MARSCAN Articles by Bill
RUNWAY DESIGNATIONS and USAGE
Last revised December 6, 2023
Every airport for fixed wing aircraft has runways, even if they are made of grass or sand, such as at Sable Island.
Each physical runway is considered to be two runways, depending on the direction of movement. Thus 05 and 23 are physically the same runway but there are two designations depending on the direction of travel.
Runways are designated by the magnetic bearing rounded to the nearest ten degrees and then divided by ten. Example:
Runway aligned 122 degrees magnetic
Rounded to 120
Divided by 10|
Yields the designation 12
In this example the runway will be expressed by voice as "one-two", not "twelve".
Some runways are in the range 010 to 090 degrees rounded, and here in Canada, when divided by ten are properly designated as 01 to 09, not 1 to 9 which is the normal in the USA. It is very common to hear American pilots refer to runway 05 at Halifax as runway 5, even when the controller is calling it 05. Speaking of controllers you will now increasingly hear the controller also referring to "5" which is perhaps just another example of creeping Americanism.
In this example diagram of the Summerside, PEI airport there is one physical runway, with two designations. Alongside the runway are arrowed numbers 054 and 234 degrees, indicating the magnetic bearing. So in this case that one piece of pavement is either Runway 05 or Runway 23, depending on the direction of movement. (You might note on the diagram, and certainly would on a photo, that there are the remains of two other physical runways, that have been closed for some time. Abandoned runways and taxiways are shown with dashed lines. The triangular pattern of the remaining runway and the two abandoned ones is discussed farther along in this article.
Runway designations change over time. This is due to the slow movement of the magnetic poles. The magnetic bearing of a fixed object will therefore change over time. The runways at Halifax were until the early 2000's all one digit higher. For example runway 32 was runway 33. The change of designation is infrequent because as you know the designation covers ten degrees of bearing. For example the designation "Runway 14" covers all bearings from 135 to 144 degrees. In our area the magnetic bearings are slowly lowering due the north magnetic pole moving. A Runway 27 with a bearing now of, for example, 272 degrees will not be changing to "Runway 26" until the magnetic bearing lowers by 8 degrees to 264 degrees, which will take a long time. One that is already near the boundary may be about to change in the upcoming months. This is why they changed at Halifax at that time but they did not change at all airports. On the diagram above you will note the indicator that shows the difference between magnetic north and true north, and as well the current annual rate at which this "magnetic variation" is changing.
Generally at airports of any major size, and at lots of small ones as well, there are two or more physical runways, in order to take advantage of different wind directions. In some cases the runways are of much the same length, but more commonly the one aligned with the prevailing winds will be longer than the other one, and in this case the shorter one might be referred to as the "crosswind runway", and would be used only when the winds are much offset from the direction of the main runway.
Here is the diagram for Halifax Stanfield International Airport. In this case there are two physical runways, yielding four designated runways. You should note that the diagrams are not all to the same scale. The runway at Summerside is 8000 feet long, whereas the main runway at Halifax is 10500 feet. Despite our metric world, many aeronautical measures remain in the old system. This includes runway lengths, altitudes, and speeds, the latter of which are in knots (nautical miles per hour).
The actual headings of the runways at Halifax are currently 144 degrees for Runway 14 and 054 degrees for Runway 05. You will note that this pair of runways are exactly perpendicular. Keep in mind that the opposite direction on these runways will be the reciprocal bearings. You will see from this that the two headings are just under the threshold' i.e. they just moved under the 145 and 055 bearings that formerly made them Runways 15 and 06, and it will be a long time before they get down to 134 and 044 necessitating the next revision.
At Halifax the usage of the two physical runways (four designated runways) varies. Naturally this depends on the wind direction at the time, but also there will be some tolerance for cross winds in order to reduce travel in taxiing or in flight. The flying part is the most important due to fuel consumption and time. For example a pilot heading to Charlottetown might prefer to take off on Runway 05 so that the aircraft is heading straight to destination on takeoff, and when coming back from Charlottetown will prefer the reciprocal which is Runway 23. Less turns ... much more straightforward. You might hear that the active runway is 14 but a pilot asks for 23. The controller will decide if that is reasonable or not and give an answer based on wind, runway condition and traffic. Pilots also make requests based on how far they have to taxi to reach the take-off start point. All of this is related to wasted fuel costs, as well as time.
At some airports outside the Maritimes there are parallel runways and these are suffixed by L and R. Thus in this diagram of Montreal Trudeau International Airport you will see a runway 06L/24R and a runway 06R/24L Notice that the Left in one direction is the Right in the reciprocal. In this case there is no cross-wind runway, which can result from various factors, whether it be lack of suitable land, or not enough need to justify the expense. In fact, there used to be cross-wind runway here but was closed comparitively recently.
In a very few airports there may be a third parallel runway. If all three runways are located close to each other one will have a C suffix. If one of the three is widely separated from the close-together pair, the third one may be given a different number that does not strictly adhere to the magnetic bearing principal. In this diagram of Toronto Pearson Airport you can see that there are two parallel pairs. 15L/33R & 15R/33L plus 06L/24R & 06R & 24L. However there is a third runway (at the left in the diagram) that is actually parallel to the latter pair, but due to being at the other side of the airport, it is designated 05/33, which deviates from what it should be if following the magnetic bearing rule (all three are oriented 057/237 degrees) This all works out fine for airport operations however as everyone knows which runway is which.
There is another suffix possible, for helicopter usage. Most formal heliports consist of one or more square pads. Some heliports, usually military, have actual runways, albeit short in length, rather than pads. Shearwater has Runways 16H and 34H, which of course is physically just one runway. The designation may seem to be superfluous if it is already known that the particular airport is just for helicopters, but it is perhaps indicates that it is for helicopters but some types of short take-off and landing fixed wing aircraft might also be able to use it.
Triangular runways:
In earlier days and mostly at military bases there was a triangle pattern where there were three runways, usually at 60 degrees of angle. It is almost a certainty when you encounter a triangle of runways on an aerial photo that you are looking at a current or former military base; though in many cases one or more of the three runways might be now abandoned. This is the case at Shearwater, Greenwood, Summerside, Chatham (Miramichi), and the former airfield at Pennfield Ridge. Here is a diagram of the Debert Airport, clearly showing the triangle pattern, and in this case all the runways are indicated to be still in operation, though one has been partly abandoned (shortened). Debert originated as a military airfield during World War II and is now very active for light aircraft. Note that most of the taxiways and ramps at Debert have been abandoned.