Aviation Topic of the Week
By Michael Oxner, June 8, 2003


Introduction
Previous Week's Topic
Following Week's Topic
Aviation in Canada Blog
Archives

This week's topic:
Canada Air Pilot, Part 1: Airport Diagrams

Taking a break (sort of) from the IFR Flight mini-series, this week we'll begin another series on charts. Plans right now are to give an overview of some of the aviation charts used in Canadian aviation. We'll start with the main topic of Charts, and break it down into some of the various categories, then break those categories down into their subparts, where applicable. For example, this week's start on the Canada Air Pilot, or CAP, will include only the Airport Diagrams, and future Subparts will go into more depth on approach plates, RNAV STARs (only the terminology and symbology for this series, the IFR Flight series will provide more on RNAV STARs and flying them later), etc. Let's get started.

Please remember, folks, that this series is simply about reading charts, so the diagrams used *will* be out of date, and out by a long shot. Real world navigation by these particular clips from charts would be just plain stupid.

Chart Example
"Outside the Box" Info
"Inside the Box" Info
    Frequency Information
        VOT
        ATIS
        Clearance Delivery
        Ground (with mention of Apron Advisory)
        Tower
        Departure/Center
        Notes
Declared Distances
    Table of Definitions
Bottom Block
    Take-Off Minima
    Chart Scale
Airport Diagram
    Runway Information
    Taxiway Information
    Apron Information
    Magnetic Variation
    Aerodrome Reference Point
    SPEC VIS, Departure Procedures, SIROs
    Other Details

Chart Example

We'll start off with an example of a chart. Have a look at the airport diagram for CYHZ, Halifax International Airport in Nova Scotia.

"Outside the Box" Info

CYHZ There are many parts of interest, here. The information outside the box, including the top and bottom, show you the basics of the diagram. The basics include the name of the airport in the top right, along with the location of the airport (in this case HALIFAX INTL, HALIFAX NOVA SCOTIA). This can be important, since there are locations across Canada that have the same, or nearly the same, name. Charlottetown, PEI, and Charlottetown, Labrador, for example. And Fox Harbour, NS, and Fox Harbour, Labrador. Each is very different, and they have notes in the approach plates about confirming correct province.

Other important information outside the box lies on the bottom of the diagram. Effective date for the data is listed on the bottom left. Any changes from the previous publication are also listed on the bottom, in the middle. I included a brief look at this information below, when I describe the "Bottom Block". The date of publication is written there, as well. Is this important in VatSim and Flight Sim? If your scenery doesn't seem to match up with the diagram chart, check this date. This may be the reason why.



"Inside the Box" Info

Now the information inside the box. Across the top of the page are a number of boxes. In here, you'll find the radio frequencies and contact information for the various ATC units and facilities you'll be required to talk to on your IFR flight. Have a look below at the enlargement of this area.

FreqBar

Starting from the left, the VOT Frequency is listed if there is one. A VOT is a VOR Test facility. This allows a pilot to check the accuracy of his VOR gauge. To be honest, I haven't felt the need to see if these were in Flight Sim, but I doubt they are. They're really not needed in Flight Sim, either, though they are good in the real world. In reality, the VOT radiates only one "radial" for the VOR receiver to display, the 360 radial. The pilot would select 360 on the Omni Bearing Selector, or OBS, and he should see the needle line up and the "From" flag should appear, indicating the aircraft is on the 360° radial. Then, dial up 180 on the OBS and the "To" flag should appear. This would give the pilot an indication of whether the VOR gauge was working, and how far out of alignment it is.

Second, the ATIS. This was introduced last week, so I won't go into detail again about it. There are two frequencies listed here for Halifax, the first is VHF and the second is the UHF. In Flight Sim, we don't use the UHF side of things, and there aren't many civilian aircraft equipped with UHF radios, either. You can disregard the UHF entries you read on any of these for our environment. The little symbol next to the word "ATIS" that looks like a half moon gives an indication of availability of the service. No symbol means 24 hours a day, 7 days a week. This symbol means "limited hours". It doesn't directly indicate what the hours are, but directs you to the Canada Flight Supplement for further details. This publication has more to say about services available at any given airport in Canada. Remember that not all airports have an ATIS, so most airport diagrams will not have an ATIS entry.

Next, Clearance Delivery. This is the frequency you'll dial up and call in on when you're looking for IFR clearance. Pretty simple. You call in and say something like, "Halifax Clearance Delivery, Golf Romeo India November with ATIS Foxtrot. Requesting IFR to Hamilton." On initial call, you give the callsign of the station you're calling, your callsign, let them know you have the current ATIS (after all, the last part of any ATIS message in the real world says, "Advise ATC on initial contact you have information 'foxtrot' ") and then what you are requesting. Wouldn't it be obvious that you're calling for clearance on the CLNC DEL frequency? Not necessarily. You could be calling to advise of a delay, cancellation, or modification of a flight plan. Let them know the reason you're calling when you call.

