class Charlie airspace as defined in the aim chapter 3 - 2 - for Class C airspace is generally that airspace from the surface up to 4,000 feet above the airport elevation charted in MSL surrounding those airports that have an operational control tower are serviced by a radar approach control and that have a certain number of IFR operations or passenger employments although the configuration of each Class C airspace is individually tailored the airspace usually consists of a 5 nautical mile radius course surface area that extends from the surface up to 4,000 feet above the airport elevation and a 10 nautical mile radius shelf area that extends no lower than 1,200 feet up to 4,000 feet above the airport elevation just like Class D airspace it is important to keep in mind that the size and shape of each Class C airspace will be designed to suit the needs of the airport in which it is surrounding Class C however does have a typical layout that can be found throughout the National Airspace System as airspace becomes more complicated and larger the shapes begin to change and are designed to encompass more area surrounding the primary airport the typical layout of Class C is a two layer design with the radius of the top or upper layer extending farther out than the lower or inner layer the first layer starts at the surface surrounding the airport and will typically have a radius of 5 nautical miles and extend up to the top of the airspace which is typically 4,000 feet AGL the next layer or shelf will start no lower than 1,200 feet above the ground and extend up to the same 4,000 feet AGL as the inner core the top shelf will normally have a radius of 10 nautical miles that's 10 nautical miles from the center of the airspace so it will extend an additional 5 miles beyond the inner core the no lower than 1,200 feet can be important since this altitude is what you will typically find but it may vary this altitude is often forgotten or confused but remember that it is no lower than so the top shelf will never start at any altitude below that when we discuss the dimensions of class echo airspace and even IFR in route altitudes this 1,200 feet will be seen again and you can start to see how they work together if you are familiar with Airways and low altitude iEARN average you might recall that they typically start at 1,200 feet above the ground but again that's another lesson now let's take a look at a couple examples the first is a typical class charlie airspace surrounding Fort Wayne Indiana on a side note remember that when we look at sectional charts all altitudes are an MSL or above sea level unless otherwise noted okay so Class C is defined on a sectional chart with the magenta line such as these surrounding Fort Wayne International Airport depicting an inner and outer ring surrounding the airport the size and shape of Fort Wayne is that of a typical Class C airspace as shown it has two rings or shells that surround the primary airport the inner ring has a radius of 5 nautical miles and begins at the surface with a ceiling of 4,800 feet MSL or above sea level the ceiling is designated in two digits which are hundreds of feet and a bottom in this case starting at the surface which is indicated by s FC as we can see here the airport elevation is 815 feet MSL if we take the 4,800 feet MSL ceiling - the 800 foot airport elevation which we did round we can see the height of the Class C airspace is 4,000 feet above the ground level the outer magenta ring displays the upper shelf of the airspace when measured from the center of the airport it has a radius of 10 nautical miles and when we look at the elevation dimension within this outer ring we can see that the bottom of the shelf starts at two thousand feet msl with the same ceiling of 4800 feet msl using the same math skills we can take the two thousand foot and shelf altitude which is above sea level - the airport elevation of 800 feet and we can find the difference of twelve hundred feet AGL in this case the upper shelf does not start until the defined no lower than twelve hundred feet when Class C does have a different configuration more often than not it does so to accommodate any overlying or surrounding airspace or airport in many cases particularly in high-traffic areas where several larger airports are close to each other different airports may have airspace that are close together now let's take a look at a Class C airspace that has its boundaries affected by other airports nearby and the surrounding geography in this example we will look at Louisville International Airport when we look at the lateral boundaries of this class charlie we can notice that the outer dimensions have the standard 10 nautical mile radius but the inner five nautical mile ring is not uniform here we can see that the northeast corner cuts inward toward the primary airport in order to accommodate the nearby Bowman Airport let's take a look at the lower altitudes of the outer ten nautical mile shelf that will start as quoted from the aim no lower than 1200 feet on the southern portion outlined here we see the top of the airspace is 4,500 feet MSL and the bottom of the shelf is 1700 feet MSO if we take the airport elevation of 501 feet and subtract that from the ceiling of 4,500 we get the top of the normal 4,000 feet AGL when we compare the bottom of 1,700 feet with the airport elevation of 501 we come up with a lower limit of 1200 feet above the ground that seems pretty standard now let's take a closer look at the northern half of the outer shelf we see the height of the same 4,500 feet which is still 4,000 feet above the ground but we can also see the bottom of this portion of the 10 nautical mile shelf is designated as 2,200 feet MSL we subtract the airport elevation of 501 from the chart at 2200 we see that this part of the airspace doesn't start until 1700 feet above the airport surface which is higher than the southern half of 1200 feet and if curious we can look further and see that the northern half of the airspace has some tall obstacles that can be upwards of 1,000 feet MSL and higher as well as the neighboring Bowman airports Class Delta airspace these elements around the airport have caused Louisville's class Charlie to start at a higher altitude the important thing to know is that the airspace again is tailored to suit the needs of the primary airport and its surrounding conditions now that we understand the size and shape of class Charlie airspace let's take a look at what we as pilots need to consider before we plan to fly in or out of them