By Tom Seeley
Purpose: This segment will provide basic understanding of airport diagrams to enable pilots to navigate safely and correctly at various airfields.
Objective: Upon completion, the pilot should have a clear understanding of the elements of an airport diagram and how to use it.
Introduction: In the U.S. every airport to which an instrument approach procedure (IAP) has been published also has an airport diagram published. These can be found in the various charting providers (NOS, Jeppesen) but are also largely available online. Examples of online sources includeAirnav∞ and FlightAware∞. For other areas of the world, almost all VATSIM FIR's include sources for online charts on their websites.
For example, to locate charts for Schiphol Airport, Netherlands, (EHAM) you would go to the VATSIM Netherlands site∞ and use the CHARTS link on the left side of the page. Charts for airports in the United Kingdom are a little more involved, but available from the UK AIP (Aeronautical Information Package) site: UK-AIP∞. You must join, but registration is free and the site is very thorough. The quality of diagrams varies throughout the world, with some providing a general overview of the airport and others more detailed. Some are quality PDF files and others are scanned JPG files which results in some quality loss.
Discussion: The image below is a partial view of the Manchester, UK Airport (EGCC) diagram available from the UK-AIP. The original can be viewed HERE∞ (PDF, 313KB). You can see that this diagram is quite detailed and colorized.
In comparison, the image below left is an airport diagram for Atlanta Hartsfield Airport (KATL). This diagram is smaller, more complex, and a bit more difficult to read. On the other hand it should be noted that Jeppesen provides larger fold-out diagrams for many high-density airports as well as "low visibility taxi route" charts and these are much easier to read and interpret. However these are only available by subscription. A partial example from the fold-out for KATL is reproduced below the full diagram.
All of these diagrams, regardless of how colorful or easy to read, provide basic information for navigating around an airport, and supplemental information which is either critical or informational. The EGCC diagram has numerous "shadow boxes" with important information such as touchdown zone elevation (TDZ) and localizer frequencies, for example. It denotes taxiways via replicas of the taxiway markings you would see looking out the cockpit window, yellow against a black background. The portrayal of runway markings and orientation is also a faithful representation of the real-world airport.
The Atlanta-Hartsfield diagram is representative of most U.S. high-density airports, and is more of a graphic layout than a look-down image. Taxiways and runways are represented only by their letter or numeric labels. Touchdown zone elevation, lighting, and notes are included just as in the UK diagram, but presented differently. One significant difference is taxiway hold points: The UK diagram shows these quite clearly, while the US diagram makes them a little more difficult to see. (Look between runways 27L and 27R at taxiways Kilo and Lima) However despite these sometime subtle differences, either diagram will facilitate on-airport navigation.
Runways, Taxiways and Ramps: A RUNWAY is differentiated from other surfaces on the airport by being the only surface an aircraft (other than a helicopter) either lands on or takes off from. Runways may also be used for taxiing aircraft and in some cases for parking aircraft. Runways are always designated (and normally marked) by a one or two number label, loosely associated with their compass bearing. In other words, a runway oriented north-south might be designated 36/18, but might also be identified as 35/17 or 01/19. You can see from these identifiers that one end of the runway is always the "reciprocal" of the other, or 180? opposite. In addition, if there are multiple runways aligned in the same direction, similar to KATL where there are five east/west runways, they will have letter designators attached, such as 27R, 27L, 27C. These would refer to a Runway "27 Right", "27 Left", or "27 Center" and that is the way they are referred to in communications, rather than saying something like, "Two Seven R". When more than three are present, the others are given numerical designators -close- to their geographical orientation. Again, as in the KATL case, you can see that the other runways are referred to as 26R and 26L, and the farthest south runway is 28. Even though all these runways are oriented east/west, their numerical designators differ. Runway markings are always white. Runways are also bordered by white lights.
Taxiways are designated surfaces provided at airports to enable aircraft to reposition from the runway to their final position on the field, or vice versa. They have different marking from runways, and are always identified by letters, with numbers if necessary. In the graphic below from London Gatwick (EGKK) you can see the approach ends of Runways 08L and 08R, with taxiway designators J5, J7, J4, G1, H and others. When communicating with ATC, these are referred to as "Juliet Four" or "Gulf One". Taxiways may have two-letter designators as well, and these are spoken, "Sierra Gulf". It is not uncommon, when calling for taxi or when clearing a runway after landing, to hear something like, "Taxi via Alpha Five, Alpha, Charlie, Hold Short Runway 26L". Pilots anticipating movement at high-density airports should anticipate such instructions and be prepared to read them back, then follow them as instructed, especially during periods of heavy traffic. Taxiway markings are always yellow. Most have yellow centerline markings to facilitate remaining in the center of, and following the taxiway in reduced visibility. They may also be bordered by blue lights and may have blue lights embedded in the centerline.
At the other end of taxiways are "Ramps" which are not really ramps at all, but different surfaces that denote where the taxiway ends and the terminal or gate area begins. It is important to note that in many cases, ATC responsibility ends with the transition from taxiway to ramp. These are often referred to as "non-movement" areas. This designation doesn't mean there is no movement, but that either the pilot or some other authority assumes responsibility, or both. At major airports each airline may have its own "ramp control" and may have a tower-like facility to control movement on its ramp. The line of demarcation between taxiway and ramp is normally a broken single or double yellow line.
The signs in the images above are the universal signs used to denote directions to taxiways and runways. A yellow letter on a black background signifies a taxiway that you are currently on. Black letters on a yellow background are directions to the taxiway represented by the letter. Black numbers on a yellow background indicate directions to the runway(s) represented by the numbers. The solid and dashed black lines indicate a "hold short" location of a taxiway approaching a runway, where you must stop if the solid line is nearest you, or which you must cross if exiting a runway and the dashed lines are nearest you.
Looking at the images above, the first shows the aircraft on Taxiway "Delta Two" denoted by the yellow numbers on a black field. It is approaching an intersection with Taxiway Delta. The hold short lines indicate the aircraft has just departed the runway and should not stop until after crossing the hold short line fully.
In the second, the aircraft is on a taxiway approaching a runway intersection. At this intersection, Runway 12/30 and Runway 18L/36R cross. In this case, the solid lines of the hold short line are toward the aircraft, and it cannot proceed past this point unless a clearance to do so has been received.
Briefly in the image above you can see runway edge identifier lights that are white, turning to yellow as the departure end of the runway gets closer. The centerline lighting, white until 3000' remaining, then alternating red and white, warning of the reduced length, and ultimately all red. In the upper right of the image you can see all blue taxiway lighting.