tower airport in controlled airspace. Look carefully at Figure 1 and you will also see a grey line that crosses our route near SPA. The line indicates a low-altitude military training route. The designation in this case is IR74. In Figure 2, I indicate the approximate location of IR74, but I placed question marks above and below since we really don’t know the true vertical dimensions of this MTR.

MTR Code

    • : Whenever you see a

military training route

    (MTR) the number of digits in their designation is an indicator of how high the route is. If the MTR has a 4-digit code, then the entire MTR is below 1,500 feet AGL. MTR’s with a 2 OR 3-digit code (like our IR74) may have segments that are both below and above 1,500 feet AGL.

Figure 2 indicates the airspace from LQK to SPA at noon when everything is open. What would the airspace look like for a return trip at midnight — when all control towers are closed and all weather observers are off duty?

BOTTOM LINE: Can you diagram a slice of airspace where you regularly fly?