as we approach land or depart from a Class C airspace there are a few requirements we must make sure we meet before doing so to enter or operate within a Class C no specific pilot certification is required any pilot including a new student pilot may operate within Class C in regards to equipment the aircraft must have an operable two-way radio in addition unless otherwise authorized by ATC we must have an altitude reporting transponder in most aircraft this would be a mode C or mode s transponder if we remember from the definition of Class C in the aim we know that Class C airspace is serviced by radar approach control since each Class C Airport has their own radar capability it makes sense that we must provide them with the information they need to fully take advantage of that radar and in this case we must have a transponder that will report our altitude not only as a transponder required to operate within a Class C but we must also have one if we plan to fly above a Class C we do not however need one if we plan to fly under the overlying shelf of the airspace and when you think about it this makes sense because if we were to fly over top of the airspace ATC should know our altitude since we could potentially fly directly over top of the airport without a mode C transponder the controller may only see our location and would have no indication if we were only a couple of feet above the airport or several thousand feet up when we fly under the shelf then an altitude reporting transponder is not needed since we will remain outside of the inner ring of that airspace also with this we can fly in and out of any non-towered airports that may be under that shelf without the need to communicate with ATC so the thing to remember is we need a mode C transponder to operate in or above a Class Charlie airspace since a two-way radio is the other required equipment it is no surprise that we must also use it to enter or operate within Class C two-way radio communication must be established and maintained with ATC when approaching a Class C the pilot should contact the appropriate ATC or approach control on the published frequency with their position altitude radar beacon code or in other words transponder code if previously given one from another ATC facility their destination and request class charlie service we should also initiate this contact with them far enough out to ensure we can establish our communication with the controller before entering the airspace here is an example so first off how do we know that we can enter again it's based on established two-way radio communication how do we know we've done that the determining factor is when the controller reads back the aircraft's tail number to the pilot here's an example once ATC responds with your tail number in this case November 1 2 3 4 then two-way radio communication has been established and we may enter the class charlie but what if ATC responds with are you allowed to enter at this point although no specific instructions were given by the controller two-way radio communication was established since the tail number was read back and the pilot is permitted to enter the Class C airspace however even if two-way radio communication is established but ATC instructs you to remain clear of the airspace then obviously the pilot should stay outside of the class charlie until told to do so now that we have established two-way radio communication and have an altitude encoding transponder that has been positively identified on ATC's radar we will receive some basic aircraft separation while in the Class C airspace VFR traffic will be provided separation from IFR aircraft it is important to understand that this is the only guaranteed separation ATC is only required to provide separation for VFR aircraft from IFR aircraft they will assist when able to keep VFR aircraft away from other VFR aircraft but in the end it is still up to the pilot operating under visual flight rules to maintain their own aircraft separation having said that in order to stay under visual flight rules we now have to consider our weather requirements within Class C airspace basic VFR weather requirements are in place in order for the airport to be considered VFR there must be at least three statute miles visibility and one thousand foot ceiling while operating under VFR with at least three statute miles visibility we must also remain 500 feet below 1,000 feet above and 2,000 feet horizontally from any cloud we also have a speed restriction while operating close to a Class C airport the fa ARS part 91.1 1:7 state that unless otherwise authorized or required by ATC no person may operate an aircraft at or below 2500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots so this restriction does not encompass all of the Class C airspace keep in mind that we do have a limit on our speed as we get close to that primary airport in summary Class C airspace has a two shelf or tier shape the first layer starts at the surface and extends to 4,000 feet AGL with a radius of 5 nautical miles the outer or upper shelf will begin no lower than 1,200 feet above the surface and extend up to 4000 feet AGL it will have a radius of 10 nautical miles from the center of the airspace to operate within Class C there is no specific pilot certification required we do need a two-way radio with established two-way radio communication in addition we also need a mode C or altitude encoding transponder while operating in or above Class Charlie we do not need this transponder when operating under the 10 nautical mile shelf as a helpful reminder this requirement is because Class C airports do have radar while operating within the airspace we need at least three Statue miles visibility and must remain 500 feet below a thousand feet above and 2,000 feet horizontally for many clouds when we are 2500 feet AGL or below within 4 nautical miles of the primary airport our speed is restricted to 200 knots indicated or less since the size and shape of each class Charlie can be individually tailored it is important to check all resources including the current airport facility directory and aeronautical charts to determine the dimensions and altitudes of the airspace at each airport you plan to fly in or out of even though it is not as common not all Class C airport control towers operate around the clock so check the current AFD to know when the tower is operating when the tower is closed the Class C will normally revert to class echo and that information can also be found in the airport facility directory you