Airways — Page 153, Lesson 156

I want to walk you through the airway symbols and airspace classifications that you'll see on aeronautical charts. Let's start with a key altitude limitation you'll encounter. Maximum Authorized Altitude, or MAA, is a published altitude that represents the maximum usable altitude or flight level for an airspace structure or a route segment. In plain terms, it's the ceiling—you cannot fly above this altitude within that particular piece of airspace or along that specific route segment. Now, let's look at the directional altitude rules you'll see marked on airways with arrows. The letter E means that even altitudes or flight levels, in thousands of feet, are used in the arrow's direction, and odd altitudes or flight levels are used in the opposite direction. This is contrary to the standard ICAO Semi-circular rules, which normally assign odd altitudes for easterly tracks and even for westerly. So when you see an E, it reverses that convention for that airway. The letter O means that odd altitudes or flight levels, in thousands of feet, are used in the arrow's direction. This marking is used only on one-way airways, so traffic flows only in that one direction. When you see E and O together, that indicates that all altitudes—both even and odd—are available in the indicated direction. So you have the full range of cruising levels to choose from. PPR stands for Prior Permission Required. This means you need advance permission from Air Traffic Control to fly in the arrow's direction on that airway. Next, we have Airway Navaid/Reporting Point Bypass symbols. These depict the bypassing of a navaid or a reporting point—you should note these symbols carefully on charts, as they show you when you can skip over a navigation aid or reporting point without having to cross it directly. For Boundaries, you need to become familiar with the boundary symbols used on charts. These define the edges of different airspace structures. Now, let's move into Controlled Airspace and ICAO Airspace Classifications. These are designated by the letters A through G. I'll walk you through each class. Class A: Only IFR flights are permitted. All flights are subject to ATC service and are separated from each other. No VFR traffic is allowed here at all. Class B: Both IFR and VFR flights are permitted. All flights are subject to ATC service, and all flights are separated from each other—so VFR gets separation just like IFR. Class C: IFR and VFR flights are permitted. All flights are subject to ATC service. IFR flights are separated from other IFR flights and also from VFR flights. VFR flights receive traffic information in respect to all other flights. Class D: IFR and VFR flights are permitted. All flights are subject to ATC service. IFR flights are separated from other IFR flights and receive traffic information in respect of VFR flights. VFR flights receive traffic information in respect to all other flights. Class E: IFR and VFR flights are permitted. IFR flights are subject to ATC service and are separated from other IFR flights. All flights receive traffic information as far as is practicable. Class F: IFR and VFR flights are permitted. All participating IFR flights receive an air traffic advisory service, and all flights receive flight information service if requested. Class G: IFR and VFR flights are permitted and receive flight information service if requested. This is uncontrolled airspace—no ATC separation or advisory service is provided. Finally, note the depiction on charts of Terminal Control Area (TMA), Control Area (CTA), and Control Zone (CTR), each shown with its airspace classification letter. These are the specific volumes of controlled airspace you'll operate in around airports and along airways, and the classification tells you exactly what services and rules apply inside them.