Everyone is familiar with Ground Control. You call Ground when you're ready to taxi. Most airport aprons in Canada are uncontrolled. If the one you're at is controlled, there should be a note somewhere on the plate, whether the frequency is listed like any other in this bar, or in a note in the airport diagram itself. The current airport chart (which I couldn't scan because my scanner still isn't working) has "APRON ADVISORY 122.125" listed after CLNC DEL. In any case, GND is the station you must call for authorization to procede on the taxiways and runways (also known as the "maneuvering area" of an airport). "Halifax Ground, Romeo India November ready for taxi". In the case of an airport with an ATIS, you would have received the active runway from the ATIS information. This is what you can expect taxi instructions to. If you want another runway, all you have to do is ask. They may say it's not available, but there's no harm in trying. Any taxi clearance including a "Hold Short" instruction must have the Hold Short instruction readback in full. This includes to hold short of any taxiway, intersection, even a pavement marking. You may be asked to hold short for a variety of reasons, but normally these will be in regard to other traffic.

TWR is the Tower. Straight forward. GND may give you instructions as to when you are to switch to tower frequency. Often this will be with taxi clearance. Other times, GND will give you the instructions to switch at a later point. This is largely a local thing, but also depends heavily on what you were given for taxi instructions. If you were to hold short of a runway, you will need further authorization. GND may have you call TWR for further, or issue further himself when he can, so he won't want you switch before he can give you any more. TWR will normally issue clearances to enter the runway to either "Taxi to position" to allow you to enter the runway and line up but wait for further instructions before you take-off, or just clear you for take-off which lets you enter, line up with and roll on the runway for take-off. TWR will give you instructions about when to contact the departure controller as well, quite typically with take-off instructions unless they have reason to hold on to your flight.

Lastly, Departure. This is the frequency you'll use to call the departure controller once you get airborne. Tower will likely provide you with this frequency but if he doesn't, or you miss it, it's written down right here.

In a previous topic I already mentioned this, but I'll say it again. If the unit name is omitted and just the function is listed, the unit name is the name of the airport. For example, the TWR in this case is "Halifax Tower", and the departure controller is "Halifax Departure". If the unit is not at the airport where you're flying, the unit name will be mentioned. Charlottetown, PEI, for example, doesn't have it's own terminal control unit. The airspace around it is controlled by Moncton Center. If you look at their airport diagram, you'll see that for arrival and departure control (ARR/DEP) you'll be talking to "Moncton Center" when you call in, rather than "Charlottetown Departure".

Also, not all airports have all the services mentioned in the list above. Some airports may have more. Where something detailed above doesn't exist at your favorite airport, it just won't be listed. Where something not mentioned above exists, there will be an additional entry. Again, checking the listing in the Canada Flight Supplement for your airport will reveal more details, including hours of operation for "limited hours" sections, etc.

Declared Distances

Next, we'll look at the Declared Distances section of the chart. Have a look:

Declared Distances

These abbreviations all refer to distances available for different operations, and include different amounts of areas in some cases. You'll notice that they are all basically the same. I'll give you some idea of what they mean in the table below.

Abbreviation
Short for
Meaning
TORA
Take-Off Run Available
The length of runway declared available and suitable for the ground run of an aeroplane taking off.
TODA
Take-Off Distance Available
The length of the TORA plus the length of the clearway, where provided. See below.
ASDA
Accelerate Stop Distance Available
The length of the TORA plus the length of the stopway, where provided. See below.
LDA
Landing Distance Available
The length of runway declared available and suitable for the ground run of an aeroplane landing.

The Clearway mentioned above in TODA refers to an area of land cleared of obstacles that would allow for an aircraft to accelerate in ground effect once airborne. Current standards allow for a maximum of 1,000 feet for a clearway, but all of the clearway must lie within the airport boundaries. The idea is that the airport authority has control over the erection of obstacles and growth of trees, thereby allowing the aircraft the use of the airspace at least up to a certain height.

A Stopway mentioned in ASDA, refers to an area at the end of a runway that is not suitable to high-speed operations like the latter portion of the take-off run, but may be suitable for use for deceleration in the event of an aborted take-off. A stopway will be marked with yellow chevrons spanning the entire width of the stopway. A stopway is not considered useable for taxiing, or for the beginning of the take-off roll if departing in the opposite direction.

These distances are declared for each runway available at the airport.

Bottom Block

Bottom Block

On the left, we see the "Take-Off Minima" block. I described this in much more detail in the "better late than never" Part 2a for the IFR Flight Series. I won't reiterate that information, but remember it is vitally important to be read and understood clearly, especially if there are any special instructions for the runway you plan to depart. In this case, there are no special procedures, and the standard take-off minimum of 1/2 statute mile applies. As long as the weather shows 1/2 mile for visibility on the METAR sequence, you're good to go off any runway at CYHZ.

Then the scale for the airport diagram. This could be useful for determining distances remaining from intersections of taxiways and runways. Sometimes a pilot might request a departure from a taxiway further along the runway, just to save on taxi time. For example, if R33 is active at Halifax, you can see that taxiing for departure on runway 24 by Golf and Foxtrot means that one would have to taxi on R15/33 to get to the threshold. This might pose some delay. Some quick figuring with the scale would reveal approximately 1,000 feet less runway available if he were to taxi Golf and Echo instead. For Dash 8, this should be plenty, don't you think? Even Delta would allow for more than 6,000 feet of runway off Runway 24. It would save you some taxi time. For those in a single engine aircraft, consider just how useless runway behind you is if your engine should fail on take-off...

I'll briefly look below the boxed information here, too. At the bottom left, you can see the effective date for the information in the diagram as published. (I told you this plate was stale) Also, the change from the previous publication, if any at all, is listed. In this case, it was considered an editorial change. Nothing of significance. If a new building was added, a new obstacle built, or a runway or taxiway decommissioned, this type of information would all be mentioned here.

Airport Diagram

Last, but certainly not least, is the airport diagram itself.
Diagram

There really is a lot of information here. First off, the runways will be "colored in" black. Additional details, visible in Runway 24 in this diagram,  include lighting associated with Category II (or III at certain other airports) ILS. In this case, runway 24 has centerline lighting (the white circles down the length of the runway) and Touchdown Zone Lighting near the threshold. The diagram doesn't really do TDZL justice, as it normally extends to 3,000 feet from the landing threshold. Near the runway thresholds, the runway numbers will be printed, along with the magnetic heading (or true heading, followed by "T" if the runway is designated by true heading) and the runway threshold elevation in feet ASL. Runway length is also marked alongside the runway graphic, as will runway width if other than the standard 200 foot width. In the case of Runway 33 at CYHZ, the runway also has a significant downslope. This is calculated the same way slopes are calculated for roads and highways, but they appear for lower values than they do on roads. They look at the average drop from one end of the runway to the other (unless otherwise noted) over each 1,000 feet of runway length. In this example, 477 - 435 = 42 feet. 42/7700=0.00545, or 0.55% down along the length of the runway. This can, therefore, be interpreted as 5.5 feet of elevation change for each 1,000 feet of runway length. For a highway, this means little. For an aircraft trying to decelerate from 140 knots on an icy runway, it means quite a bit. It might be better to use a runway with less slope even if it has a crosswind. I don't believe this kind of runway slope is accurately portrayed in Flight Simulator.

Taxiways will be outlined in black, and somewhere near the segment will be printed the name of the taxiway. Taxiways are named with letters to distinguish them from runways. At larger, more complex airports, taxiways will often have designations including numbers with the letters, like "W1, W2, W3, ..." These will normally be grouped together in a logical placement on the field.

When you get to Aprons, you'll often see Roman Numerals printed. These indicate Apron I, or Apron VIII or whatever, and should be used when calling in to Ground to let them know where you are. If you're parked at a gate, the gate number is better used instead. Some examples, are:

  • "Halifax Apron Advisory, SAC117 with you at Gate 18, ready for pushback"
  • "Moncton Ground, Foxtrot Romeo Oscar Golf at Apron III, ready for taxi."
There are also other forms of symbols shown on aprons. Some airports have de-icing spots published, helipads, or other such data. These are normally labeled if they are not drawn with a standard symbol.

Magnetic Variation will also be indicated in the airport diagram. This can be used to determine winds in Degrees Magnetic from a METAR weather sequence which reports winds in Degrees True. In the case of Halifax with 20° west, you would add the 20° to the METAR wind direction to get the magnetic direction of winds, so if you saw 09027 on a METAR, the winds at Halifax would be 110°M at 27 knots.

The Aerodrome Reference Point, or ARP is also included. This is the point published in the Canada Flight Supplement, and is the point used when designing approaches and providing for clearance from off-airport obstacles and other such items. I don't believe this is of any practical value to a pilot, but I could be wrong.

As mentioned before, any special notes about departure procedures, or SPEC VIS will be placed in the airport diagram. Other information will find its way in here, too, like the distances declared for Simultaneous Intersecting Runway Operations (or SIROs for short). These are all LDAs so no stopway is provided, since the idea is to stop and hold short of the crossing runways. These distances will include the standard 200 feet clear of the runway the cross, from the closest edge. See the examples below:

LDA

Other items marked on this sort of chart include prominent obstacles (which could include radar antennas, ASDE installations, communications towers, etc), service roads (to help pilots identify that the piece of pavement calling their name is not a taxiway), or other dangers like fuel tanks and terrain or obstruction lights (like the one shown just to the west of the threshold of runway 06 in this example). The rotating beacon for the airport is marked so pilots can get a feel for where they are if they see this, as is the control tower, to aid the pilot in interpreting just how well the TWR should be able to see things in his general area. Windsocks will be marked, as well, to show the pilot where he can look for one of these to confirm winds while he taxis. A windsock marked with three little lines emanating from the triangle symbol indicates to the pilot the windsock is lighted for night operations. No lines means it is not. Also, NAVAIDS on, or very near, the field will be marked as well, including DME, VOR, NDB, and even things like RVR (Runway Visual Range) equipment (the little "pie shapes" with A and B marked in them in this example). Oh, yeah, latitude and longitude lines are provided for reference, also.




Other CAP charts will be discussed as time goes on. You may reach me via e-mail at moxner@nbnet.nb.ca. Thanks again for the support. It's nice to know that people are reading this information and finding it useful. Feedback, good or bad is always welcome.